Greenspace exposure and associated health outcomes: a systematic review of reviews

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Osborne" }, { "@type": "Person", "name": "Gail Williams" }, { "@type": "Person", "name": "Darsy Darssan" } ], "publisher": { "@type": "Organization", "name": "F1000Research", "logo": { "@type": "ImageObject", "url": "https://f1000research.com/img/AMP/F1000Research_image.png", "height": 480, "width": 60 } }, "image": { "@type": "ImageObject", "url": "https://f1000research.com/img/AMP/F1000Research_image.png", "height": 1200, "width": 150 }, "description": " Background Numerous systematic reviews and meta-analyses have sought to clarify the relationship between greenspace exposure and health outcomes, but the results are inconsistent. We aimed to synthesise all relevant systematic reviews and meta-analyses on this association. Methods We searched five databases (PubMed, Embase, the Cumulative Index to Nursing and Allied Health Literature [CINAHL], Scopus, and the Cochrane Database of Systematic Reviews) and conducted a manual reference search for systematic reviews and meta-analyses written in English and published in peer-reviewed journals that clearly defined measures of greenspace exposure and reported health outcomes directly attributable to greenspace exposure. A total of 36 systematic reviews published between January 2010 and December 2020 were identified for inclusion in this systematic review of reviews (PROSPERO: CRD42021227422). The methodological quality and risk of bias of included systematic reviews were evaluated by two independent reviewers. Results Beneficial effects of greenspace exposure were observed for all-cause and cause-specific mortality, as well as mental health and cognitive function. Ambivalent results were found for cardiovascular and metabolic health, general health and quality of life (QOL), and respiratory health and allergies. Most of the systematic reviews included in the current umbrella review had a low to moderate methodological quality and a high risk of bias. Conclusions This umbrella review highlights the link between greenspaces and a variety of health outcomes, emphasising the importance of preserving existing greenspaces and integrating additional vegetation into urban areas to maintain public health. " } { "@context": "http://schema.org", "@type": "BreadcrumbList", "itemListElement": [ { "@type": "ListItem", "position": "1", "item": { "@id": "https://f1000research.com/", "name": "Home" } }, { "@type": "ListItem", "position": "2", "item": { "@id": "https://f1000research.com/browse/articles", "name": "Browse" } }, { "@type": "ListItem", "position": "3", "item": { "@id": "https://f1000research.com/articles/13-491", "name": "Greenspace exposure and associated health outcomes: a systematic review..." } } ] } Home Browse Greenspace exposure and associated health outcomes: a systematic review... ALL Metrics - Views Downloads Get PDF Get XML Cite How to cite this article Bryer B, Odebeatu CC, Lee WR et al. Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.12688/f1000research.148878.2 ) NOTE: If applicable, it is important to ensure the information in square brackets after the title is included in all citations of this article. Close Copy Citation Details Export Export Citation Sciwheel EndNote Ref. Manager Bibtex ProCite Sente EXPORT Select a format first Track Share ▬ ✚ Systematic Review Revised Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] Brittnee Bryer https://orcid.org/0009-0009-2910-4843 1 , Chinonso Christian Odebeatu 1 , Wen Ray Lee 2 , [...] Kathryn Vitangcol https://orcid.org/0000-0002-6279-8033 3 , Victor Gallegos-Rejas https://orcid.org/0000-0001-9856-4848 1,4,5 , Nicholas J. Osborne https://orcid.org/0000-0002-6700-2284 1,6,7 , Gail Williams 1 , Darsy Darssan https://orcid.org/0000-0001-7050-9150 1 Brittnee Bryer https://orcid.org/0009-0009-2910-4843 1 , Chinonso Christian Odebeatu 1 , [...] Wen Ray Lee 2 , Kathryn Vitangcol https://orcid.org/0000-0002-6279-8033 3 , Victor Gallegos-Rejas https://orcid.org/0000-0001-9856-4848 1,4,5 , Nicholas J. Osborne https://orcid.org/0000-0002-6700-2284 1,6,7 , Gail Williams 1 , Darsy Darssan https://orcid.org/0000-0001-7050-9150 1 PUBLISHED 30 Jul 2025 Author details Author details 1 School of Public Health, The University of Queensland, Herston, Queensland, Australia 2 Child Health Research Centre, The University of Queensland, South Brisbane, Queensland, Australia 3 Princess Alexandra Hospital Southside Clinical Unit, The University of Queensland, Woolloongabba, Queensland, Australia 4 Centre for Online Health, The University of Queensland, Woolloongabba, Queensland, Australia 5 Centre for Health Services Research, The University of Queensland, Woolloongabba, Queensland, Australia 6 School of Population Health, University of New South Wales, Sydney, New South Wales, Australia 7 European Centre for Environment and Human Health, University of Exeter, Truro, UK Brittnee Bryer Roles: Data Curation, Formal Analysis, Investigation, Methodology, Validation, Visualization, Writing – Original Draft Preparation, Writing – Review & Editing Chinonso Christian Odebeatu Roles: Data Curation, Investigation, Validation, Writing – Original Draft Preparation, Writing – Review & Editing Wen Ray Lee Roles: Data Curation, Formal Analysis, Investigation, Writing – Review & Editing Kathryn Vitangcol Roles: Data Curation, Investigation, Methodology, Writing – Review & Editing Victor Gallegos-Rejas Roles: Data Curation, Investigation, Methodology, Writing – Review & Editing Nicholas J. Osborne Roles: Conceptualization, Methodology, Supervision, Writing – Review & Editing Gail Williams Roles: Conceptualization, Methodology, Supervision, Writing – Review & Editing Darsy Darssan Roles: Conceptualization, Data Curation, Formal Analysis, Investigation, Methodology, Project Administration, Supervision, Validation, Visualization, Writing – Original Draft Preparation, Writing – Review & Editing OPEN PEER REVIEW DETAILS REVIEWER STATUS This article is included in the Ecology and Global Change gateway. This article is included in the Public Health and Environmental Health collection. Abstract Background Numerous systematic reviews and meta-analyses have sought to clarify the relationship between greenspace exposure and health outcomes, but the results are inconsistent. We aimed to synthesise all relevant systematic reviews and meta-analyses on this association. Methods We searched five databases (PubMed, Embase, the Cumulative Index to Nursing and Allied Health Literature [CINAHL], Scopus, and the Cochrane Database of Systematic Reviews) and conducted a manual reference search for systematic reviews and meta-analyses written in English and published in peer-reviewed journals that clearly defined measures of greenspace exposure and reported health outcomes directly attributable to greenspace exposure. A total of 36 systematic reviews published between January 2010 and December 2020 were identified for inclusion in this systematic review of reviews (PROSPERO: CRD42021227422). The methodological quality and risk of bias of included systematic reviews were evaluated by two independent reviewers. Results Beneficial effects of greenspace exposure were observed for all-cause and cause-specific mortality, as well as mental health and cognitive function. Ambivalent results were found for cardiovascular and metabolic health, general health and quality of life (QOL), and respiratory health and allergies. Most of the systematic reviews included in the current umbrella review had a low to moderate methodological quality and a high risk of bias. Conclusions This umbrella review highlights the link between greenspaces and a variety of health outcomes, emphasising the importance of preserving existing greenspaces and integrating additional vegetation into urban areas to maintain public health. READ ALL READ LESS Keywords Human health, natural environment, outdoor environment, umbrella review, biodiversity, greenery, urbanisation Corresponding Author(s) Darsy Darssan ( [email protected] ) Close Corresponding author: Darsy Darssan Competing interests: No competing interests were disclosed. Grant information: The author(s) declared that no grants were involved in supporting this work. Copyright: © 2025 Bryer B et al . This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. How to cite: Bryer B, Odebeatu CC, Lee WR et al. Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.12688/f1000research.148878.2 ) First published: 17 May 2024, 13 :491 ( https://doi.org/10.12688/f1000research.148878.1 ) Latest published: 30 Jul 2025, 13 :491 ( https://doi.org/10.12688/f1000research.148878.2 ) Revised Amendments from Version 1 Revisions have been made to the article based on the reviewers' comments. Specifically, several sections have been reworded to enhance clarity and comprehension, the readability of tables and figures has been improved through refined labels and footnotes, and directions to the PRISMA flowchart have been added. Revisions have been made to the article based on the reviewers' comments. Specifically, several sections have been reworded to enhance clarity and comprehension, the readability of tables and figures has been improved through refined labels and footnotes, and directions to the PRISMA flowchart have been added. See the authors' detailed response to the review by David Rojas-Rueda See the authors' detailed response to the review by Wenzhong Huang See the authors' detailed response to the review by William Mueller READ REVIEWER RESPONSES Introduction Reducing the global burden of diseases has become a public health priority, and many international bodies, including the World Health Organisation (WHO), have highlighted the need to maintain healthy, liveable, and sustainable cities ( World Health Organization, 2021 ). In response to this, changes to urban environmental design, such as the provision of access to greenspace exposure, have been proposed to enhance human health and wellbeing ( Browning et al., 2022 ; Nguyen et al., 2021 ). Greenspace may benefit human health via several mechanisms, including increased physical activity (PA), enhanced social engagement, and improved mental restoration ( Zhang et al., 2022 ). Accumulating evidence from the past two decades has suggested that exposure to greenspace may reduce the risk of all-cause and cause-specific mortality and morbidity ( Rojas-Rueda et al., 2019 ; Twohig-Bennett & Jones, 2018 ; Yuan et al., 2021 ), and birth outcomes ( Dzhambov et al., 2014 ; Lee et al., 2020 ; Twohig-Bennett & Jones, 2018 ). However, several systematic reviews did not report statistically significant findings between greenspace and health outcomes, particularly for respiratory diseases in children and adolescents ( Lambert et al., 2017 ), and the risk of cancer in adults ( Porcherie et al., 2021 ). In contrast, a study carried out in Australia found that the odds of skin cancer escalate in accordance with increased neighbourhood greenness ( Astell-Burt et al., 2014 ). These inconsistencies could be attributed, in part, to heterogeneity across different outcome measures, inconsistent definitions of greenspace exposure, or disparate study designs and confounding variables. Despite this discordance, exposure to greenspace may have beneficial effects on health outcomes. There is an increasing number of systematic reviews and meta-analyses on the relationship between greenspace exposure and health outcomes ( Houlden et al., 2018 ; Lambert et al., 2017 ; Lee et al., 2020 ; Rojas-Rueda et al., 2019 ; Twohig-Bennett & Jones, 2018 ; Yuan et al., 2021 ). However, many of these reviews only consider a narrow selection of health outcomes. Therefore, the literature needs to be assessed to understand the association between greenspace exposure and health outcomes, excluding health determinants and the influence of blue space. Addressing this gap requires a higher level of critical appraisal and synthesis of all systematic reviews and meta-analyses. Only two umbrella reviews have reviewed evidence on the link between exposure to greenspace and human health from systematic reviews and meta-analyses ( van den Bosch & Ode Sang, 2017 ; Yang et al., 2021 ). The review by van den Bosch and Ode Sang (2017) focused on the natural environment, including both green and blue spaces. The conclusions drawn do not isolate the impact of greenspace exposure alone on health outcomes, as its effects are confounded by blue space. Yang et al. (2021) evaluated the combined effects of health determinants (i.e., physical activity, time spent outdoors, prosocial behaviour, and academic achievement) and health outcomes, obscuring the isolated impact of greenspace exposure on health outcomes alone. Yang et al. (2021) also included scoping reviews in their synthesis. There is currently no umbrella review in the literature that possesses all the following qualities: i) evaluates the association between greenspace exposure and health outcomes from quantitative studies, independently of blue space and health determinants; ii) assesses both the quality and risk of bias of reviews; iii) records the frequency of greenspace exposure measure used; iv) summarises health outcomes and associated ICD-10 codes; v) reports effect measures (e.g. odds ratio [OR], mean difference [MD]) from meta-analyses. This umbrella review aims to fill this gap. Methods The protocol for this umbrella review was registered with the International Prospective Register of Systematic Reviews (PROSPERO) (registration ID: CRD42021227422) ( Gallegos-Rejas et al., 2021 ). Search strategy An electronic literature search was carried out using the following databases: PubMed, Embase, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), Scopus, and the Cochrane Database of Systematic Reviews. We restricted the search to peer-reviewed systematic reviews and meta-analyses conducted in humans and published in English between January 2010 and December 2020, including reviews first published online during this period (extended data: Supplementary Table S1). All databases were searched on 05/01/2021. To ensure that relevant systematic reviews were retrieved, we also conducted forward and backward reference searching on screened reviews, as well as manual searching of reference lists of relevant reviews. EndNote software programme was used for reference management ( The EndNote Team, 2013 ). Eligibility criteria Title and abstract screening and full-text screening of identified systematic reviews were independently conducted by two authors. The following inclusion criteria were used: i) systematic review or meta-analysis; ii) written in English and published in a peer-reviewed journal; iii) greenspace exposure clearly defined using objective or subjective measures; iv) reported health outcome(s) were directly attributable to greenspace exposure. We excluded: i) systematic reviews that failed to follow a standardised, systematic review approach, for example, no mention of databases searched; no identification of the search terms used; or no assessment of original studies quality; ii) scoping reviews; iii) systematic reviews that did not consider the effects of greenspace independently of blue space. Reviews that mentioned health outcome(s) in the title and abstract but only reported health determinants such as body mass index (BMI), physical activity (PA), or diet were excluded during full-text screening (extended data: Supplementary File S1). Disagreements were resolved via discussions with the last author. Covidence was used to conduct all stages of study screening ( Covidence systematic review software, 2022 ). Data extraction Data extraction was conducted independently by two authors. Pilot testing was conducted on 10 of the identified systematic reviews to build the data extraction form. The form included information on the design of original studies, types and measures of greenspace exposures, and types of health outcomes. Any disagreement in the data extraction process was resolved via discussions with the last author. Analysis criteria The objectives, methods, and conclusions of each systematic review included in this umbrella review were summarised. Quantitative data, reported as the effect estimate with associated confidence interval, were summarised for health outcomes if available. We could not conduct a meta-analysis as the primary aim of any umbrella review is to summarise existing systematic reviews and not to re-synthesise or conduct meta-analysis ( Aromataris et al., 2015 ). The number and types of original studies in the systematic reviews, as well as the measure(s) of greenspace exposure and health outcomes, were recorded. The International Classification of Diseases, 10 th Edition (ICD-10) was then used to allocate corresponding ICD-10 codes for each health outcome identified during data extraction ( World Health Organization, 2019 ). The methodological quality and risk of bias of included systematic reviews were evaluated independently by two authors using A MeaSurement Tool to Assess systematic Reviews 2 (AMSTAR-2) ( Shea et al., 2017 ) and the Risk of Bias Assessment Tool for Systematic Reviews (ROBIS) ( Whiting et al., 2016 ), respectively. Disagreements between researchers were solved via discussions with the last author. No systematic reviews were excluded based on the methodological quality or risk of bias assessment. Results Study selection Our initial systematic search yielded 4250 systematic reviews. After removing duplicates and screening titles and abstracts, 173 potentially relevant articles were selected for full-text assessment. After full-text evaluation, we excluded a total of 141 articles based on our inclusion criteria and retained a total of 36 systematic reviews. The PRISMA flowchart is available under the Reporting guidelines section at the end of this article. Study type and characteristics Of the 36 systematic reviews included in this umbrella review, most (n=29, 75%) were published after 2016, with only seven (25%) published before or during 2016. The number of original studies included in systematic reviews ranged from 5 to 143 ( Table 1 ), totalling 989. The majority of these were cross-sectional (n=418, 42.7%), followed by cohort (n=101, 10.3%), longitudinal studies (n=64, 6.5%), RCTs (n=61, 6.2%), and case-control studies (n=5, 0.5%) ( Table 2 ). Table 1. Characteristics of included systematic reviews. Author (year) Total number of original studies Type of study (n) Objective(s) of the study Sample size Greenspace measures Outcome measures Main finding(s) Akaraci et al. (2020) 37 Cross-sectional (30), cohort (4), case-control (2), quasi-experimental (1) To systematically review and synthesise (meta-analyse) studies on the impacts of green and/or blue spaces on birth outcomes. 427-3,026,603 NDVI within several buffer distances, increment of 10% green space measures, residential greenness following a 0.1 unit increase in NDVI. BW, PTB, SGA, LBW. A statistically significant relationship was found between increased residential greenness and higher BW and lower odds of SGA. Non-significant associations reported for LBW and PTB outcomes. Carver et al. (2020) 9 Observational (5), Quasi-experimental (4) To examine existing evidence on the association between availability and use of greenery and mental health among residents of aged care facilities. 10-211 Garden exposure/garden use. Wellbeing, stress, depression. Exposure to greenery and use of greenspace in residential aged care facilities show promise for promoting mental health. However, the findings relied mainly on non-validated measures of mental health. de Keijzer et al. (2020) 59 Cross-sectional (44), longitudinal (14), ecological (1) To systematically review existing evidence on the relationship of long-term outdoor greenspace exposure with healthy ageing. 80-429,334 NDVI within a certain buffer distance, percentage/proportion of greenspace/parklands/tree canopy/vegetation within a buffer, proximity/distance to greenspace. Mental health, cognitive function, physical capability, morbidity, weight status, hypertension, cholesterol, perceived wellbeing. Suggestive salutogenic effects of increased long-term exposure to greenspace on healthy ageing, but evidence base is limited/inadequate to draw conclusion. de Keijzer et al. (2016) 13 Cross-sectional (8), longitudinal (3), ecological (2) To systematically examine the link between long-term greenspace exposure and cognition over life span. 17-2805 Neighbourhood measures of percentage of green space, greenness surrounding schools, NDVI, rating of greenness, self-reported or views of greenspace through the window. Cognitive function, dementia. The association between greenspace exposure and cognition were inadequate but suggestive of a positive relationship. Dzhambov et al. (2014) 8 Cross-sectional (8) To explore the association between pregnant women living in green environments and BW of their infants. 2393-81,246 Residential greenness within a 100m buffer. BW A weak but positive association between residential greenness within a 100 m buffer and BW. Gascon et al. (2016) 12 Ecological (7), Cohort (3), cross-sectional (2) To systematically synthesise the existing evidence on the relationship between residential natural outdoor environments and mortality in adults. 1645-43,000,000 10% increase in residential greenness (determined via percentage greenspace in an area or NDVI), interquartile range increase as a proxy for higher vs lower greenspace exposure categories. All-cause mortality, CVD mortality, lung cancer, respiratory diseases, diabetes mortality, intentional self-harm, motor vehicle fatality. Inconsistent evidence between higher residential greenness and all-cause mortality, however the risk of CVD mortality was reduced following increased exposure to residential greenness. Gascon et al. (2015) 28 Cross-sectional (21), longitudinal (6), ecological (1) To systematically review the long-term effects of residential green spaces on mental health. ~100-345,143 Surrounding greenness, access to green spaces, quality of green spaces. General mental health, stress, distress, depression, anxiety, mood disorders, emotional and behavioural health. Limited evidence of positive association of surrounding greenness, access to green space, and quality of greenspace with mental health benefits. Gritzka et al. (2020) 10 RCT (8), preliminary cross-sectional survey (1), acute RCT (1) To systematically evaluate existing research on mental health and wellbeing outcomes on employees participating in nature-based interventions. 14-94 Green exercise, nature savouring, green office space. Mental health, cognitive ability, recovery and restoration, work and life satisfaction, psychophysiological indicators of health. Nature-based interventions had a positive impact on employees’ mental health indices. The effect was less consistent for other health outcomes. Hartley et al. (2020) 7 Cross-sectional (4), cohort (2), meta-analysis (1) To examine existing evidence on the relationship between greenness and asthma in children. 150-49,956 NDVI, land-use classification, total and native land-use types, Childhood asthma. Higher greenness had little or no impact on childhood asthma. Houlden et al. (2018) 52 Cross-sectional (37), longitudinal (6), case control (4), uncontrolled case (4), ecological (1) To systematically synthesise evidence on greenspace and mental wellbeing. 32-65,407 Amount of local-area greenspace, greenspace types, views of greenspace, greenspace accessibility, subjective connection to nature. Hedonic wellbeing (happiness and life satisfaction), eudaimonic wellbeing (fulfilment, functioning and QoL). Psychological distress, vitality, mood, attention affect. Relationship between the amount of local-area greenspace and hedonic but not eudaimonic wellbeing supported. Limited evidence observed for other greenspace measure. Islam et al. (2020) 23 Cross-sectional (11), prospective cohort (10), unknown (2) To examine existing evidence on the association between greenspace exposure and early childhood development. 253-3,026,603 Surrounding/residential greenness, distance to city parks. BW, PTB, gestational age, atopic dermatitis, PA, BMI, neuro-behavioural health, asthma, bronchitis, wheezing. Increased greenspace exposure during pregnancy was associated with decreased LBW. The risk of obesity and neurodevelopmental issues such as inattentiveness were reduced following increased exposure to greenness. Certain green plants may exacerbate asthma symptoms in children. Kabisch et al. (2017) 27 NA To examine the state of evidence on the association between urban green spaces and the health of children and older adults in urbanised areas. NA Average NDVI, urban land-use data, tree coverage based on satellite data, public parks and playground space, percentage of greenery from census block or land-use data, urban allotment garden. Children’s health: infant/neonatal mortality, BW, mental health, weight status, allergic sensitisation, asthma. Elderly health: CVD mortality, respiratory mortality, diabetes, mental health, general wellbeing, cancer, respiratory diseases. Urban greenspaces offer protective effects on children and elderly health, but the evidence base is inconclusive and may be driven by socioeconomic confounders. Kondo et al. (2018) 68 Experimental (35), longitudinal (20), quasi-experimental (9), case-crossover (3), RCT (1) To systematically synthesise existing evidence examining the association between urban green space and human health. 12-3,026,603 Average NDVI within proximity of residence, percentage of greenspace within administrative boundary of residence, distance from residence to nearest park or greenspace, percentage of natural spaces and parks near home, quantity of neighbourhood green space. BW, PTB, SGA, prostate cancer, weight status, BMI, cortisol, diabetes, cardiovascular health, mental health, PA, violence/aggression, behavioural problems. While urban greenspace exposure was associated with mortality, violence, attention, and mood, mixed or no association results were reported for weight status, depression, stress, and general health. Limited evidence to draw conclusions on BW, cancer, diabetes, and respiratory symptoms. Lachowycz and Jones (2011) 60 NA To systematically examine the link between greenspace access and obesity, obesity-related outcomes, and behaviour. 58-345,143 Distance to or count of nearest greenspace from home, percentage greenspace, audit of greenness, quality of greenspace, type of greenspace, park service areas. Obesity, CHD, diabetes, premature mortality, circulatory disease, MetS, weight status, PA. Weak but positive association between greenspace and obesity-related health indicators. The relationship varied based on age, socio-economic status, and greenspace measure. Lambert et al. (2018) 5 Cohort (5) To synthesise current literature on the relationship of surrounding greenness with atopic sensitisation in children and adolescents. 94-13,016 NDVI, land-cover database, LiDAR imagery. Atopic sensitisation. Findings were mixed with some cohorts showing protective effects from greenspace, while others reported an adverse or no effect following greenspace exposure. Lambert et al. (2017) 11 Cohort (5), ecological (3), case-control (2), cross-sectional (1) To systematically evaluate the relationship between surrounding residential greenness and allergic respiratory diseases in children and adolescents. 549-642,313 NDVI, street tree density, LiDAR. Asthma, allergic rhinitis. Relationship between residential greenness and asthmas and allergic rhinitis remains inconclusive. Pooled estimate from meta-analysis showed no significant association. Lee et al. (2020) 10 NA To investigate the link between pregnancy outcomes and the surrounding living environment such as greenness. 2393-780,435 NDVI within 100, 250, and 500m buffers from participant’s home location. LBW, very LBW, SGA, PTD, very PTD. Weak evidence of positive association found between surrounding greenness and BW, with significant decrease in the incidence of LBW, SBA, and PTD. Luo et al. (2020) 57 Cross-sectional (46), cohort (11) To synthesise epidemiological studies on the relationship of greenspace exposure with overweight/obesity. 102-97,574,613 NDVI, residential proximity to the nearest greenspace, proportion of greenspace within 30 to 1600m buffer around residential address, number of parks, other greenery and shrub density. Weight status. Over half of the included studies reported beneficial relationship of greenspace with overweight/obesity. Increased NDVI was associated with overweight/obesity but not with proximity to greenspace, proportion of greenspace or number of parks in the meta-analysis. Oh et al. (2017) 6 RCT (6) To evaluate existing evidence on the health effects of spending time in natural green environments. 18-99 Mountain forest walking, 9-day forest healing camp. Hypertension, cortisol, immune function, anxiety and depression, mood, BP, HR, inflammation, cardiac and pulmonary function, oxidative stress. Natural environment had positive effects on physiological (hypertension, stress hormone, and immune function), and psychological (anxiety and depression) responses. However, all included studies had a high risk of bias. Roberts et al. (2019) 33 Randomised crossover (16), non-randomised crossover (5), other (12) To summarise and critically synthesise previous evidence on the impacts of short-term exposure to the natural environment on depressive mood. 8-280 Exposure to high levels of unmodified greenery. Depression, affect, mood. Short-term exposure to the natural environments led to a reduction in depressive mood, though the effects is only minimal, and included studies were of low quality and highly biased. Rojas-Rueda et al. (2019) 9 Cohort (9) To meta-analyse longitudinal studies on the exposure-response function between green spaces and all-cause mortality. 1645-4,284,680 Interquartile range or 0.1 unit increase in NDVI within 500m or less from the participant’s home location. All-cause mortality. A significant inverse association found between increased residential greenness and all-cause mortality. Schulz et al. (2018) 18 Cross-sectional (14), longitudinal (4) To systematically review empirical studies on the association between the built environment and mortality/morbidity in Germany. 2001-20,000 Exposure to natural or human-built areas which are covered with grass, trees, shrubs, and other vegetations. Overall health, mental health, T2DM, cancer mortality, CVD mortality, acute respiratory illness, chronic/allergic illnesses. No association was found for chronic respiratory conditions, however acute respiratory symptoms appeared to be associated with higher greenery. Other health outcomes such as diabetes, cancer, and CVD were rarely studied in the German built environment. Shaffee and Abd Shukor (2018) 42 NA To examine the association between greenspaces and stress reduction. NA Exposure to tended greenspace, forests, specific landscape elements, restorative landscape characteristics, and nature sounds. Stress. Nature settings were significantly but independently associated with human stress reduction in most included studies. Shuda et al. (2020) 12 Cross-sectional (8), RCT (4). To systematically explore the impacts of nature exposure on physiological markers and perceived stress. 32-4338 Average NDVI, percent tree canopy, percentage of greenspace, access to garden, active use of greenspace. Perceived stress, salivary cortisol, BP, HRV. Increased exposure to nature led to a decrease in various physiological markers of stress in most included studies. Similar effects were shown for perceived stress. Shuvo et al. (2020) 22 Cross-sectional (14), observational (8) To examine studies looking into the health effects of urban greenspace in low- and middle-income countries. NA Perceived frequency and duration of using urban greenspace, quality of urban greenspace, self-reported distance to nearest urban greenspace, proximity to and density of urban greenspace. General mental health, anxiety, weight status, physical wellbeing, general health, QoL. Compared to subjective measures, objective measures of greenspace had a modest relationship with the identified health outcomes. Soga et al. (2017) 21 Case study (21) To meta-analyse available evidence on the impacts of gardening on health. 14-514 Gardening types (horticultural therapy, daily gardening, and experimental short-term gardening). Depression, cognitive function, positive affect, anxiety, stress, mood, QoL, social health, general health, self-esteem, psychological wellbeing and hope, BMD, loneliness, life satisfaction, anger, fatigue, confusion, tension, BMI, vigour. Engaging in gardening is potentially beneficial to a range of health outcomes including reduction of depression, stress, and anxiety. Twohig-Bennett and Jones (2018) 143 Cross-sectional (69), cohort (35), ecological (18), intervention (40) To systematically review studies on the association between greenspace exposure and a range of health outcomes. 9 - >63,000,000 Neighbourhood greenspace, greenspace-based intervention, proximity to large greenspaces, NDVI, land cover map, tree canopy, street tree data, self-reported neighbourhood greenspace quality, self-reported walking in a green area, viewing trees through hospital window. Cortisol, HR, cholesterol, BP, DBP, gestational age, PTB, SGA, stroke, T2DM, hypertension, CVD mortality, asthma, CHD, all-cause mortality. Findings from meta-analysis showed a decreased risk in PTB birth, T2DM, CVD mortality, stroke incidence, hypertension, CHD, and all-cause mortality following increased exposure to greenspace. Vanaken and Danckaerts (2018) 21 Cross-sectional (12), longitudinal (7), ecological (2). To determine whether there is a relationship between exposure to greenspace and children’s and adolescents’ mental health and neurocognitive development. 72 - ~3,000,000 Land cover map, NDVI data, geolocation data, self-reported time spent in or distance to greenspaces. Emotional and behavioural problems, mental wellbeing, neurocognitive development. Consistent salutogenic relationship between exposure to greenspace and children’s emotional and behavioural issues, notably with inattention and hyperactivity challenges. Evidence related to children’s mental health, including depressive symptoms, were less clear. van den Berg et al. (2015) 40 Cross-sectional (35), longitudinal (5) While assessing the methodological quality, the study aimed to examine the link between perceived general and mental health, and all-cause mortality and the amount and quality of greenspaces. NA Percentage of greenspace, NDVI, distance to nearest greenspace or parks, presence of green qualities, presence of a private garden, observation of visible green elements in streets. Perceived general health, perceived mental health, all-cause mortality. Significant positive relationships between objectively measured greenspace around participant’s home and perceived mental health and all-cause mortality. Modest evidence was found for perceived general health. Wen et al. (2019) 28 RCT (17), non-RCT (11) To explore the relationship between the forest environment and human health while assessing the methodological quality of individual studies. 4-128 Exposure to forest environment. Physical health, psychological health. Improvement in physical and psychological health was observed following forest bathing Whear et al. (2014) 17 Pre-post (6), prospective cohort (1), RCT (2), qualitative (7), mixed methods (1) To explore the effects of gardens and outdoor spaces on mental and physical well-being of individuals with dementia residing in care homes. NA Use, view or experience of gardens, horticulture therapy. Dementia-related behaviours, affect, time spent sleeping, quality of sleep, PA, medication use. Garden exposure had some beneficial impacts. Evidence suggested garden use was associated with reduced agitation. Yeo et al. (2019) 26 RCT (3), cluster RCT (4), controlled clinical trial (8), crossover study (3), one-group design (8) To synthesise the health effects of indoor nature exposure for elderly individuals in residential settings. 10-85 Active nature programs via indoor gardening, horticulture activities, or horticulture therapy. Passive nature intervention such as indoor gardens, nature corridor enhancement, aquariums, and nature photos. Dementia-related outcomes, psychological wellbeing, social health, functional and physical health, physiological health, general health, wellbeing and satisfaction. Modest evidence that indoor nature exposure may improve the health and wellbeing of older adults in residential care, but most included studies were of low quality and prone to bias. Yuan et al. (2021) * 22 Cohort (17), cross-sectional (5) To synthesise evidence on the association between mortality and cardiovascular outcomes in older adults following greenspace exposure. 1084-5,988,606 NDVI, comparison of highest and lowest greenness exposure category. All-cause mortality, CVD. Most studies found a reduced risk of all-cause mortality and total CVD with increased greenness. Meta-analysis showed similar effects, even with stroke mortality. Zhan et al. (2020) 36 Cross-sectional (19), cohorts (14), case-control (2), ecological (1) To examine dose-response relationship of residential greenness with adverse pregnancy outcomes. 427-6,567,580 NDVI, proximity to greenspace, distance to nearest greenspace, percentage of greenspace. BW, LBW, SGA, PTB, gestational age, head circumference. Participants exposed to the highest level of greenery experienced higher BW. Higher greenness led to a reduced odds of LBW and SGA. A 0.1 unit increase in NDVI within 300m buffer led to a 2% decreased risk of LBW. No association was found for PTB or gestational age. Zhang et al. (2020) 14 Cross-sectional (10), controlled experiment (3), longitudinal (1) To investigate the link between greenspace exposure and adolescents’ mental wellbeing. 60-17,249 NDVI, percentage of neighbourhood greenspace, percentage of land use, perceived greenery, percentage of total land cover. Stress, mood, depression, emotional wellbeing, mental health behaviours, psychological distress. Suggests salutogenic effects of greenspace exposure on reduction of stress, depressive symptoms, and psychological distress, as well as better emotional wellbeing, and positive mood. Zhang et al. (2017) 27 Cross-sectional (5), case series (3), RCT (3), quantitative descriptive (2), non-RCT (1), qualitative (3), phenomenology (5), case study (2), triangular (2) embedded (1) To systematically evaluate the health benefits of the use and design of natural environments for people with mobility impairments. 