Association Between Self-Reported Sleep Duration and Body Composition in Middle-Aged and Older Adults

Study Objectives: The current study sought to examine whether self-reported sleep duration is linked to an adverse body composition in 19,709 adults aged 45 to 75 years. Methods: All variables used in the current study were derived from the Swedish EpiHealth cohort study. Habitual sleep duration was measured by questionnaires. Body composition was assessed by bioimpedance. The main outcome variables were fat mass and fat-free mass (in kg). Analysis of covariance adjusting for age, sex, fat mass in the case of fat-free mass (and vice versa), leisure time physical activity, smoking, and alcohol consumption was used to investigate the association between sleep duration and body composition. Results: Short sleep (defined as <= 5 hours sleep per day) and long sleep (defined as 8 or more hours of sleep per day) were associated with lower fat-free mass and higher fat mass, compared with 6 to 7 hours of sleep duration (P < .05). Conclusions: These observations could suggest that both habitual short and long sleep may contribute to two common clinical phenotypes in middle-aged and older humans, ie, body adiposity and sarcopenia. However, the observational nature of our study does not allow for causal interpretation.