Impact of COVID-19 pandemic on physical health among children: difference-in-differences analyses of nationwide school health checkup database

Impact of COVID-19 pandemic on physical health among children: difference-in-differences analyses of nationwide school health checkup database | 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 Impact of COVID-19 pandemic on physical health among children: difference-in-differences analyses of nationwide school health checkup database Yusuke Okubo, Kazue Ishitsuka, Atsushi Goto This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3960071/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Purpose: The COVID-19 pandemic posed tremendous challenges for children, requiring them to adapt to changes in social environments. However, the long-term effects of the pandemic on various aspects of physical health at a national level remain unclear. Methods: In this retrospective cohort study, we analyzed data from nationwide health checkup records among children aged 7–15 years. The dataset comprised 3,544,146 records from 393,794 individuals who graduated from junior high school during fiscal years 2007 to 2022. Difference-indifferences (DID) analyses with multiple time periods were used to examine the impact of COVID-19 on physical health outcomes. Results: Compared with the pre-pandemic period, the COVID-19 pandemic was associated with excess increases in obesity for boys and girls, persisting over the 3 years (DID estimate, +0.42%; 95%CI, 0.23 to 0.61). Also, it was associated with excess increases in underweight (DID estimate, +0.28%; 95%CI, 0.25 to 0.32) and poor visual acuity among boys in the 3 rd year (DID estimate, +1.80%; 95%CI, 1.30 to 2.30]). There were excess reductions in dental caries (DID estimate,-1.48%; 95%CI,-2.01 to-0.95]), glucosuria (DID estimate,-0.55; 95%CI,-0.88 to-0.23), and hematuria (DID estimate,-0.43%; 95%CI,-0.73 to-0.13]) during the 3 rd year of the pandemic. Conclusions: These findings underscore the multifaceted impact of the pandemic on various health indicators for school-aged children. This information could be valuable for public health policy and pediatric healthcare planning in the post-pandemic era. SHR database COVID-19 pandemic coronavirus disease 2019 school physical exam school health checkup Figures Figure 1 Figure 2 Figure 3 What is Known COVID-19 spread from metropolitan to rural areas in Japan, with a slower spread among children until the Omicron variants. The Japanese government implemented early infection prevention measures, including school closures and mandates for masking and hand sanitization. The pandemic led to decreased outdoor activities, increased screen time, and changes in dietary habits among children, contributing to worsening physical health conditions like obesity, myopia, and dental caries. What is New: This study utilizes nationwide school health checkup records from 2007-2022 to provide a comprehensive assessment of the long-term impacts of the COVID-19 pandemic on children's physical health at a national level. It offers the first long-term, nationwide analysis of the pandemic's effects on various aspects of children's physical health, bridging a significant knowledge gap. Introduction The coronavirus disease-2019 (COVID-19) was first detected in December 2019 in China and subsequently in January 2020 in Japan.[ 1 , 2 ] COVID-19 initially spread among adults from metropolitan areas to rural regions in Japan.[ 3 ] The spread of COVID-19 among Japanese children remained relatively gradual until the emergence of the Omicron variants. This slower spread in the early phase of the pandemic can be attributed to the Japanese government’s proactive implementation of infection prevention measures. Notably, the government mandated nationwide school closures at the end of February 2020.[ 4 ] Schools were reopened until June 2020, with strict infection prevention measures, including universal masking and hand sanitization in educational institutions, where adherence rates had been notably high until March 2023.[ 5 ] The COVID-19 pandemic has posed tremendous challenges for children, requiring them to adapt not only to infection prevention measures but also to the changes in their school and social environments.[ 4 , 6 , 7 ] Previous studies have indicated that the pandemic led to decreased outdoor physical activities, increased screen time, and changes in dietary habits.[ 4 , 6 , 7 ] Correspondingly, a worsening of physical health conditions, including increases in obesity, myopia, and dental caries, has been reported.8–10] However, these studies have often been limited to single geographic locations and have only assessed short-term impacts. Consequently, the broader, long-term effects of the COVID-19 pandemic on various aspects of children’s physical health at a national level remain unclear. Utilizing nationwide school health checkup records provides us with the best opportunity to bridge this knowledge gap. Therefore, our study investigated the impact of the COVID-19 pandemic on physical health among children using nationwide school health checkup records during 2007–2022. Methods Study design, Data source, and Study population We conducted a retrospective cohort study to investigate the impact of the COVID-19 pandemic on the physical health of school children using a nationwide school health checkup records (SHR) database. This study adhered to the ethical principles outlined in the Declaration of Helsinki and received approval from the institutional review board (IRB) at the National Center for Child Health and Development in Japan (IRB number, 2022 − 176). The requirement of informed consent was waved due to the complete de-identification and subsequent anonymous nature of the SHR database. We utilized the SHR database provided by the Health, Clinic, and Education Information Evaluation Institute (HCEI) and Japan Medical Data Center (JMDC). The details of the databases have been described elsewhere.[ 11 ] Briefly, the database comprised school health records from approximately 400,000 school-aged children (Grade 1 to 9) living in 152 municipalities in Japan, where health checkups are mandated annually. The data, encompassing a 9-year record for each student, is collected up to their graduation year (Grade 9) from junior high school. The database consists of the following variables: sex, height, weight, visual acuity (uncorrected and corrected); numbers of primary and permanent teeth with treatment status for dental caries; and urine dipstick test results for protein, glucose, and occult blood. We extracted all records of children who graduated from junior high school between the fiscal years 2015 and 2022, corresponding to those who were born between the fiscal years 2000 and 2007 (Fig. 1). Then, we tracked these children’s records from their entry into elementary school (Grade 1) to the end of follow-up (Grade 9 or departure from the database) to measure the variables listed in the Measurements section. Our study used data from 393,794 individuals, amounting to 3,544,146 records. Measurements The exposure of interest is the fiscal years after the COVID-19 pandemic (2020 to 2022). In Japan, the fiscal year begins on April 1 and ends on Match 31 of the following year. As the Japanese government implemented infection prevention measures (e.g., school closure, state of emergency) at the end of the fiscal year 2019, we defined fiscal years 2020, 2021, and 2022 as the 1st, 2nd, and 3rd years after the COVID-19 pandemic, respectively. The outcome of interest included weight status (e.g., underweight, normal weight, obesity), poor visual acuity, presence of untreated dental caries, and abnormal urine dipstick test results for protein, glucose, and occult blood for each year. Weight status was determined based on z-scores of body mass index (BMI) for age, in accordance with the recommendations of the World Health Organization and previous studies.[ 12 – 18 ] We defined the z-scores less than − 2 standard deviation (SD) as underweight (moderate or severe) and those greater than + 2 SD as obese. Visual acuity was measured using a Landolt ring chart, conforming to international standards.[ 19 ] Poor visual acuity was defined as an uncorrected visual acuity of less than 20/20 in either eye. In urinalyses with dipstick tests, the presence of protein at a level of 1 + or greater (≈ urine protein ≥ 30 mg/dL), glucose at a level of ± or greater (≈ urine glucose ≥ 30 mg/dL), and hemoglobin at a level of 1 + or greater (≈ urine hemoglobin ≥ 0.06 mg/dL) were defined as proteinuria, glucosuria, and hematuria, respectively.[ 20 ] Statistical analyses The data analyses were conducted in three steps using Stata/MP software version 16.1 (StataCorp LP, TX, USA). Firstly, we summarized measurement variables by calculating frequencies with proportions stratified by birth years and sex. Secondly, we estimated the impact of the COVID-19 pandemic on the outcomes of interest using a staggered difference-in-differences (DID) approach with multiple time periods, as proposed by Callaway and Sant’Anna.