The Development of Indoor Natural Elements Had Relaxing Psychophysiological Effects on Older Adults in Taiwan During the COVID-19 Pandemic

The Development of Indoor Natural Elements Had Relaxing Psychophysiological Effects on Older Adults in Taiwan During the COVID-19 Pandemic | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article The Development of Indoor Natural Elements Had Relaxing Psychophysiological Effects on Older Adults in Taiwan During the COVID-19 Pandemic Ya-Hui Chung, Shiu-Jen Chen, Ching-Lung Lee, Yu-Sen Chang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4164401/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 06 Nov, 2024 Read the published version in Applied Psychophysiology and Biofeedback → Version 1 posted 4 You are reading this latest preprint version Abstract While the COVID-19 pandemic has affected all types of people, older adults have been disproportionately affected. Therefore, during this period we developed an indoor program inspired by art and natural elements (plant essential oils [EOs]) intended to create a relaxing effect akin to a forest atmosphere to enhance their psychophysiological health. There are for 30 Taiwanese older adults (range, 59-79 years) participated in the study. We combined art activity (still-life painting of vegetables) with breathing Pseudotsuga menziesii and Lavandula angustifolia EOs during a 100-minute experiment involving still-life painting and the inhalation of 2.5% diffused EOs. The research shows physiological measures (heart rate, normalized low-frequency heart oscillations, ratio of low- to high-frequency heart oscillations, high-beta waves, and gamma waves) decreased;correspondingly, an increased standard deviation of normal-to-normal intervals, normalized high-frequency heart oscillations, and high-alpha waves were observed, indicating relaxation physiological state. Subjective psychological assessments using the State-Trait Anxiety Inventory–Stateyielded lower post-test scores, further supporting relaxation effects. The psychophysiological data from this study provide important scientific evidence for the physical and mental health benefits of indoor nature-based activity programs for older adults, thereby improving their quality of life. Heart Rate Brainwave Relaxation Older adults Psychophysiological health Quality of life Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction The United Nations Population Fund and HelpAge International ( 2012 ) have identified population aging as one of the most significant trends of the 21st century. This phenomenon is attributed to socio-economic advancements, medical technology, and improvements in public health and environmental quality, which have helped extend the average lifespan of humans. Governments around the world have proposed active aging policies, hoping to enable older adults to spend their later years in a positive, successful, and health-optimizing way (Antunes, & Maia, 2023 ; Walker, 2009 ; World Health Organization [WHO], 2002). The aging process is a natural phenomenon of living things, just like the blooming and withering of flowers, it is a natural cycle (Ekwonye et al., 2023 ; Verdoodt et al., 2023 ). However, after aging, cells have poorer recovery capabilities and weakened immunity, thus increasing the chance of contracting diseases (Kim et al., 2014 ; Zadworna, 2020 ). Numerous studies suggest that in older adults, exposure to activities related to natural elements can help to maintain health and retard aging and have general beneficial effects on physical, psychological, cognitive, and social functioning, thereby improving their quality of life (Gagliardi & Piccinini, 2019 ; Yu et al., 2017 ). Research by White et al. ( 2019 ) revealed that spending at least 120 minutes per week in nature contributes to overall well-being. Similarly, studies by Yu et al. ( 2017 ) indicate beneficial effects on the physiological and psychological health of middle-aged and older adults after short-term (2 hours) forest bathing. Li et al. ( 2007 ) conducted a 3-day and 2-night study in a Japanese forest and observed enhanced human natural killer (NK) cell activity, NK cell number, and anti-cancer proteins in lymphocytes (Li et al., 2008 ). These findings underscore the close relationship between nature, particularly forests, and psychophysiological well-being (Sundermann et al., 2023 ). However, for modern people, the pace of life tends to be rapid, and their free time is often restricted. They cannot often visit forests to enjoy forest bathing and relaxation. Especially during the novel coronavirus disease (COVID-19) pandemic, which led to government control measures that restricted social contact and mobility to varying degrees, making it even more difficult to travel to the forest for a rest. In addition, social isolation may also lead to reduced physical activity, which can lead to immune system dysfunction, increase susceptibility to infections, and exacerbate the risk of common diseases, such as cardiovascular disease, and psychiatric disorders (Damiot et al., 2020 ). According to a scientific briefing from the World Health Organization (WHO), the global prevalence of anxiety and depression increased by 25% in the first year of the pandemic (WHO, 2022), which also prompted governments to more actively provide people with mental health support services. During a stroll in the forest, both the mind and body tend to experience relaxation and joy, one of the reasons is the breathing of phytoncides released by various plants in the air, including broadleaf and coniferous trees. Phytoncides refer to the collectively volatile organic compounds emitted by plants, with essential oils (EOs) being one of the main components (Lee et al., 2017 ). Essential oils are extracted from plant parts such as seeds, leaves, petals, peels, roots, resins, or bark, typically via methods like steam distillation or cold pressing (Ali et al., 2015 ; Bakkali et al., 2008 ). The chemical composition of EOs depends on factors such as extraction techniques, climatic variations, geographical region, plant species, the plant part used, soil composition, and time of harvesting (Ayaz et al., 2017 ; Mitić et al., 2021 ). Commercial EOs are often analyzed for chemical composition using gas chromatography-mass spectrometry (GC-MS), with relevant quality standards available in publications such as the European Pharmacopoeia and material published by the WHO and the International Organization for Standardization (ISO) (Bakkali et al., 2008 ). The use of EOs to support complementary healing is ancient (Ali et al., 2015 ); for example, in the Bible, EOs are considered spiritual and physical adjunctive healing agents. The ancient Egyptians are also famous for their expertise in the use of plant aromatherapy (for purposes such as beauty enhancement and healthcare, and its antibacterial and antiseptic properties). The ancient Greeks and Romans adopted the Egyptian method of using the EOs found in aromatic plants to improve their quality of life. For example, they used steam baths infused with jasmine, ylang-ylang, and lavender EOs to stimulate the central nervous system (CNS) and relieve stress (Ayaz et al., 2017 ). Stress, as identified by Lazarus and Folkman ( 1984 ), arises from the interaction of an individual's inner tendencies with their external environmental stimuli. Prolonged and excessive stress affects health and necessitates the release and transformation of suppressed emotions in a positive and effective manner. The primary mechanism of aromatherapy is associated with the limbic system of the brain (Cui et al., 2022 ; Kagawa et al., 2003 ), where aromatic compounds stimulate olfactory cells, triggering rapid CNS responses (Spors et al., 2006 ; Tabert et al., 2007 ). The olfactory system converts chemical signals into sensations, which involves the olfactory organs, olfactory bulbs (the primary olfactory centers in the brain), and olfactory nerves (Abbas et al., 2023 ; Angelucci et al., 2014 ; Tabert et al., 2007 ). Therefore, when the aroma of EOs enters the human nose, it stimulates olfactory cells to convert the aromatic information into chemical signals, which are transmitted to the limbic system of the brain by the olfactory nerves, affecting the autonomic nervous system (ANS) and endocrine system. This includes the hippocampus, which is related to memory, and the limbic system, which includes the central amygdala (Ali et al., 2015 ; Angelucci et al., 2014 ; Duan et al., 2007 ). The latter controls emotions; activates emotions, memory, and learning; and displays emotions such as relaxation, happiness, and anxiety through behavior. Because of the direct and clear impact of odor on emotions, cognition, and behavior, it can be used to regulate human emotions and performance (Ali et al., 2015 ; Angelucci et al., 2014 ; Ayaz et al., 2017 ). The EOs used in this study were extracted from two plant species, Lavandula angustifolia (Gymnospermae) and Pseudotsuga menziesii (Angiospermae). The former ( L. angustifolia ), which belongs to the Lamiaceae family, is native to the Mediterranean region, and research suggests its EO has calming, anxiety-relieving, relaxing, and sleep-promoting effects (Ali et al., 2015 ; Ayaz et al., 2017 ; Chien et al., 2012 ; Koulivand et al., 2013 ). The latter ( P. menziesii ), a member of the Pinaceae family, is native to the western United States and its EO has exhibited antibacterial activity (Mitić et al., 2021 ), but none of the other potential benefits of its EO remain understudied. Therefore, this study also wanted to explore whether inhaling the scent of coniferous forests, such as P. menziesii EO, could recreate the relaxing effects of forest bathing. Monitoring heart rate variability (HRV) measures continuous changes in heart rate (HR) and the response of the ANS (Ortega et al., 2024 ). Previous studies have shown that HRV can be suggested as an objective assessment of stress and physical health (Chien et al., 2012 ; Duan et al., 2007 ; Kristal-Boneh et al., 1995 ; Malik et al., 1996 ). Brain neurons emit tiny electromagnetic waves of different frequencies when sending messages to the brain. This brainwave activity can be monitored and displayed as an electroencephalogram (EEG) and has been shown to be associated with emotions (Cho et al., 2013 ; Puzi et al., 2013 ; Sugawara et al., 1998 ). Consequently, by analyzing HRV and EEG parameters, it should be possible to evaluate the impact of EOs on a person’s physiological and psychological state before and after activities (Ali et al., 2015 ; Angelucci et al., 2014 ). In addition, some studies have shown that the State-Trait Anxiety Inventory (STAI) can be used to learn more about the subjective psychological state of subjects (Karan, 2019 ; Mahmoodi et al., 2012 ; Spielberger et al., 1989). Previous research indicates that artistic creation can improve quality of life and that self-expression and personal fulfillment can benefit from the creative process, contributing to improving physical, psychological, and emotional health (Hattori et al., 2011 ; Tjasink & Soosaipillai, 2019 ). However, few studies have also explored the benefits of diffusing EOs during artistic activities such as