Self-Selected Sleep Duration and Its Impact on Next Day Physical Activity in Teens

Introduction: While previous research shows increased obesity and obesity markers in children with shortened sleep durations, there is a scarcity of research exploring the effects sleep may have on teens’ physical activity levels. The paucity of research conducted so far is conflicting with some studies showing shorter sleep durations were associated with decreased physical activity while others indicate that longer sleep durations are associated with decreased physical activity. A clear need exists for additional exploration into the connection between sleep and physical activity. The hypothesis of the current analyses was that increased actigraph-measured nighttime sleep duration will predict higher rates of next day moderate-to-vigorous physical activity. Methods: Participants were 29 normal to obese teens (mean BMI=25.1) in grades 9-12 (mean grade=10th, mean age=15.4 yrs, 73% female, 23% Hispanic) who were relatively healthy and reported sleepingassent, teens’ height(cm) and weight(kg) were assessed with a stadiometer and digital scale, which allowed for the calculation of BMI. During the study week, teens followed a self-selected schedule while wearing an actigraph to record their sleep/wake schedule. Night sleep duration (NSD) was equal to the sleep duration recorded by the actigraph during the night sleep period. Teens also completed 3 Previous Day Physical Activity Recalls (1 weekend, 2 weekdays) assessing activities engaged in the previous afternoon-evening (1500-2300). The % time engaged in moderate-vigorous physical activity (MVPA) was calculated (total time spent engaged in MVPA divided by total time spent not sleeping). These data were from a larger prospective study assessing sleep and health in teens. Multiple regression analyses examined NSD as a predictor of MVPA% with grade, race, BMI, and sex as covariates for weekdays and weekends. Results: Teens slept an average of 392.5 min/night (SD=77 min) on weekdays and 506.4 min/night (SD=85 min) on weekends. Multiple regression analyses found that NSD was not a significant predictor of MVPA% on week days (adjusted R2=-0.15, p=0.944) or weekends (adjusted R2=-0.06, p=0.226). Conclusions: NSD was not predictive of next day MVPA%, which may have been due to the small sample size and subjectively assessed physical activity. Further research should examine the connection between sleep and physical activity using objectively measured physical activity data collected throughout the day and in a larger sample.