[Associations between sleep duration and fat mass, lean mass, and body mass index in adolescents in São Luís, Maranhão State, Brazil].

The study aimed to assess the association between sleep duration and body composition in adolescents. A cross-sectional study was performed with 1,269 adolescents from the 1997/1998 birth cohort in São Luís, Maranhão State, Brazil, 18 and 19 years of age. Sleep duration was assessed with accelerometry data. Body composition was assessed with fat mass index (FMI), lean mass index (LMI), and body mass index (BMI). Confounding factors were identified in a directed acyclic graph in DAGitty 3.0. Descriptive analyses were performed for all variables, followed by linear regression, with estimation of crude and adjusted regression coefficient with respective 95% confidence intervals (95%CI). In adolescent boys, each additional hour of sleep was associated with reductions of 0.30kg/m2 in LMI (95%CI: -0.45; -0.15), 0.26kg/m2 in FMI (95%CI: -0.48; -0.03), and 0.61kg/m2 in BMI (95%CI: -0.93; -0.30). In adolescent girls, each additional hour of sleep was associated with a reduction of 0.22kg/m2 in LMI (95%CI: -0.36; -0.07). Longer duration of sleep was associated with lower LMI in both sexes and lower FMI and BMI in boys, evidencing the importance of adequate hours of sleep for improving body composition indices.