[ 21 ] We set children’s school grades (Grades 1 to 9) as time indicator variables and fiscal years 2020 to 2022 as treatment variables. Consequently, children born between 2000 and 2004 never experienced the COVID-19 pandemic during Grade 1 to 9 (the "never-treated” group), while children born in 2005, 2006, and 2007 experienced the pandemic during Grade 9, Grade 8 to 9, and Grade 7 to 9, respectively (Fig. 1). We set never-treated and not-yet-treated units as the comparison group and investigated dynamic treatment effects as DID estimates in the 1st, 2nd, and 3rd years using outcome regression estimators based on ordinary least square with wild bootstrap procedures, which generates new samples by randomly perturbing the residuals of the models, under cluster standard errors for 95% confidence intervals (95%CIs). Thirdly, to check the robustness of the primary analyses, we employed fully-saturated two-way fixed effect regression models as proposed by Sun and Abraham.[ 22 ] This method utilizes two-way fixed effects models with staggered treatment adoption to investigate dynamic DID estimates for time relative to treatment timing. We set individuals as unit-fixed effects, their school grade as time-fixed effects, and time from the COVID-19 pandemic for individual units as relative time indicator variables. Compared with conventional two-way fixed effect models, which do not accommodate heterogeneous effects and may potentially assign negative weights to certain comparison groups, these estimation methods[ 21 , 22 ] offer the advantage of reducing bias from treatment effects from other periods and allowing for heterogeneity.[ 23 ] Results Descriptive statistics of the study cohort from Grade 1 to Grade 9 Descriptive statistics are summarized in Table 1 . The number of participants increased from children born in 2000 to those in 2004, with a slight male predominance. Figures 2A and 2B show the distribution of moderate/severe underweight and obesity stratified by sex, grades, and birth years (Supplemental Table 1). Whereas the proportions of underweight in boys increased from 1.5% in Grade 1 to 4.5% in Grade 9, the proportions in girls increased from 0.8% in Grade 1 to 3.8% in Grade 6, then decreased to 1.7% in Grade 9. Obesity among boys (Fig. 2C) increased from 4.4% in Grade 1 to 7.5% in Grade 4–5, then decreased to 3–4% in Grade 9. In contrast, obesity among girls (Fig. 2D) remained relatively stable at 1–2% in Grades 1–9 (Supplemental Table 2). Table 1 Demographics of school children stratified by fiscal years Birth year 2000 2001 2002 2003 2004 2005 2006 2007 Entry to elemental school (Grade 1) 2006 2007 2008 2009 2010 2011 2012 2013 Graduation from junior high school (Grade 9) 2015 2016 2017 2018 2019 2020 2021 2022 COVID-19 pandemic experience during Grade 1–9 No No No No No Yes Yes Yes Number of municipalities 11 43 64 110 143 128 134 136 Number of Schools 51 263 422 689 776 666 702 724 Number of students 4227 23,437 39,860 67,652 72,082 57,622 63,377 65,537 Male, N 2317 11,842 20,485 34,571 36,815 29,441 32,515 33,671 (%) (54.8%) (50.5%) (51.4%) (51.1%) (51.1%) (51.1%) (51.3%) (51.4%) Female, N 1910 11,595 19,375 33,081 35,267 28,181 30,862 31,866 (%) (45.2%) (49.5%) (48.6%) (48.9%) (48.9%) (48.9%) (48.7%) (48.6%) *Abbreviations: N, sample size; COVID-19, coronavirus disease 2019 Poor visual acuity monotonically increased from 18% and 20% in Grade 1 to 49% and 55% in Grade 9 among boys and girls, respectively (Fig. 2E and 2F; Supplemental Table 3). Untreated dental caries decreased from approximately 30% in Grade 1 to 16% for both boys and girls (Fig. 2G and 2H; Supplemental Table 4). Proteinuria increased from < 0.5% in Grade 1 to 1–2% in Grade 9 (Fig. 2I and 2J; Supplemental Table 5). Similarly, glucosuria increased from < 1.0% in Grade 1 to 2–4% in Grade 9 (Fig. 2K and 2L; Supplemental Table 6). Also, hematuria increased from < 0.5% in Grade 1 to 1–2% in Grade 9 (Fig. 2M and 2N; Supplemental Table 7). These abnormal urine dipstick results had a slight male predominance. Impact of COVID-19 pandemic on physical health measures We conducted staggered DID analyses, as proposed by Callaway and Sant’Anna, to estimate the impact of the COVID-19 pandemic on students’ physical health. The COVID-19 pandemic had almost no impact on underweight status among boys and girls during the 1st and 2nd years (Fig. 3A; Supplemental Table 8) but had impacts during the 3rd year for boys (DID estimate, 0.21%; 95%CI, 0.15 to 0.28) and girls (DID estimate, 0.34%; 95%CI, 0.30 to 0.38). Obesity increased during the 3-year periods of the pandemic for both boys and girls (Fig. 3B), with the largest impact observed among boys during the 1st year (DID estimate, 0.88%; 95%CI, 0.72 to 1.04). The COVID-19 pandemic was associated with increased risks of poor visual acuity among boys and girls during the 1st and 2nd years (Fig. 3C), which persisted only among boys in the 3rd year (DID estimate, 1.90%; 95%CI, 1.30 to 2.30). In contrast, the pandemic was associated with reduced risks of untreated dental caries among boys in the 3rd year (DID estimate, -1.13%; 95%CI, -1.73 to -0.53) and girls in the 1st to 3rd years (Fig. 3D). There were almost no impacts of the COVID-19 pandemic on the risks of proteinuria among boys and girls (Fig. 3E), except for girls in the 3rd year (DID estimate, -0.17; 95%CI, -0.23 to -0.11). The risks of glucosuria for boys and girls decreased after the COVID-19 pandemic (Fig. 3F). Similar patterns were observed in the trends of hematuria among boys and girls (Fig. 3G). Sensitivity analyses with fully saturated two-way fixed models yielded findings similar to those of the primary analyses (Supplemental Table 9). Discussion The nationwide school health checkup database enabled us to quantify trends in physical health among children from Grade 1 to Grade 9 and estimate the impact of the COVID-19 pandemic. The pandemic was associated with increased risks of being underweight, obesity, and poor visual acuity, whereas it was associated with decreased risks of dental caries and abnormal findings of urinalyses. The impacts of COVID-19 on some physical health measures (e.g., obesity, visual acuity) appeared to differ slightly between boys and girls. The COVID-19 pandemic altered children’s daily lives,[ 4 , 6 ] raising concerns about its impacts on their weight status. A systematic review published in 2022[ 24 ] indicated an increase in childhood obesity in many high-income countries during the pandemic. A notable example is the United States, where obesity in children aged 12–15 years increased by approximately 5%.[ 25 ] In Japan, two studies conducted in Osaka and Tokyo, along with their surrounding areas, have presented slightly differing views. A large-scale study in public schools in Osaka found a decrease in obesity among children aged 12–14 years, with almost no change in underweight status.[ 8 ] Conversely, a study targeting private schools in Tokyo and nearby areas reported an increase in BMI among boys and a decrease among girls.[ 9 ] Our study, aiming for a larger scale to improve generalizability, found that the impact of the COVID-19 pandemic on underweight was observed in both boys and girls in the 3rd year, while the impact on obesity was more pronounced in the earlier phase. As previously reported, the increase in obesity could be attributed to complex behavioral factors, such as decreased physical activity, prolonged sedentary time, changes in food behaviors, and alterations in the socioeconomic status of parents. The increase in eating disorders and underweight among children, with a majority of the patients being girls, have been reported from several studies, which might be linked to worsening mental health (e.g., social isolation, feeling of uncertainty) and economic factors affecting both children and parents.[ 7 , 26 – 31 ] Importantly, our findings suggest that underweight is more prevalent in boys, who may not have as much access to healthcare as girls, highlighting a need for improvement in this area. Our study revealed an elevated risk of poor visual acuity immediately following the COVID-19 pandemic, consistent with a previous study conducted in 11 schools in Japan.[ 19 ] In Japan, some studies indicate reduced outdoor physical activities and increased screen time,[ 6 ] both of which are well-known risk factors for myopia.[ 32 , 33 ] Furthermore, we found that the impact on poor visual acuity is not limited to a single year, but persisted for 3 years among boys and 2 years among girls. In contrast, untreated dental caries decreased during the 3 years of the COVID-19 pandemic, which differs from previous studies. For instance, a study conducted in Tokyo reported an increase in dental caries in the 1st year of the pandemic.[ 10 ] This discrepancy may be due to variations in the target populations, but the exact mechanisms remain unclear. A decrease in abnormal urinalysis results may be attributed to changes in infectious disease epidemiology among children, as these results often accompany normal transient findings or immune responses to non-specific infections.[ 34 ] During fiscal years 2020–2022, the Japanese government implemented infection prevention measures for students, such as mandatory mask-wearing, which were highly adhered to by students and teachers.(5) Consequently, the incidence rates of most infectious diseases (e.g., group A streptococcal pharyngitis) substantially reduced during this period.