Screen use and sleep duration and quality at 15 years old: Cohort study.

Objective/background: The evidence on the association between screen use and sleep of adolescents is mainly based on studies about time watching television, with a few examining time using computers, videogames, and mobile devices. Our aim was to investigate the association between screen time for entertainment (watching TV, using computer, or playing games on tablets, smartphones, or videogame consoles) and sleep duration and self-reported sleep quality, among adolescents aged 15 years. Methods: With data from the 2004 Pelotas Birth Cohort, sleep duration was assessed with questions extracted from the Munich Chronotype Questionnaire and quality was self-reported. Adjusted β coefficients and prevalence ratios (PR) with (95% confidence intervals) were obtained, respectively, by linear and Poisson regressions. Results: 1,949 adolescents had information about screen time and sleep quality, and 1,851 about screen time and sleep duration. The median screen time was 4.5hs/24hs. The mean sleep duration was 7.6hs/24hs and the prevalence of bad sleep was 17.3% (15.7-19.0%). There was an inverse relationship between screen time and sleep duration. When compared with those with less than 2hs/24hs of screen time, adolescents with 6-8.8hs/24hs and ≥9hs experienced, respectively, 23.4 and 32.4 min reduction in sleep duration (β = -0.39; -0.62;-0.16 and β = -0.54; -0.77;-0.30). Adolescents with ≥9hs of screen time were 60% more likely to report bad sleep than those with less than 2hs/24hs (PR: 1.60; 1.10-2.32). Conclusions: The median time spent using screens was longer than recommended. Screen use for ≥6hs/24hs was associated with a shorter sleep duration, and ≥9hs/24hs with poor sleep quality.