Changes in cardiorespiratory fitness and body mass index due to COVID-19 mitigation measures in Austrian children aged 7 to 10 years.

Jarnig, G.; Jaunig, J.; Van Poppel, M.

Importance: Previous studies showed reduced self-reported physical activity levels in children due to the coronavirus disease 2019 (COVID-19) mitigation measures, whereas limited data is available for objectively assessed health parameters. Objective: To examine the influence of these measures on the longitudinal development of cardiorespiratory fitness (CRF) and body mass index (BMI) of primary school children. Design: Cohort study with baseline measurements in September 2019, before the COVID-19 mitigation measures and follow-ups in June and September 2020. Setting: Twelve randomly selected primary schools in urban and rural districts of Klagenfurt, Austria. Participants: Legal guardians of 860 children provided written consent. A total of 764 children (88.8%) aged 7-10 years completed all measurements and were included for analyses. Exposure: COVID-19 mitigation measures. Main Outcomes and Measures: The study was planned as a randomized controlled trial, but analyzed as a longitudinal study due to stopped intervention because of COVID-19 mitigation regulations. CRF was measured with a 6-min run test. Height and weight were objectively measured. Age- and gender-specific national and international standard deviation scores (SDS) were calculated for CRF and BMI. Changes over time were analysed using ANOVAs. Secondary analyses were performed for subgroups divided by gender and sports club membership. Results: From September 2019 to September 2020, CRF SDS decreased by -1.06 (95% CI, -1.13 to -1.00), with a similar rate of decrease in both boys and girls. In June 2020, BMI SDS had increased by 0.12 (95% CI, 0.06-0.16), and in September 2020 by 0.16 (95% CI, 0.12-0.20), compared to September 2019. The rate of increase in BMI SDS was higher in boys (0.23 [95% CI, 0.18-0.29]) than in girls (0.09 [95% CI, 0.04-0.15]). Over the 1-year period, the proportion of children with overweight or obesity increased from 20.3% to 24.1% (+3.8%, P < .001), according to International Obesity Taskforce thresholds. Conclusions and Relevance: COVID-19 mitigation measures have negative indirect consequences of on relevant health parameters of children. Since these mitigation measures continued after our last assessments, consequences will have increased. Collaborative efforts are required to negate and reverse these effects on children's health, to prevent long-term negative health consequences.