still-life painting. Therefore, in this study, we explored breathing plant-extracted EOs that whether have more relaxing psychophysiological benefits for older adults while doing still-life painting. Given that health is an important factor in a successful aging process (WHO, 2002), this research aims to provide older adults with an indoor natural activity program that can promote their physical and mental health, thereby enhancing immunity and reducing the threat of viral infection, thus improving their overall quality of life (Damiot et al., 2020 ). Materials and methods Participants Thirty participants aged between 59 and 79 years (mean age: 71.0 ± 4.9 years; mean ± standard deviation [SD]) were recruited for the experiment. The participants included 29 females (96.7%) and one male (3.3%). They were enrolled as students in the Senior Citizens’ Learning Camp at the Hwa Hsia University of Technology in New Taipei City, Taiwan. This initiative, similar, to the University of the Third Age (U3A), aims to inspire a lifelong motivation for diverse learning in older adults to enhance both their physical and mental health while slowing down the aging process (Zadworna, 2020 ). The Ministry of Education in Taiwan began promoting senior education in 2008, and this included the establishment of the Senior Citizens’ Learning Camp in collaboration with relevant universities and colleges. These university programs cater primarily to citizens aged 55 and above (Zadworna, 2020 ). The inclusion criteria for study participants were the absence of asthma and epilepsy, no known allergies to EOs, and the absence of nasal congestion or upper respiratory tract infections. Once they fully understood the research purpose and procedures, the participants provided their informed consent by signing a consent form. This study was approved by the Research Ethics Committee of National Taiwan University (NTU-REC No. 202104HM009). Essential oils P. menziesii EO and L. angustifolia EO were purchased from dōTERRA International LLC (Pleasant Grove, UT, USA). The concentration of EOs used in the study was 2.5% (Essential oils : water = 0.5 ml : 20ml) and was based on Rhind's (2015) recommendations for olfactory inhalation via a diffuser (dōTERRA International). The manufacturer provided a chemical analysis of P. menziesii EO via GC-MS identifying 61 chemical components. The major constituents included β-pinene (21.16%), α-pinene (14.97%), terpinolene (11.01%), delta-3-carene (8.87%), sabinene (6.37%), γ-terpinene (4.86%), limonene (3.15%), α-terpinene (3.08%), myrcene (2.38%), citronellyl acetate (2.61%). In addition, the manufacturer also provided 51 chemical components identified through chemical analysis of L. angustifolia EO by GC-MS. The major constituents included linalool (36.03%), linalyl acetate (30.67%), cis-β-ocimene (4.49%), lavandulyl acetate (4.33%), terpinen-4-ol (3.3%), trans-β-farnesene (2.78%), β-caryophyllene (2.72%). Indoor art experience activit y Still-life painting of vegetables was chosen as the indoor art experience activity for the participants of this study. The participants first did a continuous line drawing with pencils to outline the shapes of the objects (e.g. vegetables) in their artwork, followed by coloring with colored pencils. The materials supplied were B pencils (soft core), H pencils (hard core), colored pencils, sketch paper, and erasers. Under the guidance of experienced instructors, the participants completed their artworks within sixty minutes. Experimental design The study took place on 5 November 2021, from 9:30 to 11:10 AM in classrooms at Hwa Hsia University of Technology in New Taipei City, Taiwan (Senior Citizens’ Learning Camp). During the 100-minute experiment, the participants were instructed to avoid consuming caffeinated or alcoholic beverages and refrain from wearing metallic items such as necklaces, watches, earrings, and rings. The experiment involved the participants breathing P. menziesii EO and L. angustifolia EO at a concentration of 2.5% and diffused by an aromatic sprayer while doing still-life painting. The participants were also requested to wear a patch-type HRV analyzer to measure their heart rate and a patch-type EEG to measure their brainwaves. The purpose was to evaluate the effects of breathing EOs during an indoor sensory experience event by monitoring physiological parameters and collecting scale questionnaire responses before and after the entire event. The experiment consisted of seven-time stages (Fig. 1 ). Stage 1 involved the explanation of the research purpose and methods and the completion of the informed consent form (10 minutes). During stage 2, the participants wore the physiological assessment sensors to collect baseline HRV and EEG data and completed the pre-test STAI-S questionnaire (15 minutes). In stage 3, the participants were introduced to the indoor sensory experience activity (still-life painting) while EO-free water vapor was diffused into the air (15 minutes). The HRV and EEG data were collected continuously until the end of the experiment. During stage 4, water vapor containing P. menziesii EO was diffused, allowing the participants to inhale the EO via normal breathing (15 minutes). In stage 5, between the first and second EO diffusion stages, water vapor without EOs was diffused (15 minutes). During stage 6, water vapor containing L. angustifolia EO was diffused (15 minutes). Finally, in stage 7, the post-test STAI-S questionnaire was completed and the sensors were removed (15 minutes). The diffusion of EO-free water vapor served as the control for EO diffusion, since it is colorless and odorless, in contrast to EOs. Based on the short-term adaptation characteristics of the olfactory system, the 15-minute break with EO-free water vapor was inserted between the two EO-diffusion stages to allow the participants to rest and adjust, to avoid habitualization to specific odors during the experiment (Steinmetz et al., 1970 ; Tabert et al., 2007 ). Physiological indices To objectively assess each participant’s physiological state before and after these experiments, a patch-style HRV sensor (BeneGear, New Taipei City, Taiwan) was attached to the left side of their chest, over the heart, and a patch-style EEG sensor (BeneGear) was attached to their central forehead. These sensors continuously monitor physiological responses to evaluate the activity of the nervous system. Data were stored in the sensors' memory and transferred data to a computer via Wi-Fi for further processing and analysis. HRV monitors ongoing changes in heart rate (HR) and was used in this study used the HRV parameters, including HR in beats per minute, normalized low-frequency heart oscillations (nLF), normalized high-frequency heart oscillations (nHF), ratio of low- to high-frequency heart oscillations (LF/HF), and standard deviation of normal-to-normal intervals (SDNN), analyzes were performed to reveal the ANS activity and emotional status (Chien et al., 2012 ; Duan et al., 2007 ; Hjortskov et al., 2004 ; Kristal-Boneh et al., 1995 ; Malik et al., 1996 ; Thayer et al., 2012 ). An EEG records changes in potential difference between two points on the scalp over time, reflecting the brain's neural activity. In this study, alpha waves (7.0–13.0 Hz), beta waves (13.0–30.0 Hz), and gamma waves (30.0–100.0 Hz) characteristics were investigated. Recorded and analyzed brainwave activity through frequencies and power (Cho et al., 2013 ; Puzi et al., 2013 ; Sugawara et al., 1998 ). Psychological indices The State-Trait Anxiety Inventory (STAI) was used to evaluate the participants' anxiety levels. The STAI consists of 40 self-report questions divided into state anxiety (STAI-S) and trait anxiety (STAI-T) topics. The STAI-S assesses anxiety levels at a specific moment, which are indicative of transient emotional responses to particular stress situations, while the STAI-T assesses the general pattern of individual anxious feelings (Spielberger, 1989 ). In this study, we used the STAI-S to assess the subjective emotional status of the participants before and after the test. It comprises 20 questions in total, consisting of 10 positive questions and 10 negative ones. Each item is scored using a four-point Likert scale (1–4 for negative questions and 4–1 for positive questions). Higher scores indicate higher anxiety levels (Karan, 2019 ; Spielberger et al., 1989). Environmental Indices Previous research indicates that HRV is influenced by ambient temperature (Kristal-Boneh et al., 1995 ; Kunitake and Ishiko, 1992 ; Lindqvist et al., 1990 ). Air pollution and indoor environmental factors such as air quality and temperature also impact HR and changes in HRV, affecting health and the ability to learn (Pope et al., 1999 ; Satish et al., 2012 ; Zhang et al., 2017 ). To monitor the environment during the experiment, an indoor air quality monitor (AirBoxx; KD Engineering, NY, USA) was used to measure parameters such as CO 2 concentration, CO concentration, temperature, and relative humidity. Monitoring began 10 minutes before the experiment and ended 10 minutes after its termination. There was one monitoring point at the front and back of the experimental site. The recorded mean values for CO 2 concentration, CO concentration, temperature, and relative humidity in the experimental environment were 630.2 ± 15.9 ppm, 0.0 ppm, 26.8 ± 0.7°C, and 77.6 ± 1.7% (mean ± SD), respectively. Statistical analysis All data were analyzed using IBM SPSS Statistics for Windows, Version 21.0 (IBM Corporation, Armonk, NY, USA). The statistical analysis used the paired sample t -tests to compare differences between the baseline and the stages of the experiment (i.e., breathing of EO-free water vapor and the two EOs). Data are presented as mean ± standard error (SE), and a P -value < 0.05 was considered statistically significant. Results Physiological indices To assess the impact of the indoor sensory experience activity (still-life painting) combined with EOs breathing, a wearable HRV sensor was used to record parameters HR-related continuously. The baseline activity was recorded before the beginning of the still-life painting. During stages of the experiment that still-life painting with P. menziesii EO and L. angustifolia EO diffusion, the participants’ HR was significantly reduced compared to baseline ( P < 0.05) (Fig. 2 A). We next analyzed the still-life painting with EO-free water vapor diffusion, the SDNN did not change significantly from baseline (Fig. 2 B). However, when L. angustifolia EO was administered, there was a significant increase in SDNN (47.27 ± 5.61 ms, P < 0.05). During EO-free water vapor diffusion, nLF and nHF were unchanged. Nevertheless, when L. angustifolia EO was diffused, the percentage of nLF heart oscillations decreased significantly (64.76 ± 2.31%, P < 0.01) (Fig. 2 C). Correspondingly, when the participants breathed L. angustifolia EO, the percentage of their nHF heart oscillations increased significantly (35.24 ± 2.31%, P < 0.01) (Fig. 2 D). We also observed a significant decrease in LF/HF when L. angustifolia EO was administered (2.15 ± 0.17, P < 0.05), while diffusion of OE-free water vapor did not affect it (Fig. 2 E). Taken together, the above results