1-1010 Activities carried out within the context of the natural environment, including passive involvement, active interventions, and rehabilitative interventions. Physical health, mental health, social health. Exposure to natural environment provided mental health benefits. * First published online September 2020. Table 2. Study design of original studies in included systematic reviews. Study Design n (%) Cross-sectional 418 (42.7%) Cohort 101 (10.3%) Longitudinal 64 (6.5%) Randomised Controlled Trial (RCT) 61 (6.2%) Case-control 5 (0.5%) Other a 331 (33.8%) a ‘Other’: acute RCT, case study, case-crossover, case-series, controlled clinical trial, controlled case study, crossover, crossover trial, cross-sectional and observational, ecological, embedded design, experimental, factorial, field, interventional, interview, lab experiment, meta-analysis, mix methods, natural experiment, non-RCT, observational, one group, parallel groups, phenomenology, pre-post study, qualitative, quantitative, quasi-experiment, survey, systematic review, triangulation design, uncontrolled case study. Greenspace exposure Measures of greenspace exposure varied significantly between systematic reviews. Of the 36 systematic reviews included in this umbrella review, 22 (61%) reported more than one greenspace measure ( Table 3 ). The normalised difference vegetative index (NDVI) was the most common measure of greenspace, used in 21 systematic reviews (58%). This was followed by proximity to greenspace (n=12, 33%), land cover map (n=8, 22%), duration of stay in greenspace setting (n=7, 19%), quality of greenspace (n=6, 17%), tree canopy (n=5, 14%) and frequency of greenspace usage (n=4, 11%) ( Table 3 ). Table 3. Measures of greenspace exposure in included systematic reviews. Greenspace Exposure Measure Counts of Greenspace Exposure Measure (% out of 36 reviews) Review Articles NDVI a 21 (58.8%) Akaraci et al. (2020) ; de Keijzer et al. (2020) ; de Keijzer et al. (2016) ; Dzhambov et al. (2014) ; Gascon et al. (2015) ; Gascon et al. (2016) ; Hartley et al. (2020) ; Islam et al. (2020) ; Kabisch et al. (2017) ; Kondo et al. (2018) ; Lambert et al. (2017) ; Lambert et al. (2018) ; Lee et al. (2020) ; Luo et al. (2020) ; Rojas-Rueda et al. (2019) ; Shuda et al. (2020) ; Twohig-Bennett and Jones (2018) ; van den Berg et al. (2015) ; Vanaken and Danckaerts (2018) ; Yuan et al. (2021) ; Zhan et al. (2020) Proximity to greenspace 12 (33.3%) Akaraci et al. (2020) ; Gascon et al. (2015) ; Gascon et al. (2016) ; Houlden et al. (2018) ; Kondo et al. (2018) ; Lachowycz and Jones (2011) ; Luo et al. (2020) ; Shuvo et al. (2020) ; Twohig-Bennett and Jones (2018) ; van den Berg et al. (2015) ; Vanaken and Danckaerts (2018) ; Zhan et al. (2020) Land-cover map 8 (22.2%) de Keijzer et al. (2020) ; de Keijzer et al. (2016) ; Gascon et al. (2015) ; Gascon et al. (2016) ; Kabisch et al. (2017) ; Lambert et al. (2018) ; Twohig-Bennett and Jones (2018) ; Vanaken and Danckaerts (2018) Duration of stay at greenspace 7 (19.4%) Oh et al. (2017) ; Roberts et al. (2019) ; Shuvo et al. (2020) ; Vanaken and Danckaerts (2018) ; Whear et al. (2014) ; Yuan et al. (2021) ; Zhang et al. (2020) Not clearly defined 7 (19.4%) Carver et al. (2020) ; Gritzka et al. (2020) ; Shaffee and Abd Shukor (2018) ; Soga et al. (2017) ; Wen et al. (2019) ; Yeo et al. (2019) ; Zhang et al. (2017) Quality of greenspace 6 (16.7%) de Keijzer et al. (2016) ; Kondo et al. (2018) ; Shuvo et al. (2020) ; Twohig-Bennett and Jones (2018) ; van den Berg et al. (2015) ; Zhang et al. (2020) Tree canopy 5 (13.9%) Kabisch et al. (2017) ; Shuda et al. (2020) ; Twohig-Bennett and Jones (2018) ; van den Berg et al. (2015) ; Zhan et al. (2020) Frequency to greenspace 4 (11.1%) Shuvo et al. (2020) ; Twohig-Bennett and Jones (2018) ; Yuan et al. (2021) ; Zhang et al. (2020) Other b 19 (52.8%) Akaraci et al. (2020) ; de Keijzer et al. (2020) ; de Keijzer et al. (2016) ; Dzhambov et al. (2014) ; Hartley et al. (2020) ; Houlden et al. (2018) ; Kabisch et al. (2017) ; Kondo et al. (2018) ; Lambert et al. (2017) ; Lambert et al. (2018) ; Luo et al. (2020) ; Schulz et al. (2018) ; Shuvo et al. (2020) ; Twohig-Bennett and Jones (2018) ; van den Berg et al. (2015) ; Vanaken and Danckaerts (2018) ; Yuan et al. (2021) ; Zhan et al. (2020) ; Zhang et al. (2020) a NDVI: normalised difference vegetation index. b ‘Other’: loss of trees from emerald ash bore disease, effect estimates for an increment of 10% all greenspace, percentage of greenspace, vegetation continuous fields, residential greenness, greenspace quantity, GPS and geographic simulation, built environment, aerial imagery, NDVI like-questionnaire, geolocation and timing, remote sensing data, satellite images, administrative data, spatial data, GIS data, street view images, different vegetation indices, tree counts through survey, land use classification/types, self-report, nature relatedness scale, access to a garden/greenspace, LiDAR imagery, street data density, number of parks in the area, pixel-based satellite imagery, detailed maps. Health outcomes This review considered all health outcomes examined in relation to greenspace exposure. Given that over 110 health outcomes were identified ( Table 1 ), we categorised outcomes as: mental health and cognitive function, maternal health and birth outcomes, cardiovascular and metabolic outcomes, respiratory health and allergies, cancer, general health and quality of life (QoL), and all-cause and cause-specific mortality. Health outcomes which did not suit these categories were classified as other health outcomes ( Table 4 ). Table 4. Health outcomes investigated in the included systematic reviews. Health Outcome Category Health Outcome ICD-10 Code(s) Review Articles Mental health and cognitive function Dementia A50.4, B22.0, F00-F03, F84.3, G31.0 de Keijzer et al. (2016) Dementia-related behaviours R45 Whear et al. (2014) ; Yeo et al. (2019) Overall mental health/psychological outcomes F00-F99 Carver et al. (2020) ; de Keijzer et al. (2020) ; Gascon et al. (2015) ; Gritzka et al. (2020) ; Houlden et al. (2018) ; Islam et al. (2020) ; Kabisch et al. (2017) ; Kondo et al. (2018) ; Schulz et al. (2018) ; Shuvo et al. (2020) ; Soga et al. (2017) ; van den Berg et al. (2015) ; Vanaken and Danckaerts (2018) ; Wen et al. (2019) ; Zhang et al. (2017) Mood, affect F06.3, F30-F39 Oh et al. (2017) ; Whear et al. (2014) ; Zhang et al. (2020) Depression F32-F33 Carver et al. (2020) ; Oh et al. (2017) ; Roberts et al. (2019) ; Zhang et al. (2020) Stress F43, Z73 Carver et al. (2020) ; Oh et al. (2017) ; Shaffee and Abd Shukor (2018) ; Shuda et al. (2020) ; Zhang et al. (2020) Behavioural and psychological distress, emotional wellbeing, neurocognitive development F90-F98 de Keijzer et al. (2016) ; Gritzka et al. (2020) ; Islam et al. (2020) ; Kondo et al. (2018) ; Vanaken and Danckaerts (2018) ; Yeo et al. (2019) ; Zhang et al. (2020) Cognition R40-R44 de Keijzer et al. (2020) ; de Keijzer et al. (2016) Maternal health and birth outcomes Birthweight P07, P08 Akaraci et al. (2020) ; Dzhambov et al. (2014) ; Islam et al. (2020) ; Kabisch et al. (2017) ; Kondo et al. (2018) ; Lee et al. (2020) ; Zhan et al. (2020) Low birthweight P07.0, P07.1 Akaraci et al. (2020) ; Lee et al. (2020) ; Zhan et al. (2020) Preterm birth P07.2, P07.3 Akaraci et al. (2020) ; Islam et al. (2020) ; Kondo et al. (2018) ; Lee et al. (2020) ; Twohig-Bennett and Jones (2018) Gestational age P07.2, P07.3, P08.2 Islam et al. (2020) ; Twohig-Bennett and Jones (2018) ; Zhan et al. (2020) Small for gestational age P05.1 Akaraci et al. (2020) ; Dzhambov et al. (2014) ; Kondo et al. (2018) ; Twohig-Bennett and Jones (2018) ; Zhan et al. (2020) Pregnancy complications O00-O99 Zhan et al. (2020) Head circumference NA Zhan et al. (2020) Cardiovascular and metabolic outcomes Cardiovascular health I00-I99 Kondo et al. (2018) Diabetes E10-E14, E23.2, O24 Kondo et al. (2018) ; Schulz et al. (2018) ; Twohig-Bennett and Jones (2018) Cholesterol E78 de Keijzer et al. (2020) ; Twohig-Bennett and Jones (2018) Metabolic syndrome E88.8 Lachowycz and Jones (2011) Hypertension I10-I15 de Keijzer et al. (2020) ; Oh et al. (2017) ; Shaffee and Abd Shukor (2018) ; Shuda et al. (2020) ; Twohig-Bennett and Jones (2018) Stroke I64 Twohig-Bennett and Jones (2018) Atherosclerosis I70, I25.0 Oh et al. (2017) Hypotension I95, O26.5 Oh et al. (2017) ; Shaffee and Abd Shukor (2018) ; Shuda et al. (2020) ; Twohig-Bennett and Jones (2018) Coronary heart disease I25.9 Lachowycz and Jones (2011) ; Twohig-Bennett and Jones (2018) Heart rate R00 Oh et al. (2017) ; Shaffee and Abd Shukor (2018) ; Shuda et al. (2020) ; Twohig-Bennett and Jones (2018) Asthma, allergies, and respiratory health Allergic diseases D69.0, D72.1, H01.1, H65.1, H65.4, H65.9, J30, J45.0, J67.9, K52.2, L20.8, L23, L50.0, L56.1, M13.8, M30.1, T78.2, T78.4 Schulz et al. (2018) Acute respiratory illness J00-J22 Schulz et al. (2018) Respiratory diseases J00-J99 Kabisch et al. (2017) ; Kondo et al. (2018) Bronchitis J20, J40-J42, J44, J45.0, J45.9 Islam et al. (2020) Allergic rhinitis J30, J45.0 Lambert et al. (2017) Asthma J44-J46, J82, Hartley et al. (2020) ; Kabisch et al. (2017) ; Lambert et al. (2017) ; Twohig-Bennett and Jones (2018) Wheezing R06.2 Islam et al. (2020) Allergic/atopic sensitisation NA Kabisch et al. (2017) ; Lambert et al. (2018) Cancer Cancer C00-D48 Kabisch et al. (2017) ; Kondo et al. (2018) ; Schulz et al. (2018) ; Twohig-Bennett and Jones (2018) Lung cancer C34 Twohig-Bennett and Jones (2018) Skin cancer C43-C44 Twohig-Bennett and Jones (2018) Prostate cancer C61 Kondo et al. (2018) ; Twohig-Bennett and Jones (2018) General health and quality of life Overall/general health/physiological outcomes A00-Y98 Gascon et al. (2015) ; Schulz et al. (2018) ; Twohig-Bennett and Jones (2018) ; van den Berg et al. (2015) ; Wen et al. (2019) ; Yeo et al. (2019) Chronic diseases A00-Q99 Islam et al. (2020) Overall physical health E00-E90, G00-G99, I00-J99, M00-M99, R00-R99 de Keijzer et al. (2020) ; Shuvo et al. (2020) ; Soga et al. (2017) ; Yeo et al. (2019) ; Zhang et al. (2017) Sleep time and quality NA Whear et al. (2014) Medication use NA Whear et al. (2014) Quality of life NA Shuvo et al. (2020) All-cause and cause specific mortality All-cause mortality A00-V98 Gascon et al. (2016) ; Kabisch et al. (2017) ; Rojas-Rueda et al. (2019) ; Twohig-Bennett and Jones (2018) ; van den Berg et al. (2015) ; Yuan et al. (2021) Cancer mortality C00-D48 Twohig-Bennett and Jones (2018) Lung cancer mortality C34 Gascon et al. (2016) Circulatory mortality I00-I99 Lachowycz and Jones (2011) Ischaemic heart disease mortality I20-I25 Yuan et al. (2021) Cardiovascular disease mortality I51.6 Gascon et al. (2016) ; Schulz et al. (2018) ; Shuvo et al. (2020) ; Twohig-Bennett and Jones (2018) ; Yuan et al. (2021) Stroke mortality I64 Yuan et al. (2021) Respiratory disease mortality J00-J99 Yuan et al. (2021) Infant/neonatal mortality P00-P04, P07-P08 Kabisch et al. (2017) Other health outcomes Cortisol level E24, E27.1-E27.2, E27.8, E35.1 Kondo et al. (2018) ; Shaffee and Abd Shukor (2018) ; Shuda et al. (2020) ; Twohig-Bennett and Jones (2018) Atopic dermatitis L20 Islam et al. (2020) Violence and agitation R45 Kondo et al. (2018) Oxidative stress NA Oh et al. (2017) Immune markers NA Oh et al. (2017) Inflammation markers NA Oh et al. (2017) Mental health and cognitive function. Overall mental health was investigated in seven (19%) systematic reviews ( Carver et al., 2020 ; Gascon et al., 2015 ; Gritzka et al., 2020 ; Houlden et al., 2018 ; Shuvo et al., 2020 ; van den Berg et al., 2015 ; Zhang et al., 2017 ). van den Berg et al. (2015) , Shuvo et al. (2020) , Carver et al. (2020) , and Gritzka et al. (2020) observed beneficial effects of greenspace exposure on overall mental health, but did not conduct meta-analyses due to heterogeneity in exposure and outcome measures. Similar findings were reported by Zhang et al. (2017) , but the overall quality of original studies in the review was low and prone to a high risk of bias. In contrast, the relationship between surrounding greenness and overall mental health in children ( Gascon et al., 2015 ) and adults ( Gascon et al., 2015 ; Houlden et al., 2018 ) was inconclusive. Impacts of greenspace exposure on psychological stress were also reported in seven (19%) systematic reviews ( de Keijzer et al., 2020 ; Gritzka et al., 2020 ; Kondo et al., 2018 ; Shaffee & Abd Shukor, 2018 ; Shuda et al., 2020 ; Soga et al., 2017 ; Zhang et al., 2020 ). Greenspace ( Kondo et al., 2018 ; Zhang et al., 2020 ) and nature ( Shaffee & Abd Shukor, 2018 ; Shuda et al., 2020 ) exposure, as well as participation in gardening activities ( Soga et al., 2017 ), were associated with reductions in stress. Greater long-term exposure to greenspace was also beneficial for stress ( de Keijzer et al., 2020 ). Gritzka et al. (2020) reported only one original study on the perceived stress of employees. A total of 11 (31%) systematic reviews investigated mental health indicators ( Carver et al., 2020 ; Kondo et al., 2018 ; Oh et al., 2017 ; Roberts et al., 2019 ; Soga et al., 2017 ; Vanaken & Danckaerts, 2018 ; Wen et al., 2019 ; Yeo et al., 2019 ; Zhan et al., 2020 ; Zhang et al., 2020 ), although two of these reviews could not draw conclusions due to mixed results ( Kondo et al., 2018 ) and inadequate evidence ( Oh et al., 2017 ). Meta-analyses revealed that exposure to the natural environment was beneficial for depressive mood (SMD=0.38; 95%CI:0.16,0.56) ( Roberts et al., 2019 ) and that higher prenatal greenspace exposure was associated with lower odds of mental disorders (OR=0.87; 95%CI:0.77,0.99) ( Zhan et al., 2020 ). Other greenspace measures, such as gardening ( Soga et al., 2017 ), urban greenspace ( Kondo et al., 2018 ), long-term outdoor exposure ( de Keijzer et al., 2020 ), and indoor nature interventions ( Yeo et al., 2019 ) also had favourable effects on psychological wellbeing. In a narrative summary, Wen et al. (2019) found that negative emotions decreased after participating in forest bathing. Another review reported a positive association between mental health and greenspace exposure in older adults living in residential aged care facilities; however, health outcomes were primarily based on observations and perceptions of staff and relatives, which may be subject to information bias ( Carver et al., 2020 ). Greenspace exposure was also beneficially associated with emotional and behavioural difficulties in children ( Vanaken & Danckaerts, 2018 ) and psychological distress and depressive symptoms in adolescents ( Zhang et al., 2020 ). Cognitive function was also explored in 10 (28%) reviews ( de Keijzer et al., 2020 ; de Keijzer et al., 2016 ; Gritzka et al., 2020 ; Islam et al., 2020 ; Kabisch et al., 2017 ; Kondo et al., 2018 ; Twohig-Bennett & Jones, 2018 ; Vanaken & Danckaerts, 2018 ; Whear et al., 2014 ; Yeo et al., 2019 ). Greenspace exposure was associated with improved cognitive function and development in adults ( Gritzka et al., 2020 ; Kondo et al., 2018 ) and children ( Islam et al., 2020 ; Kondo et al., 2018 ). Garden use was also associated with decreased agitation in people with dementia ( Whear et al., 2014 ). Other reviews concluded that evidence on cognition was limited ( de Keijzer et al., 2020 ; de Keijzer et al., 2016 ; Vanaken & Danckaerts, 2018 ), inconsistent ( Yeo et al., 2019 ), or insufficient ( Kabisch et al., 2017 ; Twohig-Bennett & Jones, 2018 ). Maternal health and birth outcomes. The impact of greenspace exposure on pregnancy outcomes such as birthweight (BW), low birth weight (LBW), small for gestational age (SGA), and preterm birth (PTB), was assessed in eight (22%) systematic reviews ( Akaraci et al., 2020 ; Dzhambov et al., 2014 ; Islam et al., 2020 ; Kabisch et al., 2017 ; Kondo et al., 2018 ; Lee et al., 2020 ; Twohig-Bennett & Jones, 2018 ; Zhan et al., 2020 ). Kondo et al. (2018) found insufficient evidence to support a statistical association between greenspace exposure and BW, PTB, and SGA, while Kabisch et al. (2017) reported inconsistent evidence on BW. All other reviews found weak but positive associations between higher surrounding greenness and increased BW ( Akaraci et al., 2020 ; Dzhambov et al., 2014 ; Islam et al., 2020 ), decreased risk for LBW ( Islam et al., 2020 ) and PTB ( Twohig-Bennett & Jones, 2018 ), and lower odds of SGA ( Akaraci et al., 2020 ) within different greenspace buffer sizes. For example, a meta-analysis of ten studies by Zhan et al. (2020) demonstrated protective effects of residential greenness on LBW measured by NDVI at 100 (OR=0.80; 95%CI:0.75,0.99), 300 (OR=0.82; 95%CI:0.71,0.93), and 500 (OR=0.85; 95%CI:0.77,0.93) metre buffers. Lee et al. (2020) also found that BW was associated with overall greenness. The association was determined via NDVI buffer sizes of 100 (β [beta standardised regression coefficient] = 0.003; 95%CI:0.001,0.005), 250 (β=0.001; 95%CI:0.000,0.002), and 500 (β=0.002; 95%CI:0.001,0.004) metres after adjusting for air quality and civil environment. Cardiovascular and metabolic outcomes. The risk of cardiovascular outcomes following greenspace exposure was assessed in ten (28%) systematic reviews ( de Keijzer et al., 2020 ; Gritzka et al., 2020 ; Kabisch et al., 2017 ; Kondo et al., 2018 ; Lachowycz & Jones, 2011 ; Oh et al., 2017 ; Twohig-Bennett & Jones, 2018 ; Wen et al., 2019 ; Yeo et al., 2019 ; Yuan et al., 2021 ). A review of observational studies by Yuan et al. (2021) reported beneficial effects of greenspace on the risk of cardiovascular disease (CVD) events in older adult populations. The authors did not conduct a meta-analysis due to the small number of original studies on CVD events. Wen et al. (2019) reported an improvement in overall cardiovascular function and hemodynamic index in response to forest bathing. Limited evidence was found on coronary heart disease (CHD) ( Lachowycz & Jones, 2011 ) and hypertension ( de Keijzer et al., 2020 ; Twohig-Bennett & Jones, 2018 ). Gritzka et al. (2020) reported inconclusive findings on blood pressure (BP), while other reviews found only one ( Kabisch et al., 2017 ; Kondo et al., 2018 ; Yeo et al., 2019 ) or two ( Oh et al., 2017 ) original studies on the outcome. However, the meta-analyses by Twohig-Bennett and Jones (2018) demonstrated decreased diastolic blood pressure (DBP) (MD=-1.97; 95%CI:-3.45,-0.49), heart rate (HR) (MD=-2.57; 95%CI:-4.30,-0.83), and heart rate variability (HRV) (MD=91.87; 95%CI:50.92,132.82) following exposure to increased greenery. Respiratory health and allergies. We identified nine (25%) systematic reviews that assessed exposure to residential greenspace on respiratory health ( de Keijzer et al., 2020 ; Hartley et al., 2020 ; Islam et al., 2020 ; Kabisch et al., 2017 ; Kondo et al., 2018 ; Lambert et al., 2017 , 2018 ; Oh et al., 2017 ; Twohig-Bennett & Jones, 2018 ). Lambert et al. (2017) demonstrated no association between residential greenness and allergic respiratory diseases in children and adolescents. Hartley et al. (2020) undertook an updated review of Lambert et al. (2017) and found similar results. Meta-analysis showed that high greenspace areas were associated with lower odds of asthma, although this result was based on only two original studies with substantial heterogeneity ( Twohig-Bennett & Jones, 2018 ). Islam et al. (2020) and Lambert et al. (2018) investigated the respiratory health of children and adolescents, which revealed limited evidence to support the effects of greenspace exposure on asthma and atopic sensitisation, respectively. Kabisch et al. (2017) , Kondo et al. (2018) , de Keijzer et al. (2020) , and Oh et al. (2017) reported insufficient original studies to draw conclusions on respiratory diseases, pulmonary function, and aeroallergens. Cancer. Only four (11%) systematic reviews investigated the relationship between greenspace exposure and cancer ( de Keijzer et al., 2020 ; Kabisch et al., 2017 ; Kondo et al., 2018 ; Twohig-Bennett & Jones, 2018 ) due to a small number of original studies on the outcome. Kondo et al. (2018) and Twohig-Bennett and Jones (2018) suggested that greenspace exposure is beneficially associated with the risk of prostate cancer after controlling for individual factors, including PA, smoking, and medical history. de Keijzer et al. (2020) and Twohig-Bennett and Jones (2018) also suggested a harmful association between greenspace exposure and skin cancer. Inconclusive findings were reported for the effect of park availability on lung cancer ( Kabisch et al., 2017 ). General health and Quality of life (QoL). We found 11 (31%) systematic reviews that investigated the role of greenspace exposure on self-reported general health, perceived wellbeing, and QoL ( de Keijzer et al., 2020 ; Gritzka et al., 2020 ; Houlden et al., 2018 ; Kondo et al., 2018 ; Shuvo et al., 2020 ; Soga et al., 2017 ; Twohig-Bennett & Jones, 2018 ; van den Berg et al., 2015 ; Vanaken & Danckaerts, 2018 ; Whear et al., 2014 ; Yeo et al., 2019 ). Some reviews reported inconclusive findings on the effect of greenspace exposure on perceived ( de Keijzer et al., 2020 ; Gritzka et al., 2020 ) and objective ( Houlden et al., 2018 ) wellbeing and QoL, while another found a positive association ( Vanaken & Danckaerts, 2018 ). Shuvo et al. (2020) concluded that there is an association between greenspace exposure and self-reported general health, but the methodological quality of studies was low. Earlier reviews revealed mixed evidence on the relationship between greenness and general health ( Kondo et al., 2018 ; van den Berg et al., 2015 ) and falls ( Whear et al., 2014 ). A meta-analysis by Twohig-Bennett and Jones (2018) demonstrated an association between greenspace exposure and self-reported health conditions (OR=1.12; 95%CI:1.05,1.19). Another two reviews considered greenspace exposure via participation in gardening activities and reported beneficial effects on self-perceived health and QoL ( Soga et al., 2017 ; Yeo et al., 2019 ). All-cause and cause-specific mortality. A total of 11 (31%) systematic reviews and meta-analyses considered all-cause or cause-specific mortality ( Akaraci et al., 2020 ; Gascon et al., 2016 ; Islam et al., 2020 ; Kabisch et al., 2017 ; Kondo et al., 2018 ; Lachowycz & Jones, 2011 ; Rojas-Rueda et al., 2019 ; Twohig-Bennett & Jones, 2018 ; van den Berg et al., 2015 ; Yuan et al., 2021 ; Zhan et al., 2020 ). The meta-analysis by Gascon et al. (2016) found that living in areas of high greenery reduced the risk of all-cause mortality (RR=0.92; 95%CI:0.87,0.97) but not lung cancer mortality. Three meta-analyses performed after Gascon et al. (2016) presented similar findings ( Rojas-Rueda et al., 2019 ; Twohig-Bennett & Jones, 2018 ; Yuan et al., 2021 ), except for CVD mortality ( Yuan et al., 2021 ). Yuan et al. (2021) also reported that increased NDVI is associated with reduced risk of stroke mortality (HR=0.77; 95%CI:0.59,1.00). Narrative syntheses summarised moderate to strong effects of increased greenness on the risk of the following mortalities: non-accidental ( van den Berg et al., 2015 ), CVD ( Kondo et al., 2018 ), respiratory ( Kondo et al., 2018 ), heat-wave ( Kabisch et al., 2017 ) and overall cancer ( Kondo et al., 2018 ; Twohig-Bennett & Jones, 2018 ). Insufficient evidence was found on neonatal ( Akaraci et al., 2020 ), infant ( Islam et al., 2020 ; Zhan et al., 2020 ), and circulatory disease ( Lachowycz & Jones, 2011 ) mortality for synthesis. Other health outcomes. We identified 16 (44%) systematic reviews that evaluated the effect of greenspace on other health outcomes. Inconsistent associations ( Kabisch et al., 2017 ; Kondo et al., 2018 ; Lachowycz & Jones, 2011 ; Yeo et al., 2019 ) or no association ( Gritzka et al., 2020 ) were reported for greenspace exposure and obesity-related health indicators. In contrast, a meta-analysis by Luo et al. (2020) reported higher NDVI to be associated with lower odds of being overweight or obese (OR=0.88; 95%CI:0.84,0.91). Other reviews found inadequate evidence on weight status ( de Keijzer et al., 2020 ; Schulz et al., 2018 ; Shuvo et al., 2020 ). Kondo et al. (2018) reported mixed results on the association between urban greenspace exposure and cortisol concentration, while other reviews found insufficient evidence on serum ( Gritzka et al., 2020 ; Oh et al., 2017 ) and salivary ( Shuda et al., 2020 ) cortisol. In comparison, a meta-analysis by Twohig-Bennett and Jones (2018) showed that salivary cortisol was lower (MD=-0.05; 95%CI:-0.07,-0.04) when exposed to higher levels of greenspace. Narrative synthesis by Wen et al. (2019) also revealed a decrease in cortisol and adrenaline in response to forest bathing. Quantitative data summary Quantitative data collected from meta-analyses were collated according to outcome category, outcome, and measure of greenspace exposure ( Table 5 ). Effect measures reported in meta-analyses which were based on a singular original study were excluded from the quantitative data summary table. No meta-analyses were reported for cancer outcomes. Table 5. Listing of quantitative data from included reviews’ meta-analyses. Outcome Review Article No. of original studies included Exposure measure Effect measure Estimate (95%CI) from meta-analysis Mental health and cognitive function Depressive mood Roberts et al. (2019) 30 Short-term exposure to natural environment SMD 0.05 (0.04,0.05) Depressive mood Roberts et al. (2019) 3 Short-term exposure to natural environment SMD 0.38 (0.16,0.56) Maternal health and birth outcomes Birthweight Akaraci et al. (2020) 20 NDVI increase within 250/300m Standardised regression coefficient 0.001 (0.0002,0.002) Birthweight Zhan et al. (2020) 17 NDVI within 100m Standardised regression coefficient 20.22 (13.50,26.93) Birthweight Zhan et al. (2020) 14 NDVI within 250m Standardised regression coefficient 11.08 (6.79,15.37) Birthweight Zhan et al. (2020) 4 NDVI within 300m Standardised regression coefficient 23.15 (7.60,38.69) Birthweight Zhan et al. (2020) 13 NDVI within 500m Standardised regression coefficient 22.41 (11.01,33.82) Birthweight Zhan et al. (2020) 7 NDVI within 1000m Standardised regression coefficient 16.72 (0.84,32.60) Birthweight Zhan et al. (2020) 2 Percentage tree canopy within 300m Standardised regression coefficient 2.28 (0.08,4.48) Birthweight Zhan et al. (2020) 2 Percentage tree canopy within >300m Standardised regression coefficient -3.47 (-7.44,0.50) Birthweight Dzhambov et al. (2014) 7 Redidential greenness within 100m r (correlation) 0.05 (0.04,0.06) Birthweight Lee et al. (2020) 4 NDVI Standardised regression coefficient 0.001 (0.001,0.002) Birthweight Lee et al. (2020) 6 NDVI within 100m Standardised regression coefficient 0.003 (0.002,0.004) Small for gestational age Akaraci et al. (2020) 14 NDVI increase within 250/300m Pooled OR 0.95 (0.92,0.97) Small for gestational age Zhan et al. (2020) 6 NDVI within 100m OR 0.93 (0.88,1.00) Small for gestational age Zhan et al. (2020) 6 NDVI within 250m OR 0.95 (0.88,1.03) Small for gestational age Zhan et al. (2020) 4 NDVI within 300m OR 0.85 (0.67,1.09) Small for gestational age Zhan et al. (2020) 6 NDVI within 500m OR 0.90 (0.73,1.12) Small for gestational age Zhan et al. (2020) 3 NDVI within 1000m OR 0.83 (0.60,1.16) Small for gestational age Twohig-Bennett and Jones (2018) 4 High vs low * greenspace area MD 0.81 (0.76,0.86) Low birth weight Akaraci et al. (2020) 11 NDVI increase within 250/300m Pooled OR 0.96 (0.91,1.01) Low birth weight Zhan et al. (2020) 7 NDVI within 100m OR 0.86 (0.75,0.99) Low birth weight Zhan et al. (2020) 4 NDVI within 250m OR 0.90 (0.81,1.00) Low birth weight Zhan et al. (2020) 5 NDVI within 300m OR 0.82 (0.71,0.93) Low birth weight Zhan et al. (2020) 8 NDVI within 500m OR 0.85 (0.77,0.93) Low birth weight Zhan et al. (2020) 3 NDVI within 1000m OR 0.77 (0.48,1.24) Low birth weight Zhan et al. (2020) 2 Distance to nearest greenspace OR 1.10 (0.97,1.25) Low birth weight Lee et al. (2020) 5 NDVI OR 0.94 (0.92,0.97) Preterm birth Akaraci et al. (2020) 11 NDVI increase within 250/300m Pooled OR 0.99 (0.97,1.02) Preterm birth Lee et al. (2020) 5 NDVI OR 0.98 (0.97,0.99) Preterm birth Twohig-Bennett and Jones (2018) 6 High vs low greenspace area MD 0.87 (0.80,0.94) Preterm birth Zhan et al. (2020) 3 Percentage greenspace within >300m OR 1.02 (0.93,1.11) Gestational age and head circumference Zhan et al. (2020) 5 NDVI within >300m Standardised regression coefficient 1.73 (0.69,2.76) Gestational age Twohig-Bennett and Jones (2018) 3 High vs low greenspace exposure MD 300m OR 0.87 (0.77,0.99) Cardiovascular and metabolic outcomes Heart rate Twohig-Bennett and Jones (2018) 10 High vs low greenspace exposure MD -2.57 (-4.30,-0.83) Hypertension Twohig-Bennett and Jones (2018) 4 High vs low greenspace area MD 0.99 (0.81,1.20) Stroke Twohig-Bennett and Jones (2018) 3 High vs low greenspace area MD 0.82 (0.61,1.11) Coronary heart disease Twohig-Bennett and Jones (2018) 2 High vs low greenspace area MD 0.92 (0.78,1.07) HDL cholesterol Twohig-Bennett and Jones (2018) 2 High vs low greenspace exposure MD -0.03 (-0.05,0.00) LDL cholesterol Twohig-Bennett and Jones (2018) 2 High vs low greenspace exposure MD 0.04 (-0.03,0.11) Total cholesterol Twohig-Bennett and Jones (2018) 2 High vs low greenspace exposure MD 0.03 (-0.05,0.10) Diastolic blood pressure Twohig-Bennett and Jones (2018) 12 High vs low greenspace exposure MD -1.97 (-3.45,-0.49) Systolic blood pressure Twohig-Bennett and Jones (2018) 13 High vs low greenspace exposure MD -1.50 (-3.43,0.44) High frequency power of heart rate variability Twohig-Bennett and Jones (2018) 7 High vs low greenspace exposure MD 91.87 (50.92,132.82) Low frequency heart rate variability Twohig-Bennett and Jones (2018) 6 High vs low greenspace exposure MD -0.06 (-0.08,-0.03) HbA1c Twohig-Bennett and Jones (2018) 2 High vs low greenspace exposure MD -0.77 (-1.86,0.32) Fasting blood glucose Twohig-Bennett and Jones (2018) 2 High vs low greenspace exposure MD -0.01 (-0.08,0.07) Type 2 diabetes Twohig-Bennett and Jones (2018) 6 High vs low greenspace area MD 0.72 (0.61,0.85) Triglycerides Twohig-Bennett and Jones (2018) 2 High vs low greenspace exposure MD 0.06 (-0.01,0.12) Dyslipidaemia Twohig-Bennett and Jones (2018) 2 High vs low greenspace area MD 0.94 (0.75,1.17) Respiratory health and allergies Asthma Lambert et al. (2017) 4 NDVI within 100m OR 1.01 (0.93,1.09) Asthma Twohig-Bennett and Jones (2018) 2 High vs low greenspace area MD 0.93 (0.57,1.52) Allergic rhinitis Lambert et al. (2017) 6 NDVI within 500m OR 0.99 (0.87,1.12) Atopic sensitisation Lambert et al. (2018) 6 NDVI within 500m OR 0.96 (0.75,1.22) Atopic sensitisation Lambert et al. (2018) 4 NDVI within 500m OR 0.85 (0.61,1.18) General health and quality of life Overweight/obesity Luo et al. (2020) 4 Proximity to nearest greenspace OR 0.99 (0.99,1.00) Overweight/obesity Luo et al. (2020) 6 NDVI OR 0.88 (0.84,0.91) Overweight/obesity Luo et al. (2020) 4 Number of parks OR 0.98 (0.97,1.00) Overweight/obesity Luo et al. (2020) 6 Proportion of greenspace OR 0.96 (0.85,1.08) Any health outcome Soga et al. (2017) 21 Gardening vs control SMD 0.42 (0.36,0.48) Good self-reported health Twohig-Bennett and Jones (2018) 10 High vs low greenspace area MD 1.12 (1.05,1.19) All-cause and cause-specific mortality All-cause mortality Yuan et al. (2021) 8 Per 0.1 unit of NDVI Pooled HR 0.99 (0.97,1.00) All-cause mortality Rojas-Rueda et al. (2019) 9 Per 0.1 unit of NDVI within <500m Pooled HR 0.96 (0.94,0.97) All-cause mortality Gascon et al. (2016) 6 Per 10% increase in NDVI RR 0.92 (0.87,0.97) All-cause mortality Twohig-Bennett and Jones (2018) 4 High vs low greenspace area MD 0.69 (0.55,0.87) CVD mortality Yuan et al. (2021) 8 Per 0.1 unit of NDVI Pooled HR 0.99 (0.89,1.09) CVD mortality Gascon et al. (2016) 8 High vs low greenspace exposure RR 0.96 (0.94,0.97) Cardiovascular mortality Twohig-Bennett and Jones (2018) 2 High vs low greenspace area MD 0.84 (0.76,0.93) Ischaemic heart disease mortality Yuan et al. (2021) 8 Per 0.1 unit of NDVI Pooled HR 0.96 (0.88,1.05) Respiratory disease mortality Yuan et al. (2021) 8 Per 0.1 unit of NDVI Pooled HR 0.99 (0.89,1.10) Lung cancer mortality Gascon et al. (2016) 4 High vs low greenspace exposure RR 0.98 (0.95,1.02) Stroke mortality Yuan et al. (2021) 8 Per 0.1 unit of NDVI Pooled HR 0.77 (0.59,1.00) Other health outcomes Salivary cortisol Twohig-Bennett and Jones (2018) 7 NDVI MD -0.05 (-0.07,-0.04) * High vs low greenspace exposure or greenspace area was determined for each greenspace measure, which was then used to calculate the effect estimate for each health outcome. Please refer to the relevant systematic review for further information on the greenspace measures used. Quality of Evidence and the risk of bias Half of the systematic reviews (50%) had a high risk of bias, and three (8%) reviews were categorised as having ‘unclear risk’. The remaining 15 (42%) reviews were deemed low risk using the ROBIS tool ( Figure 1 ; extended data: Supplementary Table S2). Figure 1. Risk of bias assessment of included reviews using ROBIS. Rows 1-4 show judgements on individual criteria while the bottom row shows the overall risk of bias. Of the 36 systematic reviews, eight (22%) were rated as high quality, 15 (42%) as moderate quality, and 13 (36%) as low quality according to the AMSTAR-2 tool ( Table 6 ; extended data: Supplementary Figure S1). No reviews were rated as critically low-quality. Table 6. Methodological quality assessment of included systematic reviews using AMSTAR-2. Question number a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Quality Author, Year Akaraci et al. (2020) N b PY N PY Y Y N PY NA, PY N NA, Y Y N Y Y Y L Carver et al. (2020) Y PY N PY Y N N PY NA, N N NA, N N N N N Y L de Keijzer et al. (2020) N PY N PY Y N N PY NA, N N NA, N N N Y N Y H de Keijzer et al. (2016) N PY N PY N N PY PY NA, N N NA, N N N PY N Y H Dzhambov et al. (2014) Y PY N Y Y Y Y PY NA, Y N NA, PY PY Y Y Y N M Gascon et al. (2016) Y PY N PY Y Y PN PY NA, PY N NA, PY PY N PY Y N L Gascon et al. (2015) Y PY N Y Y Y Y N NA, PY N N*, N* N* PY PY N* Y H Gritzka et al. (2020) Y PY N PY Y Y Y PY NA, PY N N*, N* N* Y Y N* Y M Hartley et al. (2020) Y PY N PY Y N N PY NA, N N NA, N N N PY N Y L Houlden et al. (2018) Y PY N PY Y N Y PY NA, PY N N*, N* N* Y PY N* Y M Islam et al. (2020) N N N PY N N Y N NA, N N N*, N* N* N N N* Y L Kabisch et al. (2017) Y N N PY N N N N NA, N N N*, N* N* Y N N* Y L Kondo et al. (2018) N N Y PY N N Y PY NA, N N N*, N* N* N N N* Y L Lachowycz and Jones (2011) N PY N PY Y N Y PY NA, N N N*, N* N* N PY N* Y L Lambert et al. (2018) Y Y N PY Y Y Y PY NA, Y N N*, N* N* Y Y N* Y M Lambert et al. (2017) Y Y N PY Y Y Y PY NA, Y N NA, Y Y Y Y N Y L Lee et al. (2020) Y PY N PY N N Y PY NA, N N NA, PY Y N N Y N H Luo et al. (2020) N Y N PY Y Y Y PY NA, PY N NA, Y Y Y Y Y Y M Oh et al. (2017) Y PY N PY Y Y PY PY NA, Y N N*, N* N* Y N N* Y M Roberts et al. (2019) Y Y N PY Y Y Y Y NA, Y N NA, Y Y Y Y Y Y H Rojas-Rueda et al. (2019) N PY N PY Y Y Y PY NA, PY N NA, Y Y Y Y Y Y H Schulz et al. (2018) Y PY N PY N N Y PY NA, N N N*, N* N* Y Y N* Y H Shaffee and Abd Shukor (2018) N N N PY N N N PY NA, N N N*, N* N* N N N* Y L Shuda et al. (2020) Y PY N PY N N PY PY NA, PY N N*, N* N* Y N N* N M Shuvo et al. (2020) N PY N PY Y N Y N NA, PY N N*, N* N* Y Y N* Y M Soga et al. (2017) Y PY N PY N N Y PY NA, N N NA, Y Y N Y Y Y L Twohig-Bennett and Jones (2018) Y PY N PY Y Y Y PY NA, PY N NA, Y Y PY Y Y Y M Vanaken and Danckaerts (2018) Y N N PY N N N Y NA, N N N*, N* N* N Y N* Y L van den Berg et al. (2015) N PY N PY Y Y Y PY NA, PY N N*, N* N* PY N N* Y M Wen et al. (2019) N PY N PY N Y Y N NA, Y N N*, N* N* Y N N* Y M Whear et al. (2014) Y PY N Y Y N Y Y NA, Y N N*, N* N* Y N N* Y M Yeo et al. (2019) Y PY N Y Y N Y Y NA, PY N N*, N* N* Y N N* Y M Yuan et al. (2021) Y PY N PY Y Y Y PY NA, Y N NA, Y Y Y Y Y Y M Zhan et al. (2020) Y PY N PY Y Y Y PY NA, PY N NA, Y Y Y Y Y Y M Zhang et al. (2020) Y N Y PY N N PY PY NA, N N N*, N* N* Y Y N* Y H Zhang et al. (2017) Y PY N PY N N Y PY NA, N N N*, N* N* Y N N* Y L a 1: Participant, Intervention, Comparison, Outcome (PICO) components, 2: Pre-established protocol, 3: Explanation of included studies’ design, 4: Comprehensive search strategy, 5: Study selection in duplicate, 6: Data extraction in duplicate, 7: List of excluded studies with justification, 8: Description of included studies, 9: Assessment of risk of bias (RoB) in included studies, 10: Funding sources of included studies, 11: Use of appropriate statistical methods, 12: RoB impact on synthesised results, 13: Results interpretation with RoB reference, 14: Heterogeneity explanation, 15: Publication/small study bias investigation, 16: Conflict of interest declaration. b Y = Yes; P/Y= Partial Yes; N = No; NA = Not applicable (no meta-analysis conducted); CL = Critically low; L = Low; M = Moderate; H = High. Discussion This umbrella review summarises 36 systematic reviews on the relationship between greenspace exposure and health outcomes. Our study yielded consistent results with existing umbrella reviews for the beneficial effects of greenspace exposure on mental health and cognitive function ( Stier-Jarmer et al., 2021 ; Yang et al., 2021 ; Zare Sakhvidi et al., 2022 ), non-accidental/all-cause mortality ( van den Bosch & Ode Sang, 2017 ; Yang et al., 2021 ), and CVD-mortality ( Yang et al., 2021 ). Additionally, we observed positive associations between greenspace exposure and maternal health and birth outcomes, including PTB and SGA which were not present in other reviews ( Yang et al., 2021 ). However, these associations were less consistent than those for mental health and cognitive function. Stier-Jarmer et al. (2021) and Yang et al. (2021) also reported beneficial effects of greenspace on cardiovascular health and cardiometabolic factors, respectively, which were not replicated in our study. This may be attributable to different inclusion and exclusion criteria between umbrella reviews. Finally, we identified mixed, limited, or no association between greenspace exposure and respiratory health and allergies, general health and QoL, cancer, and other health outcomes, which is congruous with other umbrella reviews ( Yang et al., 2021 ; Zare Sakhvidi et al., 2022 ). Overall, our review suggests that there may be an association between greenspace exposure and human health and wellbeing. The variety of greenspace measures used may contribute to the ambivalent findings reported. Some studies used objective measures such as NDVI, proximity to greenspace, and land cover maps to quantify greenspace exposure whereas others used subjective measures including street view images and self-report questionnaires ( Table 3 ). This precluded many systematic reviews from conducting meta-analyses which restricted the number of pooled estimates available for synthesis in this review. Reduced access to natural spaces and biodiversity has limited the population’s access to the physical, mental, and cognitive health benefits of these spaces ( Puplampu & Boafo, 2021 ). Urbanisation has increased in response to a growing urban population and has led to fragmentation and declines in natural ecosystems ( Kingsley, 2019 ; Li et al., 2019 ). As a result, homes located near greenspaces have become more expensive, increasing inequalities in access to greenspaces based on socioeconomic status (SES) ( Sharifi et al., 2021 ). Studies have also shown that most indoor workers do not go outside during office hours, further reducing access to greenspace and the associated health benefits ( Gilchrist et al., 2015 ; Lottrup et al., 2013 ). These restrictions may have influenced the relationship between greenspace exposure and health outcomes in the included systematic reviews. A variety of pathways, mediators, and effect modifiers have been suggested for the relationship between greenspace exposure and health outcomes, including comorbidities, genetics, and PA. Comorbidities, which typically exacerbate other health conditions, may attenuate the effect of greenspace exposure on the primary health outcome ( Godina et al., 2023 ; Walsan et al., 2020 ). Genetic variation has also been suggested as an effect modifier of the relationship between greenspace and health outcomes, but initial studies have reported insignificant findings ( Cohen-Cline et al., 2015 ; Engemann et al., 2020 ). Conversely, PA and social interaction, which are beneficial for many health conditions, have been suggested as mediators of the relationship between greenspace exposure and health outcomes ( Zhang et al., 2022 ). Greenspace exposure may improve mental, physical, and cognitive health by encouraging participation in outdoor PA ( Sun et al., 2022 ; van den Berg et al., 2019 ) and social interaction ( Dadvand et al., 2019 ; Orstad et al., 2020 ). Additional investigation into the exact role of comorbidities, genetics, and PA, as well as other effect modifiers such as age, sex, SES, race, and urbanicity is required. Interactions between greenspace and other environmental factors including air pollution, chemical exposures, toxins, and smoking may also influence the effect of greenspace on health outcomes. Environmental contaminants are recognised as detrimental to human health with the ability to induce and/or exacerbate many health conditions ( Brusseau et al., 2019 ). Natural greenery can minimise the harmful effects of these environmental issues via air purification, as well as the prevention of soil contamination and erosion ( Qiu et al., 2021 ; Yang et al., 2015 ). Reduction of these environmental contaminants by green ecosystems can lead to improvements in health conditions, particularly respiratory symptoms and CVD ( Boelee et al., 2019 ; Schraufnagel et al., 2019 ). We conducted a thorough review of systematic reviews and meta-analyses on the impact of greenspace exposure on health outcomes. In addition to the wide range of databases searched, a manual reference search was conducted to ensure all relevant articles were identified. All stages of screening and data collection, as well as risk of bias and methodological quality assessment were conducted independently by two authors. We outlined the types and frequency of greenspace measures used and allocated ICD-10 codes to health outcomes investigated in each systematic review. For each health outcome reported in meta-analyses, we provided the measure of greenspace and the numerical estimate of the association, as well as the number of original articles this estimate is based on. These methods allowed for a more holistic overview of the current literature and should be considered for use in future umbrella reviews. Despite the contributions of this umbrella review, several limitations highlight the need for further research to strengthen the evidence on greenspace exposure and health outcomes. Current evidence, including this umbrella review, has been unable to establish a causal link between greenspace exposure and health outcomes, as most studies are observational. A small number of RCTs in our review, along with inconsistencies in greenspace and effect measures, pose challenges in drawing definitive conclusions on the greenspace-health association. Current evidence on potential interactions, mediators, and effect modifiers of this relationship is also limited and conflicting, and further research is needed to assess the influence of genetics and environmental exposures ( Zhang et al., 2022 ). To account for new evidence, we conducted an update of this umbrella review ( Bryer et al., 2022 ). Conclusion This umbrella review synthesised systematic reviews and meta-analyses on the effect of greenspace exposure on health outcomes. Beneficial effects were found for all-cause and CVD mortality, mental health and cognitive function, and maternal health and birth outcomes. Ambivalent results were found for cardiovascular and metabolic health, respiratory health and allergies, and general health and QOL. There were limited systematic reviews available for assessing cancer outcomes. In light of these diverse findings, it is apparent that the current evidence on the relationship between greenspace exposure and health outcomes is characterised by inconsistencies. Nevertheless, this umbrella review highlights the association between greenspace and a variety of health outcomes. Data availability Underlying data No data are associated with this article. Extended data Open Science Framework (OSF): Greenspace exposure and associated health outcomes: a systematic review of reviews. Supplementary Material. DOI 10.17605/OSF.IO/U39EK ( Bryer et al., 2024 ). This project contains the following extended data: • Supplementary Table S1. (Literature search strategies) • Supplementary Table S2. (Risk of bias assessment by domain) • Supplementary Figure S1: (Overall methodological quality) • Supplementary File S1. (Systematic reviews excluded during full-text screening) Reporting guidelines Open Science Framework (OSF): PRISMA checklist and flow chart for Greenspace exposure and associated health outcomes: a systematic review of reviews. DOI 10.17605/OSF.IO/U39EK ( Bryer et al., 2024 ). Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0). Software availability Endnote version 20 was used as a reference management tool in this study ( The EndNote Team, 2013 ). 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Reference Source Comments on this article Comments (0) Version 2 VERSION 2 PUBLISHED 17 May 2024 ADD YOUR COMMENT Comment Author details Author details 1 School of Public Health, The University of Queensland, Herston, Queensland, Australia 2 Child Health Research Centre, The University of Queensland, South Brisbane, Queensland, Australia 3 Princess Alexandra Hospital Southside Clinical Unit, The University of Queensland, Woolloongabba, Queensland, Australia 4 Centre for Online Health, The University of Queensland, Woolloongabba, Queensland, Australia 5 Centre for Health Services Research, The University of Queensland, Woolloongabba, Queensland, Australia 6 School of Population Health, University of New South Wales, Sydney, New South Wales, Australia 7 European Centre for Environment and Human Health, University of Exeter, Truro, UK Brittnee Bryer Roles: Data Curation, Formal Analysis, Investigation, Methodology, Validation, Visualization, Writing – Original Draft Preparation, Writing – Review & Editing Chinonso Christian Odebeatu Roles: Data Curation, Investigation, Validation, Writing – Original Draft Preparation, Writing – Review & Editing Wen Ray Lee Roles: Data Curation, Formal Analysis, Investigation, Writing – Review & Editing Kathryn Vitangcol Roles: Data Curation, Investigation, Methodology, Writing – Review & Editing Victor Gallegos-Rejas Roles: Data Curation, Investigation, Methodology, Writing – Review & Editing Nicholas J. Osborne Roles: Conceptualization, Methodology, Supervision, Writing – Review & Editing Gail Williams Roles: Conceptualization, Methodology, Supervision, Writing – Review & Editing Darsy Darssan Roles: Conceptualization, Data Curation, Formal Analysis, Investigation, Methodology, Project Administration, Supervision, Validation, Visualization, Writing – Original Draft Preparation, Writing – Review & Editing Competing interests No competing interests were disclosed. Grant information The author(s) declared that no grants were involved in supporting this work. Article Versions (2) version 2 Revised Published: 30 Jul 2025, 13:491 https://doi.org/10.12688/f1000research.148878.2 version 1 Published: 17 May 2024, 13:491 https://doi.org/10.12688/f1000research.148878.1 Copyright © 2025 Bryer B et al . This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Download Export To Sciwheel Bibtex EndNote ProCite Ref. Manager (RIS) Sente metrics Views Downloads F1000Research - - PubMed Central info_outline Data from PMC are received and updated monthly. - - Citations open_in_new 0 open_in_new 0 open_in_new SEE MORE DETAILS CITE how to cite this article Bryer B, Odebeatu CC, Lee WR et al. Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.12688/f1000research.148878.2 ) NOTE: If applicable, it is important to ensure the information in square brackets after the title is included in all citations of this article. COPY CITATION DETAILS track receive updates on this article Track an article to receive email alerts on any updates to this article. TRACK THIS ARTICLE Share Open Peer Review Current Reviewer Status: ? Key to Reviewer Statuses VIEW HIDE Approved The paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. Not approved Fundamental flaws in the paper seriously undermine the findings and conclusions Version 2 VERSION 2 PUBLISHED 30 Jul 2025 Revised Views 0 Cite How to cite this report: Mueller W. Reviewer Report For: Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.5256/f1000research.185657.r401603 ) The direct URL for this report is: https://f1000research.com/articles/13-491/v2#referee-response-401603 NOTE: it is important to ensure the information in square brackets after the title is included in this citation. Close Copy Citation Details Reviewer Report 25 Sep 2025 William Mueller , Institute of Occupational Medicine (IOM), Edinburgh, UK Approved VIEWS 0 https://doi.org/10.5256/f1000research.185657.r401603 Thank you for providing the author responses to my ... Continue reading READ ALL Thank you for providing the author responses to my comments. I am satisfied they have sufficiently addressed my points. Competing Interests: No competing interests were disclosed. Reviewer Expertise: Environmental and occupational epidemiology I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. Close READ LESS CITE CITE HOW TO CITE THIS REPORT Mueller W. Reviewer Report For: Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.5256/f1000research.185657.r401603 ) The direct URL for this report is: https://f1000research.com/articles/13-491/v2#referee-response-401603 NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article. COPY CITATION DETAILS Report a concern Respond or Comment COMMENT ON THIS REPORT Views 0 Cite How to cite this report: Rojas-Rueda D. Reviewer Report For: Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.5256/f1000research.185657.r408332 ) The direct URL for this report is: https://f1000research.com/articles/13-491/v2#referee-response-408332 NOTE: it is important to ensure the information in square brackets after the title is included in this citation. Close Copy Citation Details Reviewer Report 11 Sep 2025 David Rojas-Rueda , Colorado State University, Fort Collins, USA Approved with Reservations VIEWS 0 https://doi.org/10.5256/f1000research.185657.r408332 MAJOR COMMENTS 1. Critically Outdated Search Strategy The search strategy, which ended in January 2021 (over four years ago), represents a fundamental limitation that significantly undermines the review's validity and applicability. This is particularly problematic for ... Continue reading READ ALL MAJOR COMMENTS 1. Critically Outdated Search Strategy The search strategy, which ended in January 2021 (over four years ago), represents a fundamental limitation that significantly undermines the review's validity and applicability. This is particularly problematic for greenspace research given: Rapid expansion of high-quality research post-COVID-19 Multiple systematic reviews published 2021-2024 Evolution of methodological standards and exposure assessment techniques New evidence on mechanisms and dose-response relationships Recommendation: Conduct a comprehensive updated search through 2025. 2. Title Lacks Methodological Clarity The title "systematic review of reviews" should explicitly identify this as an umbrella review using standard terminology. Recommendation: Revise the title to include the term "umbrella review." 3. Critical Methodological Flaw in Meta-analysis Assessment Table 5 fails to report the study design composition of included meta-analyses, which is a fundamental methodological oversight. Many meta-analyses inappropriately pool cross-sectional studies with longitudinal studies, which: Violates basic meta-analysis principles Cannot establish causality Produces effect estimates with limited validity for causal inference Significantly affects evidence interpretation Recommendation: Add columns to Table 5 showing: Number of studies in each meta-analysis Study design composition (# cross-sectional, # cohort, # RCT, etc.) Assessment of methodological appropriateness of pooling strategies Heterogeneity statistics (I²) 4. Quality Assessment Implications Inadequately Addressed With 50% of reviews having a high risk of bias and 36% rated as low quality, the implications for evidence reliability are inadequately discussed. Recommendation: Provide a detailed analysis of which AMSTAR-2 criteria were most commonly failed. Conduct sensitivity analyses excluding low-quality reviews Discuss how quality limitations affect confidence in conclusions 5. Limited Incremental Value Over Existing Reviews The comparison with existing umbrella reviews (van den Bosch & Ode Sang 2017; Yang et al. 2021) raises questions about unique contributions. Recommendation: More clearly articulate what this review adds beyond existing umbrella reviews, particularly given the temporal limitations. MINOR COMMENTS 6. Methodological Transparency Issues Search Strategy: Include full search strategy in main text or easily accessible supplementary material Inter-rater Reliability: Provide statistics for study selection and quality assessment agreement Grey Literature: Clarify if grey literature was considered and justify exclusion if applicable 7. Results Presentation Problems PRISMA Flowchart: Reference is unclear - ensure easy accessibility or include key elements in the main manuscript Effect Size Reporting: Standardize decimal places and clarify whether estimates are from random or fixed effects models 8. Quantitative Synthesis Limitations Many meta-analyses based on very few studies (n=2-4) Missing heterogeneity assessments No discussion of the potential for publication bias potential Mixing of different exposure metrics in a single meta-analyses 9. ICD-10 Classification Concerns The post-hoc assignment of ICD-10 codes (Table 4) may not reflect how original studies defined outcomes and could be misleading. Recommendation: Remove or clearly label as authors' interpretation rather than original study classifications. 10. Discussion Deficiencies Mechanistic Pathways: Brief mention of mechanisms could be expanded Policy Implications: Insufficient discussion of urban planning and public health implications Geographic Limitations: Most studies from high-income countries inadequately addressed Equity Considerations: Missing discussion of greenspace access disparities 11. Blue Space Exclusion Rationale While focusing solely on greenspace, the exclusion of studies examining combined green-blue space effects may artificially limit the evidence base and miss important findings. 12. Temporal Analysis Missing No consideration of temporal trends in research quality, methodology, or findings over the study period. SPECIFIC TECHNICAL RECOMMENDATIONS Restructure Results: Organize findings by strength of evidence rather than just outcome categories Study Design Stratification: Re-analyze findings separately for longitudinal/cohort studies, cross-sectional studies, and intervention studies Sensitivity Analyses: Exclude low-quality reviews to assess robustness of conclusions Enhanced Quality Discussion: Provide a systematic analysis of methodological failures in included reviews Future Research Priorities: More clearly identify evidence gaps and research priorities Practical Implications: Expand discussion of what constitutes "effective" greenspace exposure for policy purposes OVERALL ASSESSMENT This umbrella review addresses an important public health topic but suffers from significant methodological limitations. The outdated search strategy, inadequate assessment of meta-analysis quality, high proportion of low-quality included reviews, and presentation challenges substantially reduce its impact and reliability. The manuscript requires major revision addressing these fundamental issues before being suitable for publication in a high-impact journal. Recommendation: Major revision required, with particular attention to updating the evidence base, critically evaluating meta-analysis methodology, and enhancing transparency of quality assessment implications. Are the rationale for, and objectives of, the Systematic Review clearly stated? Partly Are sufficient details of the methods and analysis provided to allow replication by others? Partly Is the statistical analysis and its interpretation appropriate? Partly Are the conclusions drawn adequately supported by the results presented in the review? Partly If this is a Living Systematic Review, is the ‘living’ method appropriate and is the search schedule clearly defined and justified? (‘Living Systematic Review’ or a variation of this term should be included in the title.) Not applicable Competing Interests: No competing interests were disclosed. Reviewer Expertise: Environmental epidemiology I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. Close READ LESS CITE CITE HOW TO CITE THIS REPORT Rojas-Rueda D. Reviewer Report For: Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.5256/f1000research.185657.r408332 ) The direct URL for this report is: https://f1000research.com/articles/13-491/v2#referee-response-408332 NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article. COPY CITATION DETAILS Report a concern Author Response 31 Dec 2025 Darsy Darssan , School of Public Health, The University of Queensland, Herston, Australia 31 Dec 2025 Author Response Response to reviewer comments We appreciate the feedback on the manuscript. We have carefully considered and responded to your suggestions. MAJOR COMMENTS 1. Critically Outdated Search Strategy The search ... Continue reading Response to reviewer comments We appreciate the feedback on the manuscript. We have carefully considered and responded to your suggestions. MAJOR COMMENTS 1. Critically Outdated Search Strategy The search strategy, which ended in January 2021 (over four years ago), represents a fundamental limitation that significantly undermines the review's validity and applicability. This is particularly problematic for greenspace research given: Rapid expansion of high-quality research post-COVID-19 Multiple systematic reviews published 2021-2024 Evolution of methodological standards and exposure assessment techniques New evidence on mechanisms and dose-response relationships Recommendation: Conduct a comprehensive updated search through 2025. Response: This review includes 36 systematic reviews published between January 2010 and December 2020. As you mentioned, much research on greenspace and health, including reviews, has been published since December 2020. We identified an additional 45 review articles between December 2020 and June 2024. Combining these two umbrella reviews would be too many systematic reviews to include in a single umbrella review. As per the Cochrane guidelines (Cumpston and Flemyng, 2023), we have updated the review due to “the availability of new evidence that would have a meaningful impact on the review findings”. [Please see our updated review here, https://doi.org/10.12688/f1000research.166852.1 ]. Cumpston, M., Flemyng, E., Chapter IV: Updating a review [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-iv 2. Title Lacks Methodological Clarity The title "systematic review of reviews" should explicitly identify this as an umbrella review using standard terminology. Recommendation: Revise the title to include the term "umbrella review." In the title, we prefer to use the term ‘systematic review of reviews’, but we do refer to it as an umbrella review in the text. We find this title more understandable for a lay audience. 3. Critical Methodological Flaw in Meta-analysis Assessment Table 5 fails to report the study design composition of included meta-analyses, which is a fundamental methodological oversight. Many meta-analyses inappropriately pool cross-sectional studies with longitudinal studies, which: Violates basic meta-analysis principles Cannot establish causality Produces effect estimates with limited validity for causal inference Significantly affects evidence interpretation Recommendation: Add columns to Table 5 showing: Number of studies in each meta-analysis Study design composition (# cross-sectional, # cohort, # RCT, etc.) Assessment of methodological appropriateness of pooling strategies Heterogeneity statistics (I²) Response: Number of studies: This information is already reported in Table 5. Study design composition: The composition of original studies included in the systematic reviews is presented in Table 1. For further details, readers can consult the individual systematic reviews. Appropriateness of statistical methods: This aspect has been formally assessed using AMSTAR-2, and the results are included in Table 6 of our manuscript. Heterogeneity statistics (I²): I² values are not comparable because they depend on the number of studies, sample sizes, and variance structure. Reporting them side-by-side in an umbrella review risks misleading comparisons. 4. Quality Assessment Implications Inadequately Addressed With 50% of reviews having a high risk of bias and 36% rated as low quality, the implications for evidence reliability are inadequately discussed. Recommendation: Provide a detailed analysis of which AMSTAR-2 criteria were most commonly failed. Conduct sensitivity analyses excluding low-quality reviews Discuss how quality limitations affect confidence in conclusions Response: Detailed AMSTAR‑2 results: Table 6 reports the results for each AMSTAR‑2 component across the included systematic reviews. This provides readers with a transparent view of which criteria were most commonly met or failed. Sensitivity analyses: As our study is an umbrella review rather than a meta-analysis, we did not conduct quantitative sensitivity analyses by excluding low-quality reviews. Risk of bias and methodological quality assessments are transparently reported in the Results section. 5. Limited Incremental Value Over Existing Reviews The comparison with existing umbrella reviews (van den Bosch & Ode Sang 2017; Yang et al. 2021) raises questions about unique contributions. Recommendation: More clearly articulate what this review adds beyond existing umbrella reviews, particularly given the temporal limitations. We respectfully note that the unique contributions of our umbrella review are already articulated in the last paragraph of the Introduction, which outlines five specific features distinguishing our work from prior umbrella reviews. These include: (i) evaluation of greenspace exposure and health outcomes independently of blue space and health determinants; (ii) assessment of both quality and risk of bias of reviews; (iii) recording of the frequency of greenspace exposure measures used; (iv) summarisation of health outcomes with associated ICD-10 codes; and (v) reporting of effect measures from meta-analyses. Together, these features ensure that our review provides a distinct contribution beyond earlier syntheses. As another reviewer noted, this paragraph was clear, and we believe it sufficiently addresses the concern regarding incremental value. For this reason, we have not made further changes to the manuscript. MINOR COMMENTS 6. Methodological Transparency Issues Search Strategy: Include full search strategy in main text or easily accessible supplementary material Inter-rater Reliability: Provide statistics for study selection and quality assessment agreement Grey Literature: Clarify if grey literature was considered and justify exclusion if applicable Response: Search Strategy: The full search strategy is already provided in Supplementary Table S1, ensuring that readers can access the complete details of keywords used. Inter-rater Reliability: This was not deemed necessary in our umbrella review because “Disagreements were resolved via discussions with the last author”. Because consensus was consistently achieved and disagreements were few, we did not calculate or report formal inter-rater reliability statistics. Grey literature was not included in our umbrella review. Our focus was restricted to peer-reviewed systematic reviews and meta-analyses to ensure methodological rigour, consistency in reporting standards, and comparability across included studies. 7. Results Presentation Problems PRISMA Flowchart: Reference is unclear - ensure easy accessibility or include key elements in the main manuscript Effect Size Reporting: Standardize decimal places and clarify whether estimates are from random or fixed effects models Response: As per the F1000 guidelines, a PRISMA flowchart for this review is available under the ‘Data availability’ à ‘Reporting guidelines’ section at the end of the article. Effect Size Reporting: Most effect sizes are reported to two decimal places; however, in cases where estimates are very small (e.g., beta coefficients of 0.001 with confidence intervals of 0.000–0.002), three decimal places are used to ensure precision and interpretability. In our umbrella review, we presented estimates by outcome in a comprehensive summary table (Table 5). Given the breadth of outcomes, this table is already large and adding further details (e.g. heterogeneity statistics or the specific effects model) would be redundant for the purposes of an umbrella review. The primary objective of an umbrella review is to synthesise evidence across systematic reviews, rather than to re-analyse or replicate their statistical outputs. This information is explicitly available in the original systematic reviews: of the 12 meta-analyses, 9 used random-effects models (Gascon et al., 2016; Lambert et al., 2017; Lee et al., 2020; Roberts et al., 2019; Rojas-Rueda et al., 2019; Soga et al., 2017; Twohig-Bennett and Jones, 2018; Yuan et al., 2021; Zhan et al., 2020), 1 used a fixed-effects model (Luo et al., 2020), and 2 applied quality-effects models (Akaraci et al., 2020; Dzhambov et al., 2014). 8. Quantitative Synthesis Limitations Many meta-analyses based on very few studies (n=2-4) Missing heterogeneity assessments No discussion of the potential for publication bias potential Mixing of different exposure metrics in a single meta-analyses Response: Small meta-analyses (n=2–4): We acknowledge that several meta-analyses included in our umbrella review were based on a limited number of primary studies. This limitation reflects the current evidence base rather than our methodology, and we have reported these findings transparently. Heterogeneity assessments: We did not include heterogeneity statistics (e.g., I²) in the manuscript, as our umbrella review was designed as a narrative synthesis rather than a re-analysis of quantitative data. Publication bias: Publication bias was assessed using the AMSTAR-2 tool, which explicitly evaluates whether included reviews considered publication bias (Table 6). This assessment is incorporated into our quality appraisal and reported accordingly. Exposure metrics: We recognise that some meta-analyses combined different greenspace exposure metrics. This reflects the diversity of measures used in the field. Our umbrella review records the frequency of exposure measures and highlights this variability as a methodological challenge for future research. 9. ICD-10 Classification Concerns The post-hoc assignment of ICD-10 codes (Table 4) may not reflect how original studies defined outcomes and could be misleading. Recommendation: Remove or clearly label as authors' interpretation rather than original study classifications. You are correct that the original studies may not have defined the outcomes based on the ICD codes. Based on the information available in the reviews, we allocated all potential ICD codes for each health outcome. We did this to promote standardised reporting in future articles that investigate the association between greenspace exposure and health outcomes. 10. Discussion Deficiencies Mechanistic Pathways: Brief mention of mechanisms could be expanded Policy Implications: Insufficient discussion of urban planning and public health implications Geographic Limitations: Most studies from high-income countries inadequately addressed Equity Considerations: Missing discussion of greenspace access disparities Response: Mechanistic Pathways: We briefly mention potential mechanisms linking greenspace exposure to health outcomes, as a detailed exploration of mechanistic pathways was beyond the scope of this umbrella review. These mechanisms have been explored in more depth by other researchers (Markevych et al., 2017). Markevych, I., Schoierer, J., Hartig, T., Chudnovsky, A., Hystad, P.,…. & Fuertes, E. (2017). Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental Research, 158, 301-317. https://doi.org/10.1016/j.envres.2017.06.028 Policy Implications: We acknowledge the importance of urban planning and public health implications. However, our focus was on synthesising the evidence rather than extending into policy recommendations. We believe that the evidence presented provides a foundation for future work to draw out specific policy implications. Geographic Limitations: The included systematic reviews drew upon studies conducted across a wide variety of locations worldwide. Given the diversity of study locations represented, we did not identify a single geographic imbalance that required emphasis. We agree that geographic context is important for interpreting greenspace–health relationships, and future work could more explicitly examine regional differences. Equity Considerations: We agree that disparities in greenspace access are important, which is why we have discussed inequalities in greenspace access due to urbanisation, socioeconomic status, and occupation in the third paragraph of the ‘Discussion’ section. 11. Blue Space Exclusion Rationale While focusing solely on greenspace, the exclusion of studies examining combined green-blue space effects may artificially limit the evidence base and miss important findings. We sought to evaluate the association between greenspace exposure and health outcomes independently of blue space, in order to avoid conflating effects and to provide a more precise synthesis of greenspace-specific evidence. Including studies that combined green and blue space exposures would have introduced heterogeneity in exposure definitions, making comparisons across reviews less meaningful. Additionally, previous umbrella reviews have often considered green and blue spaces together. By focusing solely on greenspace, our review addresses a distinct gap in the literature and complements existing syntheses. 12. Temporal Analysis Missing No consideration of temporal trends in research quality, methodology, or findings over the study period. We acknowledge that examining temporal trends in research quality, methodology, and findings could provide valuable insights. While such an analysis was not undertaken in the present umbrella review, we have addressed this point in our updated review, where we assessed trends in these components between studies published in 2010–2020 (covered in this review) and 2021–2024 (updated review). We believe this complementary work provides the broader temporal perspective suggested by the reviewer. [Please see our updated review here, https://doi.org/10.12688/f1000research.166852.1 ]. SPECIFIC TECHNICAL RECOMMENDATIONS Restructure Results: Organize findings by strength of evidence rather than just outcome categories Study Design Stratification: Re-analyze findings separately for longitudinal/cohort studies, cross-sectional studies, and intervention studies Sensitivity Analyses: Exclude low-quality reviews to assess robustness of conclusions Enhanced Quality Discussion: Provide a systematic analysis of methodological failures in included reviews Future Research Priorities: More clearly identify evidence gaps and research priorities Practical Implications: Expand discussion of what constitutes "effective" greenspace exposure for policy purposes Response: Restructuring Results / Study Design Stratification / Sensitivity Analyses: Our review followed a narrative synthesis approach, drawing on published systematic reviews and meta-analyses. We did not re-analyse primary data, and therefore restructuring results by strength of evidence, stratifying by study design, or conducting sensitivity analyses excluding low-quality reviews were not feasible within our methodological framework. Enhanced Quality Discussion: Table 6 reports the results for each AMSTAR‑2 component across the included systematic reviews. This provides readers with a transparent view of which criteria were most commonly met or failed. Future Research Priorities: We have highlighted evidence gaps and research needs in the Discussion, particularly regarding the diversity of exposure metrics and study design. Practical Implications: Our umbrella review was designed to summarise quantitative evidence from existing systematic reviews and meta-analyses, rather than to define optimal exposure thresholds or policy standards. The included reviews varied widely in how greenspace exposure was measured, and this heterogeneity limited our ability to draw firm conclusions about what constitutes “effective” exposure. We have highlighted this variability in the Discussion as a key methodological challenge and evidence gap. Response to reviewer comments We appreciate the feedback on the manuscript. We have carefully considered and responded to your suggestions. MAJOR COMMENTS 1. Critically Outdated Search Strategy The search strategy, which ended in January 2021 (over four years ago), represents a fundamental limitation that significantly undermines the review's validity and applicability. This is particularly problematic for greenspace research given: Rapid expansion of high-quality research post-COVID-19 Multiple systematic reviews published 2021-2024 Evolution of methodological standards and exposure assessment techniques New evidence on mechanisms and dose-response relationships Recommendation: Conduct a comprehensive updated search through 2025. Response: This review includes 36 systematic reviews published between January 2010 and December 2020. As you mentioned, much research on greenspace and health, including reviews, has been published since December 2020. We identified an additional 45 review articles between December 2020 and June 2024. Combining these two umbrella reviews would be too many systematic reviews to include in a single umbrella review. As per the Cochrane guidelines (Cumpston and Flemyng, 2023), we have updated the review due to “the availability of new evidence that would have a meaningful impact on the review findings”. [Please see our updated review here, https://doi.org/10.12688/f1000research.166852.1 ]. Cumpston, M., Flemyng, E., Chapter IV: Updating a review [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-iv 2. Title Lacks Methodological Clarity The title "systematic review of reviews" should explicitly identify this as an umbrella review using standard terminology. Recommendation: Revise the title to include the term "umbrella review." In the title, we prefer to use the term ‘systematic review of reviews’, but we do refer to it as an umbrella review in the text. We find this title more understandable for a lay audience. 3. Critical Methodological Flaw in Meta-analysis Assessment Table 5 fails to report the study design composition of included meta-analyses, which is a fundamental methodological oversight. Many meta-analyses inappropriately pool cross-sectional studies with longitudinal studies, which: Violates basic meta-analysis principles Cannot establish causality Produces effect estimates with limited validity for causal inference Significantly affects evidence interpretation Recommendation: Add columns to Table 5 showing: Number of studies in each meta-analysis Study design composition (# cross-sectional, # cohort, # RCT, etc.) Assessment of methodological appropriateness of pooling strategies Heterogeneity statistics (I²) Response: Number of studies: This information is already reported in Table 5. Study design composition: The composition of original studies included in the systematic reviews is presented in Table 1. For further details, readers can consult the individual systematic reviews. Appropriateness of statistical methods: This aspect has been formally assessed using AMSTAR-2, and the results are included in Table 6 of our manuscript. Heterogeneity statistics (I²): I² values are not comparable because they depend on the number of studies, sample sizes, and variance structure. Reporting them side-by-side in an umbrella review risks misleading comparisons. 4. Quality Assessment Implications Inadequately Addressed With 50% of reviews having a high risk of bias and 36% rated as low quality, the implications for evidence reliability are inadequately discussed. Recommendation: Provide a detailed analysis of which AMSTAR-2 criteria were most commonly failed. Conduct sensitivity analyses excluding low-quality reviews Discuss how quality limitations affect confidence in conclusions Response: Detailed AMSTAR‑2 results: Table 6 reports the results for each AMSTAR‑2 component across the included systematic reviews. This provides readers with a transparent view of which criteria were most commonly met or failed. Sensitivity analyses: As our study is an umbrella review rather than a meta-analysis, we did not conduct quantitative sensitivity analyses by excluding low-quality reviews. Risk of bias and methodological quality assessments are transparently reported in the Results section. 5. Limited Incremental Value Over Existing Reviews The comparison with existing umbrella reviews (van den Bosch & Ode Sang 2017; Yang et al. 2021) raises questions about unique contributions. Recommendation: More clearly articulate what this review adds beyond existing umbrella reviews, particularly given the temporal limitations. We respectfully note that the unique contributions of our umbrella review are already articulated in the last paragraph of the Introduction, which outlines five specific features distinguishing our work from prior umbrella reviews. These include: (i) evaluation of greenspace exposure and health outcomes independently of blue space and health determinants; (ii) assessment of both quality and risk of bias of reviews; (iii) recording of the frequency of greenspace exposure measures used; (iv) summarisation of health outcomes with associated ICD-10 codes; and (v) reporting of effect measures from meta-analyses. Together, these features ensure that our review provides a distinct contribution beyond earlier syntheses. As another reviewer noted, this paragraph was clear, and we believe it sufficiently addresses the concern regarding incremental value. For this reason, we have not made further changes to the manuscript. MINOR COMMENTS 6. Methodological Transparency Issues Search Strategy: Include full search strategy in main text or easily accessible supplementary material Inter-rater Reliability: Provide statistics for study selection and quality assessment agreement Grey Literature: Clarify if grey literature was considered and justify exclusion if applicable Response: Search Strategy: The full search strategy is already provided in Supplementary Table S1, ensuring that readers can access the complete details of keywords used. Inter-rater Reliability: This was not deemed necessary in our umbrella review because “Disagreements were resolved via discussions with the last author”. Because consensus was consistently achieved and disagreements were few, we did not calculate or report formal inter-rater reliability statistics. Grey literature was not included in our umbrella review. Our focus was restricted to peer-reviewed systematic reviews and meta-analyses to ensure methodological rigour, consistency in reporting standards, and comparability across included studies. 7. Results Presentation Problems PRISMA Flowchart: Reference is unclear - ensure easy accessibility or include key elements in the main manuscript Effect Size Reporting: Standardize decimal places and clarify whether estimates are from random or fixed effects models Response: As per the F1000 guidelines, a PRISMA flowchart for this review is available under the ‘Data availability’ à ‘Reporting guidelines’ section at the end of the article. Effect Size Reporting: Most effect sizes are reported to two decimal places; however, in cases where estimates are very small (e.g., beta coefficients of 0.001 with confidence intervals of 0.000–0.002), three decimal places are used to ensure precision and interpretability. In our umbrella review, we presented estimates by outcome in a comprehensive summary table (Table 5). Given the breadth of outcomes, this table is already large and adding further details (e.g. heterogeneity statistics or the specific effects model) would be redundant for the purposes of an umbrella review. The primary objective of an umbrella review is to synthesise evidence across systematic reviews, rather than to re-analyse or replicate their statistical outputs. This information is explicitly available in the original systematic reviews: of the 12 meta-analyses, 9 used random-effects models (Gascon et al., 2016; Lambert et al., 2017; Lee et al., 2020; Roberts et al., 2019; Rojas-Rueda et al., 2019; Soga et al., 2017; Twohig-Bennett and Jones, 2018; Yuan et al., 2021; Zhan et al., 2020), 1 used a fixed-effects model (Luo et al., 2020), and 2 applied quality-effects models (Akaraci et al., 2020; Dzhambov et al., 2014). 8. Quantitative Synthesis Limitations Many meta-analyses based on very few studies (n=2-4) Missing heterogeneity assessments No discussion of the potential for publication bias potential Mixing of different exposure metrics in a single meta-analyses Response: Small meta-analyses (n=2–4): We acknowledge that several meta-analyses included in our umbrella review were based on a limited number of primary studies. This limitation reflects the current evidence base rather than our methodology, and we have reported these findings transparently. Heterogeneity assessments: We did not include heterogeneity statistics (e.g., I²) in the manuscript, as our umbrella review was designed as a narrative synthesis rather than a re-analysis of quantitative data. Publication bias: Publication bias was assessed using the AMSTAR-2 tool, which explicitly evaluates whether included reviews considered publication bias (Table 6). This assessment is incorporated into our quality appraisal and reported accordingly. Exposure metrics: We recognise that some meta-analyses combined different greenspace exposure metrics. This reflects the diversity of measures used in the field. Our umbrella review records the frequency of exposure measures and highlights this variability as a methodological challenge for future research. 9. ICD-10 Classification Concerns The post-hoc assignment of ICD-10 codes (Table 4) may not reflect how original studies defined outcomes and could be misleading. Recommendation: Remove or clearly label as authors' interpretation rather than original study classifications. You are correct that the original studies may not have defined the outcomes based on the ICD codes. Based on the information available in the reviews, we allocated all potential ICD codes for each health outcome. We did this to promote standardised reporting in future articles that investigate the association between greenspace exposure and health outcomes. 10. Discussion Deficiencies Mechanistic Pathways: Brief mention of mechanisms could be expanded Policy Implications: Insufficient discussion of urban planning and public health implications Geographic Limitations: Most studies from high-income countries inadequately addressed Equity Considerations: Missing discussion of greenspace access disparities Response: Mechanistic Pathways: We briefly mention potential mechanisms linking greenspace exposure to health outcomes, as a detailed exploration of mechanistic pathways was beyond the scope of this umbrella review. These mechanisms have been explored in more depth by other researchers (Markevych et al., 2017). Markevych, I., Schoierer, J., Hartig, T., Chudnovsky, A., Hystad, P.,…. & Fuertes, E. (2017). Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental Research, 158, 301-317. https://doi.org/10.1016/j.envres.2017.06.028 Policy Implications: We acknowledge the importance of urban planning and public health implications. However, our focus was on synthesising the evidence rather than extending into policy recommendations. We believe that the evidence presented provides a foundation for future work to draw out specific policy implications. Geographic Limitations: The included systematic reviews drew upon studies conducted across a wide variety of locations worldwide. Given the diversity of study locations represented, we did not identify a single geographic imbalance that required emphasis. We agree that geographic context is important for interpreting greenspace–health relationships, and future work could more explicitly examine regional differences. Equity Considerations: We agree that disparities in greenspace access are important, which is why we have discussed inequalities in greenspace access due to urbanisation, socioeconomic status, and occupation in the third paragraph of the ‘Discussion’ section. 11. Blue Space Exclusion Rationale While focusing solely on greenspace, the exclusion of studies examining combined green-blue space effects may artificially limit the evidence base and miss important findings. We sought to evaluate the association between greenspace exposure and health outcomes independently of blue space, in order to avoid conflating effects and to provide a more precise synthesis of greenspace-specific evidence. Including studies that combined green and blue space exposures would have introduced heterogeneity in exposure definitions, making comparisons across reviews less meaningful. Additionally, previous umbrella reviews have often considered green and blue spaces together. By focusing solely on greenspace, our review addresses a distinct gap in the literature and complements existing syntheses. 