Attained body mass index among children attending outdoor or conventional kindergartens

BACKGROUNDStudies have shown that outdoor activities are inversely associated with adiposity, but little is known about outdoor kindergartens as a potential intervention for healthy weight development.METHODSWe included 1544 children from outdoor kindergartens and 1640 from conventional kindergartens. Anthropometry was measured by school health nurses when the children were 6 to 8 years old. The first available measure of attained body mass index z-score (BMIz) after school entrance was included as the primary outcome. Risk of attaining overweight (including obesity) was included as a secondary outcome. Register-based information was available on potential confounding factors. Regression models were constructed to examine differences in study outcomes between children attending outdoor or conventional kindergartens.RESULTSOur basic models, with information on outcome, kindergarten type and birth weight, showed a borderline statistically significantly lower attained BMIz (−0.07 [95% CI: −0.14, 0.00], P=0.060) and a lower risk of overweight (adjusted risk ratio: 0.83 [95% CI: 0.72, 0.97], P=0.016) among children attending outdoor kindergartens compared to conventional kindergartens. When adjusting for sociodemographic factors and parental BMI, there was no evidence of differences in attained BMIz (P=0.153) or overweight (P=0.967).CONCLUSIONOur results do not support outdoor kindergartens as an intervention for healthy weight development.Study importance questionsWhat is already known about this subject?One of the many suggested explanations for the increased prevalence of childhood obesity is a decline in children’s outdoor activities.Previous studies have shown outdoor activities to be inversely associated with adiposity.Little is known about outdoor kindergartens as a potential structural intervention for healthy weight development.What are the new findings in your manuscript?Our crude analysis suggested a lower risk of attained overweight after school entry among children in outdoor kindergartens than children in conventional kindergartens.After adjusting for potential confounding from parental BMI and sociodemographic factors, we found no evidence of differences in attained BMIz or overweight among children attending outdoor or conventional kindergartens.How might your results change the direction of research or the focus of clinical practice?Our results do not support outdoor kindergartens as a potential intervention for healthy weight development.These results highlight the importance of adjusting for potential confounding factors when examining the relationship between outdoor activities and childhood obesity.Given the observational design of the study, our results should be interpreted with caution, and randomized trials are warranted to confirm our findings.Article SummaryThis study examined whether children in outdoor kindergartens had a lower risk of overweight after school entrance compared to children in conventional kindergartens.