[ 35 – 38 ] Since the fiscal year 2023, infection prevention measures in schools have been relaxed, and then the incidence rates of most infectious diseases have returned to pre-pandemic levels or higher. Although addressing mild abnormalities in urinalyses often does not require medical intervention and may not be cost-effective,[ 39 ] ongoing monitoring can provide insights into the underlying health dynamics between pediatric infectious diseases and urinary tract functions. The strength of our study lies in the use of nationwide datasets that cover various physical health outcomes, analyzed with recently developed robust statistical methods. However, our study has several limitations. Firstly, as the SHR database was primarily collected from public schools, the generalizability of our study findings to the entire pediatric population is uncertain despite our analyses being the largest of their kind. Secondly, the lack of demographic data, such as socioeconomic factors, lifestyle, and underlying diseases, precluded us from analyzing data with adjustment for important time-varying confounders, although our analyses with fixed-effect models implicitly accounted for time-fixed covariates. Thirdly, the SHR database does not provide information on geographic location due to the protection of personal information. Consequently, we could not analyze data to investigate the heterogeneity of the COVID-19 pandemic across different geographic locations. Fourthly, the health checkup records were collected for all students at the time of Grade 9. Due to this scheme, our DID analyses only estimated the impact of the COVID-19 pandemic among students in Grade 7–9. Long-term data or another data source would be required to investigate the impact of the pandemic on younger students. In summary, our study highlighted essential changes in physical health among students in Japan, especially the increases in underweight, obesity, and poor visual acuity and the decreases in abnormal urinalysis findings during the COVID-19 pandemic. These findings underscore the multifaceted impact of the pandemic on children's health, revealing both direct and indirect effects on various health indicators, which could be valuable information for public health policy and pediatric healthcare planning in the post-pandemic era. Declarations Financial disclosure: The authors have no financial relationships relevant to this article to disclose. Funding source: This work was supported by grants from the Japan Science and Technology Agency (PRESTO: JPMJPR22R4). Potential conflict of interest: The authors have no conflicts of interest relevant to this article to disclose. Authorship statement: Dr. Okubo coordinated the data management, drafted the initial manuscript, and performed the initial analyses. Dr. Ishitsuka and Prof. Goto supervised the study design, revised the manuscript, and approved the final manuscript as submitted. Each author has seen and approved the submission of the manuscript and takes full responsibility for its contents. Acknowledgement: The authors would like to thank the Health, Clinic, and Education Information Evaluation Institute for developing the database used in this study. References Zhu N, Zhang D, Wang W, Li X, Yang B, Song J et al (2020) A Novel Coronavirus from Patients with Pneumonia in China, 2019. N Engl J Med 382(8):727–733 Furuse Y, Ko YK, Saito M, Shobugawa Y, Jindai K, Saito T et al (2020) Epidemiology of COVID-19 Outbreak in Japan, from January–March 2020. Jpn J Infect Dis 73(5):391–393 Imamura T, Saito T, Oshitani H (2021) Roles of Public Health Centers and Cluster-Based Approach for COVID-19 Response in Japan. Health Secur 19(2):229–231 Yamaguchi A, Hosozawa M, Hasegawa A, Okubo Y, Sampei M, Sawada N et al The coronavirus disease 2019 pandemic and the rights of the child in Japan. Pediatr Int [Internet]. 2022 Jan [cited 2023 Jun 22];64(1). Available from: https://onlinelibrary.wiley.com/doi/ 10.1111/ped.14913 Okubo Y, Uda K, Kaki M, Miyoshi S, Miyairi I Infection prevention measures and its determinants in childcare facilities during the COVID-19 pandemic: A nationwide survey (2022–2023). J Infect Chemother. 2023;S1341321X23002805. Hangai M, Piedvache A, Sawada N, Okubo Y, Sampei M, Yamaoka Y et al (2022) Children’s daily lives and well-being: Findings from the CORONA-CODOMO survey 1st wave. Pediatr Int Off J Jpn Pediatr Soc 64(1):e14981 Yamaoka Y, Hosozawa M, Sampei M, Sawada N, Okubo Y, Tanaka K et al (2021) Abusive and positive parenting behavior in Japan during the COVID-19 pandemic under the state of emergency. Child Abuse Negl 120:105212 Takaya J, Higashino H, Takaya R, Sakaguchi H, Tanoue J, Higashide T et al (2023) Effect of the COVID-19 pandemic lockdown on the physique of school-age children in Japan. Ann Pediatr Endocrinol Metab 28(2):124–130 Nagashima Y, Inokuchi M, Yasui Y, Uchida K, Tokumura M, Hasegawa T (2022) Impact of school closure due to the coronavirus disease 2019 pandemic on body mass index in Japanese children: Retrospective longitudinal study. J Paediatr Child Health 58(10):1841–1846 Matsuyama Y, Isumi A, Doi S, Fujiwara T (2022) Impacts of the COVID-19 Pandemic Exposure on Child Dental Caries: Difference-in-Differences Analysis. Caries Res 56(5–6):546–554 the Health, Clinic, and Education Information Evaluation Institute (HCEI). Abstracts of database provided by HCEI [in Japanese] [Internet]. [cited 2024 Jan 22]. Available from: https://www.hcei.or.jp/page/database Okubo Y, Michihata N, Yoshida K, Morisaki N, Matsui H, Fushimi K et al (2017) Impact of pediatric obesity on acute asthma exacerbation in Japan. Pediatr Allergy Immunol 28(8):763–767 Cole TJ, Bellizzi MC, Flegal KM, Dietz WH (2000) Establishing a standard definition for child overweight and obesity worldwide: international survey. BMJ 320(7244):1240–1243 NCD Risk Factor Collaboration (NCD-RisC) (2017) Worldwide trends in body-mass index, underweight, overweight, and obesity from 1975 to 2016: a pooled analysis of 2416 population-based measurement studies in 128·9 million children, adolescents, and adults. Lancet Lond Engl 390(10113):2627–2642 Okubo Y, Nochioka K, Testa MA (2018) The impact of pediatric obesity on hospitalized children with lower respiratory tract infections in the United States. Clin Respir J 12(4):1479–1484 Cole TJ, Flegal KM, Nicholls D, Jackson AA (2007) Body mass index cut offs to define thinness in children and adolescents: international survey. BMJ 335(7612):194 Okubo Y, Michihata N, Uda K, Morisaki N, Miyairi I, Matsui H et al (2018) Dose-response relationship between weight status and clinical outcomes in pediatric influenza-related respiratory infections. Pediatr Pulmonol 53(2):218–223 Goto R, Nianogo R, Okubo Y, Inoue K (2022) Evaluation of Obesity Trends Among US Adolescents by Socioeconomic Status, 1999–2018. JAMA Pediatr 176(9):937–940 Noi S, Shikano A, Imai N, Tamura F, Tanaka R, Kidokoro T et al (2022) The Changes in Visual Acuity Values of Japanese School Children during the COVID-19 Pandemic. Child Basel Switz 9(3):342 The Ministry of Education, Culture, Sports, Science, and Technology. Manual of school health checkups [Internet]. Available from: https://www.mext.go.jp/a_menu/kenko/hoken/1383847.htm Callaway B, Sant’Anna PHC (2021) Difference-in-Differences with multiple time periods. J Econom 225(2):200–230 Sun L, Abraham S (2021) Estimating dynamic treatment effects in event studies with heterogeneous treatment effects. J Econom 225(2):175–199 Goodman-Bacon A, National Bureau of Economic Research (2018) Difference-in-Differences with Variation in Treatment Timing [Internet]. Cambridge, MA: ; Sep [cited 2024 Jan 11] p. w25018. Report No.: w25018. Available from: http://www.nber.org/papers/w25018.pdf La Fauci G, Montalti M, Di Valerio Z, Gori D, Salomoni MG, Salussolia A et al (2022) Obesity and COVID-19 in Children and Adolescents: Reciprocal Detrimental Influence—Systematic Literature Review and Meta-Analysis. Int J Environ Res Public Health 19(13):7603 Woolford SJ, Sidell M, Li X, Else V, Young DR, Resnicow K et al (2021) Changes in Body Mass Index Among Children and Adolescents During the COVID-19 Pandemic. JAMA 326(14):1434 Goto R, Piedvache A, Hangai M, Yamaoka Y, Sampei M, Sawada N et al (2022) Time trends in emotional well-being and self-esteem in children and adolescents during the COVID-19 pandemic. Child Adolesc Psychiatry Ment Health 16(1):89 Goto R, Okubo Y, Skokauskas N (2022) Reasons and trends in youth’s suicide rates during the COVID-19 pandemic. Lancet Reg Health West Pac 27:100567 National Center for Child Health and Development. A 2022 survey on the mental health status of children during the COVID-19 pandemic [in Japanese] [Internet] (2023) Available from: https://www.ncchd.go.jp/press/2023/1114.pdf Monteleone AM, Cascino G, Barone E, Carfagno M, Monteleone P (2021) COVID-19 Pandemic and Eating Disorders: What Can We Learn About Psychopathology and Treatment? A Systematic Review. Curr Psychiatry Rep 23(12):83 Kawai K, Tachimori H, Yamamoto Y, Nakatani Y, Iwasaki S, Sekiguchi A et al (2023) Trends in the effect of COVID-19 on consultations for persons with clinical and subclinical eating disorders. Biopsychosoc Med 17(1):29 Kurisu K, Matsuoka M, Sato K, Hattori A, Yamanaka Y, Nohara N et al (2022) Increased prevalence of eating disorders in Japan since the start of the COVID-19 pandemic. Eat Weight Disord - Stud Anorex Bulim Obes 27(6):2251–2255 Wu PC, Tsai CL, Wu HL, Yang YH, Kuo HK (2013) Outdoor Activity during Class Recess Reduces Myopia Onset and Progression in School Children. Ophthalmology 120(5):1080–1085 Alvarez-Peregrina C, Sánchez-Tena MÁ, Martinez-Perez C, Villa-Collar C (2020) The Relationship Between Screen and Outdoor Time With Rates of Myopia in Spanish Children. Front Public Health 8:560378 Viteri B, Reid-Adam J (2018) Hematuria and Proteinuria in Children. Pediatr Rev 39(12):573–587 Okubo Y, Uda K, Miyairi I (2023) Trends in Influenza and Related Health Resource Use During 2005–2021 Among Children in Japan. Pediatr Infect Dis J 42(8):648–653 Ghaznavi C, Sakamoto H, Kawashima T, Horiuchi S, Ishikane M, Abe SK et al (2022) Decreased incidence followed by comeback of pediatric infections during the COVID-19 pandemic in Japan. World J Pediatr WJP 18(8):564–567 Uda K, Okubo Y, Tsuge M, Tsukahara H, Miyairi I (2023) Impacts of routine varicella vaccination program and COVID-19 pandemic on varicella and herpes zoster incidence and health resource use among children in Japan. Vaccine 41(34):4958–4966 Okubo Y, Uda K, Ogimi C, Shimabukuro R, Ito K Clinical Practice Patterns and Risk Factors for Severe Conditions in Pediatric Hospitalizations With Respiratory Syncytial Virus in Japan: A Nationwide Analyses (2018–2022). Pediatr Infect Dis J [Internet]. 