Changes in cardiorespiratory fitness and body mass index due to COVID-19 mitigation measures in Austrian children aged 7 to 10 years
Authors: Jarnig Gerald , Jaunig Johannes , van Poppel Mireille N.M. 
Published: April 2021

ABSTRACTImportancePrevious 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.ObjectiveTo examine the influence of these measures on the longitudinal development of cardiorespiratory fitness (CRF) and body mass index (BMI) of primary school children.DesignCohort study with baseline measurements in September 2019, before the COVID-19 mitigation measures and follow-ups in June and September 2020.SettingTwelve randomly selected primary schools in urban and rural districts of Klagenfurt, Austria.ParticipantsLegal 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.ExposureCOVID-19 mitigation measures.Main Outcomes and MeasuresThe 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.ResultsFrom 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 RelevanceCOVID-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.KEY POINTSQuestionDo the COVID-19 mitigation measures have an impact on cardiorespiratory fitness (CRF) and body mass index (BMI) of primary school children?FindingsIn this longitudinal study, which included 764 primary school children, substantial reductions were found in CRF, which is a parameter related to long-term cardiovascular risk factors. In addition, increases in BMI standard deviation scores and in the proportion of children who are overweight or obese were evident.MeaningCollaborative efforts are required to negate and reverse these effects on children’s health, to prevent long-term negative health consequences.