Association of COVID-19 Mitigation Measures With Cardiorespiratory Fitness and Body Mass Index Among Children in Austria
Authors: Xiaotao Zhang
Journal: JAMA Network Open (2021)

The COVID-19 pandemic has been associated with unprecedented and rapid changes in the lives of children worldwide. 1Children have experienced marked disruptions in their daily lives owing to the COVID-19 pandemic and protective mitigation measures.Although COVID-19 in children is not as severe as it is in adults, the indirect consequences of the COVID-19 pandemic and mitigation measures have become a public health issue.Whether the COVID-19 pandemic will be associated with long-term physical and mental health is unknown.Several studies have described changes in children's mental health, weight, eating habits, and physical activity associated with COVID-19 pandemic mitigation measures by using either self-or proxy-reported outcomes. 2-4Among these factors, an increase in sedentary behavior and a decrease in physical activity were associated with health-related parameters, such as cardiorespiratory fitness, which is related to long-term cardiovascular risk factors, and body mass index (BMI).However, most of these studies 3,4 were crosssectional and did not establish temporality because self-and proxy-reported outcomes are prone to recall bias.The association between COVID-19 mitigation measures and objectively measured cardiorespiratory fitness and BMI in children remains unclear.Jarnig et al 5 performed a cohort study with a 1-year follow-up period from September 2019 to September 2020.Their study included a representative sample of 764 children aged 7 to 10 years from 12 primary schools.Cardiorespiratory fitness (6-minute endurance run test) and BMI were objectively measured to investigate the association of COVID-19 mitigation measures with these parameters.The COVID-19 mitigation measures were associated with a substantial reduction in cardiorespiratory fitness, increased BMI, and an increase in the proportion of children with overweight and obesity.The study by Jarnig et al 5 began as a randomized clinical trial that aimed to evaluate the effects of a physical education intervention on motor competence, cardiorespiratory fitness, and health among primary schoolchildren aged 7 to 10 years.However, because of the COVID-19 regulations, the intervention was stopped in March 2020.Therefore, the authors analyzed the data in a cohort study and evaluated the association of the COVID-19 mitigation measures with cardiorespiratory fitness and BMI among children.In this study, the 6-minute endurance run test was used to assess cardiorespiratory fitness.Jarnig et al 5 collected both cardiorespiratory fitness and BMI at baseline in September and October 2019, BMI in May and June 2020, and both cardiorespiratory fitness and BMI in September and October 2020.The changes in cardiorespiratory fitness and BMI over time from September 2019 to September 2020 were estimated to reflect the consequences of the COVID-19 mitigation measures.The data were analyzed using multilevel mixed models and 3-way analysis of variance with repeated measurements.There was a significant decrease in the mean (SD) distance that the children could run in 6 minutes from 917.0 (141.1)m in September 2019 and 815.0 (134.3)m in September 2020.Jarnig et al 5 also observed a statistically significant increase in BMI during the follow-up period.The increase from September 2019 to June 2020 was greater than the increase from June 2020 to September 2020.Moreover, the proportion of children with overweight or obesity increased by 1.8% in June 2020 and by 3.8% in September 2020 compared with September 2019.Results of a subgroup analysis stratified by sex and sports club membership and a sensitivity analysis using different overweight and obesity thresholds are also reported in detail.This study had several strengths.First,