indicate the physiological condition of reduced sympathetic nerve activity and increased parasympathetic nerve activity during the breathing of EOs, particularly L. angustifolia EO, indicating that the participants were relaxed. We also used wearable EEG sensors to continuously record brainwave-related parameters. The participants’ high-alpha waves, which are typically associated with a state of mental relaxation and focused attention (Puzi et al., 2013 ), increased during the course of the experiment, but the difference from baseline was not statistically significant for any stage of the experiment (Fig. 3 A). Their high-beta waves, which are generally positively correlated with stress levels (Puzi et al., 2013 ; Sugawara et al., 1998 ), decreased during breathing of P. menziesii EO (104.47 ± 11.18 µV 2 , P < 0.05) and L. angustifolia EO (99.37 ± 10.91 µV 2 , P < 0.05) (Fig. 3 B), indicating a reduction in stress levels. Finally, their gamma waves, which are negatively correlated with relaxation (Cho et al., 2013 ; Oathes et al., 2008 ), decreased significantly when the participants were breathing L. angustifolia EO (415.38 ± 36.30 µV 2 , P < 0.05) (Fig. 3 C), suggesting that the participants were in a relaxed state. Overall, the EEG results indicate that EOs can reduce stress levels and enhance relaxation benefits. Psychological indices Participants' subjective emotional states were assessed using the STAI-S questionnaire. Compared to the pre-test scores, the post-test STAI-S scores decreased for all questions (Fig. 4 ). In the STAI-S scoring system, higher total scores indicate higher anxiety levels (Karan, 2019 ; Mahmoodi et al., 2012 ; Spielberger et al., 1989). Our results suggest that the participants experienced a reduction in anxiety levels during the experiment. Discussion This research established an Indoor natural activity program by analyzing physiological parameters such as HRV and EEG and evaluating the relaxing effect of breathing P. menziesii and L. angustifolia EO on 30 older adults during still-life painting activity. The results reported a relaxing effect. Activities conducted in natural environments, such as forest bathing and other related activities, are beneficial to health (White et al., 2019 ; Yu et al., 2017 ). It is difficult for older adults in the city to travel to the forest to relax frequently. To promote physical and mental health, many studies are developing plans to integrate natural environmental elements such as landscape videos, natural light, scented plants, birdsong, and the sound of running water into daily life (Mcsweeney et al., 2015 ). Therefore, in this study, we combined indoor activity (still-life painting) with breathing EOs, intending to create a relaxing atmosphere similar to the natural forest environment in an indoor environment, so that participants can immerse themselves in elements of the natural world. Thayer et al. ( 2012 ) showed that HRV can provide an index of the intensity of brainstem activity and the autonomic responses of the body. Further, Hjortskov et al. ( 2004 ) reported that HRV can be used as a reference for understanding negative emotions, mental stress, and health. We therefore used HRV to measure the effects of the experiment on stress levels. The participants’ HR decreased after EO administration (Fig. 2 A), indicating that their stress levels had been reduced. This is consistent with previous research results. When people feel stressed, the sympathetic nervous system becomes more active, and the HR increases; conversely, when stress is reduced, the parasympathetic nervous system becomes more active and the HR decreases (Kristal-Boneh et al., 1995 ; Hjortskov et al., 2004 ; Thayer et al., 2012 ). Grunebaum et al ( 2011 ) showed that in 33 patients undergoing minimally invasive surgery, parasympathetic nerve activity increased, and HR decreased after inhaling lavender aroma. In line with Hjortskov et al.'s ( 2004 ) findings under stress-reduced conditions, we observed a decrease in nLF (Fig. 2 C) and LF/HF (Fig. 2 E) after the participants had breathed EOs. Correspondingly, nHF (Fig. 2 D) and SDNN (Fig. 2 B) values increased after EO breathing. This consistency with previous research indicates that during negative emotional experiences, such as tension and anxiety, sympathetic nervous system activity increases, leading to an increase in nLF and LF/HF. Conversely, during relaxation, parasympathetic nervous system activity increases, resulting in increased nHF and SDNN. The nLF measure quantifies sympathetic nervous system activity, while nHF quantifies parasympathetic nervous system activity (Chien et al., 2012 ; Duan et al., 2007 ; Malik et al., 1996 ). The LF/HF is an indicator of ANS balance, while SDNN reflects the intensity of regulation of the sinus node of the heart by the ANS thus representing the overall activity of the autonomic nervous system (Chien et al., 2012 ; Hjortskov et al., 2004 ; Malik et al., 1996 ). Duan et al. ( 2007 ) reported that after 10 young women inhaled the scent of lavender, the subjects' parasympathetic nerve activity increased, nHF increased, and LF/HF decreased. Chien et al. ( 2012 ) showed that 67 middle-aged menopausal women experienced an increase in SDNN, mental relaxation, and improved sleep after inhaling lavender EO. Chang and Shen ( 2011 ) indicated that stress was relieved and nLF decreased after 54 primary school teachers inhaled aromatic EO. Choi's study (2022) suggested that the olfactory stimulation provided by EOs has a stabilizing effect on the prefrontal cortex and overall brain activity. Additionally, Angelucci et al. ( 2014 ) documented the impact of EO scents on neurophysiological brain activity, while Lorig and Schwartz ( 1988 ) observed temporal patterns in EEG activity related to exposure to various scents. We therefore used EEG in this study to assess the correlation between olfactory-stimulated brain activity and stress-relief benefits. The observed significant decrease in high-beta waves (Fig. 3 B) and gamma waves (Fig. 3 C) after EO breathing suggests that the participants experienced stress relief. This aligns with previous research that indicates that a decrease in high-beta and gamma waves indicates stress reduction (Cho et al., 2013 ; Sugawara et al., 1998 ). Sayorwan et al. ( 2012 ) reported that 20 participants, after inhaling lavender EO, ​​increased alpha wave activity in the brain, especially in the bilateral temporal lobes and central areas, and their emotions also felt happier and more relaxed. Sugawara et al. ( 1998 ) observed that 23 adults had good sensory evaluation after inhaling linalool EO, which was accompanied by a trend of lower beta waves. Cho et al. ( 2013 ) studied 20 right-handed healthy volunteers. After inhaling Mentha arvensis EO, mental stress levels were reduced and gamma waves decreased. The results of this study are similar to previous research on the relaxation benefits of other coniferous family EOs (such as Fir EO, and Juniper EO) (Kim & Song, 2022 ; Kim et al., 2023 ; Park, 2017 ). We observed similar physiological results when breathing P. menziesii EO compared to those found while breathing L. angustifolia EO, with a significant decrease in HR and high-beta waves, suggesting a relaxing effect. The main components of L. angustifolia EO, namely linalool (36.03%) and linalyl acetate (30.67%), which are known for their calming effects (Ali et al., 2015 ; Ayaz et al., 2017 ; Chien et al., 2012 ; Duan et al., 2007 ; Karan, 2019 ; Koulivand et al., 2013 ; Sugawara et al., 1998 ). The main components of P. menziesii EO include β-pinene (21.16%) and α-pinene (14.97%). Most studies on pinene’s anxiolytic and other neuroprotective effects have been conducted only in animal models (Bakkali et al., 2008 ; Salehi et al. 2019 ). Based on physiological data of the relaxing effects of P. menziesii EO observed in this study, we speculate that pinene may be the active ingredient responsible for this phenomenon. Hattori et al. ( 2011 ) reported that coloring and drawing can improve the vitality and quality of life of patients with mild Alzheimer's disease. Tjasink and Soosaipillai ( 2019 ) showed that art therapy reduces burnout among oncology and palliative care doctors to enhance mental and emotional well-being. The results of the present study are similar to previous research results. We also observed that still-life painting combined with breathing EOs is beneficial to the physical and mental health of participants. We conducted STAI-S questionnaires before and after the experiment to understand the participants’ subjective psychological state (Karan, 2019 ; Mahmoodi et al., 2012 ; Spielberger et al., 1989). The post-test scores of the STAI-S scale decreased relative to the pre-test scores (Fig. 4 ), indicating that inhaling EO combined with still-life painting has subjective psychological benefits for older adults, leading to reduced anxiety. This aligns with previous research using the STAI-S, which suggested that the aroma of EOs can alleviate anxiety in dental patients (Karan et al., 2019), patients before coronary angiography (Mahmoodi et al., 2012 ), and primiparous women (Rashidi Fakari et al., 2015 ). To mitigate the impact of inherent differences in stress resistance among individuals and ensure the accuracy of our stress-relief findings, we used a within-subject design, comparing participants with themselves and using EO-free water-vapor diffusion as a control for EO diffusion. However, this design is still subject to some limitations. First, although the study was conducted during the period when the local COVID-19 epidemic was easing, we strove to avoid infection by not using the salivary amylase monitor to measure salivary amylase activity, which can be used as an index of stress. This reduced the physiological data available for analysis. Second, the study's representativeness was limited by the small sample size which resulted from the effect of the COVID-19 pandemic during recruitment. Third, the EEG used in this study was worn in the center of the forehead, so only the brainwaves of the prefrontal cortex were evaluated, and those of other brain regions were not measured. Furthermore, given that the sense of smell plays an important role in the biopsychosocial effects of stress, mood, and workability (Angelucci et al., 2014 ; DeGuzman et al., 2020 ; Herz et al., 2009; Kiecolt-Glaser et al., 2008 ). Future research may be able to take advantage of olfaction's ability to rapidly affect the nervous system (Spors et al., 2006 ; Tabert et al., 2007 ), when performing biofeedback intervention (Weerdmeester et al., 2020 ), one may be able to inhale EOs at the same time, which will help strengthen and improve the psychophysiological health. Conclusions In this study, Sympathetic and parasympathetic nervous system activity changes were measured using a Heart Rate Variability Sensor, brain wave changes were monitored using an Electroencephalography Sensor, and anxiety levels were assessed through STAI-S questionnaire. To assess changes in the psychophysiological state of older adults after breathing L. angustifolia and P. menziesii EOs while doing still-life painting. We observed an increase in SDNN, nHF, and high-alpha waves and a decrease in HR, nLF, LF/HF, high-beta waves, and gamma waves. The relaxing and stress-relieving effects of this indoor natural activity are considered beneficial for the health of older adults. This program offers a simple relaxation method that older adults can engage in in their daily lives. Compared to forest therapy, it is not subject to geographical restrictions, and the required materials are readily accessible. This beneficial activity promotes psychophysiological well-being among older adults, thereby enhancing their immune function, reducing the risk of viral infections, and increasing satisfaction and happiness with life. Declarations Author Contribution Conceptualization: Y-SC; data acquisition, Y-HC; methodology: S-JC, C-LL, Y-SC; analysis: Y-HC, Y-SC; investigation: Y-HC; resources: S-JC, C-LL, Y-SC; writing original draft: Y-HC; writing, review and editing: Y-HC, S-JC, C-LL, Y-SC; supervision: Y-SC. References Abbas, F., Zhou, Y., O'Neill Rothenberg, D., Alam, I., Ke, Y., & Wang, H. C. (2023). Aroma Components in Horticultural Crops: Chemical Diversity and Usage of Metabolic Engineering for Industrial Applications. Plants (Basel, Switzerland) , 12 (9), 1748. https://doi.org/10.3390/plants12091748 Ali, B., Al-Wabel, N. A., Shams, S., Ahamad, A., Khan, S. A., & Anwar, F. (2015). Essential oils used in aromatherapy: A systemic review. 