Effects of school neighborhood food environments on childhood obesity at multiple scales: a longitudinal kindergarten cohort study in the USA

School neighborhood food environment is recognized as an important contributor to childhood obesity; however, large-scale and longitudinal studies remain limited. This study aimed to examine this association and its variation across gender and urbanicity at multiple geographic scales. We used the US nationally representative Early Childhood Longitudinal Study-Kindergarten cohort data and included 7530 kindergarteners followed up from 1998 to 2007. The Census, road network, and Dun and Bradstreet commercial datasets were used to construct time-varying measurements of 11 types of food outlet within 800-m straight-line and road-network buffer zones of schools and school ZIP codes, including supermarket, convenience store, full-service restaurant, fast-food restaurant, retail bakery, dairy product store, health/dietetic food store, candy store, fruit/vegetable market, meat/fish market, and beverage store. Two-level mixed-effect and cluster-robust logistic regression models were performed to examine the association. A higher body mass index (BMI) in 2007 was observed among children experiencing an increase of convenience stores in school neighborhoods during 1998-2007 (β = 0.39, p