Greater screen time is associated with adolescent obesity: a longitudinal study of the BMI distribution from ages 14 to 18

Previous research has examined the association between screen time and average changes in adolescent body mass index (BMI). Until now, no study has evaluated the longitudinal relationship between screen time and changes in the BMI distribution across mid to late adolescence. Participants (n=1,336) were adolescents who were followed from age 14 to age 18 and surveyed every six months. Time spent watching television/videos and playing video games was self-reported (<1hr/d, 1hr/d, 2hrs/d, 3hrs/d, 4hrs/d, or 5+hrs/d). BMI (kg/m(2)) was calculated from self-reported height and weight. Longitudinal quantile regression was used to model the 10(th), 25(th), 50(th), 75(th) and 90(th) BMI percentiles as dependent variables. Study wave and screen time were the main predictors, and adjustment was made for gender, race, maternal education, hours of sleep and physical activity. We observed increases at all the BMI percentiles over time, with the greatest increase at the 90(th) BMI percentile. Screen time was positively associated with changes in BMI at the 50(th) (0.17, 95% CI: 0.06, 0.27), 75(th) (0.31, 95% CI: 0.10, 0.52) and 90(th) BMI percentiles (0.56, 95% CI: 0.27, 0.82). No associations were observed between screen time and changes at the 10(th) and 25(th) BMI percentiles. We observed positive associations between screen time and changes in the BMI at the upper tail of the BMI distribution. Therefore lowering screen time, especially among overweight and obese adolescents, could contribute to reducing the prevalence of adolescent obesity.