2023 Nov 21 [cited 2023 Nov 22]; Available from: https://journals.lww.com/ 10.1097/INF.0000000000004181 Sekhar DL, Wang L, Hollenbeak CS, Widome MD, Paul IM (2010) A cost-effectiveness analysis of screening urine dipsticks in well-child care. Pediatrics 125(4):660–663 Additional Declarations No competing interests reported. Supplementary Files SupplementalMaterials.docx Cite Share Download PDF Status: Posted Version 1 posted 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. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-3960071","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":273961247,"identity":"454831ee-9e32-465b-b534-aaaad28a9197","order_by":0,"name":"Yusuke Okubo","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAy0lEQVRIiWNgGAWjYDACHgY2ECUHxGxADggcIE6LMelaEhsQWggAfp4zZg8+MBxO385++NmDNwy1cgyMZ/FbI9nbY244g+Fw7s6eNHPDOQzHgS48l4BXi8F5HjNp3n+Hczfc4GGT5mE4BnThGQPCWniADjMgXsvZHrCWBKiWGsJaJHuOlQP9km644UyameQcgwPGbIT8ws+TvA0YYtbyBscPP5N4U1Enxy9BIMSgoBnmzsMMbBJniNHBUIfE4O8hSssoGAWjYBSMHAAAoEhBB/fSKx0AAAAASUVORK5CYII=","orcid":"","institution":"National Center for Child Health and Development","correspondingAuthor":true,"prefix":"","firstName":"Yusuke","middleName":"","lastName":"Okubo","suffix":""},{"id":273961248,"identity":"9b31f008-5f22-48de-86a5-0c6f9d48d8f0","order_by":1,"name":"Kazue Ishitsuka","email":"","orcid":"","institution":"National Center for Child Health and Development","correspondingAuthor":false,"prefix":"","firstName":"Kazue","middleName":"","lastName":"Ishitsuka","suffix":""},{"id":273961249,"identity":"671e9927-43d7-4818-ad46-d39b0cea99dd","order_by":2,"name":"Atsushi Goto","email":"","orcid":"","institution":"Yokohama City University","correspondingAuthor":false,"prefix":"","firstName":"Atsushi","middleName":"","lastName":"Goto","suffix":""}],"badges":[],"createdAt":"2024-02-16 01:59:24","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3960071/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3960071/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":51511226,"identity":"ca8c0163-1cc4-4ef7-9cdd-c66e8cb0b070","added_by":"auto","created_at":"2024-02-22 21:07:52","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":76743,"visible":true,"origin":"","legend":"\u003cp\u003eTiming of entering elementary school (Grade 1), graduating junior high school (Grade 9), and COVID-19 pandemic among children born between 2000-2007\u003c/p\u003e","description":"","filename":"Fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-3960071/v1/2dc2ac89d2b9455ed95912f0.png"},{"id":51511228,"identity":"d6bd3fc6-a598-409f-b0e9-0d681cbc1731","added_by":"auto","created_at":"2024-02-22 21:07:52","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":924368,"visible":true,"origin":"","legend":"\u003cp\u003eTrends in underweight (A, B), obesity (C, D), poor visual acuity (E, F), dental caries (G, H), proteinuria (I, J), glucosuria (K, L), and hematuria (M, N) for boys and girls. The orange-filled square represents the experience of COVID-19.\u003c/p\u003e","description":"","filename":"Fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-3960071/v1/0bc60c536a851043d6159e00.png"},{"id":51511227,"identity":"2ee602a0-46aa-4242-8a7f-0167071212f3","added_by":"auto","created_at":"2024-02-22 21:07:52","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":591828,"visible":true,"origin":"","legend":"\u003cp\u003eDifference-in-differences (DID) analyses with dynamic treatment timing for underweight (A), obesity (B), poor visual acuity (C), dental caries (D), proteinuria (E), glucosuria (F), and hematuria (G) for boys and girls\u003c/p\u003e","description":"","filename":"Fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-3960071/v1/aa20528468a1b392011c6c68.png"},{"id":51814789,"identity":"553817df-0394-4e1c-9221-1fbecfe7cbb3","added_by":"auto","created_at":"2024-02-29 14:18:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":610761,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3960071/v1/fc1f363c-650f-408a-87f3-879a25de6df5.pdf"},{"id":51511229,"identity":"04fa8126-df1a-4e6c-b759-fb124647d375","added_by":"auto","created_at":"2024-02-22 21:07:52","extension":"docx","order_by":25,"title":"","display":"","copyAsset":false,"role":"supplement","size":83029,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementalMaterials.docx","url":"https://assets-eu.researchsquare.com/files/rs-3960071/v1/5be97ae7ddfb684494b758b5.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Impact of COVID-19 pandemic on physical health among children: difference-in-differences analyses of nationwide school health checkup database","fulltext":[{"header":"What is Known","content":"\u003cul\u003e\n\u003cli\u003eCOVID-19 spread from metropolitan to rural areas in Japan, with a slower spread among children until the Omicron variants.\u003c/li\u003e\n\u003cli\u003eThe Japanese government implemented early infection prevention measures, including school closures and mandates for masking and hand sanitization.\u003c/li\u003e\n\u003cli\u003eThe pandemic led to decreased outdoor activities, increased screen time, and changes in dietary habits among children, contributing to worsening physical health conditions like obesity, myopia, and dental caries.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eWhat is New:\u003c/p\u003e\n\u003cul\u003e\n\u003cli\u003eThis study utilizes nationwide school health checkup records from 2007-2022 to provide a comprehensive assessment of the long-term impacts of the COVID-19 pandemic on children's physical health at a national level.\u003c/li\u003e\n\u003cli\u003eIt offers the first long-term, nationwide analysis of the pandemic's effects on various aspects of children's physical health, bridging a significant knowledge gap.\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"Introduction","content":"\u003cp\u003eThe coronavirus disease-2019 (COVID-19) was first detected in December 2019 in China and subsequently in January 2020 in Japan.[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] COVID-19 initially spread among adults from metropolitan areas to rural regions in Japan.[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] The spread of COVID-19 among Japanese children remained relatively gradual until the emergence of the Omicron variants. This slower spread in the early phase of the pandemic can be attributed to the Japanese government\u0026rsquo;s proactive implementation of infection prevention measures. Notably, the government mandated nationwide school closures at the end of February 2020.[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] Schools were reopened until June 2020, with strict infection prevention measures, including universal masking and hand sanitization in educational institutions, where adherence rates had been notably high until March 2023.[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eThe COVID-19 pandemic has posed tremendous challenges for children, requiring them to adapt not only to infection prevention measures but also to the changes in their school and social environments.[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] Previous studies have indicated that the pandemic led to decreased outdoor physical activities, increased screen time, and changes in dietary habits.[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] Correspondingly, a worsening of physical health conditions, including increases in obesity, myopia, and dental caries, has been reported.8\u0026ndash;10] However, these studies have often been limited to single geographic locations and have only assessed short-term impacts. Consequently, the broader, long-term effects of the COVID-19 pandemic on various aspects of children\u0026rsquo;s physical health at a national level remain unclear. Utilizing nationwide school health checkup records provides us with the best opportunity to bridge this knowledge gap. Therefore, our study investigated the impact of the COVID-19 pandemic on physical health among children using nationwide school health checkup records during 2007\u0026ndash;2022.