12. Temporal Analysis Missing No consideration of temporal trends in research quality, methodology, or findings over the study period. We acknowledge that examining temporal trends in research quality, methodology, and findings could provide valuable insights. While such an analysis was not undertaken in the present umbrella review, we have addressed this point in our updated review, where we assessed trends in these components between studies published in 2010–2020 (covered in this review) and 2021–2024 (updated review). We believe this complementary work provides the broader temporal perspective suggested by the reviewer. [Please see our updated review here, https://doi.org/10.12688/f1000research.166852.1 ]. SPECIFIC TECHNICAL RECOMMENDATIONS Restructure Results: Organize findings by strength of evidence rather than just outcome categories Study Design Stratification: Re-analyze findings separately for longitudinal/cohort studies, cross-sectional studies, and intervention studies Sensitivity Analyses: Exclude low-quality reviews to assess robustness of conclusions Enhanced Quality Discussion: Provide a systematic analysis of methodological failures in included reviews Future Research Priorities: More clearly identify evidence gaps and research priorities Practical Implications: Expand discussion of what constitutes "effective" greenspace exposure for policy purposes Response: Restructuring Results / Study Design Stratification / Sensitivity Analyses: Our review followed a narrative synthesis approach, drawing on published systematic reviews and meta-analyses. We did not re-analyse primary data, and therefore restructuring results by strength of evidence, stratifying by study design, or conducting sensitivity analyses excluding low-quality reviews were not feasible within our methodological framework. Enhanced Quality Discussion: Table 6 reports the results for each AMSTAR‑2 component across the included systematic reviews. This provides readers with a transparent view of which criteria were most commonly met or failed. Future Research Priorities: We have highlighted evidence gaps and research needs in the Discussion, particularly regarding the diversity of exposure metrics and study design. Practical Implications: Our umbrella review was designed to summarise quantitative evidence from existing systematic reviews and meta-analyses, rather than to define optimal exposure thresholds or policy standards. The included reviews varied widely in how greenspace exposure was measured, and this heterogeneity limited our ability to draw firm conclusions about what constitutes “effective” exposure. We have highlighted this variability in the Discussion as a key methodological challenge and evidence gap. Competing Interests: No competing interests. Close Report a concern Respond or Comment COMMENTS ON THIS REPORT Author Response 31 Dec 2025 Darsy Darssan , School of Public Health, The University of Queensland, Herston, Australia 31 Dec 2025 Author Response Response to reviewer comments We appreciate the feedback on the manuscript. We have carefully considered and responded to your suggestions. MAJOR COMMENTS 1. Critically Outdated Search Strategy The search ... Continue reading Response to reviewer comments We appreciate the feedback on the manuscript. We have carefully considered and responded to your suggestions. MAJOR COMMENTS 1. Critically Outdated Search Strategy The search strategy, which ended in January 2021 (over four years ago), represents a fundamental limitation that significantly undermines the review's validity and applicability. This is particularly problematic for greenspace research given: Rapid expansion of high-quality research post-COVID-19 Multiple systematic reviews published 2021-2024 Evolution of methodological standards and exposure assessment techniques New evidence on mechanisms and dose-response relationships Recommendation: Conduct a comprehensive updated search through 2025. Response: This review includes 36 systematic reviews published between January 2010 and December 2020. As you mentioned, much research on greenspace and health, including reviews, has been published since December 2020. We identified an additional 45 review articles between December 2020 and June 2024. Combining these two umbrella reviews would be too many systematic reviews to include in a single umbrella review. As per the Cochrane guidelines (Cumpston and Flemyng, 2023), we have updated the review due to “the availability of new evidence that would have a meaningful impact on the review findings”. [Please see our updated review here, https://doi.org/10.12688/f1000research.166852.1 ]. Cumpston, M., Flemyng, E., Chapter IV: Updating a review [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-iv 2. Title Lacks Methodological Clarity The title "systematic review of reviews" should explicitly identify this as an umbrella review using standard terminology. Recommendation: Revise the title to include the term "umbrella review." In the title, we prefer to use the term ‘systematic review of reviews’, but we do refer to it as an umbrella review in the text. We find this title more understandable for a lay audience. 3. Critical Methodological Flaw in Meta-analysis Assessment Table 5 fails to report the study design composition of included meta-analyses, which is a fundamental methodological oversight. Many meta-analyses inappropriately pool cross-sectional studies with longitudinal studies, which: Violates basic meta-analysis principles Cannot establish causality Produces effect estimates with limited validity for causal inference Significantly affects evidence interpretation Recommendation: Add columns to Table 5 showing: Number of studies in each meta-analysis Study design composition (# cross-sectional, # cohort, # RCT, etc.) Assessment of methodological appropriateness of pooling strategies Heterogeneity statistics (I²) Response: Number of studies: This information is already reported in Table 5. Study design composition: The composition of original studies included in the systematic reviews is presented in Table 1. For further details, readers can consult the individual systematic reviews. Appropriateness of statistical methods: This aspect has been formally assessed using AMSTAR-2, and the results are included in Table 6 of our manuscript. Heterogeneity statistics (I²): I² values are not comparable because they depend on the number of studies, sample sizes, and variance structure. Reporting them side-by-side in an umbrella review risks misleading comparisons. 4. Quality Assessment Implications Inadequately Addressed With 50% of reviews having a high risk of bias and 36% rated as low quality, the implications for evidence reliability are inadequately discussed. Recommendation: Provide a detailed analysis of which AMSTAR-2 criteria were most commonly failed. Conduct sensitivity analyses excluding low-quality reviews Discuss how quality limitations affect confidence in conclusions Response: Detailed AMSTAR‑2 results: Table 6 reports the results for each AMSTAR‑2 component across the included systematic reviews. This provides readers with a transparent view of which criteria were most commonly met or failed. Sensitivity analyses: As our study is an umbrella review rather than a meta-analysis, we did not conduct quantitative sensitivity analyses by excluding low-quality reviews. Risk of bias and methodological quality assessments are transparently reported in the Results section. 5. Limited Incremental Value Over Existing Reviews The comparison with existing umbrella reviews (van den Bosch & Ode Sang 2017; Yang et al. 2021) raises questions about unique contributions. Recommendation: More clearly articulate what this review adds beyond existing umbrella reviews, particularly given the temporal limitations. We respectfully note that the unique contributions of our umbrella review are already articulated in the last paragraph of the Introduction, which outlines five specific features distinguishing our work from prior umbrella reviews. These include: (i) evaluation of greenspace exposure and health outcomes independently of blue space and health determinants; (ii) assessment of both quality and risk of bias of reviews; (iii) recording of the frequency of greenspace exposure measures used; (iv) summarisation of health outcomes with associated ICD-10 codes; and (v) reporting of effect measures from meta-analyses. Together, these features ensure that our review provides a distinct contribution beyond earlier syntheses. As another reviewer noted, this paragraph was clear, and we believe it sufficiently addresses the concern regarding incremental value. For this reason, we have not made further changes to the manuscript. MINOR COMMENTS 6. Methodological Transparency Issues Search Strategy: Include full search strategy in main text or easily accessible supplementary material Inter-rater Reliability: Provide statistics for study selection and quality assessment agreement Grey Literature: Clarify if grey literature was considered and justify exclusion if applicable Response: Search Strategy: The full search strategy is already provided in Supplementary Table S1, ensuring that readers can access the complete details of keywords used. Inter-rater Reliability: This was not deemed necessary in our umbrella review because “Disagreements were resolved via discussions with the last author”. Because consensus was consistently achieved and disagreements were few, we did not calculate or report formal inter-rater reliability statistics. Grey literature was not included in our umbrella review. Our focus was restricted to peer-reviewed systematic reviews and meta-analyses to ensure methodological rigour, consistency in reporting standards, and comparability across included studies. 7. Results Presentation Problems PRISMA Flowchart: Reference is unclear - ensure easy accessibility or include key elements in the main manuscript Effect Size Reporting: Standardize decimal places and clarify whether estimates are from random or fixed effects models Response: As per the F1000 guidelines, a PRISMA flowchart for this review is available under the ‘Data availability’ à ‘Reporting guidelines’ section at the end of the article. Effect Size Reporting: Most effect sizes are reported to two decimal places; however, in cases where estimates are very small (e.g., beta coefficients of 0.001 with confidence intervals of 0.000–0.002), three decimal places are used to ensure precision and interpretability. In our umbrella review, we presented estimates by outcome in a comprehensive summary table (Table 5). Given the breadth of outcomes, this table is already large and adding further details (e.g. heterogeneity statistics or the specific effects model) would be redundant for the purposes of an umbrella review. The primary objective of an umbrella review is to synthesise evidence across systematic reviews, rather than to re-analyse or replicate their statistical outputs. This information is explicitly available in the original systematic reviews: of the 12 meta-analyses, 9 used random-effects models (Gascon et al., 2016; Lambert et al., 2017; Lee et al., 2020; Roberts et al., 2019; Rojas-Rueda et al., 2019; Soga et al., 2017; Twohig-Bennett and Jones, 2018; Yuan et al., 2021; Zhan et al., 2020), 1 used a fixed-effects model (Luo et al., 2020), and 2 applied quality-effects models (Akaraci et al., 2020; Dzhambov et al., 2014). 8. Quantitative Synthesis Limitations Many meta-analyses based on very few studies (n=2-4) Missing heterogeneity assessments No discussion of the potential for publication bias potential Mixing of different exposure metrics in a single meta-analyses Response: Small meta-analyses (n=2–4): We acknowledge that several meta-analyses included in our umbrella review were based on a limited number of primary studies. This limitation reflects the current evidence base rather than our methodology, and we have reported these findings transparently. Heterogeneity assessments: We did not include heterogeneity statistics (e.g., I²) in the manuscript, as our umbrella review was designed as a narrative synthesis rather than a re-analysis of quantitative data. Publication bias: Publication bias was assessed using the AMSTAR-2 tool, which explicitly evaluates whether included reviews considered publication bias (Table 6). This assessment is incorporated into our quality appraisal and reported accordingly. Exposure metrics: We recognise that some meta-analyses combined different greenspace exposure metrics. This reflects the diversity of measures used in the field. Our umbrella review records the frequency of exposure measures and highlights this variability as a methodological challenge for future research. 9. ICD-10 Classification Concerns The post-hoc assignment of ICD-10 codes (Table 4) may not reflect how original studies defined outcomes and could be misleading. Recommendation: Remove or clearly label as authors' interpretation rather than original study classifications. You are correct that the original studies may not have defined the outcomes based on the ICD codes. Based on the information available in the reviews, we allocated all potential ICD codes for each health outcome. We did this to promote standardised reporting in future articles that investigate the association between greenspace exposure and health outcomes. 10. Discussion Deficiencies Mechanistic Pathways: Brief mention of mechanisms could be expanded Policy Implications: Insufficient discussion of urban planning and public health implications Geographic Limitations: Most studies from high-income countries inadequately addressed Equity Considerations: Missing discussion of greenspace access disparities Response: Mechanistic Pathways: We briefly mention potential mechanisms linking greenspace exposure to health outcomes, as a detailed exploration of mechanistic pathways was beyond the scope of this umbrella review. These mechanisms have been explored in more depth by other researchers (Markevych et al., 2017). Markevych, I., Schoierer, J., Hartig, T., Chudnovsky, A., Hystad, P.,…. & Fuertes, E. (2017). Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental Research, 158, 301-317. https://doi.org/10.1016/j.envres.2017.06.028 Policy Implications: We acknowledge the importance of urban planning and public health implications. However, our focus was on synthesising the evidence rather than extending into policy recommendations. We believe that the evidence presented provides a foundation for future work to draw out specific policy implications. Geographic Limitations: The included systematic reviews drew upon studies conducted across a wide variety of locations worldwide. Given the diversity of study locations represented, we did not identify a single geographic imbalance that required emphasis. We agree that geographic context is important for interpreting greenspace–health relationships, and future work could more explicitly examine regional differences. Equity Considerations: We agree that disparities in greenspace access are important, which is why we have discussed inequalities in greenspace access due to urbanisation, socioeconomic status, and occupation in the third paragraph of the ‘Discussion’ section. 11. Blue Space Exclusion Rationale While focusing solely on greenspace, the exclusion of studies examining combined green-blue space effects may artificially limit the evidence base and miss important findings. We sought to evaluate the association between greenspace exposure and health outcomes independently of blue space, in order to avoid conflating effects and to provide a more precise synthesis of greenspace-specific evidence. Including studies that combined green and blue space exposures would have introduced heterogeneity in exposure definitions, making comparisons across reviews less meaningful. Additionally, previous umbrella reviews have often considered green and blue spaces together. By focusing solely on greenspace, our review addresses a distinct gap in the literature and complements existing syntheses. 12. Temporal Analysis Missing No consideration of temporal trends in research quality, methodology, or findings over the study period. We acknowledge that examining temporal trends in research quality, methodology, and findings could provide valuable insights. While such an analysis was not undertaken in the present umbrella review, we have addressed this point in our updated review, where we assessed trends in these components between studies published in 2010–2020 (covered in this review) and 2021–2024 (updated review). We believe this complementary work provides the broader temporal perspective suggested by the reviewer. [Please see our updated review here, https://doi.org/10.12688/f1000research.166852.1 ]. SPECIFIC TECHNICAL RECOMMENDATIONS Restructure Results: Organize findings by strength of evidence rather than just outcome categories Study Design Stratification: Re-analyze findings separately for longitudinal/cohort studies, cross-sectional studies, and intervention studies Sensitivity Analyses: Exclude low-quality reviews to assess robustness of conclusions Enhanced Quality Discussion: Provide a systematic analysis of methodological failures in included reviews Future Research Priorities: More clearly identify evidence gaps and research priorities Practical Implications: Expand discussion of what constitutes "effective" greenspace exposure for policy purposes Response: Restructuring Results / Study Design Stratification / Sensitivity Analyses: Our review followed a narrative synthesis approach, drawing on published systematic reviews and meta-analyses. We did not re-analyse primary data, and therefore restructuring results by strength of evidence, stratifying by study design, or conducting sensitivity analyses excluding low-quality reviews were not feasible within our methodological framework. Enhanced Quality Discussion: Table 6 reports the results for each AMSTAR‑2 component across the included systematic reviews. This provides readers with a transparent view of which criteria were most commonly met or failed. Future Research Priorities: We have highlighted evidence gaps and research needs in the Discussion, particularly regarding the diversity of exposure metrics and study design. Practical Implications: Our umbrella review was designed to summarise quantitative evidence from existing systematic reviews and meta-analyses, rather than to define optimal exposure thresholds or policy standards. The included reviews varied widely in how greenspace exposure was measured, and this heterogeneity limited our ability to draw firm conclusions about what constitutes “effective” exposure. We have highlighted this variability in the Discussion as a key methodological challenge and evidence gap. Response to reviewer comments We appreciate the feedback on the manuscript. We have carefully considered and responded to your suggestions. MAJOR COMMENTS 1. Critically Outdated Search Strategy The search strategy, which ended in January 2021 (over four years ago), represents a fundamental limitation that significantly undermines the review's validity and applicability. This is particularly problematic for greenspace research given: Rapid expansion of high-quality research post-COVID-19 Multiple systematic reviews published 2021-2024 Evolution of methodological standards and exposure assessment techniques New evidence on mechanisms and dose-response relationships Recommendation: Conduct a comprehensive updated search through 2025. Response: This review includes 36 systematic reviews published between January 2010 and December 2020. As you mentioned, much research on greenspace and health, including reviews, has been published since December 2020. We identified an additional 45 review articles between December 2020 and June 2024. Combining these two umbrella reviews would be too many systematic reviews to include in a single umbrella review. As per the Cochrane guidelines (Cumpston and Flemyng, 2023), we have updated the review due to “the availability of new evidence that would have a meaningful impact on the review findings”. [Please see our updated review here, https://doi.org/10.12688/f1000research.166852.1 ]. Cumpston, M., Flemyng, E., Chapter IV: Updating a review [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-iv 2. Title Lacks Methodological Clarity The title "systematic review of reviews" should explicitly identify this as an umbrella review using standard terminology. Recommendation: Revise the title to include the term "umbrella review." In the title, we prefer to use the term ‘systematic review of reviews’, but we do refer to it as an umbrella review in the text. We find this title more understandable for a lay audience. 3. Critical Methodological Flaw in Meta-analysis Assessment Table 5 fails to report the study design composition of included meta-analyses, which is a fundamental methodological oversight. Many meta-analyses inappropriately pool cross-sectional studies with longitudinal studies, which: Violates basic meta-analysis principles Cannot establish causality Produces effect estimates with limited validity for causal inference Significantly affects evidence interpretation Recommendation: Add columns to Table 5 showing: Number of studies in each meta-analysis Study design composition (# cross-sectional, # cohort, # RCT, etc.) Assessment of methodological appropriateness of pooling strategies Heterogeneity statistics (I²) Response: Number of studies: This information is already reported in Table 5. Study design composition: The composition of original studies included in the systematic reviews is presented in Table 1. For further details, readers can consult the individual systematic reviews. Appropriateness of statistical methods: This aspect has been formally assessed using AMSTAR-2, and the results are included in Table 6 of our manuscript. Heterogeneity statistics (I²): I² values are not comparable because they depend on the number of studies, sample sizes, and variance structure. Reporting them side-by-side in an umbrella review risks misleading comparisons. 4. Quality Assessment Implications Inadequately Addressed With 50% of reviews having a high risk of bias and 36% rated as low quality, the implications for evidence reliability are inadequately discussed. Recommendation: Provide a detailed analysis of which AMSTAR-2 criteria were most commonly failed. Conduct sensitivity analyses excluding low-quality reviews Discuss how quality limitations affect confidence in conclusions Response: Detailed AMSTAR‑2 results: Table 6 reports the results for each AMSTAR‑2 component across the included systematic reviews. This provides readers with a transparent view of which criteria were most commonly met or failed. Sensitivity analyses: As our study is an umbrella review rather than a meta-analysis, we did not conduct quantitative sensitivity analyses by excluding low-quality reviews. Risk of bias and methodological quality assessments are transparently reported in the Results section. 5. Limited Incremental Value Over Existing Reviews The comparison with existing umbrella reviews (van den Bosch & Ode Sang 2017; Yang et al. 2021) raises questions about unique contributions. Recommendation: More clearly articulate what this review adds beyond existing umbrella reviews, particularly given the temporal limitations. We respectfully note that the unique contributions of our umbrella review are already articulated in the last paragraph of the Introduction, which outlines five specific features distinguishing our work from prior umbrella reviews. These include: (i) evaluation of greenspace exposure and health outcomes independently of blue space and health determinants; (ii) assessment of both quality and risk of bias of reviews; (iii) recording of the frequency of greenspace exposure measures used; (iv) summarisation of health outcomes with associated ICD-10 codes; and (v) reporting of effect measures from meta-analyses. Together, these features ensure that our review provides a distinct contribution beyond earlier syntheses. As another reviewer noted, this paragraph was clear, and we believe it sufficiently addresses the concern regarding incremental value. For this reason, we have not made further changes to the manuscript. MINOR COMMENTS 6. Methodological Transparency Issues Search Strategy: Include full search strategy in main text or easily accessible supplementary material Inter-rater Reliability: Provide statistics for study selection and quality assessment agreement Grey Literature: Clarify if grey literature was considered and justify exclusion if applicable Response: Search Strategy: The full search strategy is already provided in Supplementary Table S1, ensuring that readers can access the complete details of keywords used. Inter-rater Reliability: This was not deemed necessary in our umbrella review because “Disagreements were resolved via discussions with the last author”. Because consensus was consistently achieved and disagreements were few, we did not calculate or report formal inter-rater reliability statistics. Grey literature was not included in our umbrella review. Our focus was restricted to peer-reviewed systematic reviews and meta-analyses to ensure methodological rigour, consistency in reporting standards, and comparability across included studies. 7. Results Presentation Problems PRISMA Flowchart: Reference is unclear - ensure easy accessibility or include key elements in the main manuscript Effect Size Reporting: Standardize decimal places and clarify whether estimates are from random or fixed effects models Response: As per the F1000 guidelines, a PRISMA flowchart for this review is available under the ‘Data availability’ à ‘Reporting guidelines’ section at the end of the article. Effect Size Reporting: Most effect sizes are reported to two decimal places; however, in cases where estimates are very small (e.g., beta coefficients of 0.001 with confidence intervals of 0.000–0.002), three decimal places are used to ensure precision and interpretability. In our umbrella review, we presented estimates by outcome in a comprehensive summary table (Table 5). Given the breadth of outcomes, this table is already large and adding further details (e.g. heterogeneity statistics or the specific effects model) would be redundant for the purposes of an umbrella review. The primary objective of an umbrella review is to synthesise evidence across systematic reviews, rather than to re-analyse or replicate their statistical outputs. This information is explicitly available in the original systematic reviews: of the 12 meta-analyses, 9 used random-effects models (Gascon et al., 2016; Lambert et al., 2017; Lee et al., 2020; Roberts et al., 2019; Rojas-Rueda et al., 2019; Soga et al., 2017; Twohig-Bennett and Jones, 2018; Yuan et al., 2021; Zhan et al., 2020), 1 used a fixed-effects model (Luo et al., 2020), and 2 applied quality-effects models (Akaraci et al., 2020; Dzhambov et al., 2014). 8. Quantitative Synthesis Limitations Many meta-analyses based on very few studies (n=2-4) Missing heterogeneity assessments No discussion of the potential for publication bias potential Mixing of different exposure metrics in a single meta-analyses Response: Small meta-analyses (n=2–4): We acknowledge that several meta-analyses included in our umbrella review were based on a limited number of primary studies. This limitation reflects the current evidence base rather than our methodology, and we have reported these findings transparently. Heterogeneity assessments: We did not include heterogeneity statistics (e.g., I²) in the manuscript, as our umbrella review was designed as a narrative synthesis rather than a re-analysis of quantitative data. Publication bias: Publication bias was assessed using the AMSTAR-2 tool, which explicitly evaluates whether included reviews considered publication bias (Table 6). This assessment is incorporated into our quality appraisal and reported accordingly. Exposure metrics: We recognise that some meta-analyses combined different greenspace exposure metrics. This reflects the diversity of measures used in the field. Our umbrella review records the frequency of exposure measures and highlights this variability as a methodological challenge for future research. 9. ICD-10 Classification Concerns The post-hoc assignment of ICD-10 codes (Table 4) may not reflect how original studies defined outcomes and could be misleading. Recommendation: Remove or clearly label as authors' interpretation rather than original study classifications. You are correct that the original studies may not have defined the outcomes based on the ICD codes. Based on the information available in the reviews, we allocated all potential ICD codes for each health outcome. We did this to promote standardised reporting in future articles that investigate the association between greenspace exposure and health outcomes. 10. Discussion Deficiencies Mechanistic Pathways: Brief mention of mechanisms could be expanded Policy Implications: Insufficient discussion of urban planning and public health implications Geographic Limitations: Most studies from high-income countries inadequately addressed Equity Considerations: Missing discussion of greenspace access disparities Response: Mechanistic Pathways: We briefly mention potential mechanisms linking greenspace exposure to health outcomes, as a detailed exploration of mechanistic pathways was beyond the scope of this umbrella review. These mechanisms have been explored in more depth by other researchers (Markevych et al., 2017). Markevych, I., Schoierer, J., Hartig, T., Chudnovsky, A., Hystad, P.,…. & Fuertes, E. (2017). Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental Research, 158, 301-317. https://doi.org/10.1016/j.envres.2017.06.028 Policy Implications: We acknowledge the importance of urban planning and public health implications. However, our focus was on synthesising the evidence rather than extending into policy recommendations. We believe that the evidence presented provides a foundation for future work to draw out specific policy implications. Geographic Limitations: The included systematic reviews drew upon studies conducted across a wide variety of locations worldwide. Given the diversity of study locations represented, we did not identify a single geographic imbalance that required emphasis. We agree that geographic context is important for interpreting greenspace–health relationships, and future work could more explicitly examine regional differences. Equity Considerations: We agree that disparities in greenspace access are important, which is why we have discussed inequalities in greenspace access due to urbanisation, socioeconomic status, and occupation in the third paragraph of the ‘Discussion’ section. 11. Blue Space Exclusion Rationale While focusing solely on greenspace, the exclusion of studies examining combined green-blue space effects may artificially limit the evidence base and miss important findings. We sought to evaluate the association between greenspace exposure and health outcomes independently of blue space, in order to avoid conflating effects and to provide a more precise synthesis of greenspace-specific evidence. Including studies that combined green and blue space exposures would have introduced heterogeneity in exposure definitions, making comparisons across reviews less meaningful. Additionally, previous umbrella reviews have often considered green and blue spaces together. By focusing solely on greenspace, our review addresses a distinct gap in the literature and complements existing syntheses. 12. Temporal Analysis Missing No consideration of temporal trends in research quality, methodology, or findings over the study period. We acknowledge that examining temporal trends in research quality, methodology, and findings could provide valuable insights. While such an analysis was not undertaken in the present umbrella review, we have addressed this point in our updated review, where we assessed trends in these components between studies published in 2010–2020 (covered in this review) and 2021–2024 (updated review). We believe this complementary work provides the broader temporal perspective suggested by the reviewer. [Please see our updated review here, https://doi.org/10.12688/f1000research.166852.1 ]. SPECIFIC TECHNICAL RECOMMENDATIONS Restructure Results: Organize findings by strength of evidence rather than just outcome categories Study Design Stratification: Re-analyze findings separately for longitudinal/cohort studies, cross-sectional studies, and intervention studies Sensitivity Analyses: Exclude low-quality reviews to assess robustness of conclusions Enhanced Quality Discussion: Provide a systematic analysis of methodological failures in included reviews Future Research Priorities: More clearly identify evidence gaps and research priorities Practical Implications: Expand discussion of what constitutes "effective" greenspace exposure for policy purposes Response: Restructuring Results / Study Design Stratification / Sensitivity Analyses: Our review followed a narrative synthesis approach, drawing on published systematic reviews and meta-analyses. We did not re-analyse primary data, and therefore restructuring results by strength of evidence, stratifying by study design, or conducting sensitivity analyses excluding low-quality reviews were not feasible within our methodological framework. Enhanced Quality Discussion: Table 6 reports the results for each AMSTAR‑2 component across the included systematic reviews. This provides readers with a transparent view of which criteria were most commonly met or failed. Future Research Priorities: We have highlighted evidence gaps and research needs in the Discussion, particularly regarding the diversity of exposure metrics and study design. Practical Implications: Our umbrella review was designed to summarise quantitative evidence from existing systematic reviews and meta-analyses, rather than to define optimal exposure thresholds or policy standards. The included reviews varied widely in how greenspace exposure was measured, and this heterogeneity limited our ability to draw firm conclusions about what constitutes “effective” exposure. We have highlighted this variability in the Discussion as a key methodological challenge and evidence gap. Competing Interests: No competing interests. Close Report a concern COMMENT ON THIS REPORT Views 0 Cite How to cite this report: Huang W. Reviewer Report For: Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.5256/f1000research.185657.r401604 ) The direct URL for this report is: https://f1000research.com/articles/13-491/v2#referee-response-401604 NOTE: it is important to ensure the information in square brackets after the title is included in this citation. Close Copy Citation Details Reviewer Report 23 Aug 2025 Wenzhong Huang , Monash University, Melbourne, Australia Approved VIEWS 0 https://doi.org/10.5256/f1000research.185657.r401604 I appreciate the authors' efforts. The manuscript is now much clearer and improved over previous versions, particularly in clarifying ... Continue reading READ ALL I appreciate the authors' efforts. The manuscript is now much clearer and improved over previous versions, particularly in clarifying its unique strengths and the comparisons with similar studies. The results have also been enhanced. I have no further comments. Competing Interests: No competing interests were disclosed. Reviewer Expertise: Environmental epidemiolgy; greenness, air pollution, climate change and health I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. Close READ LESS CITE CITE HOW TO CITE THIS REPORT Huang W. Reviewer Report For: Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.5256/f1000research.185657.r401604 ) The direct URL for this report is: https://f1000research.com/articles/13-491/v2#referee-response-401604 NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article. COPY CITATION DETAILS Report a concern Respond or Comment COMMENT ON THIS REPORT Version 1 VERSION 1 PUBLISHED 17 May 2024 Views 0 Cite How to cite this report: Mueller W. Reviewer Report For: Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.5256/f1000research.163252.r284715 ) The direct URL for this report is: https://f1000research.com/articles/13-491/v1#referee-response-284715 NOTE: it is important to ensure the information in square brackets after the title is included in this citation. Close Copy Citation Details Reviewer Report 28 Jun 2024 William Mueller , Institute of Occupational Medicine (IOM), Edinburgh, UK Approved with Reservations VIEWS 0 https://doi.org/10.5256/f1000research.163252.r284715 Overall This is a well-conducted and well-written review about greenspace exposure and human health, a very active research area that would benefit from a broad synthesis of the evidence. I have outlined my comments below, which are mostly minor, ... Continue reading READ ALL Overall This is a well-conducted and well-written review about greenspace exposure and human health, a very active research area that would benefit from a broad synthesis of the evidence. I have outlined my comments below, which are mostly minor, but I do note an important Major comment for the authors and editor’s consideration. Major Much research on greenspace and health, including reviews, has been published since December 2020. If an updated review is underway, wouldn’t it be more valuable to wait to publish the more up to date work? Also given the reviews themselves have earlier cut-offs, so the current review would already be quite out of date with the most recent research. Minor Consider changing title to refer to an ‘umbrella review’ Abstract - The abstract states that beneficial effects were observed for cardiovascular disease mortality, but that ambivalent results were found for cardiovascular health. The former is a subset of the latter, so please change wording to be consistent. [I see later that cardiovascular and metabolic health was combined as one category, but this is not clear from a read of the abstract.] Abstract – it is always helpful to include some quantitative results, even if ranges of effect sizes, to better characterise findings Introduction – ‘These studies did not consider overall health impacts’ – what does this statement mean exactly? Rephrase to make clear that full weight of evidence needs to be assessed to understand the nature of greenspace and health via an umbrella review, as described in the following sentence. Introduction – Following the above point, what about reviews that address multiple health outcomes (e.g., Twohig-Bennett & Jones, 2018) [REF1]? Can they not provide useful information on overall health impacts as well? Methods – Why are cardiovascular and metabolic outcomes combined? Results – Did you search the references of included papers? If so, were any additional papers identified? Typically, reviews include flow charts to show the start and end number of papers. Table 1- Why is the sample size for Carver et al. ‘NA’? Table 1 – Define ‘NA’ with other short-forms Table 3 – Add a ‘*’ or similar next to ‘Other’ to indicate that the specific exposures are given below. Results – ‘Maternal health…’ – Change to ‘OR=0.80…’ for consistency. Results – ‘Maternal health…’ – What do the Lee et al βs represent? Table 5 – Title should refer to ‘meta-analyses’, otherwise it is not clear how the effect estimates were calculated. It would also be helpful to add the increment that the estimates represent (e.g. per 0.1 increase in NDVI) Figure 1 – The methods should state how the overall risk of bias was determined (e.g., highest individual risk?). Also, the text accompanying the Figure, ‘…lighter colours concern judgments’ is not clear. Are these the individual risk of bias criteria? If so, state that. Results – Risk of bias – why was the risk in some cases ‘unclear’? Was there not enough information to determine if a criterion was met? Wouldn’t that suggest it was not met and that it is likely to be a source of bias? This point should be considered. Discussion – A stronger conclusion should be reached other than there may be an association between greenspace and health. For example, there appears to be stronger evidence for mental health, all-cause and CVD mortality. Are the specific pathways to health offered by greenspace more relevant for these outcomes? Table 6 – Without knowing the AMSTAR-2 questions or how they were rated, this table is not very intuitive. The other tables are informative and effective at summarising the reviews and results. Discussion – discussion of study limitations should be mentioned. Are the rationale for, and objectives of, the Systematic Review clearly stated? Yes Are sufficient details of the methods and analysis provided to allow replication by others? Yes Is the statistical analysis and its interpretation appropriate? Yes Are the conclusions drawn adequately supported by the results presented in the review? Partly If this is a Living Systematic Review, is the ‘living’ method appropriate and is the search schedule clearly defined and justified? (‘Living Systematic Review’ or a variation of this term should be included in the title.) Not applicable References 1. Twohig-Bennett C, Jones A: The health benefits of the great outdoors: A systematic review and meta-analysis of greenspace exposure and health outcomes. Environ Res . 