Sleep duration rather than sleep timing is associated with obesity in adolescents

Objective: In this study, we investigated differences in sleep patterns between obese and non-obese adolescents, and determined which sleep-related parameters were associated with a risk of adolescent obesity. Methods: In this cross-sectional study, we evaluated 22,906 adolescents between 12 and 18 years of age (mean 15.2 ± 1.7 years; male 50.9%). Self-report questionnaires were used to assess body mass index (BMI) and sleep habits. Obesity was defined as a BMI-for-age ≥ 95th percentile. Weekend catch-up sleep (CUS) duration was calculated as the sleep duration on free days minus sleep duration on school days. We estimated mid-sleep time on free days corrected for oversleep on free days (MSFsc) and social jet lag. Then, we performed multivariate analysis for adolescent obesity and BMI, respectively. Results: The prevalence of obesity was 6.0%. The average sleep duration (P = 0.017) and weekend CUS duration (P < 0.001) of obese adolescents were shorter than those of non-obese adolescents. However, there was no significant difference in MSFsc or social jet lag by the obesity status. After adjustment, obesity was significantly associated with short average sleep duration (odds ratio [OR] 0.91, 95% confidence interval [CI] 0.86–0.96) and short weekend CUS duration (OR 0.92, 95% CI 0.89–0.95). Similarly, BMI was inversely correlated with average sleep duration (B = −0.15, 95% CI -0.19 to −0.11) and weekend CUS duration (B = −0.09, 95% CI -0.11 to −0.06). Conclusions: Our observations suggest that short sleep duration, rather than late MSFsc or social jet lag, was associated with adolescent obesity.