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design, Data source, and Study population\u003c/h2\u003e \u003cp\u003eWe conducted a retrospective cohort study to investigate the impact of the COVID-19 pandemic on the physical health of school children using a nationwide school health checkup records (SHR) database. This study adhered to the ethical principles outlined in the Declaration of Helsinki and received approval from the institutional review board (IRB) at the National Center for Child Health and Development in Japan (IRB number, 2022\u0026thinsp;\u0026minus;\u0026thinsp;176). The requirement of informed consent was waved due to the complete de-identification and subsequent anonymous nature of the SHR database.\u003c/p\u003e \u003cp\u003eWe utilized the SHR database provided by the Health, Clinic, and Education Information Evaluation Institute (HCEI) and Japan Medical Data Center (JMDC). The details of the databases have been described elsewhere.[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] Briefly, the database comprised school health records from approximately 400,000 school-aged children (Grade 1 to 9) living in 152 municipalities in Japan, where health checkups are mandated annually. The data, encompassing a 9-year record for each student, is collected up to their graduation year (Grade 9) from junior high school. The database consists of the following variables: sex, height, weight, visual acuity (uncorrected and corrected); numbers of primary and permanent teeth with treatment status for dental caries; and urine dipstick test results for protein, glucose, and occult blood.\u003c/p\u003e \u003cp\u003eWe extracted all records of children who graduated from junior high school between the fiscal years 2015 and 2022, corresponding to those who were born between the fiscal years 2000 and 2007 (Fig.\u0026nbsp;1). Then, we tracked these children\u0026rsquo;s records from their entry into elementary school (Grade 1) to the end of follow-up (Grade 9 or departure from the database) to measure the variables listed in the \u003cspan refid=\"Sec4\" class=\"InternalRef\"\u003eMeasurements\u003c/span\u003e section. Our study used data from 393,794 individuals, amounting to 3,544,146 records.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eMeasurements\u003c/h2\u003e \u003cp\u003eThe exposure of interest is the fiscal years after the COVID-19 pandemic (2020 to 2022). In Japan, the fiscal year begins on April 1 and ends on Match 31 of the following year. As the Japanese government implemented infection prevention measures (e.g., school closure, state of emergency) at the end of the fiscal year 2019, we defined fiscal years 2020, 2021, and 2022 as the 1st, 2nd, and 3rd years after the COVID-19 pandemic, respectively.\u003c/p\u003e \u003cp\u003eThe outcome of interest included weight status (e.g., underweight, normal weight, obesity), poor visual acuity, presence of untreated dental caries, and abnormal urine dipstick test results for protein, glucose, and occult blood for each year. Weight status was determined based on z-scores of body mass index (BMI) for age, in accordance with the recommendations of the World Health Organization and previous studies.[\u003cspan additionalcitationids=\"CR13 CR14 CR15 CR16 CR17\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] We defined the z-scores less than \u0026minus;\u0026thinsp;2 standard deviation (SD) as underweight (moderate or severe) and those greater than +\u0026thinsp;2 SD as obese. Visual acuity was measured using a Landolt ring chart, conforming to international standards.[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] Poor visual acuity was defined as an uncorrected visual acuity of less than 20/20 in either eye. In urinalyses with dipstick tests, the presence of protein at a level of 1\u0026thinsp;+\u0026thinsp;or greater (\u0026asymp;\u0026thinsp;urine protein\u0026thinsp;\u0026ge;\u0026thinsp;30 mg/dL), glucose at a level of \u0026plusmn;\u0026thinsp;or greater (\u0026asymp;\u0026thinsp;urine glucose\u0026thinsp;\u0026ge;\u0026thinsp;30 mg/dL), and hemoglobin at a level of 1\u0026thinsp;+\u0026thinsp;or greater (\u0026asymp;\u0026thinsp;urine hemoglobin\u0026thinsp;\u0026ge;\u0026thinsp;0.06 mg/dL) were defined as proteinuria, glucosuria, and hematuria, respectively.[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analyses\u003c/h2\u003e \u003cp\u003eThe data analyses were conducted in three steps using Stata/MP software version 16.1 (StataCorp LP, TX, USA). Firstly, we summarized measurement variables by calculating frequencies with proportions stratified by birth years and sex. Secondly, we estimated the impact of the COVID-19 pandemic on the outcomes of interest using a staggered difference-in-differences (DID) approach with multiple time periods, as proposed by Callaway and Sant\u0026rsquo;Anna.[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] We set children\u0026rsquo;s school grades (Grades 1 to 9) as time indicator variables and fiscal years 2020 to 2022 as treatment variables. Consequently, children born between 2000 and 2004 never experienced the COVID-19 pandemic during Grade 1 to 9 (the \"never-treated\u0026rdquo; group), while children born in 2005, 2006, and 2007 experienced the pandemic during Grade 9, Grade 8 to 9, and Grade 7 to 9, respectively (Fig.\u0026nbsp;1). We set never-treated and not-yet-treated units as the comparison group and investigated dynamic treatment effects as DID estimates in the 1st, 2nd, and 3rd years using outcome regression estimators based on ordinary least square with wild bootstrap procedures, which generates new samples by randomly perturbing the residuals of the models, under cluster standard errors for 95% confidence intervals (95%CIs).\u003c/p\u003e \u003cp\u003eThirdly, to check the robustness of the primary analyses, we employed fully-saturated two-way fixed effect regression models as proposed by Sun and Abraham.[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] This method utilizes two-way fixed effects models with staggered treatment adoption to investigate dynamic DID estimates for time relative to treatment timing. We set individuals as unit-fixed effects, their school grade as time-fixed effects, and time from the COVID-19 pandemic for individual units as relative time indicator variables. Compared with conventional two-way fixed effect models, which do not accommodate heterogeneous effects and may potentially assign negative weights to certain comparison groups, these estimation methods[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] offer the advantage of reducing bias from treatment effects from other periods and allowing for heterogeneity.[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eDescriptive statistics of the study cohort from Grade 1 to Grade 9\u003c/h2\u003e \u003cp\u003eDescriptive statistics are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The number of participants increased from children born in 2000 to those in 2004, with a slight male predominance. Figures\u0026nbsp;2A and 2B show the distribution of moderate/severe underweight and obesity stratified by sex, grades, and birth years (Supplemental Table\u0026nbsp;1). Whereas the proportions of underweight in boys increased from 1.5% in Grade 1 to 4.5% in Grade 9, the proportions in girls increased from 0.8% in Grade 1 to 3.8% in Grade 6, then decreased to 1.7% in Grade 9. Obesity among boys (Fig.\u0026nbsp;2C) increased from 4.4% in Grade 1 to 7.5% in Grade 4\u0026ndash;5, then decreased to 3\u0026ndash;4% in Grade 9. In contrast, obesity among girls (Fig.\u0026nbsp;2D) remained relatively stable at 1\u0026ndash;2% in Grades 1\u0026ndash;9 (Supplemental Table\u0026nbsp;2).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDemographics of school children stratified by fiscal years\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBirth year\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2000\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2001\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2002\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2003\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2004\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2005\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2006\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2007\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eEntry to elemental school (Grade 1)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2007\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2009\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2012\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eGraduation from junior high school (Grade 9)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2018\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2020\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2022\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCOVID-19 pandemic experience during Grade 1\u0026ndash;9\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eNumber of municipalities\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e110\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e143\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e128\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e134\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e136\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eNumber of