2018; 166 : 628-637 PubMed Abstract | Publisher Full Text Competing Interests: No competing interests were disclosed. Reviewer Expertise: Environmental and occupational epidemiology I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. Close READ LESS CITE CITE HOW TO CITE THIS REPORT Mueller W. Reviewer Report For: Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.5256/f1000research.163252.r284715 ) The direct URL for this report is: https://f1000research.com/articles/13-491/v1#referee-response-284715 NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article. COPY CITATION DETAILS Report a concern Author Response 09 Aug 2025 Darsy Darssan , School of Public Health, The University of Queensland, Herston, Australia 09 Aug 2025 Author Response Response to reviewer comments We sincerely appreciate the thorough and insightful feedback on the manuscript. We have carefully considered and incorporated your suggestions wherever feasible. Major Much research on ... Continue reading Response to reviewer comments We sincerely appreciate the thorough and insightful feedback on the manuscript. We have carefully considered and incorporated your suggestions wherever feasible. Major Much research on greenspace and health, including reviews, has been published since December 2020. If an updated review is underway, wouldn’t it be more valuable to wait to publish the more up to date work? Also given the reviews themselves have earlier cut-offs, so the current review would already be quite out of date with the most recent research. Response: As per the Cochrane guidelines (Cumpston and Flemyng, 2023), we have updated the review due to “the availability of new evidence that would have a meaningful impact on the review findings”. [ https://doi.org/10.12688/f1000research.166852.1 ]. Cumpston, M., Flemyng, E., Chapter IV: Updating a review [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-iv This review includes 36 systematic reviews published between January 2010 and December 2020. As you mentioned, much research on greenspace and health, including reviews, has been published since December 2020. We identified an additional 45 review articles between December 2020 and June 2024. Combining these two umbrella reviews would be too many systematic reviews to include in a single umbrella review. Minor 1. Consider changing title to refer to an ‘umbrella review’ In the title, we prefer to use the term ‘systematic review of reviews’, but we do refer to it as an umbrella review in the text. We find this title more understandable for a lay audience. 2. Abstract - The abstract states that beneficial effects were observed for cardiovascular disease mortality, but that ambivalent results were found for cardiovascular health. The former is a subset of the latter, so please change wording to be consistent. [I see later that cardiovascular and metabolic health was combined as one category, but this is not clear from a read of the abstract.] We have changed the wording in the abstract. In the results section, cardiovascular and metabolic health are reported under one category, but the results of the two outcomes are not combined. 3. Abstract – it is always helpful to include some quantitative results, even if ranges of effect sizes, to better characterise findings We have thought this through carefully and have concluded that synthesising the quantitative results could lead to bias, as we would be pooling the already pooled results from the systematic reviews. As per Aromataris et al. 2015 our umbrella review is intended to summarise the current evidence rather than re-synthesising the data. Aromataris, E., Fernandez, R., Godfrey, C. M., Holly, C., Khalil, H., & Tungpunkom, P. (2015). Summarizing systematic reviews: methodological development, conduct and reporting of an umbrella review approach. JBI Evidence Implementation , 13 (3). https://doi.org/10.1097/XEB.0000000000000055 4. Introduction – ‘These studies did not consider overall health impacts’ – what does this statement mean exactly? Rephrase to make clear that full weight of evidence needs to be assessed to understand the nature of greenspace and health via an umbrella review, as described in the following sentence. We reworded this section of the Introduction for better understanding. 5. Introduction – Following the above point, what about reviews that address multiple health outcomes (e.g., Twohig-Bennett & Jones, 2018) [REF1]? Can they not provide useful information on overall health impacts as well? We reworded this section and have referenced Twohig-Bennett & Jones et al. 2018 in this section of the introduction. 6. Methods – Why are cardiovascular and metabolic outcomes combined? Cardiovascular and metabolic outcomes share common pathophysiological pathways and risk factors, making it logical to categorise them together. Greenspace exposure is hypothesised to influence these outcomes through shared mechanisms. 7. Results – Did you search the references of included papers? If so, were any additional papers identified? Typically, reviews include flow charts to show the start and end number of papers. Manual reference search is described in the ‘Search strategy’ section of the methods. As per the F1000 guidelines, a PRISMA flowchart for this review is available under the ‘Data availability’ -> ‘Reporting guidelines’ section at the end of the article. 8. Table 1- Why is the sample size for Carver et al. ‘NA’? This has been fixed to show the minimum and maximum sample size for Carver et al. 2020. 9. Table 1 – Define ‘NA’ with other short-forms This has been added. 10. Table 3 – Add a ‘*’ or similar next to ‘Other’ to indicate that the specific exposures are given below. This has been adjusted. 11. Results – ‘Maternal health…’ – Change to ‘OR=0.80…’ for consistency. This has been adjusted. 12. Results – ‘Maternal health…’ – What do the Lee et al βs represent? The definition has been added to the first instance of β. 13. Table 5 – Title should refer to ‘meta-analyses’, otherwise it is not clear how the effect estimates were calculated. It would also be helpful to add the increment that the estimates represent (e.g. per 0.1 increase in NDVI) This has been adjusted. Also, we thoroughly reviewed this Table. 14. Figure 1 – The methods should state how the overall risk of bias was determined (e.g., highest individual risk?). Also, the text accompanying the Figure, ‘…lighter colours concern judgments’ is not clear. Are these the individual risk of bias criteria? If so, state that. ROBIS was used to assess the risk of bias of each systematic review. ROBIS consists of four domains, and within each domain, there are five to six signalling questions. Two reviewers went through each signalling question, and judgments were made independently. These domains were then used to determine the overall risk of bias of each review. Conflicts between the reviewers were resolved through discussion with the last author. For each review, the final decision on four domains and the overall risk of bias is listed in Supplementary Table S2. Figure 1 is a summary of Supplementary Table S2, as per ROBIS guidelines. More information about ROBIS is available from Whiting et al. 2016. Whiting, P., Savovic, J., Higgins, J. P., Caldwell, D. M., Reeves, B. C., Shea, B., Davies, P., Kleijnen, J., Churchill, R., & group, R. (2016). ROBIS: A new tool to assess risk of bias in systematic reviews was developed. Journal of Clinical Epidemiology , 69 , 225-234. https://doi.org/10.1016/j.jclinepi.2015.06.005 We have altered the Figure caption to improve the readability of the graph. 15. Results – Risk of bias – why was the risk in some cases ‘unclear’? Was there not enough information to determine if a criterion was met? Wouldn’t that suggest it was not met and that it is likely to be a source of bias? This point should be considered. As per the guidance on how to use ROBIS, an ‘unclear’ rating indicates that insufficient data were reported to permit a judgment for signalling questions within a domain (Phase 2). If something is not reported, it could be a potential source of bias. That’s why ROBIS has the unclear category, because if the information isn’t reported, you cannot make a definitive statement about whether the bias is high or low. 16. Discussion – A stronger conclusion should be reached other than there may be an association between greenspace and health. For example, there appears to be stronger evidence for mental health, all-cause and CVD mortality. Are the specific pathways to health offered by greenspace more relevant for these outcomes? In this narrative synthesis, stronger conclusions for each health outcome could lead to overstatements of the associations. Inconsistent findings within each health outcome, with varying effect measures, also make it challenging to report definitive conclusions. Some pathways may be more related to specific health outcomes and have been explored in more depth by other researchers (Markevych et al., 2017). However, these biological mechanisms are beyond the scope of this Discussion section. Markevych, I., Schoierer, J., Hartig, T., Chudnovsky, A., Hystad, P.,…. & Fuertes, E. (2017). Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental Research, 158, 301-317. https://doi.org/10.1016/j.envres.2017.06.028 17. Table 6 – Without knowing the AMSTAR-2 questions or how they were rated, this table is not very intuitive. The other tables are informative and effective at summarising the reviews and results. We have added the shortened AMSTAR-2 questions as a footnote to the table. The other reviewer also mentioned this table and we have coloured the overall quality column to improve readability. A graph showing the distribution of high, moderate, and low-quality reviews is also available in the supplementary material. 18. Discussion – discussion of study limitations should be mentioned. The limitations of the review have been discussed in the last paragraph of the discussion. We revisited this paragraph to improve the clarity. Response to reviewer comments We sincerely appreciate the thorough and insightful feedback on the manuscript. We have carefully considered and incorporated your suggestions wherever feasible. Major Much research on greenspace and health, including reviews, has been published since December 2020. If an updated review is underway, wouldn’t it be more valuable to wait to publish the more up to date work? Also given the reviews themselves have earlier cut-offs, so the current review would already be quite out of date with the most recent research. Response: As per the Cochrane guidelines (Cumpston and Flemyng, 2023), we have updated the review due to “the availability of new evidence that would have a meaningful impact on the review findings”. [ https://doi.org/10.12688/f1000research.166852.1 ]. Cumpston, M., Flemyng, E., Chapter IV: Updating a review [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-iv This review includes 36 systematic reviews published between January 2010 and December 2020. As you mentioned, much research on greenspace and health, including reviews, has been published since December 2020. We identified an additional 45 review articles between December 2020 and June 2024. Combining these two umbrella reviews would be too many systematic reviews to include in a single umbrella review. Minor 1. Consider changing title to refer to an ‘umbrella review’ In the title, we prefer to use the term ‘systematic review of reviews’, but we do refer to it as an umbrella review in the text. We find this title more understandable for a lay audience. 2. Abstract - The abstract states that beneficial effects were observed for cardiovascular disease mortality, but that ambivalent results were found for cardiovascular health. The former is a subset of the latter, so please change wording to be consistent. [I see later that cardiovascular and metabolic health was combined as one category, but this is not clear from a read of the abstract.] We have changed the wording in the abstract. In the results section, cardiovascular and metabolic health are reported under one category, but the results of the two outcomes are not combined. 3. Abstract – it is always helpful to include some quantitative results, even if ranges of effect sizes, to better characterise findings We have thought this through carefully and have concluded that synthesising the quantitative results could lead to bias, as we would be pooling the already pooled results from the systematic reviews. As per Aromataris et al. 2015 our umbrella review is intended to summarise the current evidence rather than re-synthesising the data. Aromataris, E., Fernandez, R., Godfrey, C. M., Holly, C., Khalil, H., & Tungpunkom, P. (2015). Summarizing systematic reviews: methodological development, conduct and reporting of an umbrella review approach. JBI Evidence Implementation , 13 (3). https://doi.org/10.1097/XEB.0000000000000055 4. Introduction – ‘These studies did not consider overall health impacts’ – what does this statement mean exactly? Rephrase to make clear that full weight of evidence needs to be assessed to understand the nature of greenspace and health via an umbrella review, as described in the following sentence. We reworded this section of the Introduction for better understanding. 5. Introduction – Following the above point, what about reviews that address multiple health outcomes (e.g., Twohig-Bennett & Jones, 2018) [REF1]? Can they not provide useful information on overall health impacts as well? We reworded this section and have referenced Twohig-Bennett & Jones et al. 2018 in this section of the introduction. 6. Methods – Why are cardiovascular and metabolic outcomes combined? Cardiovascular and metabolic outcomes share common pathophysiological pathways and risk factors, making it logical to categorise them together. Greenspace exposure is hypothesised to influence these outcomes through shared mechanisms. 7. Results – Did you search the references of included papers? If so, were any additional papers identified? Typically, reviews include flow charts to show the start and end number of papers. Manual reference search is described in the ‘Search strategy’ section of the methods. As per the F1000 guidelines, a PRISMA flowchart for this review is available under the ‘Data availability’ -> ‘Reporting guidelines’ section at the end of the article. 8. Table 1- Why is the sample size for Carver et al. ‘NA’? This has been fixed to show the minimum and maximum sample size for Carver et al. 2020. 9. Table 1 – Define ‘NA’ with other short-forms This has been added. 10. Table 3 – Add a ‘*’ or similar next to ‘Other’ to indicate that the specific exposures are given below. This has been adjusted. 11. Results – ‘Maternal health…’ – Change to ‘OR=0.80…’ for consistency. This has been adjusted. 12. Results – ‘Maternal health…’ – What do the Lee et al βs represent? The definition has been added to the first instance of β. 13. Table 5 – Title should refer to ‘meta-analyses’, otherwise it is not clear how the effect estimates were calculated. It would also be helpful to add the increment that the estimates represent (e.g. per 0.1 increase in NDVI) This has been adjusted. Also, we thoroughly reviewed this Table. 14. Figure 1 – The methods should state how the overall risk of bias was determined (e.g., highest individual risk?). Also, the text accompanying the Figure, ‘…lighter colours concern judgments’ is not clear. Are these the individual risk of bias criteria? If so, state that. ROBIS was used to assess the risk of bias of each systematic review. ROBIS consists of four domains, and within each domain, there are five to six signalling questions. Two reviewers went through each signalling question, and judgments were made independently. These domains were then used to determine the overall risk of bias of each review. Conflicts between the reviewers were resolved through discussion with the last author. For each review, the final decision on four domains and the overall risk of bias is listed in Supplementary Table S2. Figure 1 is a summary of Supplementary Table S2, as per ROBIS guidelines. More information about ROBIS is available from Whiting et al. 2016. Whiting, P., Savovic, J., Higgins, J. P., Caldwell, D. M., Reeves, B. C., Shea, B., Davies, P., Kleijnen, J., Churchill, R., & group, R. (2016). ROBIS: A new tool to assess risk of bias in systematic reviews was developed. Journal of Clinical Epidemiology , 69 , 225-234. https://doi.org/10.1016/j.jclinepi.2015.06.005 We have altered the Figure caption to improve the readability of the graph. 15. Results – Risk of bias – why was the risk in some cases ‘unclear’? Was there not enough information to determine if a criterion was met? Wouldn’t that suggest it was not met and that it is likely to be a source of bias? This point should be considered. As per the guidance on how to use ROBIS, an ‘unclear’ rating indicates that insufficient data were reported to permit a judgment for signalling questions within a domain (Phase 2). If something is not reported, it could be a potential source of bias. That’s why ROBIS has the unclear category, because if the information isn’t reported, you cannot make a definitive statement about whether the bias is high or low. 16. Discussion – A stronger conclusion should be reached other than there may be an association between greenspace and health. For example, there appears to be stronger evidence for mental health, all-cause and CVD mortality. Are the specific pathways to health offered by greenspace more relevant for these outcomes? In this narrative synthesis, stronger conclusions for each health outcome could lead to overstatements of the associations. Inconsistent findings within each health outcome, with varying effect measures, also make it challenging to report definitive conclusions. Some pathways may be more related to specific health outcomes and have been explored in more depth by other researchers (Markevych et al., 2017). However, these biological mechanisms are beyond the scope of this Discussion section. Markevych, I., Schoierer, J., Hartig, T., Chudnovsky, A., Hystad, P.,…. & Fuertes, E. (2017). Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental Research, 158, 301-317. https://doi.org/10.1016/j.envres.2017.06.028 17. Table 6 – Without knowing the AMSTAR-2 questions or how they were rated, this table is not very intuitive. The other tables are informative and effective at summarising the reviews and results. We have added the shortened AMSTAR-2 questions as a footnote to the table. The other reviewer also mentioned this table and we have coloured the overall quality column to improve readability. A graph showing the distribution of high, moderate, and low-quality reviews is also available in the supplementary material. 18. Discussion – discussion of study limitations should be mentioned. The limitations of the review have been discussed in the last paragraph of the discussion. We revisited this paragraph to improve the clarity. Competing Interests: No competing interests. Close Report a concern Respond or Comment COMMENTS ON THIS REPORT Author Response 09 Aug 2025 Darsy Darssan , School of Public Health, The University of Queensland, Herston, Australia 09 Aug 2025 Author Response Response to reviewer comments We sincerely appreciate the thorough and insightful feedback on the manuscript. We have carefully considered and incorporated your suggestions wherever feasible. Major Much research on ... Continue reading Response to reviewer comments We sincerely appreciate the thorough and insightful feedback on the manuscript. We have carefully considered and incorporated your suggestions wherever feasible. Major Much research on greenspace and health, including reviews, has been published since December 2020. If an updated review is underway, wouldn’t it be more valuable to wait to publish the more up to date work? Also given the reviews themselves have earlier cut-offs, so the current review would already be quite out of date with the most recent research. Response: As per the Cochrane guidelines (Cumpston and Flemyng, 2023), we have updated the review due to “the availability of new evidence that would have a meaningful impact on the review findings”. [ https://doi.org/10.12688/f1000research.166852.1 ]. Cumpston, M., Flemyng, E., Chapter IV: Updating a review [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-iv This review includes 36 systematic reviews published between January 2010 and December 2020. As you mentioned, much research on greenspace and health, including reviews, has been published since December 2020. We identified an additional 45 review articles between December 2020 and June 2024. Combining these two umbrella reviews would be too many systematic reviews to include in a single umbrella review. Minor 1. Consider changing title to refer to an ‘umbrella review’ In the title, we prefer to use the term ‘systematic review of reviews’, but we do refer to it as an umbrella review in the text. We find this title more understandable for a lay audience. 2. Abstract - The abstract states that beneficial effects were observed for cardiovascular disease mortality, but that ambivalent results were found for cardiovascular health. The former is a subset of the latter, so please change wording to be consistent. [I see later that cardiovascular and metabolic health was combined as one category, but this is not clear from a read of the abstract.] We have changed the wording in the abstract. In the results section, cardiovascular and metabolic health are reported under one category, but the results of the two outcomes are not combined. 3. Abstract – it is always helpful to include some quantitative results, even if ranges of effect sizes, to better characterise findings We have thought this through carefully and have concluded that synthesising the quantitative results could lead to bias, as we would be pooling the already pooled results from the systematic reviews. As per Aromataris et al. 2015 our umbrella review is intended to summarise the current evidence rather than re-synthesising the data. Aromataris, E., Fernandez, R., Godfrey, C. M., Holly, C., Khalil, H., & Tungpunkom, P. (2015). Summarizing systematic reviews: methodological development, conduct and reporting of an umbrella review approach. JBI Evidence Implementation , 13 (3). https://doi.org/10.1097/XEB.0000000000000055 4. Introduction – ‘These studies did not consider overall health impacts’ – what does this statement mean exactly? Rephrase to make clear that full weight of evidence needs to be assessed to understand the nature of greenspace and health via an umbrella review, as described in the following sentence. We reworded this section of the Introduction for better understanding. 5. Introduction – Following the above point, what about reviews that address multiple health outcomes (e.g., Twohig-Bennett & Jones, 2018) [REF1]? Can they not provide useful information on overall health impacts as well? We reworded this section and have referenced Twohig-Bennett & Jones et al. 2018 in this section of the introduction. 6. Methods – Why are cardiovascular and metabolic outcomes combined? Cardiovascular and metabolic outcomes share common pathophysiological pathways and risk factors, making it logical to categorise them together. Greenspace exposure is hypothesised to influence these outcomes through shared mechanisms. 7. Results – Did you search the references of included papers? If so, were any additional papers identified? Typically, reviews include flow charts to show the start and end number of papers. Manual reference search is described in the ‘Search strategy’ section of the methods. As per the F1000 guidelines, a PRISMA flowchart for this review is available under the ‘Data availability’ -> ‘Reporting guidelines’ section at the end of the article. 8. Table 1- Why is the sample size for Carver et al. ‘NA’? This has been fixed to show the minimum and maximum sample size for Carver et al. 2020. 9. Table 1 – Define ‘NA’ with other short-forms This has been added. 10. Table 3 – Add a ‘*’ or similar next to ‘Other’ to indicate that the specific exposures are given below. This has been adjusted. 11. Results – ‘Maternal health…’ – Change to ‘OR=0.80…’ for consistency. This has been adjusted. 12. Results – ‘Maternal health…’ – What do the Lee et al βs represent? The definition has been added to the first instance of β. 13. Table 5 – Title should refer to ‘meta-analyses’, otherwise it is not clear how the effect estimates were calculated. It would also be helpful to add the increment that the estimates represent (e.g. per 0.1 increase in NDVI) This has been adjusted. Also, we thoroughly reviewed this Table. 14. Figure 1 – The methods should state how the overall risk of bias was determined (e.g., highest individual risk?). Also, the text accompanying the Figure, ‘…lighter colours concern judgments’ is not clear. Are these the individual risk of bias criteria? If so, state that. ROBIS was used to assess the risk of bias of each systematic review. ROBIS consists of four domains, and within each domain, there are five to six signalling questions. Two reviewers went through each signalling question, and judgments were made independently. These domains were then used to determine the overall risk of bias of each review. Conflicts between the reviewers were resolved through discussion with the last author. For each review, the final decision on four domains and the overall risk of bias is listed in Supplementary Table S2. Figure 1 is a summary of Supplementary Table S2, as per ROBIS guidelines. More information about ROBIS is available from Whiting et al. 2016. Whiting, P., Savovic, J., Higgins, J. P., Caldwell, D. M., Reeves, B. C., Shea, B., Davies, P., Kleijnen, J., Churchill, R., & group, R. (2016). ROBIS: A new tool to assess risk of bias in systematic reviews was developed. Journal of Clinical Epidemiology , 69 , 225-234. https://doi.org/10.1016/j.jclinepi.2015.06.005 We have altered the Figure caption to improve the readability of the graph. 15. Results – Risk of bias – why was the risk in some cases ‘unclear’? Was there not enough information to determine if a criterion was met? Wouldn’t that suggest it was not met and that it is likely to be a source of bias? This point should be considered. As per the guidance on how to use ROBIS, an ‘unclear’ rating indicates that insufficient data were reported to permit a judgment for signalling questions within a domain (Phase 2). If something is not reported, it could be a potential source of bias. That’s why ROBIS has the unclear category, because if the information isn’t reported, you cannot make a definitive statement about whether the bias is high or low. 16. Discussion – A stronger conclusion should be reached other than there may be an association between greenspace and health. For example, there appears to be stronger evidence for mental health, all-cause and CVD mortality. Are the specific pathways to health offered by greenspace more relevant for these outcomes? In this narrative synthesis, stronger conclusions for each health outcome could lead to overstatements of the associations. Inconsistent findings within each health outcome, with varying effect measures, also make it challenging to report definitive conclusions. Some pathways may be more related to specific health outcomes and have been explored in more depth by other researchers (Markevych et al., 2017). However, these biological mechanisms are beyond the scope of this Discussion section. Markevych, I., Schoierer, J., Hartig, T., Chudnovsky, A., Hystad, P.,…. & Fuertes, E. (2017). Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental Research, 158, 301-317. https://doi.org/10.1016/j.envres.2017.06.028 17. Table 6 – Without knowing the AMSTAR-2 questions or how they were rated, this table is not very intuitive. The other tables are informative and effective at summarising the reviews and results. We have added the shortened AMSTAR-2 questions as a footnote to the table. The other reviewer also mentioned this table and we have coloured the overall quality column to improve readability. A graph showing the distribution of high, moderate, and low-quality reviews is also available in the supplementary material. 18. Discussion – discussion of study limitations should be mentioned. The limitations of the review have been discussed in the last paragraph of the discussion. We revisited this paragraph to improve the clarity. Response to reviewer comments We sincerely appreciate the thorough and insightful feedback on the manuscript. We have carefully considered and incorporated your suggestions wherever feasible. Major Much research on greenspace and health, including reviews, has been published since December 2020. If an updated review is underway, wouldn’t it be more valuable to wait to publish the more up to date work? Also given the reviews themselves have earlier cut-offs, so the current review would already be quite out of date with the most recent research. Response: As per the Cochrane guidelines (Cumpston and Flemyng, 2023), we have updated the review due to “the availability of new evidence that would have a meaningful impact on the review findings”. [ https://doi.org/10.12688/f1000research.166852.1 ]. Cumpston, M., Flemyng, E., Chapter IV: Updating a review [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-iv This review includes 36 systematic reviews published between January 2010 and December 2020. As you mentioned, much research on greenspace and health, including reviews, has been published since December 2020. We identified an additional 45 review articles between December 2020 and June 2024. Combining these two umbrella reviews would be too many systematic reviews to include in a single umbrella review. Minor 1. Consider changing title to refer to an ‘umbrella review’ In the title, we prefer to use the term ‘systematic review of reviews’, but we do refer to it as an umbrella review in the text. We find this title more understandable for a lay audience. 2. Abstract - The abstract states that beneficial effects were observed for cardiovascular disease mortality, but that ambivalent results were found for cardiovascular health. The former is a subset of the latter, so please change wording to be consistent. [I see later that cardiovascular and metabolic health was combined as one category, but this is not clear from a read of the abstract.] We have changed the wording in the abstract. In the results section, cardiovascular and metabolic health are reported under one category, but the results of the two outcomes are not combined. 3. Abstract – it is always helpful to include some quantitative results, even if ranges of effect sizes, to better characterise findings We have thought this through carefully and have concluded that synthesising the quantitative results could lead to bias, as we would be pooling the already pooled results from the systematic reviews. As per Aromataris et al. 2015 our umbrella review is intended to summarise the current evidence rather than re-synthesising the data. Aromataris, E., Fernandez, R., Godfrey, C. M., Holly, C., Khalil, H., & Tungpunkom, P. (2015). Summarizing systematic reviews: methodological development, conduct and reporting of an umbrella review approach. JBI Evidence Implementation , 13 (3). https://doi.org/10.1097/XEB.0000000000000055 4. Introduction – ‘These studies did not consider overall health impacts’ – what does this statement mean exactly? Rephrase to make clear that full weight of evidence needs to be assessed to understand the nature of greenspace and health via an umbrella review, as described in the following sentence. We reworded this section of the Introduction for better understanding. 5. Introduction – Following the above point, what about reviews that address multiple health outcomes (e.g., Twohig-Bennett & Jones, 2018) [REF1]? Can they not provide useful information on overall health impacts as well? We reworded this section and have referenced Twohig-Bennett & Jones et al. 2018 in this section of the introduction. 6. Methods – Why are cardiovascular and metabolic outcomes combined? Cardiovascular and metabolic outcomes share common pathophysiological pathways and risk factors, making it logical to categorise them together. Greenspace exposure is hypothesised to influence these outcomes through shared mechanisms. 7. Results – Did you search the references of included papers? If so, were any additional papers identified? Typically, reviews include flow charts to show the start and end number of papers. Manual reference search is described in the ‘Search strategy’ section of the methods. As per the F1000 guidelines, a PRISMA flowchart for this review is available under the ‘Data availability’ -> ‘Reporting guidelines’ section at the end of the article. 8. Table 1- Why is the sample size for Carver et al. ‘NA’? This has been fixed to show the minimum and maximum sample size for Carver et al. 2020. 9. Table 1 – Define ‘NA’ with other short-forms This has been added. 10. Table 3 – Add a ‘*’ or similar next to ‘Other’ to indicate that the specific exposures are given below. This has been adjusted. 11. Results – ‘Maternal health…’ – Change to ‘OR=0.80…’ for consistency. This has been adjusted. 12. Results – ‘Maternal health…’ – What do the Lee et al βs represent? The definition has been added to the first instance of β. 13. Table 5 – Title should refer to ‘meta-analyses’, otherwise it is not clear how the effect estimates were calculated. It would also be helpful to add the increment that the estimates represent (e.g. per 0.1 increase in NDVI) This has been adjusted. Also, we thoroughly reviewed this Table. 14. Figure 1 – The methods should state how the overall risk of bias was determined (e.g., highest individual risk?). Also, the text accompanying the Figure, ‘…lighter colours concern judgments’ is not clear. Are these the individual risk of bias criteria? If so, state that. ROBIS was used to assess the risk of bias of each systematic review. ROBIS consists of four domains, and within each domain, there are five to six signalling questions. Two reviewers went through each signalling question, and judgments were made independently. These domains were then used to determine the overall risk of bias of each review. Conflicts between the reviewers were resolved through discussion with the last author. For each review, the final decision on four domains and the overall risk of bias is listed in Supplementary Table S2. Figure 1 is a summary of Supplementary Table S2, as per ROBIS guidelines. More information about ROBIS is available from Whiting et al. 2016. Whiting, P., Savovic, J., Higgins, J. P., Caldwell, D. M., Reeves, B. C., Shea, B., Davies, P., Kleijnen, J., Churchill, R., & group, R. (2016). ROBIS: A new tool to assess risk of bias in systematic reviews was developed. Journal of Clinical Epidemiology , 69 , 225-234. https://doi.org/10.1016/j.jclinepi.2015.06.005 We have altered the Figure caption to improve the readability of the graph. 15. Results – Risk of bias – why was the risk in some cases ‘unclear’? Was there not enough information to determine if a criterion was met? Wouldn’t that suggest it was not met and that it is likely to be a source of bias? This point should be considered. As per the guidance on how to use ROBIS, an ‘unclear’ rating indicates that insufficient data were reported to permit a judgment for signalling questions within a domain (Phase 2). If something is not reported, it could be a potential source of bias. That’s why ROBIS has the unclear category, because if the information isn’t reported, you cannot make a definitive statement about whether the bias is high or low. 16. Discussion – A stronger conclusion should be reached other than there may be an association between greenspace and health. For example, there appears to be stronger evidence for mental health, all-cause and CVD mortality. Are the specific pathways to health offered by greenspace more relevant for these outcomes? In this narrative synthesis, stronger conclusions for each health outcome could lead to overstatements of the associations. Inconsistent findings within each health outcome, with varying effect measures, also make it challenging to report definitive conclusions. Some pathways may be more related to specific health outcomes and have been explored in more depth by other researchers (Markevych et al., 2017). However, these biological mechanisms are beyond the scope of this Discussion section. Markevych, I., Schoierer, J., Hartig, T., Chudnovsky, A., Hystad, P.,…. & Fuertes, E. (2017). Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental Research, 158, 301-317. https://doi.org/10.1016/j.envres.2017.06.028 17. Table 6 – Without knowing the AMSTAR-2 questions or how they were rated, this table is not very intuitive. The other tables are informative and effective at summarising the reviews and results. We have added the shortened AMSTAR-2 questions as a footnote to the table. The other reviewer also mentioned this table and we have coloured the overall quality column to improve readability. A graph showing the distribution of high, moderate, and low-quality reviews is also available in the supplementary material. 18. Discussion – discussion of study limitations should be mentioned. The limitations of the review have been discussed in the last paragraph of the discussion. We revisited this paragraph to improve the clarity. Competing Interests: No competing interests. Close Report a concern COMMENT ON THIS REPORT Views 0 Cite How to cite this report: Huang W. Reviewer Report For: Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.5256/f1000research.163252.r284710 ) The direct URL for this report is: https://f1000research.com/articles/13-491/v1#referee-response-284710 NOTE: it is important to ensure the information in square brackets after the title is included in this citation. Close Copy Citation Details Reviewer Report 10 Jun 2024 Wenzhong Huang , Monash University, Melbourne, Australia Approved with Reservations VIEWS 0 https://doi.org/10.5256/f1000research.163252.r284710 mandatory reviewer questions Is the topic of the review discussed comprehensively in the context of the current literature? Yes Are all factual statements correct and adequately supported by citations? Mostly Is ... Continue reading READ ALL mandatory reviewer questions Is the topic of the review discussed comprehensively in the context of the current literature? Yes Are all factual statements correct and adequately supported by citations? Mostly Is the review written in accessible language? Yes Are the conclusions drawn appropriate in the context of the current research literature? Yes Specific comments: This study is a well-written umbrella review that synthesized systematic reviews on the associations of greenness and all kinds of health outcomes. I appreciate the great amount of work by the authors. I believe this study does have some value and can advance knowledge in this field. However, given the similarities to recent work by Stier-Jarmer et al. (2021)[Ref 1] and Yang et al. (2021)[Ref 2], I had the following suggestions/comments in an attempt to enhance the significance of this study. Introduction I appreciate the authors' introduction of two highly relevant umbrella reviews that incorporate the latest research advancements. Highlighting the advances of this study compared to these two reviews is crucial to justify its significance. However, the clarity of the following points could be improved: For instance, the review by van den Bosch and Ode Sang (2017) [Ref 3] includes both green and blue spaces, suggesting their work is more comprehensive than reviews focusing solely on green spaces. Therefore, it seems illogical for the authors to claim that the conclusions drawn from this study do not adequately represent the impact of green space exposure. Regarding the high-impact umbrella review by Yang et al., the authors mention a limitation involving the grouping of cancer and respiratory mortality into the section of ”other health outcomes”. This grouping likely resulted from the small number of studies on these topics and should not lead to outcome misclassification. Because Yang et al. could still discuss the findings for cancer and respiratory mortality separately. Additionally, including systematic reviews with variables such as physical activity, time spent outdoors, prosocial behavior, and murder as health outcomes does not appear to be a limitation. These reviews should encompass the health effects of greenness, (e.g., studies investigating the association of green spaces with health and the role of physical activity on the associations). In summary, the limitations mentioned by the authors are unclear and illogical to me. I understand and appreciate that this work possesses four important qualities compared to previous studies, as clearly mentioned in the last sentence of the Introduction. However, the significance of this research would be greatly enhanced if the authors provided clearer clarifications regarding the mentioned limitations of previous studies and how this study advances the field by addressing those limitations. Methods "We restricted the search to peer-reviewed systematic reviews and meta-analyses conducted in humans and published in English between January 2010 and December 2020, including reviews first published online during this period". Given the dramatic increase in publications on greenness and health in recent years, the quality of this study would be substantially improved if the authors included up-to-date reviews (i.e., from 2010 to the present, rather than 2010-2020). This inclusion can be mentioned as a major strength compared to previous umbrella reviews, as many high-quality studies and reviews have been published in the past three years. Full names should be provided for the abbreviations when they first appear in the main text (e.g., BMI, PA). Results It would be beneficial to include a flowchart illustrating the process used to select the final 36 systematic reviews (e.g., the number of studies excluded due to each specific exclusion criterion). It might be better to visualize the study design, measures of greenness, location of studies (country/territory), and outcomes in a figure rather than in several separate tables. A good example can be seen in https://link.springer.com/article/10.1007/s40572-023-00420-9 (Figure 2) Table 4. I appreciate the authors' usage of ICD-code to define the outcomes. However, if I understand it correctly, the original studies in these included reviews may not necessarily and consistently define their outcomes based on these ICD codes, right? If so, this table might be misleading. Why not combine Table 5 and Table 1, they have duplicated information. "Half of the systematic reviews (50%) had a high risk of bias“. This proportion is quite high. It would be better for the authors to clarify how they assigned the level of ROB to each of the reviews (e.g., using a table with the same structure as Table S2 to list the reason why each level was assigned). This was just a recommendation, but at least the authors should provide more clarifications and discuss this point. Currently, there are very few words on it. Consistent with the previous comment, a relatively high proportion of the included reviews were also classified as low quality. Providing more clarifications on this point would make this study stronger. Table 6, please clarify the meanings of these words (e.g., N, PY, NA) in the table caption. It would be better to assign the cell background with a color to indicate the quality level (e.g., red for low quality, green for high quality). This can improve the readability dramatically. Discussion "Additionally, we observed positive associations between greenspace exposure and maternal health and birth outcomes including PTB and SGA which were not present in other studies (Yang et al., 2021).” These observed positive associations between greenspace exposure and maternal health and birth outcomes including PTB and SGA were not that consistent compared to the outcomes of mental health and cognitive function, right? If so, this may be the reason why previous studies hadn't reported them in the main findings. "Conversely, Stier-Jarmer et al. (2021) and Yang et al. (2021) reported beneficial effects of greenspace on cardiovascular health and cardiometabolic factors, respectively, which was not replicated in our study.” This may be attributable to the fact that some reviews on this aspect were excluded in this umbrella review, while included in Stier-Jarmer et al. (2021) and Yang et al. (2021) due to the different inclusion and exclusion criteria (e.g., scoping reviews on greenness and CVD). Anyway, this should be discussed. "Current evidence, including this umbrella review, have been unable to establish a causal link between greenspace exposure and health outcomes as most studies are observational. This highlights the need for additional experimental studies to be conducted” Population-based experimental studies are often unfeasible and also subject to numerous biases (e.g., usually very small sample size, non-adherence). Given the very large proportion of cross-sectional studies, it is more practical to suggest more studies with longitudinal or cohort design and causal inference models (e.g., Instrumental Variables Analysis). "Most systematic reviews included in this review were limited by their methodological quality and/or risk of bias, and systematic reviews on the association between greenspace exposure and health outcomes have multiplied since 2020.” I am confused. The authors only included reviews between 2010-2020 and did not include reviews after 2020, as stated in the method section. Are the rationale for, and objectives of, the Systematic Review clearly stated? Yes Are sufficient details of the methods and analysis provided to allow replication by others? Yes Is the statistical analysis and its interpretation appropriate? Partly Are the conclusions drawn adequately supported by the results presented in the review? Yes If this is a Living Systematic Review, is the ‘living’ method appropriate and is the search schedule clearly defined and justified? (‘Living Systematic Review’ or a variation of this term should be included in the title.) Not applicable References 1. Stier-Jarmer M, Throner V, Kirschneck M, Immich G, et al.: The Psychological and Physical Effects of Forests on Human Health: A Systematic Review of Systematic Reviews and Meta-Analyses. Int J Environ Res Public Health . 