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Effects of exposure to carbon dioxide and bioeffluents on perceived air quality, self-assessed acute health symptoms, and cognitive performance. Indoor air , 27 (1), 47–64. https://doi.org/10.1111/ina.12284 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 06 Nov, 2024 Read the published version in Applied Psychophysiology and Biofeedback → Version 1 posted Editorial decision: Revision requested 27 Mar, 2024 Submission checks completed at journal 27 Mar, 2024 Editor assigned by journal 27 Mar, 2024 First submitted to journal 25 Mar, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4164401","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":284568401,"identity":"e2fd4f5a-f6b0-4064-a0b9-18295e129940","order_by":0,"name":"Ya-Hui Chung","email":"","orcid":"","institution":"National Taiwan University","correspondingAuthor":false,"prefix":"","firstName":"Ya-Hui","middleName":"","lastName":"Chung","suffix":""},{"id":284568402,"identity":"4d69a1b2-5dd8-43c0-842b-f31f35f767fb","order_by":1,"name":"Shiu-Jen Chen","email":"","orcid":"","institution":"Kang Ning University","correspondingAuthor":false,"prefix":"","firstName":"Shiu-Jen","middleName":"","lastName":"Chen","suffix":""},{"id":284568403,"identity":"f0d67b0e-c99c-482c-b5a5-0928b563e430","order_by":2,"name":"Ching-Lung Lee","email":"","orcid":"","institution":"National Taiwan University","correspondingAuthor":false,"prefix":"","firstName":"Ching-Lung","middleName":"","lastName":"Lee","suffix":""},{"id":284568404,"identity":"1ca7df36-bb2e-488f-b2c0-957a76df40c8","order_by":3,"name":"Yu-Sen Chang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAyklEQVRIiWNgGAWjYHACNhAhh8QmUosxhAISPMRqSWwgWovB+cPPHvzcUZu+Xb7HgOFD2WEGe4kEAlpupJkb9p45nruzjceAcca5www8hLXwsEnwth3L3XCMx4CZtw2oRZqQlvNn2CT/th1LNwBp+UuUlgM5bNK8bTUJYC2MxGiRvJFmJi3bdsBww7G0goM959J5eO4/wK+FDxhikm/b6uQNDh/e+OBHmbUce88B/FoUIPKHwSSITTgm5RvAVB1BhaNgFIyCUTCCAQBpDEIrK+lv0QAAAABJRU5ErkJggg==","orcid":"","institution":"National Taiwan University","correspondingAuthor":true,"prefix":"","firstName":"Yu-Sen","middleName":"","lastName":"Chang","suffix":""}],"badges":[],"createdAt":"2024-03-25 15:36:00","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4164401/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4164401/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10484-024-09676-9","type":"published","date":"2024-11-06T15:57:55+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":53729582,"identity":"197c2170-5b06-41a0-94e1-4edfa46b8260","added_by":"auto","created_at":"2024-03-29 12:46:30","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":65418,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental procedure and timing.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4164401/v1/6763802d88091cf5a70e03d6.png"},{"id":53730638,"identity":"78ca83e2-9d0c-46d5-8bc0-370e4b6b114c","added_by":"auto","created_at":"2024-03-29 13:02:30","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":50439,"visible":true,"origin":"","legend":"\u003cp\u003eChange in heart rate variability (HRV) -related physiological parameters during the experiment. Following the baseline period, an indoor sensory experience activity, still-life painting, began. During the still-life painting procedure, water vapor (Water), water vapor with \u003cem\u003ePseudotsuga menziesii \u003c/em\u003eessential oil (P.m. EO), water vapor (Water), and water vapor with \u003cem\u003eLavandula angustifolia \u003c/em\u003eessential oil (L.a. EO) were given in an orderly manner. The participants’ HR (heart rate) decreased during their exposure to both essential oils (EOs) (A). Their SDNN (standard deviation of normal-to-normal intervals) values increased during their exposure to \u003cem\u003eL. angustifolia\u003c/em\u003e EO (B). The percentages of nLF (normalized low-frequency heart oscillations) decreased while the participants breathed \u003cem\u003eL. angustifolia\u003c/em\u003e EO (C). Correspondingly, the percentages of nHF (normalized high-frequency heart oscillations) increased while they breathed \u003cem\u003eL. angustifolia\u003c/em\u003e EO (D). The LF/HF (low frequency to high frequency) ratio decreased during exposure to L. angustifolia EO (E). Data were collected from 30 participants and are presented as mean ± SE. * \u003cem\u003eP\u003c/em\u003e\u0026lt; 0.05; ** \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.01; paired sample \u003cem\u003et\u003c/em\u003e-test.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4164401/v1/8af4cff4eb6fe9d2f042db99.png"},{"id":53729972,"identity":"95f1b211-51e5-465a-812e-e81b376be443","added_by":"auto","created_at":"2024-03-29 12:54:30","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":131222,"visible":true,"origin":"","legend":"\u003cp\u003eChange in electroencephalogram (EEG) -related physiological parameters during the experiment. After the baseline period, an indoor sensory experience activity, still-life painting, was introduced. In the meantime, water vapor (Water), water vapor with \u003cem\u003ePseudotsuga menziesii\u003c/em\u003eessential oil (P.m. EO), water vapor (Water), and water vapor with \u003cem\u003eLavandula angustifolia\u003c/em\u003e essential oil (L.a. EO) were diffused to the air in an orderly manner. The participants’ high-alpha waves did not change significantly throughout the experiment (A). Their high-beta waves decreased during breathing of \u003cem\u003eP. menziesii \u003c/em\u003eEO and\u003cem\u003e L. angustifolia\u003c/em\u003eEO administration (B), while their gamma waves decreased while they breathed \u003cem\u003eL. angustifolia \u003c/em\u003eEO (C). Data were collected from 30 participants and are presented as mean ± SE. * \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05; paired sample \u003cem\u003et\u003c/em\u003e-test.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4164401/v1/72807b5254ff00c347128bab.png"},{"id":53729585,"identity":"44d800d5-b358-4374-8f00-b176baf215c4","added_by":"auto","created_at":"2024-03-29 12:46:30","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":49114,"visible":true,"origin":"","legend":"\u003cp\u003eSTAI-S scores before and after the experiment. In all questions, the scores decreased in the post-test STAI-S questionnaire. # indicates a positive question. Data were collected from 30 participants and are presented as mean ± SE. * \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05; ** \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.01; *** \u003cem\u003eP\u003c/em\u003e\u0026lt; 0.001; paired sample \u003cem\u003et\u003c/em\u003e-test.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4164401/v1/fda230bc3763b619f9176ee5.png"},{"id":68750697,"identity":"b3535a1f-36c8-448d-ab75-72941dacca54","added_by":"auto","created_at":"2024-11-11 16:12:12","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":820754,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4164401/v1/e7abd719-243c-4d89-87af-dc7101066436.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"The Development of Indoor Natural Elements Had Relaxing Psychophysiological Effects on Older Adults in Taiwan During the COVID-19 Pandemic","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe United Nations Population Fund and HelpAge International (\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) have identified population aging as one of the most significant trends of the 21st century. This phenomenon is attributed to socio-economic advancements, medical technology, and improvements in public health and environmental quality, which have helped extend the average lifespan of humans. Governments around the world have proposed active aging policies, hoping to enable older adults to spend their later years in a positive, successful, and health-optimizing way (Antunes, \u0026amp; Maia, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Walker, \u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; World Health Organization [WHO], 2002). The aging process is a natural phenomenon of living things, just like the blooming and withering of flowers, it is a natural cycle (Ekwonye et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Verdoodt et al., \u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). However, after aging, cells have poorer recovery capabilities and weakened immunity, thus increasing the chance of contracting diseases (Kim et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Zadworna, \u003cspan citationid=\"CR88\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Numerous studies suggest that in older adults, exposure to activities related to natural elements can help to maintain health and retard aging and have general beneficial effects on physical, psychological, cognitive, and social functioning, thereby improving their quality of life (Gagliardi \u0026amp; Piccinini, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Yu et al., \u003cspan citationid=\"CR87\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eResearch by White et al. (\u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) revealed that spending at least 120 minutes per week in nature contributes to overall well-being. Similarly, studies by Yu et al. (\u003cspan citationid=\"CR87\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) indicate beneficial effects on the physiological and psychological health of middle-aged and older adults after short-term (2 hours) forest bathing. Li et al. (\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2007\u003c/span\u003e) conducted a 3-day and 2-night study in a Japanese forest and observed enhanced human natural killer (NK) cell activity, NK cell number, and anti-cancer proteins in lymphocytes (Li et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). These findings underscore the close relationship between nature, particularly forests, and psychophysiological well-being (Sundermann et al., \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). However, for modern people, the pace of life tends to be rapid, and their free time is often restricted. They cannot often visit forests to enjoy forest bathing and relaxation. Especially during the novel coronavirus disease (COVID-19) pandemic, which led to government control measures that restricted social contact and mobility to varying degrees, making it even more difficult to travel to the forest for a rest. In addition, social isolation may also lead to reduced physical activity, which can lead to immune system dysfunction, increase susceptibility to infections, and exacerbate the risk of common diseases, such as cardiovascular disease, and psychiatric disorders (Damiot et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). According to a scientific briefing from the World Health Organization (WHO), the global prevalence of anxiety and depression increased by 25% in the first year of the pandemic (WHO, 2022), which also prompted governments to more actively provide people with mental health support services.