Previous longitudinal studies involving adolescents have modeled average changes in BMI ( ( 4- 6)), but there is evidence from cross-sectional studies that screen time is not uniformly associated with BMI across the BMI distribution in young children ( ( 7)). Further, in one longitudinal study the association between screen time and changes in mean BMI was positive when the participants were children, but null when the participants were adolescents ( ( 4)).ĭisparate findings across studies and developmental periods may be explained, in part, by how changes in BMI were statistically modeled. While these ecological data suggest that greater time spent in screen-based sedentary behavior may have contributed to the high prevalence of adolescent obesity, a recent review of longitudinal association studies concluded that there was insufficient evidence ( ( 3)). In recent decades, increases in the use of electronic media have paralleled the increase in adolescent obesity ( ( 1), ( 2)). Therefore, lowering screen time, especially among overweight and obese adolescents, could contribute to reducing the prevalence of adolescent obesity. Positive associations between screen time and changes in the BMI at the upper tail of the BMI distribution were observed. No associations were observed between screen time and changes at the 10th and 25th BMI percentiles. Increases at all the BMI percentiles over time were observed, with the greatest increase observed at the 90th BMI percentile. Study wave and screen time were the main predictors, and adjustment was made for gender, race, maternal education, hours of sleep, and physical activity. Longitudinal quantile regression was used to model the 10th, 25th, 50th, 75th, and 90th BMI percentiles as dependent variables. BMI (kg m −2) was calculated from self-reported height and weight. Time spent watching television/videos and playing video games was self-reported (<1 h day −1, 1 h day −1, 2 h day −1, 3 h day −1, 4 h day −1, or 5+ h day −1). Participants ( n = 1,336) were adolescents who were followed from age 14 to age 18 and surveyed every 6 months. Until now, no study has evaluated the longitudinal relationship between screen time and changes in the BMI distribution across mid to late adolescence. Previous research has examined the association between screen time and average changes in adolescent body mass index (BMI).
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