Longitudinal, Time-Varying Behavioral Exposures and Changes in Childhood Adiposity

Abstract

Problem: Our objective was to exam associations between time-varying behaviors in childhood and changes in adiposity. Our aim in Paper 1 was to assess patterns and regional trends in seasonal variation of moderate-vigorous (MVPA) and vigorous (VPA) physical activity in adolescence. In Paper 2, our aim was to determine how seasonal variations in meeting activity guidelines relate to adolescent weight change. In Paper 3, our aim was to assess the time-varying effects of television time starting in early childhood on adiposity, and the extent to which sleep and diet quality mediated its effects. Methods and Procedures: For Paper 1, we used data from the Growing Up Today Study (GUTS) 2 to prospectively identify the prevalence of not meeting MVPA and VPA guidelines by season, climate region and other characteristics. For Paper 2, we used data from GUTS 1 and 2 to examine the relation between the number of seasons per year that adolescents met guidelines and incident overweight. In paper 3, we used data from Project Viva to categorize hours per week of television viewing, using American Academy of Pediatrics (AAP) age-based recommendations on screen time. The main outcome was incident overweight from age 3 years to 7 years. We fit generalized linear models for longitudinal binary data using generalized estimating equations to model the outcomes in aims 1, 2, and 3. Main results: In Paper 1, we found that over three-quarters of youth did not meet MVPA or VPA recommendations for at least one season during adolescence. Regardless of U.S. climate region, gender, race/ethnicity, or age group, adolescents were less likely to meet activity recommendations in the winter than the summer. In Paper 2, the risk of becoming overweight or obese was 17% (5%, 30%) higher for girls meeting the recommendations for MVPA on less than 3 seasons when compared to girls meeting these recommendations on 3 or 4 seasons. In Paper 3, children who watched more than the AAP recommended amount of television (2 hrs/day) had an adjusted 1.36 times the odds of becoming overweight each year (OR 1.36, 95%CI 0.89, 2.08).