\u003c/p\u003e \u003cp\u003eDuring a stroll in the forest, both the mind and body tend to experience relaxation and joy, one of the reasons is the breathing of phytoncides released by various plants in the air, including broadleaf and coniferous trees. Phytoncides refer to the collectively volatile organic compounds emitted by plants, with essential oils (EOs) being one of the main components (Lee et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Essential oils are extracted from plant parts such as seeds, leaves, petals, peels, roots, resins, or bark, typically via methods like steam distillation or cold pressing (Ali et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Bakkali et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). The chemical composition of EOs depends on factors such as extraction techniques, climatic variations, geographical region, plant species, the plant part used, soil composition, and time of harvesting (Ayaz et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Mitić et al., \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Commercial EOs are often analyzed for chemical composition using gas chromatography-mass spectrometry (GC-MS), with relevant quality standards available in publications such as the European Pharmacopoeia and material published by the WHO and the International Organization for Standardization (ISO) (Bakkali et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2008\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe use of EOs to support complementary healing is ancient (Ali et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2015\u003c/span\u003e); for example, in the Bible, EOs are considered spiritual and physical adjunctive healing agents. The ancient Egyptians are also famous for their expertise in the use of plant aromatherapy (for purposes such as beauty enhancement and healthcare, and its antibacterial and antiseptic properties). The ancient Greeks and Romans adopted the Egyptian method of using the EOs found in aromatic plants to improve their quality of life. For example, they used steam baths infused with jasmine, ylang-ylang, and lavender EOs to stimulate the central nervous system (CNS) and relieve stress (Ayaz et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Stress, as identified by Lazarus and Folkman (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e1984\u003c/span\u003e), arises from the interaction of an individual's inner tendencies with their external environmental stimuli. Prolonged and excessive stress affects health and necessitates the release and transformation of suppressed emotions in a positive and effective manner.\u003c/p\u003e \u003cp\u003eThe primary mechanism of aromatherapy is associated with the limbic system of the brain (Cui et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Kagawa et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2003\u003c/span\u003e), where aromatic compounds stimulate olfactory cells, triggering rapid CNS responses (Spors et al., \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Tabert et al., \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). The olfactory system converts chemical signals into sensations, which involves the olfactory organs, olfactory bulbs (the primary olfactory centers in the brain), and olfactory nerves (Abbas et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Angelucci et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Tabert et al., \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Therefore, when the aroma of EOs enters the human nose, it stimulates olfactory cells to convert the aromatic information into chemical signals, which are transmitted to the limbic system of the brain by the olfactory nerves, affecting the autonomic nervous system (ANS) and endocrine system. This includes the hippocampus, which is related to memory, and the limbic system, which includes the central amygdala (Ali et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Angelucci et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Duan et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). The latter controls emotions; activates emotions, memory, and learning; and displays emotions such as relaxation, happiness, and anxiety through behavior. Because of the direct and clear impact of odor on emotions, cognition, and behavior, it can be used to regulate human emotions and performance (Ali et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Angelucci et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Ayaz et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe EOs used in this study were extracted from two plant species, \u003cem\u003eLavandula angustifolia\u003c/em\u003e (Gymnospermae) and \u003cem\u003ePseudotsuga menziesii\u003c/em\u003e (Angiospermae). The former (\u003cem\u003eL. angustifolia\u003c/em\u003e), which belongs to the Lamiaceae family, is native to the Mediterranean region, and research suggests its EO has calming, anxiety-relieving, relaxing, and sleep-promoting effects (Ali et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Ayaz et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Chien et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Koulivand et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). The latter (\u003cem\u003eP. menziesii\u003c/em\u003e), a member of the Pinaceae family, is native to the western United States and its EO has exhibited antibacterial activity (Mitić et al., \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), but none of the other potential benefits of its EO remain understudied. Therefore, this study also wanted to explore whether inhaling the scent of coniferous forests, such as \u003cem\u003eP. menziesii\u003c/em\u003e EO, could recreate the relaxing effects of forest bathing.\u003c/p\u003e \u003cp\u003eMonitoring heart rate variability (HRV) measures continuous changes in heart rate (HR) and the response of the ANS (Ortega et al., \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Previous studies have shown that HRV can be suggested as an objective assessment of stress and physical health (Chien et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Duan et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Kristal-Boneh et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Malik et al., \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e1996\u003c/span\u003e). Brain neurons emit tiny electromagnetic waves of different frequencies when sending messages to the brain. This brainwave activity can be monitored and displayed as an electroencephalogram (EEG) and has been shown to be associated with emotions (Cho et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Puzi et al., \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Sugawara et al., \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e1998\u003c/span\u003e). Consequently, by analyzing HRV and EEG parameters, it should be possible to evaluate the impact of EOs on a person\u0026rsquo;s physiological and psychological state before and after activities (Ali et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Angelucci et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). In addition, some studies have shown that the State-Trait Anxiety Inventory (STAI) can be used to learn more about the subjective psychological state of subjects (Karan, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Mahmoodi et al., \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Spielberger et al., 1989).\u003c/p\u003e \u003cp\u003ePrevious research indicates that artistic creation can improve quality of life and that self-expression and personal fulfillment can benefit from the creative process, contributing to improving physical, psychological, and emotional health (Hattori et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Tjasink \u0026amp; Soosaipillai, \u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). However, few studies have also explored the benefits of diffusing EOs during artistic activities such as still-life painting. Therefore, in this study, we explored breathing plant-extracted EOs that whether have more relaxing psychophysiological benefits for older adults while doing still-life painting. Given that health is an important factor in a successful aging process (WHO, 2002), this research aims to provide older adults with an indoor natural activity program that can promote their physical and mental health, thereby enhancing immunity and reducing the threat of viral infection, thus improving their overall quality of life (Damiot et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eParticipants\u003c/h2\u003e \u003cp\u003eThirty participants aged between 59 and 79 years (mean age: 71.0\u0026thinsp;\u0026plusmn;\u0026thinsp;4.9 years; mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation [SD]) were recruited for the experiment. The participants included 29 females (96.7%) and one male (3.3%). They were enrolled as students in the Senior Citizens\u0026rsquo; Learning Camp at the Hwa Hsia University of Technology in New Taipei City, Taiwan. This initiative, similar, to the University of the Third Age (U3A), aims to inspire a lifelong motivation for diverse learning in older adults to enhance both their physical and mental health while slowing down the aging process (Zadworna, \u003cspan citationid=\"CR88\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The Ministry of Education in Taiwan began promoting senior education in 2008, and this included the establishment of the Senior Citizens\u0026rsquo; Learning Camp in collaboration with relevant universities and colleges. These university programs cater primarily to citizens aged 55 and above (Zadworna, \u003cspan citationid=\"CR88\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe inclusion criteria for study participants were the absence of asthma and epilepsy, no known allergies to EOs, and the absence of nasal congestion or upper respiratory tract infections. Once they fully understood the research purpose and procedures, the participants provided their informed consent by signing a consent form. This study was approved by the Research Ethics Committee of National Taiwan University (NTU-REC No. 202104HM009).