Active Commuting to Elementary School and Adiposity: An Observational Study

BACKGROUND: Active commuting to school (ACS; walking or cycling to school) appears promising for decreasing children's obesity risk, although long-term studies are sparse. The aim was to examine whether kindergarten ACS was associated with fifth-grade adiposity. METHODS: This study was a secondary analysis of the Early Childhood Longitudinal Study, Kindergarten (n=7938). Enrollment in kindergarten (1998-1999) was nationally representative of the United States and follow-up occurred in 2004. Kindergarten ACS was the main exposure variable and fifth-grade BMI z-score was the main outcome measure. Covariates included (1) neighborhood safety and BMI z-score in kindergarten and (2) demographics (i.e., age, gender, race/ethnicity, socioeconomic status, single- vs. two-parent households, region of country, and urbanicity in fifth grade). Three interactions were included: school travel*neighborhood safety; school travel*BMI z-score (kindergarten); and school travel*socioeconomic status. Analysis of covariance accounted for the complex sampling design. RESULTS: Kindergarten ACS was associated with lower BMI z-score in fifth grade. The interaction of school travel*neighborhood safety indicated that children from less-safe neighborhoods who did ACS in kindergarten had a lower fifth-grade BMI z-score (p<0.05) than their peers who did not do ACS in kindergarten (i.e., in terms of BMI, this difference was -0.49 kg/m(2) for children of average height in less-safe neighborhoods). CONCLUSION: Among children from less-safe neighborhoods, kindergarten ACS independently predicted lower BMI z-score in fifth grade among a national US cohort. Interventions and policies to increase ACS among young children, especially from unsafe neighborhoods, are warranted and should address parents' safety concerns.