Sociodemographic and behavioral predictors of bed time and wake time among US adolescents aged 15 to 17 years.

OBJECTIVE To examine bed times and wake times in US adolescents aged 15 to 17 years using time diaries to determine whether adolescent sleep has changed in recent years and what factors determine bed times and wake times. STUDY DESIGN Time diary analysis using 2 national probability samples: 1981 Time Use Longitudinal Panel Study (n = 130) and 2003-2006 American Time Use Survey (n = 2978). RESULTS Average time in bed on school days was about 8 hours and was 1 to 2 hours longer on non-school days. Bed times and wake times were similar in 1981 and 2003-2006. Sociodemographic factors and daytime activities, specifically computer use and social activities, predicted bed time. On school days, school start time was the strongest predictor of wake time. Every hour earlier that school started, wake time was about 25 minutes earlier. CONCLUSIONS Adolescents spent less than the recommended 9 hours in bed on school days. There is no evidence that this is a recent change in bed times and wake times, however. Although many factors influence bed time, school start time is the strongest determinant of wake time on school days. Increased computer use and earlier school days may be contributing to insufficient sleep in adolescents.