2021; 18 (4). PubMed Abstract | Publisher Full Text 2. Yang BY, Zhao T, Hu LX, Browning MHEM, et al.: Greenspace and human health: An umbrella review. Innovation (Camb) . 2021; 2 (4): 100164 PubMed Abstract | Publisher Full Text 3. van den Bosch M, Ode Sang Å: Urban natural environments as nature-based solutions for improved public health - A systematic review of reviews. Environ Res . 2017; 158 : 373-384 PubMed Abstract | Publisher Full Text Competing Interests: No competing interests were disclosed. Reviewer Expertise: Environmental epidemiolgy; greenness, air pollution, climate change and health I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. Close READ LESS CITE CITE HOW TO CITE THIS REPORT Huang W. Reviewer Report For: Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.5256/f1000research.163252.r284710 ) The direct URL for this report is: https://f1000research.com/articles/13-491/v1#referee-response-284710 NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article. COPY CITATION DETAILS Report a concern Author Response 09 Aug 2025 Darsy Darssan , School of Public Health, The University of Queensland, Herston, Australia 09 Aug 2025 Author Response Response to reviewer comments We are grateful for the valuable and detailed comments on our manuscript. We have thoughtfully reviewed and integrated your recommendations to the extent possible. Introduction ... Continue reading Response to reviewer comments We are grateful for the valuable and detailed comments on our manuscript. We have thoughtfully reviewed and integrated your recommendations to the extent possible. Introduction I appreciate the authors' introduction of two highly relevant umbrella reviews that incorporate the latest research advancements. Highlighting the advances of this study compared to these two reviews is crucial to justify its significance. However, the clarity of the following points could be improved: For instance, the review by van den Bosch and Ode Sang (2017) [Ref 3] includes both green and blue spaces, suggesting their work is more comprehensive than reviews focusing solely on green spaces. Therefore, it seems illogical for the authors to claim that the conclusions drawn from this study do not adequately represent the impact of green space exposure. Our introduction does not claim that it inadequately represents the impact of greenspace exposure; rather, it assesses a composite of both greenspace and blue space effects on health. We have also amended the sentence to make this clearer. Regarding the high-impact umbrella review by Yang et al., the authors mention a limitation involving the grouping of cancer and respiratory mortality into the section of ”other health outcomes”. This grouping likely resulted from the small number of studies on these topics and should not lead to outcome misclassification. Because Yang et al. could still discuss the findings for cancer and respiratory mortality separately. We have removed the section about cancer and respiratory health from this sentence. Additionally, including systematic reviews with variables such as physical activity, time spent outdoors, prosocial behavior, and murder as health outcomes does not appear to be a limitation. These reviews should encompass the health effects of greenness, (e.g., studies investigating the association of green spaces with health and the role of physical activity on the associations). In summary, the limitations mentioned by the authors are unclear and illogical to me. Per the World Health Organization (WHO), “The determinants of health include: the social and economic environment, the physical environment, and the person’s individual characteristics and behaviours” (AIHW, 2024). Physical activity is classified as a behaviour (Chevance et al., 2019), making it a health determinant. Health determinants, such as physical activity or diet, contribute to health outcomes; however, as explained in our methods section, our review excluded studies that only considered health determinants. As you mention, physical activity plays a role in the association between greenspace and health outcomes (Chen et al., 2021), but it is not a health outcome itself. In our discussion, we explore physical activity as a pathway between greenspace exposure and health outcomes. World Health Organization (WHO). (2024). Determinants of health. https://www.who.int/news-room/questions-and-answers/item/determinants-of-health Chevance, G., Bernard, P., Chamberland, P. E., & Rebar, A. (2019). The association between implicit attitudes toward physical activity and physical activity behaviour: a systematic review and correlational meta-analysis. Health Psychology Review , 13 (3), 248–276. https://doi.org/10.1080/17437199.2019.1618726 Chen, K., Zhang, T., Liu, F., Zhang, Y., & Song, Y. (2021). How Does Urban Green Space Impact Residents' Mental Health: A Literature Review of Mediators. International journal of environmental research and public health , 18 (22), 11746. https://doi.org/10.3390/ijerph182211746 Australian Institute of Health and Welfare. (2024). Social determinants of health. Retrieved from https://www.aihw.gov.au/reports/australias-health/social-determinants-of-health We revisited this section of the Introduction to improve the clarity. I understand and appreciate that this work possesses four important qualities compared to previous studies, as clearly mentioned in the last sentence of the Introduction. Thank you, these four qualities are a major strength of this research. However, the significance of this research would be greatly enhanced if the authors provided clearer clarifications regarding the mentioned limitations of previous studies and how this study advances the field by addressing those limitations. The limitations of the previous studies are: 1. Do not isolate the impact of greenspace exposure alone on health outcomes, as its effects are confounded by blue space. 2. Do not isolate the impact of greenspace exposure on health outcomes alone, independent of health determinants 3. Included scoping reviews in their umbrella review. To address these limitations, our review assesses the association between greenspace exposure and health outcomes, independent of blue space and health determinants. As per Pollack et al. 2023 and Aromataris 2015, an umbrella review should only include systematic reviews and meta-analyses. Therefore, we excluded scoping reviews. Pollock, M., Fernandes, R. M., Becker, L. A., Pieper, D., Hartling, L. Chapter V: Overviews of Reviews [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from www.training.cochrane.org/handbook . Aromataris, E., Fernandez, R., Godfrey, C. M., Holly, C., Khalil, H., & Tungpunkom, P. (2015). Summarizing systematic reviews: methodological development, conduct and reporting of an umbrella review approach. JBI Evidence Implementation , 13 (3). https://doi.org/10.1097/XEB.0000000000000055 Methods "We restricted the search to peer-reviewed systematic reviews and meta-analyses conducted in humans and published in English between January 2010 and December 2020, including reviews first published online during this period". Given the dramatic increase in publications on greenness and health in recent years, the quality of this study would be substantially improved if the authors included up-to-date reviews (i.e., from 2010 to the present, rather than 2010-2020). This inclusion can be mentioned as a major strength compared to previous umbrella reviews, as many high-quality studies and reviews have been published in the past three years. This review includes 36 systematic reviews published between January 2010 and December 2020. As you mentioned, much research on greenspace and health, including reviews, has been published since December 2020. We identified an additional 45 review articles between December 2020 and June 2024. Combining these two umbrella reviews would be too many systematic reviews to include in a single umbrella review. As per the Cochrane guidelines (Cumpston and Flemyng, 2023), we have updated the review due to “the availability of new evidence that would have a meaningful impact on the review findings”. [Please see our updated review here, https://doi.org/10.12688/f1000research.166852.1 ]. Cumpston, M., Flemyng, E., Chapter IV: Updating a review [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-iv Full names should be provided for the abbreviations when they first appear in the main text (e.g., BMI, PA). This has been fixed. Results It would be beneficial to include a flowchart illustrating the process used to select the final 36 systematic reviews (e.g., the number of studies excluded due to each specific exclusion criterion). As per the F1000 guidelines, a PRISMA flowchart for this review is available under the ‘Data availability’ à ‘Reporting guidelines’ section at the end of the article. It might be better to visualize the study design, measures of greenness, location of studies (country/territory), and outcomes in a figure rather than in several separate tables. A good example can be seen in https://link.springer.com/article/10.1007/s40572-023-00420-9 (Figure 2) We agree that visualising these tables would be useful. However, the example given here, Figure 2, may be misleading. For instance, Figure 2 suggests that all ecological studies investigate respiratory outcomes; however, this is not the case, as indicated in Table S6 of the example. We attempted to create multi-level pie charts to visualise our Tables but found that this was too crowded and inefficient. After several attempts, we decided not to present these multi-level pie charts. Table 4. I appreciate the authors' usage of ICD-code to define the outcomes. However, if I understand it correctly, the original studies in these included reviews may not necessarily and consistently define their outcomes based on these ICD codes, right? If so, this table might be misleading. You are correct that the original studies may not have defined the outcomes based on the ICD codes. Based on the information available in the reviews, we allocated all potential ICD codes for each health outcome. We did this to promote standardised reporting in future articles that investigate the association between greenspace exposure and health outcomes. Why not combine Table 5 and Table 1, they have duplicated information. Table 5 summarises the quantitative results from the included reviews and does not duplicate information from Table 1. "Half of the systematic reviews (50%) had a high risk of bias“. This proportion is quite high. It would be better for the authors to clarify how they assigned the level of ROB to each of the reviews (e.g., using a table with the same structure as Table S2 to list the reason why each level was assigned). This was just a recommendation, but at least the authors should provide more clarifications and discuss this point. Currently, there are very few words on it. ROBIS consists of four domains, and within each domain, there are five to six signalling questions. Two reviewers went through each signalling question, and judgments were made independently. These domains were then used to determine the overall risk of bias of each review. Conflicts between the reviewers were resolved through discussion with the last author. For each review, the final decision on four domains and the overall risk of bias is listed in Supplementary Table S2. More information about ROBIS is available from Whiting et al. 2016. Whiting, P., Savovic, J., Higgins, J. P., Caldwell, D. M., Reeves, B. C., Shea, B., Davies, P., Kleijnen, J., Churchill, R., & group, R. (2016). ROBIS: A new tool to assess risk of bias in systematic reviews was developed. Journal of Clinical Epidemiology , 69 , 225-234. https://doi.org/10.1016/j.jclinepi.2015.06.005 Consistent with the previous comment, a relatively high proportion of the included reviews were also classified as low quality. Providing more clarifications on this point would make this study stronger. Table 6, please clarify the meanings of these words (e.g., N, PY, NA) in the table caption. It would be better to assign the cell background with a color to indicate the quality level (e.g., red for low quality, green for high quality). This can improve the readability dramatically. We have added the meanings of the AMSTAR abbreviations and have added colour to the overall quality column to increase readability. We have also added a footnote explaining the AMSTAR-2 questions, so the reader understands how the quality rating was decided. Discussion "Additionally, we observed positive associations between greenspace exposure and maternal health and birth outcomes including PTB and SGA which were not present in other studies (Yang et al., 2021).” These observed positive associations between greenspace exposure and maternal health and birth outcomes including PTB and SGA were not that consistent compared to the outcomes of mental health and cognitive function, right? If so, this may be the reason why previous studies hadn't reported them in the main findings. We revised this sentence. "Conversely, Stier-Jarmer et al. (2021) and Yang et al. (2021) reported beneficial effects of greenspace on cardiovascular health and cardiometabolic factors, respectively, which was not replicated in our study.” This may be attributable to the fact that some reviews on this aspect were excluded in this umbrella review, while included in Stier-Jarmer et al. (2021) and Yang et al. (2021) due to the different inclusion and exclusion criteria (e.g., scoping reviews on greenness and CVD). Anyway, this should be discussed. We revised this sentence. "Current evidence, including this umbrella review, have been unable to establish a causal link between greenspace exposure and health outcomes as most studies are observational. This highlights the need for additional experimental studies to be conducted” Population-based experimental studies are often unfeasible and also subject to numerous biases (e.g., usually very small sample size, non-adherence). Given the very large proportion of cross-sectional studies, it is more practical to suggest more studies with longitudinal or cohort design and causal inference models (e.g., Instrumental Variables Analysis). We agree that population-based experimental studies are rare. We have revised this sentence accordingly. "Most systematic reviews included in this review were limited by their methodological quality and/or risk of bias, and systematic reviews on the association between greenspace exposure and health outcomes have multiplied since 2020.” I am confused. The authors only included reviews between 2010-2020 and did not include reviews after 2020, as stated in the method section. We revised this sentence Response to reviewer comments We are grateful for the valuable and detailed comments on our manuscript. We have thoughtfully reviewed and integrated your recommendations to the extent possible. Introduction I appreciate the authors' introduction of two highly relevant umbrella reviews that incorporate the latest research advancements. Highlighting the advances of this study compared to these two reviews is crucial to justify its significance. However, the clarity of the following points could be improved: For instance, the review by van den Bosch and Ode Sang (2017) [Ref 3] includes both green and blue spaces, suggesting their work is more comprehensive than reviews focusing solely on green spaces. Therefore, it seems illogical for the authors to claim that the conclusions drawn from this study do not adequately represent the impact of green space exposure. Our introduction does not claim that it inadequately represents the impact of greenspace exposure; rather, it assesses a composite of both greenspace and blue space effects on health. We have also amended the sentence to make this clearer. Regarding the high-impact umbrella review by Yang et al., the authors mention a limitation involving the grouping of cancer and respiratory mortality into the section of ”other health outcomes”. This grouping likely resulted from the small number of studies on these topics and should not lead to outcome misclassification. Because Yang et al. could still discuss the findings for cancer and respiratory mortality separately. We have removed the section about cancer and respiratory health from this sentence. Additionally, including systematic reviews with variables such as physical activity, time spent outdoors, prosocial behavior, and murder as health outcomes does not appear to be a limitation. These reviews should encompass the health effects of greenness, (e.g., studies investigating the association of green spaces with health and the role of physical activity on the associations). In summary, the limitations mentioned by the authors are unclear and illogical to me. Per the World Health Organization (WHO), “The determinants of health include: the social and economic environment, the physical environment, and the person’s individual characteristics and behaviours” (AIHW, 2024). Physical activity is classified as a behaviour (Chevance et al., 2019), making it a health determinant. Health determinants, such as physical activity or diet, contribute to health outcomes; however, as explained in our methods section, our review excluded studies that only considered health determinants. As you mention, physical activity plays a role in the association between greenspace and health outcomes (Chen et al., 2021), but it is not a health outcome itself. In our discussion, we explore physical activity as a pathway between greenspace exposure and health outcomes. World Health Organization (WHO). (2024). Determinants of health. https://www.who.int/news-room/questions-and-answers/item/determinants-of-health Chevance, G., Bernard, P., Chamberland, P. E., & Rebar, A. (2019). The association between implicit attitudes toward physical activity and physical activity behaviour: a systematic review and correlational meta-analysis. Health Psychology Review , 13 (3), 248–276. https://doi.org/10.1080/17437199.2019.1618726 Chen, K., Zhang, T., Liu, F., Zhang, Y., & Song, Y. (2021). How Does Urban Green Space Impact Residents' Mental Health: A Literature Review of Mediators. International journal of environmental research and public health , 18 (22), 11746. https://doi.org/10.3390/ijerph182211746 Australian Institute of Health and Welfare. (2024). Social determinants of health. Retrieved from https://www.aihw.gov.au/reports/australias-health/social-determinants-of-health We revisited this section of the Introduction to improve the clarity. I understand and appreciate that this work possesses four important qualities compared to previous studies, as clearly mentioned in the last sentence of the Introduction. Thank you, these four qualities are a major strength of this research. However, the significance of this research would be greatly enhanced if the authors provided clearer clarifications regarding the mentioned limitations of previous studies and how this study advances the field by addressing those limitations. The limitations of the previous studies are: 1. Do not isolate the impact of greenspace exposure alone on health outcomes, as its effects are confounded by blue space. 2. Do not isolate the impact of greenspace exposure on health outcomes alone, independent of health determinants 3. Included scoping reviews in their umbrella review. To address these limitations, our review assesses the association between greenspace exposure and health outcomes, independent of blue space and health determinants. As per Pollack et al. 2023 and Aromataris 2015, an umbrella review should only include systematic reviews and meta-analyses. Therefore, we excluded scoping reviews. Pollock, M., Fernandes, R. M., Becker, L. A., Pieper, D., Hartling, L. Chapter V: Overviews of Reviews [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from www.training.cochrane.org/handbook . Aromataris, E., Fernandez, R., Godfrey, C. M., Holly, C., Khalil, H., & Tungpunkom, P. (2015). Summarizing systematic reviews: methodological development, conduct and reporting of an umbrella review approach. JBI Evidence Implementation , 13 (3). https://doi.org/10.1097/XEB.0000000000000055 Methods "We restricted the search to peer-reviewed systematic reviews and meta-analyses conducted in humans and published in English between January 2010 and December 2020, including reviews first published online during this period". Given the dramatic increase in publications on greenness and health in recent years, the quality of this study would be substantially improved if the authors included up-to-date reviews (i.e., from 2010 to the present, rather than 2010-2020). This inclusion can be mentioned as a major strength compared to previous umbrella reviews, as many high-quality studies and reviews have been published in the past three years. This review includes 36 systematic reviews published between January 2010 and December 2020. As you mentioned, much research on greenspace and health, including reviews, has been published since December 2020. We identified an additional 45 review articles between December 2020 and June 2024. Combining these two umbrella reviews would be too many systematic reviews to include in a single umbrella review. As per the Cochrane guidelines (Cumpston and Flemyng, 2023), we have updated the review due to “the availability of new evidence that would have a meaningful impact on the review findings”. [Please see our updated review here, https://doi.org/10.12688/f1000research.166852.1 ]. Cumpston, M., Flemyng, E., Chapter IV: Updating a review [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-iv Full names should be provided for the abbreviations when they first appear in the main text (e.g., BMI, PA). This has been fixed. Results It would be beneficial to include a flowchart illustrating the process used to select the final 36 systematic reviews (e.g., the number of studies excluded due to each specific exclusion criterion). As per the F1000 guidelines, a PRISMA flowchart for this review is available under the ‘Data availability’ à ‘Reporting guidelines’ section at the end of the article. It might be better to visualize the study design, measures of greenness, location of studies (country/territory), and outcomes in a figure rather than in several separate tables. A good example can be seen in https://link.springer.com/article/10.1007/s40572-023-00420-9 (Figure 2) We agree that visualising these tables would be useful. However, the example given here, Figure 2, may be misleading. For instance, Figure 2 suggests that all ecological studies investigate respiratory outcomes; however, this is not the case, as indicated in Table S6 of the example. We attempted to create multi-level pie charts to visualise our Tables but found that this was too crowded and inefficient. After several attempts, we decided not to present these multi-level pie charts. Table 4. I appreciate the authors' usage of ICD-code to define the outcomes. However, if I understand it correctly, the original studies in these included reviews may not necessarily and consistently define their outcomes based on these ICD codes, right? If so, this table might be misleading. You are correct that the original studies may not have defined the outcomes based on the ICD codes. Based on the information available in the reviews, we allocated all potential ICD codes for each health outcome. We did this to promote standardised reporting in future articles that investigate the association between greenspace exposure and health outcomes. Why not combine Table 5 and Table 1, they have duplicated information. Table 5 summarises the quantitative results from the included reviews and does not duplicate information from Table 1. "Half of the systematic reviews (50%) had a high risk of bias“. This proportion is quite high. It would be better for the authors to clarify how they assigned the level of ROB to each of the reviews (e.g., using a table with the same structure as Table S2 to list the reason why each level was assigned). This was just a recommendation, but at least the authors should provide more clarifications and discuss this point. Currently, there are very few words on it. ROBIS consists of four domains, and within each domain, there are five to six signalling questions. Two reviewers went through each signalling question, and judgments were made independently. These domains were then used to determine the overall risk of bias of each review. Conflicts between the reviewers were resolved through discussion with the last author. For each review, the final decision on four domains and the overall risk of bias is listed in Supplementary Table S2. More information about ROBIS is available from Whiting et al. 2016. Whiting, P., Savovic, J., Higgins, J. P., Caldwell, D. M., Reeves, B. C., Shea, B., Davies, P., Kleijnen, J., Churchill, R., & group, R. (2016). ROBIS: A new tool to assess risk of bias in systematic reviews was developed. Journal of Clinical Epidemiology , 69 , 225-234. https://doi.org/10.1016/j.jclinepi.2015.06.005 Consistent with the previous comment, a relatively high proportion of the included reviews were also classified as low quality. Providing more clarifications on this point would make this study stronger. Table 6, please clarify the meanings of these words (e.g., N, PY, NA) in the table caption. It would be better to assign the cell background with a color to indicate the quality level (e.g., red for low quality, green for high quality). This can improve the readability dramatically. We have added the meanings of the AMSTAR abbreviations and have added colour to the overall quality column to increase readability. We have also added a footnote explaining the AMSTAR-2 questions, so the reader understands how the quality rating was decided. Discussion "Additionally, we observed positive associations between greenspace exposure and maternal health and birth outcomes including PTB and SGA which were not present in other studies (Yang et al., 2021).” These observed positive associations between greenspace exposure and maternal health and birth outcomes including PTB and SGA were not that consistent compared to the outcomes of mental health and cognitive function, right? If so, this may be the reason why previous studies hadn't reported them in the main findings. We revised this sentence. "Conversely, Stier-Jarmer et al. (2021) and Yang et al. (2021) reported beneficial effects of greenspace on cardiovascular health and cardiometabolic factors, respectively, which was not replicated in our study.” This may be attributable to the fact that some reviews on this aspect were excluded in this umbrella review, while included in Stier-Jarmer et al. (2021) and Yang et al. (2021) due to the different inclusion and exclusion criteria (e.g., scoping reviews on greenness and CVD). Anyway, this should be discussed. We revised this sentence. "Current evidence, including this umbrella review, have been unable to establish a causal link between greenspace exposure and health outcomes as most studies are observational. This highlights the need for additional experimental studies to be conducted” Population-based experimental studies are often unfeasible and also subject to numerous biases (e.g., usually very small sample size, non-adherence). Given the very large proportion of cross-sectional studies, it is more practical to suggest more studies with longitudinal or cohort design and causal inference models (e.g., Instrumental Variables Analysis). We agree that population-based experimental studies are rare. We have revised this sentence accordingly. "Most systematic reviews included in this review were limited by their methodological quality and/or risk of bias, and systematic reviews on the association between greenspace exposure and health outcomes have multiplied since 2020.” I am confused. The authors only included reviews between 2010-2020 and did not include reviews after 2020, as stated in the method section. We revised this sentence Competing Interests: No competing interests. Close Report a concern Respond or Comment COMMENTS ON THIS REPORT Author Response 09 Aug 2025 Darsy Darssan , School of Public Health, The University of Queensland, Herston, Australia 09 Aug 2025 Author Response Response to reviewer comments We are grateful for the valuable and detailed comments on our manuscript. We have thoughtfully reviewed and integrated your recommendations to the extent possible. Introduction ... Continue reading Response to reviewer comments We are grateful for the valuable and detailed comments on our manuscript. We have thoughtfully reviewed and integrated your recommendations to the extent possible. Introduction I appreciate the authors' introduction of two highly relevant umbrella reviews that incorporate the latest research advancements. Highlighting the advances of this study compared to these two reviews is crucial to justify its significance. However, the clarity of the following points could be improved: For instance, the review by van den Bosch and Ode Sang (2017) [Ref 3] includes both green and blue spaces, suggesting their work is more comprehensive than reviews focusing solely on green spaces. Therefore, it seems illogical for the authors to claim that the conclusions drawn from this study do not adequately represent the impact of green space exposure. Our introduction does not claim that it inadequately represents the impact of greenspace exposure; rather, it assesses a composite of both greenspace and blue space effects on health. We have also amended the sentence to make this clearer. Regarding the high-impact umbrella review by Yang et al., the authors mention a limitation involving the grouping of cancer and respiratory mortality into the section of ”other health outcomes”. This grouping likely resulted from the small number of studies on these topics and should not lead to outcome misclassification. Because Yang et al. could still discuss the findings for cancer and respiratory mortality separately. We have removed the section about cancer and respiratory health from this sentence. Additionally, including systematic reviews with variables such as physical activity, time spent outdoors, prosocial behavior, and murder as health outcomes does not appear to be a limitation. These reviews should encompass the health effects of greenness, (e.g., studies investigating the association of green spaces with health and the role of physical activity on the associations). In summary, the limitations mentioned by the authors are unclear and illogical to me. Per the World Health Organization (WHO), “The determinants of health include: the social and economic environment, the physical environment, and the person’s individual characteristics and behaviours” (AIHW, 2024). Physical activity is classified as a behaviour (Chevance et al., 2019), making it a health determinant. Health determinants, such as physical activity or diet, contribute to health outcomes; however, as explained in our methods section, our review excluded studies that only considered health determinants. As you mention, physical activity plays a role in the association between greenspace and health outcomes (Chen et al., 2021), but it is not a health outcome itself. In our discussion, we explore physical activity as a pathway between greenspace exposure and health outcomes. World Health Organization (WHO). (2024). Determinants of health. https://www.who.int/news-room/questions-and-answers/item/determinants-of-health Chevance, G., Bernard, P., Chamberland, P. E., & Rebar, A. (2019). The association between implicit attitudes toward physical activity and physical activity behaviour: a systematic review and correlational meta-analysis. Health Psychology Review , 13 (3), 248–276. https://doi.org/10.1080/17437199.2019.1618726 Chen, K., Zhang, T., Liu, F., Zhang, Y., & Song, Y. (2021). How Does Urban Green Space Impact Residents' Mental Health: A Literature Review of Mediators. International journal of environmental research and public health , 18 (22), 11746. https://doi.org/10.3390/ijerph182211746 Australian Institute of Health and Welfare. (2024). Social determinants of health. Retrieved from https://www.aihw.gov.au/reports/australias-health/social-determinants-of-health We revisited this section of the Introduction to improve the clarity. I understand and appreciate that this work possesses four important qualities compared to previous studies, as clearly mentioned in the last sentence of the Introduction. Thank you, these four qualities are a major strength of this research. However, the significance of this research would be greatly enhanced if the authors provided clearer clarifications regarding the mentioned limitations of previous studies and how this study advances the field by addressing those limitations. The limitations of the previous studies are: 1. Do not isolate the impact of greenspace exposure alone on health outcomes, as its effects are confounded by blue space. 