Schools\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e263\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e422\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e689\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e776\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e666\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e702\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e724\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eNumber of students\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e4227\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e23,437\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e39,860\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e67,652\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e72,082\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e57,622\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e63,377\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e65,537\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eMale, N\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2317\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11,842\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e20,485\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e34,571\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e36,815\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e29,441\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e32,515\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e33,671\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(54.8%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e(50.5%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(51.4%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e(51.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e(51.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e(51.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e(51.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e(51.4%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFemale, N\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1910\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11,595\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e19,375\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e33,081\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e35,267\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e28,181\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e30,862\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e31,866\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(45.2%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e(49.5%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(48.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e(48.9%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e(48.9%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e(48.9%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e(48.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e(48.6%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"9\"\u003e*Abbreviations: N, sample size; COVID-19, coronavirus disease 2019\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003ePoor visual acuity monotonically increased from 18% and 20% in Grade 1 to 49% and 55% in Grade 9 among boys and girls, respectively (Fig.\u0026nbsp;2E and 2F; Supplemental Table\u0026nbsp;3). Untreated dental caries decreased from approximately 30% in Grade 1 to 16% for both boys and girls (Fig.\u0026nbsp;2G and 2H; Supplemental Table\u0026nbsp;4).\u003c/p\u003e \u003cp\u003eProteinuria increased from \u0026lt;\u0026thinsp;0.5% in Grade 1 to 1\u0026ndash;2% in Grade 9 (Fig.\u0026nbsp;2I and 2J; Supplemental Table\u0026nbsp;5). Similarly, glucosuria increased from \u0026lt;\u0026thinsp;1.0% in Grade 1 to 2\u0026ndash;4% in Grade 9 (Fig.\u0026nbsp;2K and 2L; Supplemental Table\u0026nbsp;6). Also, hematuria increased from \u0026lt;\u0026thinsp;0.5% in Grade 1 to 1\u0026ndash;2% in Grade 9 (Fig.\u0026nbsp;2M and 2N; Supplemental Table\u0026nbsp;7). These abnormal urine dipstick results had a slight male predominance.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eImpact of COVID-19 pandemic on physical health measures\u003c/h3\u003e\n\u003cp\u003eWe conducted staggered DID analyses, as proposed by Callaway and Sant\u0026rsquo;Anna, to estimate the impact of the COVID-19 pandemic on students\u0026rsquo; physical health. The COVID-19 pandemic had almost no impact on underweight status among boys and girls during the 1st and 2nd years (Fig.\u0026nbsp;3A; Supplemental Table\u0026nbsp;8) but had impacts during the 3rd year for boys (DID estimate, 0.21%; 95%CI, 0.15 to 0.28) and girls (DID estimate, 0.34%; 95%CI, 0.30 to 0.38). Obesity increased during the 3-year periods of the pandemic for both boys and girls (Fig.\u0026nbsp;3B), with the largest impact observed among boys during the 1st year (DID estimate, 0.88%; 95%CI, 0.72 to 1.04).\u003c/p\u003e \u003cp\u003eThe COVID-19 pandemic was associated with increased risks of poor visual acuity among boys and girls during the 1st and 2nd years (Fig.\u0026nbsp;3C), which persisted only among boys in the 3rd year (DID estimate, 1.90%; 95%CI, 1.30 to 2.30). In contrast, the pandemic was associated with reduced risks of untreated dental caries among boys in the 3rd year (DID estimate, -1.13%; 95%CI, -1.73 to -0.53) and girls in the 1st to 3rd years (Fig.\u0026nbsp;3D).\u003c/p\u003e \u003cp\u003eThere were almost no impacts of the COVID-19 pandemic on the risks of proteinuria among boys and girls (Fig.\u0026nbsp;3E), except for girls in the 3rd year (DID estimate, -0.17; 95%CI, -0.23 to -0.11). The risks of glucosuria for boys and girls decreased after the COVID-19 pandemic (Fig.\u0026nbsp;3F). Similar patterns were observed in the trends of hematuria among boys and girls (Fig.\u0026nbsp;3G). Sensitivity analyses with fully saturated two-way fixed models yielded findings similar to those of the primary analyses (Supplemental Table\u0026nbsp;9).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe nationwide school health checkup database enabled us to quantify trends in physical health among children from Grade 1 to Grade 9 and estimate the impact of the COVID-19 pandemic. The pandemic was associated with increased risks of being underweight, obesity, and poor visual acuity, whereas it was associated with decreased risks of dental caries and abnormal findings of urinalyses. The impacts of COVID-19 on some physical health measures (e.g., obesity, visual acuity) appeared to differ slightly between boys and girls.\u003c/p\u003e \u003cp\u003eThe COVID-19 pandemic altered children\u0026rsquo;s daily lives,[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] raising concerns about its impacts on their weight status. A systematic review published in 2022[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] indicated an increase in childhood obesity in many high-income countries during the pandemic. A notable example is the United States, where obesity in children aged 12\u0026ndash;15 years increased by approximately 5%.[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] In Japan, two studies conducted in Osaka and Tokyo, along with their surrounding areas, have presented slightly differing views. A large-scale study in public schools in Osaka found a decrease in obesity among children aged 12\u0026ndash;14 years, with almost no change in underweight status.[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] Conversely, a study targeting private schools in Tokyo and nearby areas reported an increase in BMI among boys and a decrease among girls.[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] Our study, aiming for a larger scale to improve generalizability, found that the impact of the COVID-19 pandemic on underweight was observed in both boys and girls in the 3rd year, while the impact on obesity was more pronounced in the earlier phase. As previously reported, the increase in obesity could be attributed to complex behavioral factors, such as decreased physical activity, prolonged sedentary time, changes in food behaviors, and alterations in the socioeconomic status of parents. The increase in eating disorders and underweight among children, with a majority of the patients being girls, have been reported from several studies, which might be linked to worsening mental health (e.g., social isolation, feeling of uncertainty) and economic factors affecting both children and parents.[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan additionalcitationids=\"CR27 CR28 CR29 CR30\" citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] Importantly, our findings suggest that underweight is more prevalent in boys, who may not have as much access to healthcare as girls, highlighting a need for improvement in this area.\u003c/p\u003e \u003cp\u003eOur study revealed an elevated risk of poor visual acuity immediately following the COVID-19 pandemic, consistent with a previous study conducted in 11 schools in Japan.[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] In Japan, some studies indicate reduced outdoor physical activities and increased screen time,[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] both of which are well-known risk factors for myopia.