Multilevel predictors of adolescent physical activity: a longitudinal analysis.

Mary O Hearst,Carrie D Patnode,John R Sirard,Kian Farbakhsh,Leslie A Lytle

doi:10.1186/1479-5868-9-8

Abstract

BackgroundTo examine how factors from a social ecologic model predict physical activity (PA) among adolescents using a longitudinal analysis.MethodsParticipants in this longitudinal study were adolescents (ages 10-16 at baseline) and one parent enrolled in the Transdisciplinary Research on Energetics and Cancer-Identifying Determinants of Eating and Activity (TREC-IDEA) and the Etiology of Childhood Obesity (ECHO). Both studies were designed to assess a socio-ecologic model of adolescent obesity risk. PA was collected using ActiGraph activity monitors at two time points 24 months apart. Other measures included objective height and weight, adolescent and parent questionnaires on multilevel psychological, behavioral and social determinants of PA, and a home PA equipment inventory. Analysis was conducted using SAS, including descriptive characteristics, bivariate and stepped multivariate mixed models, using baseline adjustment. Models were stratified by gender.ResultsThere were 578 adolescents with complete data. Results suggest few statistically significant longitudinal associations with physical activity measured as minutes of MVPA or total counts from accelerometers. For boys, greater self-efficacy (B = 0.75, p = 0.01) and baseline MVPA (B = 0.55, p < 0.01) remained significantly associated with MVPA at follow-up. A similar pattern was observed for total counts. For girls, baseline MVPA (B = 0.58, p = 0.01) and barriers (B = -0.32, p = 0.05) significantly predicted MVPA at follow-up in the full model. The full multilevel model explained 30% of the variance in PA among boys and 24% among girls.ConclusionsPA change in adolescents is a complex issue that is not easily understood. Our findings suggest early PA habits are the most important predictor of PA levels in adolescence. Intervention may be necessary prior to middle school to maintain PA through adolescence.

Highlights

To examine how factors from a social ecologic model predict physical activity (PA) among adolescents using a longitudinal analysis
Study design The data from this study came from two longitudinal studies comprised of adolescents and one of their parents: the Transdisciplinary Research on Energetics and Cancer - Identifying Determinants of Eating and Activity (TREC-IDEA) and Etiology of Childhood Obesity (ECHO) study
We tested for differences between IDEA and ECHO participants on demographic factors (t-test and chi-square) and conducted post-hoc regression modeling with each study sample as described above

Summary

Introduction

To examine how factors from a social ecologic model predict physical activity (PA) among adolescents using a longitudinal analysis. The U.S Department and of Health and Human Services recommends that children and adolescents engage in 60 min or more of physical activity (PA) every day, with most of that time in moderate- to vigorous-intensity [1]. Engagement in moderate-to-vigorous physical activity (MVPA) typically decreases as adolescents move through their teen years. There have been several review articles in the past decade describing the correlates of PA among adolescents [3,6,7,8]. Even studies using the most complex multilevel models only explain a low percentage (5.3-5.7%) of the variance in PA levels among children and adolescents [3]. There are relatively few longitudinal and intervention studies that help to describe potential causal factors or determinants of change in PA [9,10]

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Results

Conclusion