Can rural middle schools moderate the relationship between income trajectories and adolescent body mass index?

Introduction: Rural and low-income adolescents are a vulnerable population at increased risk for obesity. In addition, growing evidence and consensus in the scientific community indicates obesogenic environments significantly increase obesity rates. The goal of this study is to test whether middle school nutrition and physical activity (N&PA) environments can moderate the association between income trajectory and BMI during adolescence, in a rural context.

Methods: The study sample of interest is a rural upstate New York birth cohort, ages 12 to 15 years (n=352), enrolled in 20 schools. The study uses previously collected longitudinal data on adolescent BMI and income trajectory. The outcome, 3-year change in BMI, is derived from measured heights and weights from medical chart audits. The exposure, income trajectory, is based on latent-class modeling which will group students based on their movement in and out of low-income. The moderating variables, middle school N&PA environments, will be assessed based on physical, economic, political, and socio-cultural factors. The tool will consist of researcher observation, questionnaires for the school's key staff, and analysis of written school policies.

Expected Results: Linear mixed models will be used to test the hypothesis that middle school N&PA environments have the greatest impact for adolescents with poorer income trajectories, in terms of 3-year change in BMI.

Discussion: This study builds off current recommendations for research on the environmental influences of childhood obesity by: (1) focusing on populations that are rural and vary in income; (2) using longitudinal rather than cross-sectional data; and (3) combining N&PA variables.