[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e] Furthermore, we found that the impact on poor visual acuity is not limited to a single year, but persisted for 3 years among boys and 2 years among girls. In contrast, untreated dental caries decreased during the 3 years of the COVID-19 pandemic, which differs from previous studies. For instance, a study conducted in Tokyo reported an increase in dental caries in the 1st year of the pandemic.[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] This discrepancy may be due to variations in the target populations, but the exact mechanisms remain unclear.\u003c/p\u003e \u003cp\u003eA decrease in abnormal urinalysis results may be attributed to changes in infectious disease epidemiology among children, as these results often accompany normal transient findings or immune responses to non-specific infections.[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] During fiscal years 2020\u0026ndash;2022, the Japanese government implemented infection prevention measures for students, such as mandatory mask-wearing, which were highly adhered to by students and teachers.(5) Consequently, the incidence rates of most infectious diseases (e.g., group A streptococcal pharyngitis) substantially reduced during this period.[\u003cspan additionalcitationids=\"CR36 CR37\" citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e] Since the fiscal year 2023, infection prevention measures in schools have been relaxed, and then the incidence rates of most infectious diseases have returned to pre-pandemic levels or higher. Although addressing mild abnormalities in urinalyses often does not require medical intervention and may not be cost-effective,[\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e] ongoing monitoring can provide insights into the underlying health dynamics between pediatric infectious diseases and urinary tract functions.\u003c/p\u003e \u003cp\u003eThe strength of our study lies in the use of nationwide datasets that cover various physical health outcomes, analyzed with recently developed robust statistical methods. However, our study has several limitations. Firstly, as the SHR database was primarily collected from public schools, the generalizability of our study findings to the entire pediatric population is uncertain despite our analyses being the largest of their kind. Secondly, the lack of demographic data, such as socioeconomic factors, lifestyle, and underlying diseases, precluded us from analyzing data with adjustment for important time-varying confounders, although our analyses with fixed-effect models implicitly accounted for time-fixed covariates. Thirdly, the SHR database does not provide information on geographic location due to the protection of personal information. Consequently, we could not analyze data to investigate the heterogeneity of the COVID-19 pandemic across different geographic locations. Fourthly, the health checkup records were collected for all students at the time of Grade 9. Due to this scheme, our DID analyses only estimated the impact of the COVID-19 pandemic among students in Grade 7\u0026ndash;9. Long-term data or another data source would be required to investigate the impact of the pandemic on younger students.\u003c/p\u003e \u003cp\u003eIn summary, our study highlighted essential changes in physical health among students in Japan, especially the increases in underweight, obesity, and poor visual acuity and the decreases in abnormal urinalysis findings during the COVID-19 pandemic. These findings underscore the multifaceted impact of the pandemic on children's health, revealing both direct and indirect effects on various health indicators, which could be valuable information for public health policy and pediatric healthcare planning in the post-pandemic era.\u003c/p\u003e "},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFinancial disclosure: \u003c/strong\u003e\u0026nbsp;\u003cbr /\u003e The authors have no financial relationships relevant to this article to disclose.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding source: \u003c/strong\u003e\u0026nbsp;\u003cbr /\u003e This work was supported by grants from the Japan Science and Technology Agency (PRESTO: JPMJPR22R4).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePotential conflict of interest:\u003c/strong\u003e\u0026nbsp;\u003cbr /\u003e The authors have no conflicts of interest relevant to this article to disclose.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthorship statement:\u003c/strong\u003e\u0026nbsp;\u003cbr /\u003e Dr. Okubo coordinated the data management, drafted the initial manuscript, and performed the initial analyses. Dr. Ishitsuka and Prof. Goto supervised the study design, revised the manuscript, and approved the final manuscript as submitted. Each author has seen and approved the submission of the manuscript and takes full responsibility for its contents.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank the Health, Clinic, and Education Information Evaluation Institute for developing the database used in this study.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eZhu N, Zhang D, Wang W, Li X, Yang B, Song J et al (2020) A Novel Coronavirus from Patients with Pneumonia in China, 2019. N Engl J Med 382(8):727\u0026ndash;733\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFuruse Y, Ko YK, Saito M, Shobugawa Y, Jindai K, Saito T et al (2020) Epidemiology of COVID-19 Outbreak in Japan, from January\u0026ndash;March 2020. Jpn J Infect Dis 73(5):391\u0026ndash;393\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eImamura T, Saito T, Oshitani H (2021) Roles of Public Health Centers and Cluster-Based Approach for COVID-19 Response in Japan. Health Secur 19(2):229\u0026ndash;231\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYamaguchi A, Hosozawa M, Hasegawa A, Okubo Y, Sampei M, Sawada N et al The coronavirus disease 2019 pandemic and the rights of the child in Japan. Pediatr Int [Internet]. 2022 Jan [cited 2023 Jun 22];64(1). Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://onlinelibrary.wiley.com/doi/\u003c/span\u003e\u003cspan address=\"https://onlinelibrary.wiley.com/doi/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1111/ped.14913\u003c/span\u003e\u003cspan address=\"10.1111/ped.14913\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOkubo Y, Uda K, Kaki M, Miyoshi S, Miyairi I Infection prevention measures and its determinants in childcare facilities during the COVID-19 pandemic: A nationwide survey (2022\u0026ndash;2023). J Infect Chemother. 2023;S1341321X23002805.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHangai M, Piedvache A, Sawada N, Okubo Y, Sampei M, Yamaoka Y et al (2022) Children\u0026rsquo;s daily lives and well-being: Findings from the CORONA-CODOMO survey 1st wave. Pediatr Int Off J Jpn Pediatr Soc 64(1):e14981\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYamaoka Y, Hosozawa M, Sampei M, Sawada N, Okubo Y, Tanaka K et al (2021) Abusive and positive parenting behavior in Japan during the COVID-19 pandemic under the state of emergency. Child Abuse Negl 120:105212\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTakaya J, Higashino H, Takaya R, Sakaguchi H, Tanoue J, Higashide T et al (2023) Effect of the COVID-19 pandemic lockdown on the physique of school-age children in Japan. Ann Pediatr Endocrinol Metab 28(2):124\u0026ndash;130\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNagashima Y, Inokuchi M, Yasui Y, Uchida K, Tokumura M, Hasegawa T (2022) Impact of school closure due to the coronavirus disease 2019 pandemic on body mass index in Japanese children: Retrospective longitudinal study. J Paediatr Child Health 58(10):1841\u0026ndash;1846\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMatsuyama Y, Isumi A, Doi S, Fujiwara T (2022) Impacts of the COVID-19 Pandemic Exposure on Child Dental Caries: Difference-in-Differences Analysis. Caries Res 56(5\u0026ndash;6):546\u0026ndash;554\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ethe Health, Clinic, and Education Information Evaluation Institute (HCEI). Abstracts of database provided by HCEI [in Japanese] [Internet]. [cited 2024 Jan 22]. Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.hcei.or.jp/page/database\u003c/span\u003e\u003cspan address=\"https://www.hcei.or.jp/page/database\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOkubo Y, Michihata N, Yoshida K, Morisaki N, Matsui H, Fushimi K et al (2017) Impact of pediatric obesity on acute asthma exacerbation in Japan. Pediatr Allergy Immunol 28(8):763\u0026ndash;767\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCole TJ, Bellizzi MC, Flegal KM, Dietz WH (2000) Establishing a standard definition for child overweight and obesity worldwide: international survey. BMJ 320(7244):1240\u0026ndash;1243\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNCD Risk Factor Collaboration (NCD-RisC) (2017) Worldwide trends in body-mass index, underweight, overweight, and obesity from 1975 to 2016: a pooled analysis of 2416 population-based measurement studies in 128\u0026middot;9 million children, adolescents, and adults. Lancet Lond Engl 390(10113):2627\u0026ndash;2642\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOkubo Y, Nochioka K, Testa MA (2018) The impact of pediatric obesity on hospitalized children with lower respiratory tract infections in the United States. Clin Respir J 12(4):1479\u0026ndash;1484\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCole TJ, Flegal KM, Nicholls D, Jackson AA (2007) Body mass index cut offs to define thinness in children and adolescents: international survey. BMJ 335(7612):194\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOkubo Y, Michihata N, Uda K, Morisaki N, Miyairi I, Matsui H et al (2018) Dose-response relationship between weight status and clinical outcomes in pediatric influenza-related respiratory infections. Pediatr Pulmonol 53(2):218\u0026ndash;223\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGoto R, Nianogo R, Okubo Y, Inoue K (2022) Evaluation of Obesity Trends Among US Adolescents by Socioeconomic Status, 1999\u0026ndash;2018. JAMA Pediatr 176(9):937\u0026ndash;940\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNoi S, Shikano A, Imai N, Tamura F, Tanaka R, Kidokoro T et al (2022) The Changes in Visual Acuity Values of Japanese School Children during the COVID-19 Pandemic. Child Basel Switz 9(3):342\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eThe Ministry of Education, Culture, Sports, Science, and Technology. Manual of school health checkups [Internet]. Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.mext.go.jp/a_menu/kenko/hoken/1383847.htm\u003c/span\u003e\u003cspan address=\"https://www.mext.go.jp/a_menu/kenko/hoken/1383847.htm\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCallaway B, Sant\u0026rsquo;Anna PHC (2021) Difference-in-Differences with multiple time periods. J Econom 225(2):200\u0026ndash;230\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSun L, Abraham S (2021) Estimating dynamic treatment effects in event studies with heterogeneous treatment effects. J Econom 225(2):175\u0026ndash;199\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGoodman-Bacon A, National Bureau of Economic Research (2018) Difference-in-Differences with Variation in Treatment Timing [Internet]. Cambridge, MA: ; Sep [cited 2024 Jan 11] p. w25018. Report No.: w25018. Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://www.nber.org/papers/w25018.pdf\u003c/span\u003e\u003cspan address=\"http://www.nber.org/papers/w25018.pdf\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLa Fauci G, Montalti M, Di Valerio Z, Gori D, Salomoni MG, Salussolia A et al (2022) Obesity and COVID-19 in Children and Adolescents: Reciprocal Detrimental Influence\u0026mdash;Systematic Literature Review and Meta-Analysis. Int J Environ Res Public Health 19(13):7603\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWoolford SJ, Sidell M, Li X, Else V, Young DR, Resnicow K et al (2021) Changes in Body Mass Index Among Children and Adolescents During the COVID-19 Pandemic. JAMA 326(14):1434\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGoto R, Piedvache A, Hangai M, Yamaoka Y, Sampei M, Sawada N et al (2022) Time trends in emotional well-being and self-esteem in children and adolescents during the COVID-19 pandemic. Child Adolesc Psychiatry Ment Health 16(1):89\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGoto R, Okubo Y, Skokauskas N (2022) Reasons and trends in youth\u0026rsquo;s suicide rates during the COVID-19 pandemic. Lancet Reg Health West Pac 27:100567\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNational Center for Child Health and Development. A 2022 survey on the mental health status of children during the COVID-19 pandemic [in Japanese] [Internet] (2023) Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.ncchd.go.jp/press/2023/1114.pdf\u003c/span\u003e\u003cspan address=\"https://www.ncchd.go.jp/press/2023/1114.pdf\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMonteleone AM, Cascino G, Barone E, Carfagno M, Monteleone P (2021) COVID-19 Pandemic and Eating Disorders: What Can We Learn About Psychopathology and Treatment? A Systematic Review. Curr Psychiatry Rep 23(12):83\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKawai K, Tachimori H, Yamamoto Y, Nakatani Y, Iwasaki S, Sekiguchi A et al (2023) Trends in the effect of COVID-19 on consultations for persons with clinical and subclinical eating disorders. Biopsychosoc Med 17(1):29\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKurisu K, Matsuoka M, Sato K, Hattori A, Yamanaka Y, Nohara N et al (2022) Increased prevalence of eating disorders in Japan since the start of the COVID-19 pandemic. Eat Weight Disord - Stud Anorex Bulim Obes 27(6):2251\u0026ndash;2255\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWu PC, Tsai CL, Wu HL, Yang YH, Kuo HK (2013) Outdoor Activity during Class Recess Reduces Myopia Onset and Progression in School Children. Ophthalmology 120(5):1080\u0026ndash;1085\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlvarez-Peregrina C, S\u0026aacute;nchez-Tena M\u0026Aacute;, Martinez-Perez C, Villa-Collar C (2020) The Relationship Between Screen and Outdoor Time With Rates of Myopia in Spanish Children. Front Public Health 8:560378\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eViteri B, Reid-Adam J (2018) Hematuria and Proteinuria in Children. Pediatr Rev 39(12):573\u0026ndash;587\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOkubo Y, Uda K, Miyairi I (2023) Trends in Influenza and Related Health Resource Use During 2005\u0026ndash;2021 Among Children in Japan. Pediatr Infect Dis J 42(8):648\u0026ndash;653\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGhaznavi C, Sakamoto H, Kawashima T, Horiuchi S, Ishikane M, Abe SK et al (2022) Decreased incidence followed by comeback of pediatric infections during the COVID-19 pandemic in Japan. World J Pediatr WJP 18(8):564\u0026ndash;567\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUda K, Okubo Y, Tsuge M, Tsukahara H, Miyairi I (2023) Impacts of routine varicella vaccination program and COVID-19 pandemic on varicella and herpes zoster incidence and health resource use among children in Japan. Vaccine 41(34):4958\u0026ndash;4966\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOkubo Y, Uda K, Ogimi C, Shimabukuro R, Ito K Clinical Practice Patterns and Risk Factors for Severe Conditions in Pediatric Hospitalizations With Respiratory Syncytial Virus in Japan: A Nationwide Analyses (2018\u0026ndash;2022). Pediatr Infect Dis J [Internet]. 2023 Nov 21 [cited 2023 Nov 22]; Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://journals.lww.com/\u003c/span\u003e\u003cspan address=\"https://journals.lww.com/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1097/INF.0000000000004181\u003c/span\u003e\u003cspan address=\"10.1097/INF.0000000000004181\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSekhar DL, Wang L, Hollenbeak CS, Widome MD, Paul IM (2010) A cost-effectiveness analysis of screening urine dipsticks in well-child care. Pediatrics 125(4):660\u0026ndash;663\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"SHR database, COVID-19 pandemic, coronavirus disease 2019, school physical exam, school health checkup","lastPublishedDoi":"10.21203/rs.3.rs-3960071/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3960071/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Purpose: The COVID-19 pandemic posed tremendous challenges for children, requiring them to adapt to changes in social environments. However, the long-term effects of the pandemic on various aspects of physical health at a national level remain unclear.\nMethods: In this retrospective cohort study, we analyzed data from nationwide health checkup records among children aged 7–15 years. The dataset comprised 3,544,146 records from 393,794 individuals who graduated from junior high school during fiscal years 2007 to 2022. Difference-indifferences (DID) analyses with multiple time periods were used to examine the impact of COVID-19 on physical health outcomes.\nResults: Compared with the pre-pandemic period, the COVID-19 pandemic was associated with excess increases in obesity for boys and girls, persisting over the 3 years (DID estimate, +0.42%; 95%CI, 0.23 to 0.61). Also, it was associated with excess increases in underweight (DID estimate, +0.28%; 95%CI, 0.25 to 0.32) and poor visual acuity among boys in the 3 rd year (DID estimate, +1.80%; 95%CI, 1.30 to 2.30]). There were excess reductions in dental caries (DID estimate,-1.48%; 95%CI,-2.01 to-0.95]), glucosuria (DID estimate,-0.55; 95%CI,-0.88 to-0.23), and hematuria (DID estimate,-0.43%; 95%CI,-0.73 to-0.13]) during the 3 rd year of the pandemic.\nConclusions: These findings underscore the multifaceted impact of the pandemic on various health indicators for school-aged children. This information could be valuable for public health policy and pediatric healthcare planning in the post-pandemic era. ","manuscriptTitle":"Impact of COVID-19 pandemic on physical health among children: difference-in-differences analyses of nationwide school health checkup database","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-02-22 21:07:47","doi":"10.21203/rs.3.rs-3960071/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"8fbc2d7e-c601-4622-a517-b86c8225406b","owner":[],"postedDate":"February 22nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-02-29T14:18:15+00:00","versionOfRecord":[],"versionCreatedAt":"2024-02-22 21:07:47","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3960071","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3960071","identity":"rs-3960071","version":["v1"]},"buildId":"_2-kVJe1T_tPrBINL-cwx","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}