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eEssential oils\u003c/h2\u003e \u003cp\u003e \u003cem\u003eP. menziesii\u003c/em\u003e EO and \u003cem\u003eL. angustifolia\u003c/em\u003e EO were purchased from dōTERRA International LLC (Pleasant Grove, UT, USA). The concentration of EOs used in the study was 2.5% (Essential oils : water\u0026thinsp;=\u0026thinsp;0.5 ml : 20ml) and was based on Rhind's (2015) recommendations for olfactory inhalation via a diffuser (dōTERRA International).\u003c/p\u003e \u003cp\u003eThe manufacturer provided a chemical analysis of \u003cem\u003eP. menziesii\u003c/em\u003e EO via GC-MS identifying 61 chemical components. The major constituents included β-pinene (21.16%), α-pinene (14.97%), terpinolene (11.01%), delta-3-carene (8.87%), sabinene (6.37%), γ-terpinene (4.86%), limonene (3.15%), α-terpinene (3.08%), myrcene (2.38%), citronellyl acetate (2.61%).\u003c/p\u003e \u003cp\u003eIn addition, the manufacturer also provided 51 chemical components identified through chemical analysis of \u003cem\u003eL. angustifolia\u003c/em\u003e EO by GC-MS. The major constituents included linalool (36.03%), linalyl acetate (30.67%), cis-β-ocimene (4.49%), lavandulyl acetate (4.33%), terpinen-4-ol (3.3%), trans-β-farnesene (2.78%), β-caryophyllene (2.72%).\u003c/p\u003e \u003cp\u003e \u003cb\u003eIndoor art experience activit\u003c/b\u003e \u003cb\u003ey\u003c/b\u003e \u003c/p\u003e \u003cp\u003eStill-life painting of vegetables was chosen as the indoor art experience activity for the participants of this study. The participants first did a continuous line drawing with pencils to outline the shapes of the objects (e.g. vegetables) in their artwork, followed by coloring with colored pencils. The materials supplied were B pencils (soft core), H pencils (hard core), colored pencils, sketch paper, and erasers. Under the guidance of experienced instructors, the participants completed their artworks within sixty minutes.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eExperimental design\u003c/h2\u003e \u003cp\u003eThe study took place on 5 November 2021, from 9:30 to 11:10 AM in classrooms at Hwa Hsia University of Technology in New Taipei City, Taiwan (Senior Citizens\u0026rsquo; Learning Camp). During the 100-minute experiment, the participants were instructed to avoid consuming caffeinated or alcoholic beverages and refrain from wearing metallic items such as necklaces, watches, earrings, and rings. The experiment involved the participants breathing \u003cem\u003eP. menziesii\u003c/em\u003e EO and \u003cem\u003eL. angustifolia\u003c/em\u003e EO at a concentration of 2.5% and diffused by an aromatic sprayer while doing still-life painting. The participants were also requested to wear a patch-type HRV analyzer to measure their heart rate and a patch-type EEG to measure their brainwaves. The purpose was to evaluate the effects of breathing EOs during an indoor sensory experience event by monitoring physiological parameters and collecting scale questionnaire responses before and after the entire event.\u003c/p\u003e \u003cp\u003eThe experiment consisted of seven-time stages (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Stage 1 involved the explanation of the research purpose and methods and the completion of the informed consent form (10 minutes). During stage 2, the participants wore the physiological assessment sensors to collect baseline HRV and EEG data and completed the pre-test STAI-S questionnaire (15 minutes). In stage 3, the participants were introduced to the indoor sensory experience activity (still-life painting) while EO-free water vapor was diffused into the air (15 minutes). The HRV and EEG data were collected continuously until the end of the experiment. During stage 4, water vapor containing \u003cem\u003eP. menziesii\u003c/em\u003e EO was diffused, allowing the participants to inhale the EO via normal breathing (15 minutes). In stage 5, between the first and second EO diffusion stages, water vapor without EOs was diffused (15 minutes). During stage 6, water vapor containing \u003cem\u003eL. angustifolia\u003c/em\u003e EO was diffused (15 minutes). Finally, in stage 7, the post-test STAI-S questionnaire was completed and the sensors were removed (15 minutes). The diffusion of EO-free water vapor served as the control for EO diffusion, since it is colorless and odorless, in contrast to EOs. Based on the short-term adaptation characteristics of the olfactory system, the 15-minute break with EO-free water vapor was inserted between the two EO-diffusion stages to allow the participants to rest and adjust, to avoid habitualization to specific odors during the experiment (Steinmetz et al., \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e1970\u003c/span\u003e; Tabert et al., \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2007\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003ePhysiological indices\u003c/h2\u003e \u003cp\u003eTo objectively assess each participant\u0026rsquo;s physiological state before and after these experiments, a patch-style HRV sensor (BeneGear, New Taipei City, Taiwan) was attached to the left side of their chest, over the heart, and a patch-style EEG sensor (BeneGear) was attached to their central forehead. These sensors continuously monitor physiological responses to evaluate the activity of the nervous system. Data were stored in the sensors' memory and transferred data to a computer via Wi-Fi for further processing and analysis.\u003c/p\u003e \u003cp\u003eHRV monitors ongoing changes in heart rate (HR) and was used in this study used the HRV parameters, including HR in beats per minute, normalized low-frequency heart oscillations (nLF), normalized high-frequency heart oscillations (nHF), ratio of low- to high-frequency heart oscillations (LF/HF), and standard deviation of normal-to-normal intervals (SDNN), analyzes were performed to reveal the ANS activity and emotional status (Chien et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Duan et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Hjortskov et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Kristal-Boneh et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Malik et al., \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e1996\u003c/span\u003e; Thayer et al., \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). An EEG records changes in potential difference between two points on the scalp over time, reflecting the brain's neural activity. In this study, alpha waves (7.0\u0026ndash;13.0 Hz), beta waves (13.0\u0026ndash;30.0 Hz), and gamma waves (30.0\u0026ndash;100.0 Hz) characteristics were investigated. Recorded and analyzed brainwave activity through frequencies and power (Cho et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Puzi et al., \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Sugawara et al., \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e1998\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003ePsychological indices\u003c/h2\u003e \u003cp\u003eThe State-Trait Anxiety Inventory (STAI) was used to evaluate the participants' anxiety levels. The STAI consists of 40 self-report questions divided into state anxiety (STAI-S) and trait anxiety (STAI-T) topics. The STAI-S assesses anxiety levels at a specific moment, which are indicative of transient emotional responses to particular stress situations, while the STAI-T assesses the general pattern of individual anxious feelings (Spielberger, \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). In this study, we used the STAI-S to assess the subjective emotional status of the participants before and after the test. It comprises 20 questions in total, consisting of 10 positive questions and 10 negative ones. Each item is scored using a four-point Likert scale (1\u0026ndash;4 for negative questions and 4\u0026ndash;1 for positive questions). Higher scores indicate higher anxiety levels (Karan, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Spielberger et al., 1989).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eEnvironmental Indices\u003c/h2\u003e \u003cp\u003ePrevious research indicates that HRV is influenced by ambient temperature (Kristal-Boneh et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Kunitake and Ishiko, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Lindqvist et al., \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e1990\u003c/span\u003e). Air pollution and indoor environmental factors such as air quality and temperature also impact HR and changes in HRV, affecting health and the ability to learn (Pope et al., \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Satish et al., \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Zhang et al., \u003cspan citationid=\"CR89\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). To monitor the environment during the experiment, an indoor air quality monitor (AirBoxx; KD Engineering, NY, USA) was used to measure parameters such as CO\u003csub\u003e2\u003c/sub\u003e concentration, CO concentration, temperature, and relative humidity. Monitoring began 10 minutes before the experiment and ended 10 minutes after its termination. There was one monitoring point at the front and back of the experimental site. The recorded mean values for CO\u003csub\u003e2\u003c/sub\u003e concentration, CO concentration, temperature, and relative humidity in the experimental environment were 630.2\u0026thinsp;\u0026plusmn;\u0026thinsp;15.9 ppm, 0.0 ppm, 26.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.7\u0026deg;C, and 77.6\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7% (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD), respectively.