2. Do not isolate the impact of greenspace exposure on health outcomes alone, independent of health determinants 3. Included scoping reviews in their umbrella review. To address these limitations, our review assesses the association between greenspace exposure and health outcomes, independent of blue space and health determinants. As per Pollack et al. 2023 and Aromataris 2015, an umbrella review should only include systematic reviews and meta-analyses. Therefore, we excluded scoping reviews. Pollock, M., Fernandes, R. M., Becker, L. A., Pieper, D., Hartling, L. Chapter V: Overviews of Reviews [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from www.training.cochrane.org/handbook . Aromataris, E., Fernandez, R., Godfrey, C. M., Holly, C., Khalil, H., & Tungpunkom, P. (2015). Summarizing systematic reviews: methodological development, conduct and reporting of an umbrella review approach. JBI Evidence Implementation , 13 (3). https://doi.org/10.1097/XEB.0000000000000055 Methods "We restricted the search to peer-reviewed systematic reviews and meta-analyses conducted in humans and published in English between January 2010 and December 2020, including reviews first published online during this period". Given the dramatic increase in publications on greenness and health in recent years, the quality of this study would be substantially improved if the authors included up-to-date reviews (i.e., from 2010 to the present, rather than 2010-2020). This inclusion can be mentioned as a major strength compared to previous umbrella reviews, as many high-quality studies and reviews have been published in the past three years. This review includes 36 systematic reviews published between January 2010 and December 2020. As you mentioned, much research on greenspace and health, including reviews, has been published since December 2020. We identified an additional 45 review articles between December 2020 and June 2024. Combining these two umbrella reviews would be too many systematic reviews to include in a single umbrella review. As per the Cochrane guidelines (Cumpston and Flemyng, 2023), we have updated the review due to “the availability of new evidence that would have a meaningful impact on the review findings”. [Please see our updated review here, https://doi.org/10.12688/f1000research.166852.1 ]. Cumpston, M., Flemyng, E., Chapter IV: Updating a review [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-iv Full names should be provided for the abbreviations when they first appear in the main text (e.g., BMI, PA). This has been fixed. Results It would be beneficial to include a flowchart illustrating the process used to select the final 36 systematic reviews (e.g., the number of studies excluded due to each specific exclusion criterion). As per the F1000 guidelines, a PRISMA flowchart for this review is available under the ‘Data availability’ à ‘Reporting guidelines’ section at the end of the article. It might be better to visualize the study design, measures of greenness, location of studies (country/territory), and outcomes in a figure rather than in several separate tables. A good example can be seen in https://link.springer.com/article/10.1007/s40572-023-00420-9 (Figure 2) We agree that visualising these tables would be useful. However, the example given here, Figure 2, may be misleading. For instance, Figure 2 suggests that all ecological studies investigate respiratory outcomes; however, this is not the case, as indicated in Table S6 of the example. We attempted to create multi-level pie charts to visualise our Tables but found that this was too crowded and inefficient. After several attempts, we decided not to present these multi-level pie charts. Table 4. I appreciate the authors' usage of ICD-code to define the outcomes. However, if I understand it correctly, the original studies in these included reviews may not necessarily and consistently define their outcomes based on these ICD codes, right? If so, this table might be misleading. You are correct that the original studies may not have defined the outcomes based on the ICD codes. Based on the information available in the reviews, we allocated all potential ICD codes for each health outcome. We did this to promote standardised reporting in future articles that investigate the association between greenspace exposure and health outcomes. Why not combine Table 5 and Table 1, they have duplicated information. Table 5 summarises the quantitative results from the included reviews and does not duplicate information from Table 1. "Half of the systematic reviews (50%) had a high risk of bias“. This proportion is quite high. It would be better for the authors to clarify how they assigned the level of ROB to each of the reviews (e.g., using a table with the same structure as Table S2 to list the reason why each level was assigned). This was just a recommendation, but at least the authors should provide more clarifications and discuss this point. Currently, there are very few words on it. ROBIS consists of four domains, and within each domain, there are five to six signalling questions. Two reviewers went through each signalling question, and judgments were made independently. These domains were then used to determine the overall risk of bias of each review. Conflicts between the reviewers were resolved through discussion with the last author. For each review, the final decision on four domains and the overall risk of bias is listed in Supplementary Table S2. More information about ROBIS is available from Whiting et al. 2016. Whiting, P., Savovic, J., Higgins, J. P., Caldwell, D. M., Reeves, B. C., Shea, B., Davies, P., Kleijnen, J., Churchill, R., & group, R. (2016). ROBIS: A new tool to assess risk of bias in systematic reviews was developed. Journal of Clinical Epidemiology , 69 , 225-234. https://doi.org/10.1016/j.jclinepi.2015.06.005 Consistent with the previous comment, a relatively high proportion of the included reviews were also classified as low quality. Providing more clarifications on this point would make this study stronger. Table 6, please clarify the meanings of these words (e.g., N, PY, NA) in the table caption. It would be better to assign the cell background with a color to indicate the quality level (e.g., red for low quality, green for high quality). This can improve the readability dramatically. We have added the meanings of the AMSTAR abbreviations and have added colour to the overall quality column to increase readability. We have also added a footnote explaining the AMSTAR-2 questions, so the reader understands how the quality rating was decided. Discussion "Additionally, we observed positive associations between greenspace exposure and maternal health and birth outcomes including PTB and SGA which were not present in other studies (Yang et al., 2021).” These observed positive associations between greenspace exposure and maternal health and birth outcomes including PTB and SGA were not that consistent compared to the outcomes of mental health and cognitive function, right? If so, this may be the reason why previous studies hadn't reported them in the main findings. We revised this sentence. "Conversely, Stier-Jarmer et al. (2021) and Yang et al. (2021) reported beneficial effects of greenspace on cardiovascular health and cardiometabolic factors, respectively, which was not replicated in our study.” This may be attributable to the fact that some reviews on this aspect were excluded in this umbrella review, while included in Stier-Jarmer et al. (2021) and Yang et al. (2021) due to the different inclusion and exclusion criteria (e.g., scoping reviews on greenness and CVD). Anyway, this should be discussed. We revised this sentence. "Current evidence, including this umbrella review, have been unable to establish a causal link between greenspace exposure and health outcomes as most studies are observational. This highlights the need for additional experimental studies to be conducted” Population-based experimental studies are often unfeasible and also subject to numerous biases (e.g., usually very small sample size, non-adherence). Given the very large proportion of cross-sectional studies, it is more practical to suggest more studies with longitudinal or cohort design and causal inference models (e.g., Instrumental Variables Analysis). We agree that population-based experimental studies are rare. We have revised this sentence accordingly. "Most systematic reviews included in this review were limited by their methodological quality and/or risk of bias, and systematic reviews on the association between greenspace exposure and health outcomes have multiplied since 2020.” I am confused. The authors only included reviews between 2010-2020 and did not include reviews after 2020, as stated in the method section. We revised this sentence Response to reviewer comments We are grateful for the valuable and detailed comments on our manuscript. We have thoughtfully reviewed and integrated your recommendations to the extent possible. Introduction I appreciate the authors' introduction of two highly relevant umbrella reviews that incorporate the latest research advancements. Highlighting the advances of this study compared to these two reviews is crucial to justify its significance. However, the clarity of the following points could be improved: For instance, the review by van den Bosch and Ode Sang (2017) [Ref 3] includes both green and blue spaces, suggesting their work is more comprehensive than reviews focusing solely on green spaces. Therefore, it seems illogical for the authors to claim that the conclusions drawn from this study do not adequately represent the impact of green space exposure. Our introduction does not claim that it inadequately represents the impact of greenspace exposure; rather, it assesses a composite of both greenspace and blue space effects on health. We have also amended the sentence to make this clearer. Regarding the high-impact umbrella review by Yang et al., the authors mention a limitation involving the grouping of cancer and respiratory mortality into the section of ”other health outcomes”. This grouping likely resulted from the small number of studies on these topics and should not lead to outcome misclassification. Because Yang et al. could still discuss the findings for cancer and respiratory mortality separately. We have removed the section about cancer and respiratory health from this sentence. Additionally, including systematic reviews with variables such as physical activity, time spent outdoors, prosocial behavior, and murder as health outcomes does not appear to be a limitation. These reviews should encompass the health effects of greenness, (e.g., studies investigating the association of green spaces with health and the role of physical activity on the associations). In summary, the limitations mentioned by the authors are unclear and illogical to me. Per the World Health Organization (WHO), “The determinants of health include: the social and economic environment, the physical environment, and the person’s individual characteristics and behaviours” (AIHW, 2024). Physical activity is classified as a behaviour (Chevance et al., 2019), making it a health determinant. Health determinants, such as physical activity or diet, contribute to health outcomes; however, as explained in our methods section, our review excluded studies that only considered health determinants. As you mention, physical activity plays a role in the association between greenspace and health outcomes (Chen et al., 2021), but it is not a health outcome itself. In our discussion, we explore physical activity as a pathway between greenspace exposure and health outcomes. World Health Organization (WHO). (2024). Determinants of health. https://www.who.int/news-room/questions-and-answers/item/determinants-of-health Chevance, G., Bernard, P., Chamberland, P. E., & Rebar, A. (2019). The association between implicit attitudes toward physical activity and physical activity behaviour: a systematic review and correlational meta-analysis. Health Psychology Review , 13 (3), 248–276. https://doi.org/10.1080/17437199.2019.1618726 Chen, K., Zhang, T., Liu, F., Zhang, Y., & Song, Y. (2021). How Does Urban Green Space Impact Residents' Mental Health: A Literature Review of Mediators. International journal of environmental research and public health , 18 (22), 11746. https://doi.org/10.3390/ijerph182211746 Australian Institute of Health and Welfare. (2024). Social determinants of health. Retrieved from https://www.aihw.gov.au/reports/australias-health/social-determinants-of-health We revisited this section of the Introduction to improve the clarity. I understand and appreciate that this work possesses four important qualities compared to previous studies, as clearly mentioned in the last sentence of the Introduction. Thank you, these four qualities are a major strength of this research. However, the significance of this research would be greatly enhanced if the authors provided clearer clarifications regarding the mentioned limitations of previous studies and how this study advances the field by addressing those limitations. The limitations of the previous studies are: 1. Do not isolate the impact of greenspace exposure alone on health outcomes, as its effects are confounded by blue space. 2. Do not isolate the impact of greenspace exposure on health outcomes alone, independent of health determinants 3. Included scoping reviews in their umbrella review. To address these limitations, our review assesses the association between greenspace exposure and health outcomes, independent of blue space and health determinants. As per Pollack et al. 2023 and Aromataris 2015, an umbrella review should only include systematic reviews and meta-analyses. Therefore, we excluded scoping reviews. Pollock, M., Fernandes, R. M., Becker, L. A., Pieper, D., Hartling, L. Chapter V: Overviews of Reviews [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from www.training.cochrane.org/handbook . Aromataris, E., Fernandez, R., Godfrey, C. M., Holly, C., Khalil, H., & Tungpunkom, P. (2015). Summarizing systematic reviews: methodological development, conduct and reporting of an umbrella review approach. JBI Evidence Implementation , 13 (3). https://doi.org/10.1097/XEB.0000000000000055 Methods "We restricted the search to peer-reviewed systematic reviews and meta-analyses conducted in humans and published in English between January 2010 and December 2020, including reviews first published online during this period". Given the dramatic increase in publications on greenness and health in recent years, the quality of this study would be substantially improved if the authors included up-to-date reviews (i.e., from 2010 to the present, rather than 2010-2020). This inclusion can be mentioned as a major strength compared to previous umbrella reviews, as many high-quality studies and reviews have been published in the past three years. This review includes 36 systematic reviews published between January 2010 and December 2020. As you mentioned, much research on greenspace and health, including reviews, has been published since December 2020. We identified an additional 45 review articles between December 2020 and June 2024. Combining these two umbrella reviews would be too many systematic reviews to include in a single umbrella review. As per the Cochrane guidelines (Cumpston and Flemyng, 2023), we have updated the review due to “the availability of new evidence that would have a meaningful impact on the review findings”. [Please see our updated review here, https://doi.org/10.12688/f1000research.166852.1 ]. Cumpston, M., Flemyng, E., Chapter IV: Updating a review [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-iv Full names should be provided for the abbreviations when they first appear in the main text (e.g., BMI, PA). This has been fixed. Results It would be beneficial to include a flowchart illustrating the process used to select the final 36 systematic reviews (e.g., the number of studies excluded due to each specific exclusion criterion). As per the F1000 guidelines, a PRISMA flowchart for this review is available under the ‘Data availability’ à ‘Reporting guidelines’ section at the end of the article. It might be better to visualize the study design, measures of greenness, location of studies (country/territory), and outcomes in a figure rather than in several separate tables. A good example can be seen in https://link.springer.com/article/10.1007/s40572-023-00420-9 (Figure 2) We agree that visualising these tables would be useful. However, the example given here, Figure 2, may be misleading. For instance, Figure 2 suggests that all ecological studies investigate respiratory outcomes; however, this is not the case, as indicated in Table S6 of the example. We attempted to create multi-level pie charts to visualise our Tables but found that this was too crowded and inefficient. After several attempts, we decided not to present these multi-level pie charts. Table 4. I appreciate the authors' usage of ICD-code to define the outcomes. However, if I understand it correctly, the original studies in these included reviews may not necessarily and consistently define their outcomes based on these ICD codes, right? If so, this table might be misleading. You are correct that the original studies may not have defined the outcomes based on the ICD codes. Based on the information available in the reviews, we allocated all potential ICD codes for each health outcome. We did this to promote standardised reporting in future articles that investigate the association between greenspace exposure and health outcomes. Why not combine Table 5 and Table 1, they have duplicated information. Table 5 summarises the quantitative results from the included reviews and does not duplicate information from Table 1. "Half of the systematic reviews (50%) had a high risk of bias“. This proportion is quite high. It would be better for the authors to clarify how they assigned the level of ROB to each of the reviews (e.g., using a table with the same structure as Table S2 to list the reason why each level was assigned). This was just a recommendation, but at least the authors should provide more clarifications and discuss this point. Currently, there are very few words on it. ROBIS consists of four domains, and within each domain, there are five to six signalling questions. Two reviewers went through each signalling question, and judgments were made independently. These domains were then used to determine the overall risk of bias of each review. Conflicts between the reviewers were resolved through discussion with the last author. For each review, the final decision on four domains and the overall risk of bias is listed in Supplementary Table S2. More information about ROBIS is available from Whiting et al. 2016. Whiting, P., Savovic, J., Higgins, J. P., Caldwell, D. M., Reeves, B. C., Shea, B., Davies, P., Kleijnen, J., Churchill, R., & group, R. (2016). ROBIS: A new tool to assess risk of bias in systematic reviews was developed. Journal of Clinical Epidemiology , 69 , 225-234. https://doi.org/10.1016/j.jclinepi.2015.06.005 Consistent with the previous comment, a relatively high proportion of the included reviews were also classified as low quality. Providing more clarifications on this point would make this study stronger. Table 6, please clarify the meanings of these words (e.g., N, PY, NA) in the table caption. It would be better to assign the cell background with a color to indicate the quality level (e.g., red for low quality, green for high quality). This can improve the readability dramatically. We have added the meanings of the AMSTAR abbreviations and have added colour to the overall quality column to increase readability. We have also added a footnote explaining the AMSTAR-2 questions, so the reader understands how the quality rating was decided. Discussion "Additionally, we observed positive associations between greenspace exposure and maternal health and birth outcomes including PTB and SGA which were not present in other studies (Yang et al., 2021).” These observed positive associations between greenspace exposure and maternal health and birth outcomes including PTB and SGA were not that consistent compared to the outcomes of mental health and cognitive function, right? If so, this may be the reason why previous studies hadn't reported them in the main findings. We revised this sentence. "Conversely, Stier-Jarmer et al. (2021) and Yang et al. (2021) reported beneficial effects of greenspace on cardiovascular health and cardiometabolic factors, respectively, which was not replicated in our study.” This may be attributable to the fact that some reviews on this aspect were excluded in this umbrella review, while included in Stier-Jarmer et al. (2021) and Yang et al. (2021) due to the different inclusion and exclusion criteria (e.g., scoping reviews on greenness and CVD). Anyway, this should be discussed. We revised this sentence. "Current evidence, including this umbrella review, have been unable to establish a causal link between greenspace exposure and health outcomes as most studies are observational. This highlights the need for additional experimental studies to be conducted” Population-based experimental studies are often unfeasible and also subject to numerous biases (e.g., usually very small sample size, non-adherence). Given the very large proportion of cross-sectional studies, it is more practical to suggest more studies with longitudinal or cohort design and causal inference models (e.g., Instrumental Variables Analysis). We agree that population-based experimental studies are rare. We have revised this sentence accordingly. "Most systematic reviews included in this review were limited by their methodological quality and/or risk of bias, and systematic reviews on the association between greenspace exposure and health outcomes have multiplied since 2020.” I am confused. The authors only included reviews between 2010-2020 and did not include reviews after 2020, as stated in the method section. We revised this sentence Competing Interests: No competing interests. Close Report a concern COMMENT ON THIS REPORT Comments on this article Comments (0) Version 2 VERSION 2 PUBLISHED 17 May 2024 ADD YOUR COMMENT Comment keyboard_arrow_left keyboard_arrow_right Open Peer Review Reviewer Status info_outline Alongside their report, reviewers assign a status to the article: Approved The paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. Not approved Fundamental flaws in the paper seriously undermine the findings and conclusions Reviewer Reports Invited Reviewers 1 2 3 Version 2 (revision) 30 Jul 25 read read read Version 1 17 May 24 read read Wenzhong Huang , Monash University, Melbourne, Australia William Mueller , Institute of Occupational Medicine (IOM), Edinburgh, UK David Rojas-Rueda , Colorado State University, Fort Collins, USA Comments on this article All Comments (0) Add a comment Sign up for content alerts Sign Up You are now signed up to receive this alert Browse by related subjects keyboard_arrow_left Back to all reports Reviewer Report 0 Views copyright © 2025 Mueller W. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 25 Sep 2025 | for Version 2 William Mueller , Institute of Occupational Medicine (IOM), Edinburgh, UK 0 Views copyright © 2025 Mueller W. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. format_quote Cite this report speaker_notes Responses (0) Approved info_outline Alongside their report, reviewers assign a status to the article: Approved The paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. Not approved Fundamental flaws in the paper seriously undermine the findings and conclusions Thank you for providing the author responses to my comments. I am satisfied they have sufficiently addressed my points. Competing Interests No competing interests were disclosed. Reviewer Expertise Environmental and occupational epidemiology I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. reply Respond to this report Responses (0) Mueller W. Peer Review Report For: Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.5256/f1000research.185657.r401603) NOTE: it is important to ensure the information in square brackets after the title is included in this citation. The direct URL for this report is: https://f1000research.com/articles/13-491/v2#referee-response-401603 keyboard_arrow_left Back to all reports Reviewer Report 0 Views copyright © 2025 Rojas-Rueda D. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 11 Sep 2025 | for Version 2 David Rojas-Rueda , Colorado State University, Fort Collins, USA 0 Views copyright © 2025 Rojas-Rueda D. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. format_quote Cite this report speaker_notes Responses (1) Approved With Reservations info_outline Alongside their report, reviewers assign a status to the article: Approved The paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. Not approved Fundamental flaws in the paper seriously undermine the findings and conclusions MAJOR COMMENTS 1. Critically Outdated Search Strategy The search strategy, which ended in January 2021 (over four years ago), represents a fundamental limitation that significantly undermines the review's validity and applicability. This is particularly problematic for greenspace research given: Rapid expansion of high-quality research post-COVID-19 Multiple systematic reviews published 2021-2024 Evolution of methodological standards and exposure assessment techniques New evidence on mechanisms and dose-response relationships Recommendation: Conduct a comprehensive updated search through 2025. 2. Title Lacks Methodological Clarity The title "systematic review of reviews" should explicitly identify this as an umbrella review using standard terminology. Recommendation: Revise the title to include the term "umbrella review." 3. Critical Methodological Flaw in Meta-analysis Assessment Table 5 fails to report the study design composition of included meta-analyses, which is a fundamental methodological oversight. Many meta-analyses inappropriately pool cross-sectional studies with longitudinal studies, which: Violates basic meta-analysis principles Cannot establish causality Produces effect estimates with limited validity for causal inference Significantly affects evidence interpretation Recommendation: Add columns to Table 5 showing: Number of studies in each meta-analysis Study design composition (# cross-sectional, # cohort, # RCT, etc.) Assessment of methodological appropriateness of pooling strategies Heterogeneity statistics (I²) 4. Quality Assessment Implications Inadequately Addressed With 50% of reviews having a high risk of bias and 36% rated as low quality, the implications for evidence reliability are inadequately discussed. Recommendation: Provide a detailed analysis of which AMSTAR-2 criteria were most commonly failed. Conduct sensitivity analyses excluding low-quality reviews Discuss how quality limitations affect confidence in conclusions 5. Limited Incremental Value Over Existing Reviews The comparison with existing umbrella reviews (van den Bosch & Ode Sang 2017; Yang et al. 2021) raises questions about unique contributions. Recommendation: More clearly articulate what this review adds beyond existing umbrella reviews, particularly given the temporal limitations. MINOR COMMENTS 6. Methodological Transparency Issues Search Strategy: Include full search strategy in main text or easily accessible supplementary material Inter-rater Reliability: Provide statistics for study selection and quality assessment agreement Grey Literature: Clarify if grey literature was considered and justify exclusion if applicable 7. Results Presentation Problems PRISMA Flowchart: Reference is unclear - ensure easy accessibility or include key elements in the main manuscript Effect Size Reporting: Standardize decimal places and clarify whether estimates are from random or fixed effects models 8. Quantitative Synthesis Limitations Many meta-analyses based on very few studies (n=2-4) Missing heterogeneity assessments No discussion of the potential for publication bias potential Mixing of different exposure metrics in a single meta-analyses 9. ICD-10 Classification Concerns The post-hoc assignment of ICD-10 codes (Table 4) may not reflect how original studies defined outcomes and could be misleading. Recommendation: Remove or clearly label as authors' interpretation rather than original study classifications. 10. Discussion Deficiencies Mechanistic Pathways: Brief mention of mechanisms could be expanded Policy Implications: Insufficient discussion of urban planning and public health implications Geographic Limitations: Most studies from high-income countries inadequately addressed Equity Considerations: Missing discussion of greenspace access disparities 11. Blue Space Exclusion Rationale While focusing solely on greenspace, the exclusion of studies examining combined green-blue space effects may artificially limit the evidence base and miss important findings. 12. Temporal Analysis Missing No consideration of temporal trends in research quality, methodology, or findings over the study period. SPECIFIC TECHNICAL RECOMMENDATIONS Restructure Results: Organize findings by strength of evidence rather than just outcome categories Study Design Stratification: Re-analyze findings separately for longitudinal/cohort studies, cross-sectional studies, and intervention studies Sensitivity Analyses: Exclude low-quality reviews to assess robustness of conclusions Enhanced Quality Discussion: Provide a systematic analysis of methodological failures in included reviews Future Research Priorities: More clearly identify evidence gaps and research priorities Practical Implications: Expand discussion of what constitutes "effective" greenspace exposure for policy purposes OVERALL ASSESSMENT This umbrella review addresses an important public health topic but suffers from significant methodological limitations. The outdated search strategy, inadequate assessment of meta-analysis quality, high proportion of low-quality included reviews, and presentation challenges substantially reduce its impact and reliability. The manuscript requires major revision addressing these fundamental issues before being suitable for publication in a high-impact journal. Recommendation: Major revision required, with particular attention to updating the evidence base, critically evaluating meta-analysis methodology, and enhancing transparency of quality assessment implications. Are the rationale for, and objectives of, the Systematic Review clearly stated? Partly Are sufficient details of the methods and analysis provided to allow replication by others? Partly Is the statistical analysis and its interpretation appropriate? Partly Are the conclusions drawn adequately supported by the results presented in the review? Partly If this is a Living Systematic Review, is the ‘living’ method appropriate and is the search schedule clearly defined and justified? (‘Living Systematic Review’ or a variation of this term should be included in the title.) Not applicable Competing Interests No competing interests were disclosed. Reviewer Expertise Environmental epidemiology I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. reply Respond to this report Responses (1) Author Response 31 Dec 2025 Darsy Darssan, School of Public Health, The University of Queensland, Herston, Australia Response to reviewer comments We appreciate the feedback on the manuscript. We have carefully considered and responded to your suggestions. MAJOR COMMENTS 1. Critically Outdated Search Strategy The search strategy, which ended in January 2021 (over four years ago), represents a fundamental limitation that significantly undermines the review's validity and applicability. This is particularly problematic for greenspace research given: Rapid expansion of high-quality research post-COVID-19 Multiple systematic reviews published 2021-2024 Evolution of methodological standards and exposure assessment techniques New evidence on mechanisms and dose-response relationships Recommendation: Conduct a comprehensive updated search through 2025. Response: This review includes 36 systematic reviews published between January 2010 and December 2020. As you mentioned, much research on greenspace and health, including reviews, has been published since December 2020. We identified an additional 45 review articles between December 2020 and June 2024. Combining these two umbrella reviews would be too many systematic reviews to include in a single umbrella review. As per the Cochrane guidelines (Cumpston and Flemyng, 2023), we have updated the review due to “the availability of new evidence that would have a meaningful impact on the review findings”. [Please see our updated review here, https://doi.org/10.12688/f1000research.166852.1 ]. Cumpston, M., Flemyng, E., Chapter IV: Updating a review [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-iv 2. Title Lacks Methodological Clarity The title "systematic review of reviews" should explicitly identify this as an umbrella review using standard terminology. Recommendation: Revise the title to include the term "umbrella review." In the title, we prefer to use the term ‘systematic review of reviews’, but we do refer to it as an umbrella review in the text. We find this title more understandable for a lay audience. 3. Critical Methodological Flaw in Meta-analysis Assessment Table 5 fails to report the study design composition of included meta-analyses, which is a fundamental methodological oversight. Many meta-analyses inappropriately pool cross-sectional studies with longitudinal studies, which: Violates basic meta-analysis principles Cannot establish causality Produces effect estimates with limited validity for causal inference Significantly affects evidence interpretation Recommendation: Add columns to Table 5 showing: Number of studies in each meta-analysis Study design composition (# cross-sectional, # cohort, # RCT, etc.) Assessment of methodological appropriateness of pooling strategies Heterogeneity statistics (I²) Response: Number of studies: This information is already reported in Table 5. Study design composition: The composition of original studies included in the systematic reviews is presented in Table 1. For further details, readers can consult the individual systematic reviews. Appropriateness of statistical methods: This aspect has been formally assessed using AMSTAR-2, and the results are included in Table 6 of our manuscript. Heterogeneity statistics (I²): I² values are not comparable because they depend on the number of studies, sample sizes, and variance structure. Reporting them side-by-side in an umbrella review risks misleading comparisons. 4. Quality Assessment Implications Inadequately Addressed With 50% of reviews having a high risk of bias and 36% rated as low quality, the implications for evidence reliability are inadequately discussed. Recommendation: Provide a detailed analysis of which AMSTAR-2 criteria were most commonly failed. Conduct sensitivity analyses excluding low-quality reviews Discuss how quality limitations affect confidence in conclusions Response: Detailed AMSTAR‑2 results: Table 6 reports the results for each AMSTAR‑2 component across the included systematic reviews. This provides readers with a transparent view of which criteria were most commonly met or failed. Sensitivity analyses: As our study is an umbrella review rather than a meta-analysis, we did not conduct quantitative sensitivity analyses by excluding low-quality reviews. Risk of bias and methodological quality assessments are transparently reported in the Results section. 5. Limited Incremental Value Over Existing Reviews The comparison with existing umbrella reviews (van den Bosch & Ode Sang 2017; Yang et al. 2021) raises questions about unique contributions. Recommendation: More clearly articulate what this review adds beyond existing umbrella reviews, particularly given the temporal limitations. We respectfully note that the unique contributions of our umbrella review are already articulated in the last paragraph of the Introduction, which outlines five specific features distinguishing our work from prior umbrella reviews. These include: (i) evaluation of greenspace exposure and health outcomes independently of blue space and health determinants; (ii) assessment of both quality and risk of bias of reviews; (iii) recording of the frequency of greenspace exposure measures used; (iv) summarisation of health outcomes with associated ICD-10 codes; and (v) reporting of effect measures from meta-analyses. Together, these features ensure that our review provides a distinct contribution beyond earlier syntheses. As another reviewer noted, this paragraph was clear, and we believe it sufficiently addresses the concern regarding incremental value. For this reason, we have not made further changes to the manuscript. MINOR COMMENTS 6. Methodological Transparency Issues Search Strategy: Include full search strategy in main text or easily accessible supplementary material Inter-rater Reliability: Provide statistics for study selection and quality assessment agreement Grey Literature: Clarify if grey literature was considered and justify exclusion if applicable Response: Search Strategy: The full search strategy is already provided in Supplementary Table S1, ensuring that readers can access the complete details of keywords used. Inter-rater Reliability: This was not deemed necessary in our umbrella review because “Disagreements were resolved via discussions with the last author”. Because consensus was consistently achieved and disagreements were few, we did not calculate or report formal inter-rater reliability statistics. Grey literature was not included in our umbrella review. Our focus was restricted to peer-reviewed systematic reviews and meta-analyses to ensure methodological rigour, consistency in reporting standards, and comparability across included studies. 7. Results Presentation Problems PRISMA Flowchart: Reference is unclear - ensure easy accessibility or include key elements in the main manuscript Effect Size Reporting: Standardize decimal places and clarify whether estimates are from random or fixed effects models Response: As per the F1000 guidelines, a PRISMA flowchart for this review is available under the ‘Data availability’ à ‘Reporting guidelines’ section at the end of the article. Effect Size Reporting: Most effect sizes are reported to two decimal places; however, in cases where estimates are very small (e.g., beta coefficients of 0.001 with confidence intervals of 0.000–0.002), three decimal places are used to ensure precision and interpretability. In our umbrella review, we presented estimates by outcome in a comprehensive summary table (Table 5). Given the breadth of outcomes, this table is already large and adding further details (e.g. heterogeneity statistics or the specific effects model) would be redundant for the purposes of an umbrella review. The primary objective of an umbrella review is to synthesise evidence across systematic reviews, rather than to re-analyse or replicate their statistical outputs. This information is explicitly available in the original systematic reviews: of the 12 meta-analyses, 9 used random-effects models (Gascon et al., 2016; Lambert et al., 2017; Lee et al., 2020; Roberts et al., 2019; Rojas-Rueda et al., 2019; Soga et al., 2017; Twohig-Bennett and Jones, 2018; Yuan et al., 2021; Zhan et al., 2020), 1 used a fixed-effects model (Luo et al., 2020), and 2 applied quality-effects models (Akaraci et al., 2020; Dzhambov et al., 2014). 8. Quantitative Synthesis Limitations Many meta-analyses based on very few studies (n=2-4) Missing heterogeneity assessments No discussion of the potential for publication bias potential Mixing of different exposure metrics in a single meta-analyses Response: Small meta-analyses (n=2–4): We acknowledge that several meta-analyses included in our umbrella review were based on a limited number of primary studies. This limitation reflects the current evidence base rather than our methodology, and we have reported these findings transparently. Heterogeneity assessments: We did not include heterogeneity statistics (e.g., I²) in the manuscript, as our umbrella review was designed as a narrative synthesis rather than a re-analysis of quantitative data. Publication bias: Publication bias was assessed using the AMSTAR-2 tool, which explicitly evaluates whether included reviews considered publication bias (Table 6). This assessment is incorporated into our quality appraisal and reported accordingly. Exposure metrics: We recognise that some meta-analyses combined different greenspace exposure metrics. This reflects the diversity of measures used in the field. Our umbrella review records the frequency of exposure measures and highlights this variability as a methodological challenge for future research. 9. ICD-10 Classification Concerns The post-hoc assignment of ICD-10 codes (Table 4) may not reflect how original studies defined outcomes and could be misleading. Recommendation: Remove or clearly label as authors' interpretation rather than original study classifications. You are correct that the original studies may not have defined the outcomes based on the ICD codes. Based on the information available in the reviews, we allocated all potential ICD codes for each health outcome. We did this to promote standardised reporting in future articles that investigate the association between greenspace exposure and health outcomes. 10. Discussion Deficiencies Mechanistic Pathways: Brief mention of mechanisms could be expanded Policy Implications: Insufficient discussion of urban planning and public health implications Geographic Limitations: Most studies from high-income countries inadequately addressed Equity Considerations: Missing discussion of greenspace access disparities Response: Mechanistic Pathways: We briefly mention potential mechanisms linking greenspace exposure to health outcomes, as a detailed exploration of mechanistic pathways was beyond the scope of this umbrella review. These mechanisms have been explored in more depth by other researchers (Markevych et al., 2017). Markevych, I., Schoierer, J., Hartig, T., Chudnovsky, A., Hystad, P.,…. & Fuertes, E. (2017). Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental Research, 158, 301-317. https://doi.org/10.1016/j.envres.2017.06.028 Policy Implications: We acknowledge the importance of urban planning and public health implications. However, our focus was on synthesising the evidence rather than extending into policy recommendations. We believe that the evidence presented provides a foundation for future work to draw out specific policy implications. Geographic Limitations: The included systematic reviews drew upon studies conducted across a wide variety of locations worldwide. Given the diversity of study locations represented, we did not identify a single geographic imbalance that required emphasis. We agree that geographic context is important for interpreting greenspace–health relationships, and future work could more explicitly examine regional differences. Equity Considerations: We agree that disparities in greenspace access are important, which is why we have discussed inequalities in greenspace access due to urbanisation, socioeconomic status, and occupation in the third paragraph of the ‘Discussion’ section. 11. Blue Space Exclusion Rationale While focusing solely on greenspace, the exclusion of studies examining combined green-blue space effects may artificially limit the evidence base and miss important findings. We sought to evaluate the association between greenspace exposure and health outcomes independently of blue space, in order to avoid conflating effects and to provide a more precise synthesis of greenspace-specific evidence. Including studies that combined green and blue space exposures would have introduced heterogeneity in exposure definitions, making comparisons across reviews less meaningful. Additionally, previous umbrella reviews have often considered green and blue spaces together. By focusing solely on greenspace, our review addresses a distinct gap in the literature and complements existing syntheses. 12. Temporal Analysis Missing No consideration of temporal trends in research quality, methodology, or findings over the study period. We acknowledge that examining temporal trends in research quality, methodology, and findings could provide valuable insights. While such an analysis was not undertaken in the present umbrella review, we have addressed this point in our updated review, where we assessed trends in these components between studies published in 2010–2020 (covered in this review) and 2021–2024 (updated review). We believe this complementary work provides the broader temporal perspective suggested by the reviewer. [Please see our updated review here, https://doi.org/10.12688/f1000research.166852.1 ]. SPECIFIC TECHNICAL RECOMMENDATIONS Restructure Results: Organize findings by strength of evidence rather than just outcome categories Study Design Stratification: Re-analyze findings separately for longitudinal/cohort studies, cross-sectional studies, and intervention studies Sensitivity Analyses: Exclude low-quality reviews to assess robustness of conclusions Enhanced Quality Discussion: Provide a systematic analysis of methodological failures in included reviews Future Research Priorities: More clearly identify evidence gaps and research priorities Practical Implications: Expand discussion of what constitutes "effective" greenspace exposure for policy purposes Response: Restructuring Results / Study Design Stratification / Sensitivity Analyses: Our review followed a narrative synthesis approach, drawing on published systematic reviews and meta-analyses. We did not re-analyse primary data, and therefore restructuring results by strength of evidence, stratifying by study design, or conducting sensitivity analyses excluding low-quality reviews were not feasible within our methodological framework. Enhanced Quality Discussion: Table 6 reports the results for each AMSTAR‑2 component across the included systematic reviews. This provides readers with a transparent view of which criteria were most commonly met or failed. Future Research Priorities: We have highlighted evidence gaps and research needs in the Discussion, particularly regarding the diversity of exposure metrics and study design. Practical Implications: Our umbrella review was designed to summarise quantitative evidence from existing systematic reviews and meta-analyses, rather than to define optimal exposure thresholds or policy standards. The included reviews varied widely in how greenspace exposure was measured, and this heterogeneity limited our ability to draw firm conclusions about what constitutes “effective” exposure. We have highlighted this variability in the Discussion as a key methodological challenge and evidence gap. View more View less Competing Interests No competing interests. reply Respond Report a concern Rojas-Rueda D. Peer Review Report For: Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.5256/f1000research.185657.r408332) NOTE: it is important to ensure the information in square brackets after the title is included in this citation. The direct URL for this report is: https://f1000research.com/articles/13-491/v2#referee-response-408332 keyboard_arrow_left Back to all reports Reviewer Report 0 Views copyright © 2025 Huang W. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 23 Aug 2025 | for Version 2 Wenzhong Huang , Monash University, Melbourne, Australia 0 Views copyright © 2025 Huang W. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. format_quote Cite this report speaker_notes Responses (0) Approved info_outline Alongside their report, reviewers assign a status to the article: Approved The paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. Not approved Fundamental flaws in the paper seriously undermine the findings and conclusions I appreciate the authors' efforts. The manuscript is now much clearer and improved over previous versions, particularly in clarifying its unique strengths and the comparisons with similar studies. The results have also been enhanced. I have no further comments. Competing Interests No competing interests were disclosed. Reviewer Expertise Environmental epidemiolgy; greenness, air pollution, climate change and health I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. reply Respond to this report Responses (0) Huang W. Peer Review Report For: Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.5256/f1000research.185657.r401604) NOTE: it is important to ensure the information in square brackets after the title is included in this citation. The direct URL for this report is: https://f1000research.com/articles/13-491/v2#referee-response-401604 keyboard_arrow_left Back to all reports Reviewer Report 0 Views copyright © 2024 Mueller W. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 28 Jun 2024 | for Version 1 William Mueller , Institute of Occupational Medicine (IOM), Edinburgh, UK 0 Views copyright © 2024 Mueller W. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. format_quote Cite this report speaker_notes Responses (1) Approved With Reservations info_outline Alongside their report, reviewers assign a status to the article: Approved The paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. Not approved Fundamental flaws in the paper seriously undermine the findings and conclusions Overall This is a well-conducted and well-written review about greenspace exposure and human health, a very active research area that would benefit from a broad synthesis of the evidence. I have outlined my comments below, which are mostly minor, but I do note an important Major comment for the authors and editor’s consideration. Major Much research on greenspace and health, including reviews, has been published since December 2020. If an updated review is underway, wouldn’t it be more valuable to wait to publish the more up to date work? Also given the reviews themselves have earlier cut-offs, so the current review would already be quite out of date with the most recent research. Minor Consider changing title to refer to an ‘umbrella review’ Abstract - The abstract states that beneficial effects were observed for cardiovascular disease mortality, but that ambivalent results were found for cardiovascular health. The former is a subset of the latter, so please change wording to be consistent. [I see later that cardiovascular and metabolic health was combined as one category, but this is not clear from a read of the abstract.] Abstract – it is always helpful to include some quantitative results, even if ranges of effect sizes, to better characterise findings Introduction – ‘These studies did not consider overall health impacts’ – what does this statement mean exactly? Rephrase to make clear that full weight of evidence needs to be assessed to understand the nature of greenspace and health via an umbrella review, as described in the following sentence. Introduction – Following the above point, what about reviews that address multiple health outcomes (e.g., Twohig-Bennett & Jones, 2018) [REF1]? Can they not provide useful information on overall health impacts as well? Methods – Why are cardiovascular and metabolic outcomes combined? Results – Did you search the references of included papers? If so, were any additional papers identified? Typically, reviews include flow charts to show the start and end number of papers. Table 1- Why is the sample size for Carver et al. ‘NA’? Table 1 – Define ‘NA’ with other short-forms Table 3 – Add a ‘*’ or similar next to ‘Other’ to indicate that the specific exposures are given below. Results – ‘Maternal health…’ – Change to ‘OR=0.80…’ for consistency. Results – ‘Maternal health…’ – What do the Lee et al βs represent? Table 5 – Title should refer to ‘meta-analyses’, otherwise it is not clear how the effect estimates were calculated. It would also be helpful to add the increment that the estimates represent (e.g. per 0.1 increase in NDVI) Figure 1 – The methods should state how the overall risk of bias was determined (e.g., highest individual risk?). Also, the text accompanying the Figure, ‘…lighter colours concern judgments’ is not clear. Are these the individual risk of bias criteria? If so, state that. Results – Risk of bias – why was the risk in some cases ‘unclear’? Was there not enough information to determine if a criterion was met? Wouldn’t that suggest it was not met and that it is likely to be a source of bias? This point should be considered. Discussion – A stronger conclusion should be reached other than there may be an association between greenspace and health. For example, there appears to be stronger evidence for mental health, all-cause and CVD mortality. Are the specific pathways to health offered by greenspace more relevant for these outcomes? Table 6 – Without knowing the AMSTAR-2 questions or how they were rated, this table is not very intuitive. The other tables are informative and effective at summarising the reviews and results. Discussion – discussion of study limitations should be mentioned. Are the rationale for, and objectives of, the Systematic Review clearly stated? Yes Are sufficient details of the methods and analysis provided to allow replication by others? Yes Is the statistical analysis and its interpretation appropriate? Yes Are the conclusions drawn adequately supported by the results presented in the review? Partly If this is a Living Systematic Review, is the ‘living’ method appropriate and is the search schedule clearly defined and justified? (‘Living Systematic Review’ or a variation of this term should be included in the title.) Not applicable References 1. Twohig-Bennett C, Jones A: The health benefits of the great outdoors: A systematic review and meta-analysis of greenspace exposure and health outcomes. Environ Res . 2018; 166 : 628-637 PubMed Abstract | Publisher Full Text Competing Interests No competing interests were disclosed. Reviewer Expertise Environmental and occupational epidemiology I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. reply Respond to this report Responses (1) Author Response 09 Aug 2025 Darsy Darssan, School of Public Health, The University of Queensland, Herston, Australia Response to reviewer comments We sincerely appreciate the thorough and insightful feedback on the manuscript. We have carefully considered and incorporated your suggestions wherever feasible. Major Much research on greenspace and health, including reviews, has been published since December 2020. If an updated review is underway, wouldn’t it be more valuable to wait to publish the more up to date work? Also given the reviews themselves have earlier cut-offs, so the current review would already be quite out of date with the most recent research. Response: As per the Cochrane guidelines (Cumpston and Flemyng, 2023), we have updated the review due to “the availability of new evidence that would have a meaningful impact on the review findings”. [ https://doi.org/10.12688/f1000research.166852.1 ]. Cumpston, M., Flemyng, E., Chapter IV: Updating a review [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-iv This review includes 36 systematic reviews published between January 2010 and December 2020. As you mentioned, much research on greenspace and health, including reviews, has been published since December 2020. We identified an additional 45 review articles between December 2020 and June 2024. Combining these two umbrella reviews would be too many systematic reviews to include in a single umbrella review. Minor 1. Consider changing title to refer to an ‘umbrella review’ In the title, we prefer to use the term ‘systematic review of reviews’, but we do refer to it as an umbrella review in the text. We find this title more understandable for a lay audience. 2. Abstract - The abstract states that beneficial effects were observed for cardiovascular disease mortality, but that ambivalent results were found for cardiovascular health. The former is a subset of the latter, so please change wording to be consistent. [I see later that cardiovascular and metabolic health was combined as one category, but this is not clear from a read of the abstract.] We have changed the wording in the abstract. In the results section, cardiovascular and metabolic health are reported under one category, but the results of the two outcomes are not combined. 3. Abstract – it is always helpful to include some quantitative results, even if ranges of effect sizes, to better characterise findings We have thought this through carefully and have concluded that synthesising the quantitative results could lead to bias, as we would be pooling the already pooled results from the systematic reviews. As per Aromataris et al. 2015 our umbrella review is intended to summarise the current evidence rather than re-synthesising the data. Aromataris, E., Fernandez, R., Godfrey, C. M., Holly, C., Khalil, H., & Tungpunkom, P. (2015). Summarizing systematic reviews: methodological development, conduct and reporting of an umbrella review approach. JBI Evidence Implementation , 13 (3). https://doi.org/10.1097/XEB.0000000000000055 4. Introduction – ‘These studies did not consider overall health impacts’ – what does this statement mean exactly? Rephrase to make clear that full weight of evidence needs to be assessed to understand the nature of greenspace and health via an umbrella review, as described in the following sentence. We reworded this section of the Introduction for better understanding. 5. Introduction – Following the above point, what about reviews that address multiple health outcomes (e.g., Twohig-Bennett & Jones, 2018) [REF1]? Can they not provide useful information on overall health impacts as well? We reworded this section and have referenced Twohig-Bennett & Jones et al. 2018 in this section of the introduction. 6. Methods – Why are cardiovascular and metabolic outcomes combined? Cardiovascular and metabolic outcomes share common pathophysiological pathways and risk factors, making it logical to categorise them together. Greenspace exposure is hypothesised to influence these outcomes through shared mechanisms. 7. Results – Did you search the references of included papers? If so, were any additional papers identified? Typically, reviews include flow charts to show the start and end number of papers. Manual reference search is described in the ‘Search strategy’ section of the methods. As per the F1000 guidelines, a PRISMA flowchart for this review is available under the ‘Data availability’ -> ‘Reporting guidelines’ section at the end of the article. 8. Table 1- Why is the sample size for Carver et al. ‘NA’? This has been fixed to show the minimum and maximum sample size for Carver et al. 2020. 9. Table 1 – Define ‘NA’ with other short-forms This has been added. 10. Table 3 – Add a ‘*’ or similar next to ‘Other’ to indicate that the specific exposures are given below. This has been adjusted. 11. Results – ‘Maternal health…’ – Change to ‘OR=0.80…’ for consistency. This has been adjusted. 12. Results – ‘Maternal health…’ – What do the Lee et al βs represent? The definition has been added to the first instance of β. 13. Table 5 – Title should refer to ‘meta-analyses’, otherwise it is not clear how the effect estimates were calculated. It would also be helpful to add the increment that the estimates represent (e.g. per 0.1 increase in NDVI) This has been adjusted. Also, we thoroughly reviewed this Table. 14. Figure 1 – The methods should state how the overall risk of bias was determined (e.g., highest individual risk?). Also, the text accompanying the Figure, ‘…lighter colours concern judgments’ is not clear. Are these the individual risk of bias criteria? If so, state that. ROBIS was used to assess the risk of bias of each systematic review. ROBIS consists of four domains, and within each domain, there are five to six signalling questions. Two reviewers went through each signalling question, and judgments were made independently. These domains were then used to determine the overall risk of bias of each review. Conflicts between the reviewers were resolved through discussion with the last author. For each review, the final decision on four domains and the overall risk of bias is listed in Supplementary Table S2. Figure 1 is a summary of Supplementary Table S2, as per ROBIS guidelines. More information about ROBIS is available from Whiting et al. 2016. Whiting, P., Savovic, J., Higgins, J. P., Caldwell, D. M., Reeves, B. C., Shea, B., Davies, P., Kleijnen, J., Churchill, R., & group, R. (2016). ROBIS: A new tool to assess risk of bias in systematic reviews was developed. Journal of Clinical Epidemiology , 69 , 225-234. https://doi.org/10.1016/j.jclinepi.2015.06.005 We have altered the Figure caption to improve the readability of the graph. 15. Results – Risk of bias – why was the risk in some cases ‘unclear’? Was there not enough information to determine if a criterion was met? Wouldn’t that suggest it was not met and that it is likely to be a source of bias? This point should be considered. As per the guidance on how to use ROBIS, an ‘unclear’ rating indicates that insufficient data were reported to permit a judgment for signalling questions within a domain (Phase 2). If something is not reported, it could be a potential source of bias. That’s why ROBIS has the unclear category, because if the information isn’t reported, you cannot make a definitive statement about whether the bias is high or low. 16. Discussion – A stronger conclusion should be reached other than there may be an association between greenspace and health. For example, there appears to be stronger evidence for mental health, all-cause and CVD mortality. Are the specific pathways to health offered by greenspace more relevant for these outcomes? In this narrative synthesis, stronger conclusions for each health outcome could lead to overstatements of the associations. Inconsistent findings within each health outcome, with varying effect measures, also make it challenging to report definitive conclusions. Some pathways may be more related to specific health outcomes and have been explored in more depth by other researchers (Markevych et al., 2017). However, these biological mechanisms are beyond the scope of this Discussion section. Markevych, I., Schoierer, J., Hartig, T., Chudnovsky, A., Hystad, P.,…. & Fuertes, E. (2017). Exploring pathways linking greenspace to health: Theoretical and methodological guidance. Environmental Research, 158, 301-317. https://doi.org/10.1016/j.envres.2017.06.028 17. Table 6 – Without knowing the AMSTAR-2 questions or how they were rated, this table is not very intuitive. The other tables are informative and effective at summarising the reviews and results. We have added the shortened AMSTAR-2 questions as a footnote to the table. The other reviewer also mentioned this table and we have coloured the overall quality column to improve readability. A graph showing the distribution of high, moderate, and low-quality reviews is also available in the supplementary material. 18. Discussion – discussion of study limitations should be mentioned. The limitations of the review have been discussed in the last paragraph of the discussion. We revisited this paragraph to improve the clarity. View more View less Competing Interests No competing interests. reply Respond Report a concern Mueller W. Peer Review Report For: Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.5256/f1000research.163252.r284715) NOTE: it is important to ensure the information in square brackets after the title is included in this citation. The direct URL for this report is: https://f1000research.com/articles/13-491/v1#referee-response-284715 keyboard_arrow_left Back to all reports Reviewer Report 0 Views copyright © 2024 Huang W. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 10 Jun 2024 | for Version 1 Wenzhong Huang , Monash University, Melbourne, Australia 0 Views copyright © 2024 Huang W. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. format_quote Cite this report speaker_notes Responses (1) Approved With Reservations info_outline Alongside their report, reviewers assign a status to the article: Approved The paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. Not approved Fundamental flaws in the paper seriously undermine the findings and conclusions mandatory reviewer questions Is the topic of the review discussed comprehensively in the context of the current literature? Yes Are all factual statements correct and adequately supported by citations? Mostly Is the review written in accessible language? Yes Are the conclusions drawn appropriate in the context of the current research literature? Yes Specific comments: This study is a well-written umbrella review that synthesized systematic reviews on the associations of greenness and all kinds of health outcomes. I appreciate the great amount of work by the authors. I believe this study does have some value and can advance knowledge in this field. However, given the similarities to recent work by Stier-Jarmer et al. (2021)[Ref 1] and Yang et al. (2021)[Ref 2], I had the following suggestions/comments in an attempt to enhance the significance of this study. Introduction I appreciate the authors' introduction of two highly relevant umbrella reviews that incorporate the latest research advancements. Highlighting the advances of this study compared to these two reviews is crucial to justify its significance. However, the clarity of the following points could be improved: For instance, the review by van den Bosch and Ode Sang (2017) [Ref 3] includes both green and blue spaces, suggesting their work is more comprehensive than reviews focusing solely on green spaces. Therefore, it seems illogical for the authors to claim that the conclusions drawn from this study do not adequately represent the impact of green space exposure. Regarding the high-impact umbrella review by Yang et al., the authors mention a limitation involving the grouping of cancer and respiratory mortality into the section of ”other health outcomes”. This grouping likely resulted from the small number of studies on these topics and should not lead to outcome misclassification. Because Yang et al. could still discuss the findings for cancer and respiratory mortality separately. Additionally, including systematic reviews with variables such as physical activity, time spent outdoors, prosocial behavior, and murder as health outcomes does not appear to be a limitation. These reviews should encompass the health effects of greenness, (e.g., studies investigating the association of green spaces with health and the role of physical activity on the associations). In summary, the limitations mentioned by the authors are unclear and illogical to me. I understand and appreciate that this work possesses four important qualities compared to previous studies, as clearly mentioned in the last sentence of the Introduction. However, the significance of this research would be greatly enhanced if the authors provided clearer clarifications regarding the mentioned limitations of previous studies and how this study advances the field by addressing those limitations. Methods "We restricted the search to peer-reviewed systematic reviews and meta-analyses conducted in humans and published in English between January 2010 and December 2020, including reviews first published online during this period". Given the dramatic increase in publications on greenness and health in recent years, the quality of this study would be substantially improved if the authors included up-to-date reviews (i.e., from 2010 to the present, rather than 2010-2020). This inclusion can be mentioned as a major strength compared to previous umbrella reviews, as many high-quality studies and reviews have been published in the past three years. Full names should be provided for the abbreviations when they first appear in the main text (e.g., BMI, PA). Results It would be beneficial to include a flowchart illustrating the process used to select the final 36 systematic reviews (e.g., the number of studies excluded due to each specific exclusion criterion). It might be better to visualize the study design, measures of greenness, location of studies (country/territory), and outcomes in a figure rather than in several separate tables. A good example can be seen in https://link.springer.com/article/10.1007/s40572-023-00420-9 (Figure 2) Table 4. I appreciate the authors' usage of ICD-code to define the outcomes. However, if I understand it correctly, the original studies in these included reviews may not necessarily and consistently define their outcomes based on these ICD codes, right? If so, this table might be misleading. Why not combine Table 5 and Table 1, they have duplicated information. "Half of the systematic reviews (50%) had a high risk of bias“. This proportion is quite high. It would be better for the authors to clarify how they assigned the level of ROB to each of the reviews (e.g., using a table with the same structure as Table S2 to list the reason why each level was assigned). This was just a recommendation, but at least the authors should provide more clarifications and discuss this point. Currently, there are very few words on it. Consistent with the previous comment, a relatively high proportion of the included reviews were also classified as low quality. Providing more clarifications on this point would make this study stronger. Table 6, please clarify the meanings of these words (e.g., N, PY, NA) in the table caption. It would be better to assign the cell background with a color to indicate the quality level (e.g., red for low quality, green for high quality). This can improve the readability dramatically. Discussion "Additionally, we observed positive associations between greenspace exposure and maternal health and birth outcomes including PTB and SGA which were not present in other studies (Yang et al., 2021).” These observed positive associations between greenspace exposure and maternal health and birth outcomes including PTB and SGA were not that consistent compared to the outcomes of mental health and cognitive function, right? If so, this may be the reason why previous studies hadn't reported them in the main findings. "Conversely, Stier-Jarmer et al. (2021) and Yang et al. (2021) reported beneficial effects of greenspace on cardiovascular health and cardiometabolic factors, respectively, which was not replicated in our study.” This may be attributable to the fact that some reviews on this aspect were excluded in this umbrella review, while included in Stier-Jarmer et al. (2021) and Yang et al. (2021) due to the different inclusion and exclusion criteria (e.g., scoping reviews on greenness and CVD). Anyway, this should be discussed. "Current evidence, including this umbrella review, have been unable to establish a causal link between greenspace exposure and health outcomes as most studies are observational. This highlights the need for additional experimental studies to be conducted” Population-based experimental studies are often unfeasible and also subject to numerous biases (e.g., usually very small sample size, non-adherence). Given the very large proportion of cross-sectional studies, it is more practical to suggest more studies with longitudinal or cohort design and causal inference models (e.g., Instrumental Variables Analysis). "Most systematic reviews included in this review were limited by their methodological quality and/or risk of bias, and systematic reviews on the association between greenspace exposure and health outcomes have multiplied since 2020.” I am confused. The authors only included reviews between 2010-2020 and did not include reviews after 2020, as stated in the method section. Are the rationale for, and objectives of, the Systematic Review clearly stated? Yes Are sufficient details of the methods and analysis provided to allow replication by others? Yes Is the statistical analysis and its interpretation appropriate? Partly Are the conclusions drawn adequately supported by the results presented in the review? Yes If this is a Living Systematic Review, is the ‘living’ method appropriate and is the search schedule clearly defined and justified? (‘Living Systematic Review’ or a variation of this term should be included in the title.) Not applicable References 1. Stier-Jarmer M, Throner V, Kirschneck M, Immich G, et al.: The Psychological and Physical Effects of Forests on Human Health: A Systematic Review of Systematic Reviews and Meta-Analyses. Int J Environ Res Public Health . 2021; 18 (4). PubMed Abstract | Publisher Full Text 2. Yang BY, Zhao T, Hu LX, Browning MHEM, et al.: Greenspace and human health: An umbrella review. Innovation (Camb) . 2021; 2 (4): 100164 PubMed Abstract | Publisher Full Text 3. van den Bosch M, Ode Sang Å: Urban natural environments as nature-based solutions for improved public health - A systematic review of reviews. Environ Res . 2017; 158 : 373-384 PubMed Abstract | Publisher Full Text Competing Interests No competing interests were disclosed. Reviewer Expertise Environmental epidemiolgy; greenness, air pollution, climate change and health I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. reply Respond to this report Responses (1) Author Response 09 Aug 2025 Darsy Darssan, School of Public Health, The University of Queensland, Herston, Australia Response to reviewer comments We are grateful for the valuable and detailed comments on our manuscript. We have thoughtfully reviewed and integrated your recommendations to the extent possible. Introduction I appreciate the authors' introduction of two highly relevant umbrella reviews that incorporate the latest research advancements. Highlighting the advances of this study compared to these two reviews is crucial to justify its significance. However, the clarity of the following points could be improved: For instance, the review by van den Bosch and Ode Sang (2017) [Ref 3] includes both green and blue spaces, suggesting their work is more comprehensive than reviews focusing solely on green spaces. Therefore, it seems illogical for the authors to claim that the conclusions drawn from this study do not adequately represent the impact of green space exposure. Our introduction does not claim that it inadequately represents the impact of greenspace exposure; rather, it assesses a composite of both greenspace and blue space effects on health. We have also amended the sentence to make this clearer. Regarding the high-impact umbrella review by Yang et al., the authors mention a limitation involving the grouping of cancer and respiratory mortality into the section of ”other health outcomes”. This grouping likely resulted from the small number of studies on these topics and should not lead to outcome misclassification. Because Yang et al. could still discuss the findings for cancer and respiratory mortality separately. We have removed the section about cancer and respiratory health from this sentence. Additionally, including systematic reviews with variables such as physical activity, time spent outdoors, prosocial behavior, and murder as health outcomes does not appear to be a limitation. These reviews should encompass the health effects of greenness, (e.g., studies investigating the association of green spaces with health and the role of physical activity on the associations). In summary, the limitations mentioned by the authors are unclear and illogical to me. Per the World Health Organization (WHO), “The determinants of health include: the social and economic environment, the physical environment, and the person’s individual characteristics and behaviours” (AIHW, 2024). Physical activity is classified as a behaviour (Chevance et al., 2019), making it a health determinant. Health determinants, such as physical activity or diet, contribute to health outcomes; however, as explained in our methods section, our review excluded studies that only considered health determinants. As you mention, physical activity plays a role in the association between greenspace and health outcomes (Chen et al., 2021), but it is not a health outcome itself. In our discussion, we explore physical activity as a pathway between greenspace exposure and health outcomes. World Health Organization (WHO). (2024). Determinants of health. https://www.who.int/news-room/questions-and-answers/item/determinants-of-health Chevance, G., Bernard, P., Chamberland, P. E., & Rebar, A. (2019). The association between implicit attitudes toward physical activity and physical activity behaviour: a systematic review and correlational meta-analysis. Health Psychology Review , 13 (3), 248–276. https://doi.org/10.1080/17437199.2019.1618726 Chen, K., Zhang, T., Liu, F., Zhang, Y., & Song, Y. (2021). How Does Urban Green Space Impact Residents' Mental Health: A Literature Review of Mediators. International journal of environmental research and public health , 18 (22), 11746. https://doi.org/10.3390/ijerph182211746 Australian Institute of Health and Welfare. (2024). Social determinants of health. Retrieved from https://www.aihw.gov.au/reports/australias-health/social-determinants-of-health We revisited this section of the Introduction to improve the clarity. I understand and appreciate that this work possesses four important qualities compared to previous studies, as clearly mentioned in the last sentence of the Introduction. Thank you, these four qualities are a major strength of this research. However, the significance of this research would be greatly enhanced if the authors provided clearer clarifications regarding the mentioned limitations of previous studies and how this study advances the field by addressing those limitations. The limitations of the previous studies are: 1. Do not isolate the impact of greenspace exposure alone on health outcomes, as its effects are confounded by blue space. 2. Do not isolate the impact of greenspace exposure on health outcomes alone, independent of health determinants 3. Included scoping reviews in their umbrella review. To address these limitations, our review assesses the association between greenspace exposure and health outcomes, independent of blue space and health determinants. As per Pollack et al. 2023 and Aromataris 2015, an umbrella review should only include systematic reviews and meta-analyses. Therefore, we excluded scoping reviews. Pollock, M., Fernandes, R. M., Becker, L. A., Pieper, D., Hartling, L. Chapter V: Overviews of Reviews [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from www.training.cochrane.org/handbook . Aromataris, E., Fernandez, R., Godfrey, C. M., Holly, C., Khalil, H., & Tungpunkom, P. (2015). Summarizing systematic reviews: methodological development, conduct and reporting of an umbrella review approach. JBI Evidence Implementation , 13 (3). https://doi.org/10.1097/XEB.0000000000000055 Methods "We restricted the search to peer-reviewed systematic reviews and meta-analyses conducted in humans and published in English between January 2010 and December 2020, including reviews first published online during this period". Given the dramatic increase in publications on greenness and health in recent years, the quality of this study would be substantially improved if the authors included up-to-date reviews (i.e., from 2010 to the present, rather than 2010-2020). This inclusion can be mentioned as a major strength compared to previous umbrella reviews, as many high-quality studies and reviews have been published in the past three years. This review includes 36 systematic reviews published between January 2010 and December 2020. As you mentioned, much research on greenspace and health, including reviews, has been published since December 2020. We identified an additional 45 review articles between December 2020 and June 2024. Combining these two umbrella reviews would be too many systematic reviews to include in a single umbrella review. As per the Cochrane guidelines (Cumpston and Flemyng, 2023), we have updated the review due to “the availability of new evidence that would have a meaningful impact on the review findings”. [Please see our updated review here, https://doi.org/10.12688/f1000research.166852.1 ]. Cumpston, M., Flemyng, E., Chapter IV: Updating a review [last updated August 2023]. In: Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., Welch, V. A. (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-iv Full names should be provided for the abbreviations when they first appear in the main text (e.g., BMI, PA). This has been fixed. Results It would be beneficial to include a flowchart illustrating the process used to select the final 36 systematic reviews (e.g., the number of studies excluded due to each specific exclusion criterion). As per the F1000 guidelines, a PRISMA flowchart for this review is available under the ‘Data availability’ à ‘Reporting guidelines’ section at the end of the article. It might be better to visualize the study design, measures of greenness, location of studies (country/territory), and outcomes in a figure rather than in several separate tables. A good example can be seen in https://link.springer.com/article/10.1007/s40572-023-00420-9 (Figure 2) We agree that visualising these tables would be useful. However, the example given here, Figure 2, may be misleading. For instance, Figure 2 suggests that all ecological studies investigate respiratory outcomes; however, this is not the case, as indicated in Table S6 of the example. We attempted to create multi-level pie charts to visualise our Tables but found that this was too crowded and inefficient. After several attempts, we decided not to present these multi-level pie charts. Table 4. I appreciate the authors' usage of ICD-code to define the outcomes. However, if I understand it correctly, the original studies in these included reviews may not necessarily and consistently define their outcomes based on these ICD codes, right? If so, this table might be misleading. You are correct that the original studies may not have defined the outcomes based on the ICD codes. Based on the information available in the reviews, we allocated all potential ICD codes for each health outcome. We did this to promote standardised reporting in future articles that investigate the association between greenspace exposure and health outcomes. Why not combine Table 5 and Table 1, they have duplicated information. Table 5 summarises the quantitative results from the included reviews and does not duplicate information from Table 1. "Half of the systematic reviews (50%) had a high risk of bias“. This proportion is quite high. It would be better for the authors to clarify how they assigned the level of ROB to each of the reviews (e.g., using a table with the same structure as Table S2 to list the reason why each level was assigned). This was just a recommendation, but at least the authors should provide more clarifications and discuss this point. Currently, there are very few words on it. ROBIS consists of four domains, and within each domain, there are five to six signalling questions. Two reviewers went through each signalling question, and judgments were made independently. These domains were then used to determine the overall risk of bias of each review. Conflicts between the reviewers were resolved through discussion with the last author. For each review, the final decision on four domains and the overall risk of bias is listed in Supplementary Table S2. More information about ROBIS is available from Whiting et al. 2016. Whiting, P., Savovic, J., Higgins, J. P., Caldwell, D. M., Reeves, B. C., Shea, B., Davies, P., Kleijnen, J., Churchill, R., & group, R. (2016). ROBIS: A new tool to assess risk of bias in systematic reviews was developed. Journal of Clinical Epidemiology , 69 , 225-234. https://doi.org/10.1016/j.jclinepi.2015.06.005 Consistent with the previous comment, a relatively high proportion of the included reviews were also classified as low quality. Providing more clarifications on this point would make this study stronger. Table 6, please clarify the meanings of these words (e.g., N, PY, NA) in the table caption. It would be better to assign the cell background with a color to indicate the quality level (e.g., red for low quality, green for high quality). This can improve the readability dramatically. We have added the meanings of the AMSTAR abbreviations and have added colour to the overall quality column to increase readability. We have also added a footnote explaining the AMSTAR-2 questions, so the reader understands how the quality rating was decided. Discussion "Additionally, we observed positive associations between greenspace exposure and maternal health and birth outcomes including PTB and SGA which were not present in other studies (Yang et al., 2021).” These observed positive associations between greenspace exposure and maternal health and birth outcomes including PTB and SGA were not that consistent compared to the outcomes of mental health and cognitive function, right? If so, this may be the reason why previous studies hadn't reported them in the main findings. We revised this sentence. "Conversely, Stier-Jarmer et al. (2021) and Yang et al. (2021) reported beneficial effects of greenspace on cardiovascular health and cardiometabolic factors, respectively, which was not replicated in our study.” This may be attributable to the fact that some reviews on this aspect were excluded in this umbrella review, while included in Stier-Jarmer et al. (2021) and Yang et al. (2021) due to the different inclusion and exclusion criteria (e.g., scoping reviews on greenness and CVD). Anyway, this should be discussed. We revised this sentence. "Current evidence, including this umbrella review, have been unable to establish a causal link between greenspace exposure and health outcomes as most studies are observational. This highlights the need for additional experimental studies to be conducted” Population-based experimental studies are often unfeasible and also subject to numerous biases (e.g., usually very small sample size, non-adherence). Given the very large proportion of cross-sectional studies, it is more practical to suggest more studies with longitudinal or cohort design and causal inference models (e.g., Instrumental Variables Analysis). We agree that population-based experimental studies are rare. We have revised this sentence accordingly. "Most systematic reviews included in this review were limited by their methodological quality and/or risk of bias, and systematic reviews on the association between greenspace exposure and health outcomes have multiplied since 2020.” I am confused. The authors only included reviews between 2010-2020 and did not include reviews after 2020, as stated in the method section. We revised this sentence View more View less Competing Interests No competing interests. reply Respond Report a concern Huang W. Peer Review Report For: Greenspace exposure and associated health outcomes: a systematic review of reviews [version 2; peer review: 2 approved, 1 approved with reservations] . F1000Research 2025, 13 :491 ( https://doi.org/10.5256/f1000research.163252.r284710) NOTE: it is important to ensure the information in square brackets after the title is included in this citation. The direct URL for this report is: https://f1000research.com/articles/13-491/v1#referee-response-284710 Alongside their report, reviewers assign a status to the article: Approved - the paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations - A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. 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