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 questionsO_ST_ABSWhat is already known about this subject?C_ST_ABSO_LIOne of the many suggested explanations for the increased prevalence of childhood obesity is a decline in childrens outdoor activities. C_LIO_LIPrevious studies have shown outdoor activities to be inversely associated with adiposity. C_LIO_LILittle is known about outdoor kindergartens as a potential structural intervention for healthy weight development. C_LI What are the new findings in your manuscript?O_LIOur crude analysis suggested a lower risk of attained overweight after school entry among children in outdoor kindergartens than children in conventional kindergartens. C_LIO_LIAfter 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. C_LI How might your results change the direction of research or the focus of clinical practice?O_LIOur results do not support outdoor kindergartens as a potential intervention for healthy weight development. C_LIO_LIThese results highlight the importance of adjusting for potential confounding factors when examining the relationship between outdoor activities and childhood obesity. C_LIO_LIGiven the observational design of the study, our results should be interpreted with caution, and randomized trials are warranted to confirm our findings. C_LI Article SummaryThis study examined whether children in outdoor kindergartens had a lower risk of overweight after school entrance compared to children in conventional kindergartens.