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eAll data were analyzed using IBM SPSS Statistics for Windows, Version 21.0 (IBM Corporation, Armonk, NY, USA). The statistical analysis used the paired sample \u003cem\u003et\u003c/em\u003e-tests to compare differences between the baseline and the stages of the experiment (i.e., breathing of EO-free water vapor and the two EOs). Data are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard error (SE), and a \u003cem\u003eP\u003c/em\u003e-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003ePhysiological indices\u003c/h2\u003e \u003cp\u003eTo assess the impact of the indoor sensory experience activity (still-life painting) combined with EOs breathing, a wearable HRV sensor was used to record parameters HR-related continuously. The baseline activity was recorded before the beginning of the still-life painting. During stages of the experiment that still-life painting with \u003cem\u003eP. menziesii\u003c/em\u003e EO and \u003cem\u003eL. angustifolia\u003c/em\u003e EO diffusion, the participants\u0026rsquo; HR was significantly reduced compared to baseline (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA). We next analyzed the still-life painting with EO-free water vapor diffusion, the SDNN did not change significantly from baseline (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB). However, when \u003cem\u003eL. angustifolia\u003c/em\u003e EO was administered, there was a significant increase in SDNN (47.27\u0026thinsp;\u0026plusmn;\u0026thinsp;5.61 ms, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). During EO-free water vapor diffusion, nLF and nHF were unchanged. Nevertheless, when \u003cem\u003eL. angustifolia\u003c/em\u003e EO was diffused, the percentage of nLF heart oscillations decreased significantly (64.76\u0026thinsp;\u0026plusmn;\u0026thinsp;2.31%, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC). Correspondingly, when the participants breathed \u003cem\u003eL. angustifolia\u003c/em\u003e EO, the percentage of their nHF heart oscillations increased significantly (35.24\u0026thinsp;\u0026plusmn;\u0026thinsp;2.31%, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD). We also observed a significant decrease in LF/HF when \u003cem\u003eL. angustifolia\u003c/em\u003e EO was administered (2.15\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), while diffusion of OE-free water vapor did not affect it (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eE). Taken together, the above results indicate the physiological condition of reduced sympathetic nerve activity and increased parasympathetic nerve activity during the breathing of EOs, particularly \u003cem\u003eL. angustifolia\u003c/em\u003e EO, indicating that the participants were relaxed.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWe also used wearable EEG sensors to continuously record brainwave-related parameters. The participants\u0026rsquo; high-alpha waves, which are typically associated with a state of mental relaxation and focused attention (Puzi et al., \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2013\u003c/span\u003e), increased during the course of the experiment, but the difference from baseline was not statistically significant for any stage of the experiment (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA). Their high-beta waves, which are generally positively correlated with stress levels (Puzi et al., \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Sugawara et al., \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e1998\u003c/span\u003e), decreased during breathing of \u003cem\u003eP. menziesii\u003c/em\u003e EO (104.47\u0026thinsp;\u0026plusmn;\u0026thinsp;11.18 \u0026micro;V\u003csup\u003e2\u003c/sup\u003e, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and \u003cem\u003eL. angustifolia\u003c/em\u003e EO (99.37\u0026thinsp;\u0026plusmn;\u0026thinsp;10.91 \u0026micro;V\u003csup\u003e2\u003c/sup\u003e, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB), indicating a reduction in stress levels. Finally, their gamma waves, which are negatively correlated with relaxation (Cho et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Oathes et al., \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2008\u003c/span\u003e), decreased significantly when the participants were breathing \u003cem\u003eL. angustifolia\u003c/em\u003e EO (415.38\u0026thinsp;\u0026plusmn;\u0026thinsp;36.30 \u0026micro;V\u003csup\u003e2\u003c/sup\u003e, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC), suggesting that the participants were in a relaxed state. Overall, the EEG results indicate that EOs can reduce stress levels and enhance relaxation benefits.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003ePsychological indices\u003c/h2\u003e \u003cp\u003eParticipants' subjective emotional states were assessed using the STAI-S questionnaire. Compared to the pre-test scores, the post-test STAI-S scores decreased for all questions (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). In the STAI-S scoring system, higher total scores indicate higher anxiety levels (Karan, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Mahmoodi et al., \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Spielberger et al., 1989). Our results suggest that the participants experienced a reduction in anxiety levels during the experiment.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis research established an Indoor natural activity program by analyzing physiological parameters such as HRV and EEG and evaluating the relaxing effect of breathing \u003cem\u003eP. menziesii\u003c/em\u003e and \u003cem\u003eL. angustifolia\u003c/em\u003e EO on 30 older adults during still-life painting activity. The results reported a relaxing effect.\u003c/p\u003e \u003cp\u003eActivities conducted in natural environments, such as forest bathing and other related activities, are beneficial to health (White et al., \u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Yu et al., \u003cspan citationid=\"CR87\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). It is difficult for older adults in the city to travel to the forest to relax frequently. To promote physical and mental health, many studies are developing plans to integrate natural environmental elements such as landscape videos, natural light, scented plants, birdsong, and the sound of running water into daily life (Mcsweeney et al., \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Therefore, in this study, we combined indoor activity (still-life painting) with breathing EOs, intending to create a relaxing atmosphere similar to the natural forest environment in an indoor environment, so that participants can immerse themselves in elements of the natural world.\u003c/p\u003e \u003cp\u003eThayer et al. (\u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) showed that HRV can provide an index of the intensity of brainstem activity and the autonomic responses of the body. Further, Hjortskov et al. (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2004\u003c/span\u003e) reported that HRV can be used as a reference for understanding negative emotions, mental stress, and health. We therefore used HRV to measure the effects of the experiment on stress levels. The participants\u0026rsquo; HR decreased after EO administration (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA), indicating that their stress levels had been reduced. This is consistent with previous research results. When people feel stressed, the sympathetic nervous system becomes more active, and the HR increases; conversely, when stress is reduced, the parasympathetic nervous system becomes more active and the HR decreases (Kristal-Boneh et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Hjortskov et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Thayer et al., \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Grunebaum et al (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) showed that in 33 patients undergoing minimally invasive surgery, parasympathetic nerve activity increased, and HR decreased after inhaling lavender aroma.\u003c/p\u003e \u003cp\u003eIn line with Hjortskov et al.'s (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2004\u003c/span\u003e) findings under stress-reduced conditions, we observed a decrease in nLF (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC) and LF/HF (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eE) after the participants had breathed EOs. Correspondingly, nHF (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD) and SDNN (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB) values increased after EO breathing. This consistency with previous research indicates that during negative emotional experiences, such as tension and anxiety, sympathetic nervous system activity increases, leading to an increase in nLF and LF/HF. Conversely, during relaxation, parasympathetic nervous system activity increases, resulting in increased nHF and SDNN. The nLF measure quantifies sympathetic nervous system activity, while nHF quantifies parasympathetic nervous system activity (Chien et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Duan et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Malik et al., \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e1996\u003c/span\u003e). The LF/HF is an indicator of ANS balance, while SDNN reflects the intensity of regulation of the sinus node of the heart by the ANS thus representing the overall activity of the autonomic nervous system (Chien et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Hjortskov et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Malik et al., \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e1996\u003c/span\u003e). Duan et al. (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2007\u003c/span\u003e) reported that after 10 young women inhaled the scent of lavender, the subjects' parasympathetic nerve activity increased, nHF increased, and LF/HF decreased. Chien et al. (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) showed that 67 middle-aged menopausal women experienced an increase in SDNN, mental relaxation, and improved sleep after inhaling lavender EO. Chang and Shen (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) indicated that stress was relieved and nLF decreased after 54 primary school teachers inhaled aromatic EO.\u003c/p\u003e \u003cp\u003e Choi's study (2022) suggested that the olfactory stimulation provided by EOs has a stabilizing effect on the prefrontal cortex and overall brain activity. Additionally, Angelucci et al. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2014\u003c/span\u003e) documented the impact of EO scents on neurophysiological brain activity, while Lorig and Schwartz (\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e1988\u003c/span\u003e) observed temporal patterns in EEG activity related to exposure to various scents. We therefore used EEG in this study to assess the correlation between olfactory-stimulated brain activity and stress-relief benefits. The observed significant decrease in high-beta waves (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB) and gamma waves (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC) after EO breathing suggests that the participants experienced stress relief. This aligns with previous research that indicates that a decrease in high-beta and gamma waves indicates stress reduction (Cho et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Sugawara et al., \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e1998\u003c/span\u003e). Sayorwan et al. (\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) reported that 20 participants, after inhaling lavender EO, ​​increased alpha wave activity in the brain, especially in the bilateral temporal lobes and central areas, and their emotions also felt happier and more relaxed. Sugawara et al. (\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e1998\u003c/span\u003e) observed that 23 adults had good sensory evaluation after inhaling linalool EO, which was accompanied by a trend of lower beta waves. Cho et al. (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) studied 20 right-handed healthy volunteers. After inhaling Mentha arvensis EO, mental stress levels were reduced and gamma waves decreased.\u003c/p\u003e \u003cp\u003eThe results of this study are similar to previous research on the relaxation benefits of other coniferous family EOs (such as Fir EO, and Juniper EO) (Kim \u0026amp; Song, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Kim et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Park, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). We observed similar physiological results when breathing \u003cem\u003eP. menziesii\u003c/em\u003e EO compared to those found while breathing \u003cem\u003eL. angustifolia\u003c/em\u003e EO, with a significant decrease in HR and high-beta waves, suggesting a relaxing effect. The main components of \u003cem\u003eL. angustifolia\u003c/em\u003e EO, namely linalool (36.03%) and linalyl acetate (30.67%), which are known for their calming effects (Ali et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Ayaz et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Chien et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Duan et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Karan, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Koulivand et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Sugawara et al., \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e1998\u003c/span\u003e). The main components of \u003cem\u003eP. menziesii\u003c/em\u003e EO include β-pinene (21.16%) and α-pinene (14.97%). Most studies on pinene\u0026rsquo;s anxiolytic and other neuroprotective effects have been conducted only in animal models (Bakkali et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Salehi et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Based on physiological data of the relaxing effects of \u003cem\u003eP. menziesii\u003c/em\u003e EO observed in this study, we speculate that pinene may be the active ingredient responsible for this phenomenon.\u003c/p\u003e \u003cp\u003eHattori et al. (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) reported that coloring and drawing can improve the vitality and quality of life of patients with mild Alzheimer's disease. Tjasink and Soosaipillai (\u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) showed that art therapy reduces burnout among oncology and palliative care doctors to enhance mental and emotional well-being. The results of the present study are similar to previous research results. We also observed that still-life painting combined with breathing EOs is beneficial to the physical and mental health of participants.\u003c/p\u003e \u003cp\u003eWe conducted STAI-S questionnaires before and after the experiment to understand the participants\u0026rsquo; subjective psychological state (Karan, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Mahmoodi et al., \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Spielberger et al., 1989). The post-test scores of the STAI-S scale decreased relative to the pre-test scores (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), indicating that inhaling EO combined with still-life painting has subjective psychological benefits for older adults, leading to reduced anxiety. This aligns with previous research using the STAI-S, which suggested that the aroma of EOs can alleviate anxiety in dental patients (Karan et al., 2019), patients before coronary angiography (Mahmoodi et al., \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), and primiparous women (Rashidi Fakari et al., \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTo mitigate the impact of inherent differences in stress resistance among individuals and ensure the accuracy of our stress-relief findings, we used a within-subject design, comparing participants with themselves and using EO-free water-vapor diffusion as a control for EO diffusion. However, this design is still subject to some limitations. First, although the study was conducted during the period when the local COVID-19 epidemic was easing, we strove to avoid infection by not using the salivary amylase monitor to measure salivary amylase activity, which can be used as an index of stress. This reduced the physiological data available for analysis. Second, the study's representativeness was limited by the small sample size which resulted from the effect of the COVID-19 pandemic during recruitment. Third, the EEG used in this study was worn in the center of the forehead, so only the brainwaves of the prefrontal cortex were evaluated, and those of other brain regions were not measured.\u003c/p\u003e \u003cp\u003eFurthermore, given that the sense of smell plays an important role in the biopsychosocial effects of stress, mood, and workability (Angelucci et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; DeGuzman et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Herz et al., 2009; Kiecolt-Glaser et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). Future research may be able to take advantage of olfaction's ability to rapidly affect the nervous system (Spors et al., \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Tabert et al., \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2007\u003c/span\u003e), when performing biofeedback intervention (Weerdmeester et al., \u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), one may be able to inhale EOs at the same time, which will help strengthen and improve the psychophysiological health.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIn this study, Sympathetic and parasympathetic nervous system activity changes were measured using a Heart Rate Variability Sensor, brain wave changes were monitored using an Electroencephalography Sensor, and anxiety levels were assessed through STAI-S questionnaire. To assess changes in the psychophysiological state of older adults after breathing \u003cem\u003eL. angustifolia\u003c/em\u003e and \u003cem\u003eP. menziesii\u003c/em\u003e EOs while doing still-life painting. We observed an increase in SDNN, nHF, and high-alpha waves and a decrease in HR, nLF, LF/HF, high-beta waves, and gamma waves. The relaxing and stress-relieving effects of this indoor natural activity are considered beneficial for the health of older adults. This program offers a simple relaxation method that older adults can engage in in their daily lives. Compared to forest therapy, it is not subject to geographical restrictions, and the required materials are readily accessible. This beneficial activity promotes psychophysiological well-being among older adults, thereby enhancing their immune function, reducing the risk of viral infections, and increasing satisfaction and happiness with life.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eConceptualization: Y-SC; data acquisition, Y-HC; methodology: S-JC, C-LL, Y-SC; analysis: Y-HC, Y-SC; investigation: Y-HC; resources: S-JC, C-LL, Y-SC; writing original draft: Y-HC; writing, review and editing: Y-HC, S-JC, C-LL, Y-SC; supervision: Y-SC.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAbbas, F., Zhou, Y., O\u0026apos;Neill Rothenberg, D., Alam, I., Ke, Y., \u0026amp; Wang, H. C. (2023). 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Effects of exposure to carbon dioxide and bioeffluents on perceived air quality, self-assessed acute health symptoms, and cognitive performance. \u003cem\u003eIndoor air\u003c/em\u003e, \u003cem\u003e27\u003c/em\u003e(1), 47\u0026ndash;64. https://doi.org/10.1111/ina.12284\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"applied-psychophysiology-and-biofeedback","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"apbi","sideBox":"Learn more about [Applied Psychophysiology and Biofeedback](http://link.springer.com/journal/10484)","snPcode":"10484","submissionUrl":"https://submission.nature.com/new-submission/10484/3","title":"Applied Psychophysiology and Biofeedback","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Heart Rate, Brainwave, Relaxation, Older adults, Psychophysiological health, Quality of life","lastPublishedDoi":"10.21203/rs.3.rs-4164401/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4164401/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eWhile the COVID-19 pandemic has affected all types of people, older adults have been disproportionately affected. Therefore, during this period we developed an indoor program inspired by art and natural elements (plant essential oils [EOs]) intended to create a relaxing effect akin to a forest atmosphere to enhance their psychophysiological health. There are for 30 Taiwanese older adults (range, 59-79 years) participated in the study. We combined art activity (still-life painting of vegetables) with breathing \u003cem\u003ePseudotsuga menziesii\u003c/em\u003e and \u003cem\u003eLavandula angustifolia \u003c/em\u003eEOs during a 100-minute experiment involving still-life painting and the inhalation of 2.5% diffused EOs. The research shows physiological measures (heart rate, normalized low-frequency heart oscillations, ratio of low- to high-frequency heart oscillations, high-beta waves, and gamma waves) decreased;correspondingly, an increased standard deviation of normal-to-normal intervals, normalized high-frequency heart oscillations, and high-alpha waves were observed, indicating relaxation physiological state. Subjective psychological assessments using the State-Trait Anxiety Inventory–Stateyielded lower post-test scores, further supporting relaxation effects. The psychophysiological data from this study provide important scientific evidence for the physical and mental health benefits of indoor nature-based activity programs for older adults, thereby improving their quality of life.\u003c/p\u003e","manuscriptTitle":"The Development of Indoor Natural Elements Had Relaxing Psychophysiological Effects on Older Adults in Taiwan During the COVID-19 Pandemic","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-29 12:46:25","doi":"10.21203/rs.3.rs-4164401/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-03-27T13:54:25+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-03-27T04:46:19+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-03-27T04:46:19+00:00","index":"","fulltext":""},{"type":"submitted","content":"Applied Psychophysiology and Biofeedback","date":"2024-03-25T15:34:43+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"applied-psychophysiology-and-biofeedback","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"apbi","sideBox":"Learn more about [Applied Psychophysiology and Biofeedback](http://link.springer.com/journal/10484)","snPcode":"10484","submissionUrl":"https://submission.nature.com/new-submission/10484/3","title":"Applied Psychophysiology and Biofeedback","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"596cc680-72c3-4120-8a9f-834d324fa5f4","owner":[],"postedDate":"March 29th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-11-11T16:08:10+00:00","versionOfRecord":{"articleIdentity":"rs-4164401","link":"https://doi.org/10.1007/s10484-024-09676-9","journal":{"identity":"applied-psychophysiology-and-biofeedback","isVorOnly":false,"title":"Applied Psychophysiology and Biofeedback"},"publishedOn":"2024-11-06 15:57:55","publishedOnDateReadable":"November 6th, 2024"},"versionCreatedAt":"2024-03-29 12:46:25","video":"","vorDoi":"10.1007/s10484-024-09676-9","vorDoiUrl":"https://doi.org/10.1007/s10484-024-09676-9","workflowStages":[]},"version":"v1","identity":"rs-4164401","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4164401","identity":"rs-4164401","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}