The Relationship between Sleep Duration and Body Mass Index Depends on Age

OBJECTIVE: Sleep duration is associated with obesity and cardiometabolic disease. It is unclear, though, how these relationship differs across age groups. METHODS: Data from the 2007–2008 National Health and Nutrition Examination Survey (NHANES) were used, including respondents aged 16+ with complete data (N=5,607). Sleep duration and age were evaluated by self-report and body mass index (BMI) was assessed objectively. Sleep duration was evaluated continuously and categorically [very short (≤4h), short (5–6h), and long (≥9h) versus average (7–8h)]. Age was also evaluated continuously and categorically [adolescent (16–17yrs), young adult (18–29yrs), early middle age (30–49 yrs), late middle age (50–6 4yrs), and older adult (≥65 yrs)]. RESULTS: There was a significant interaction with age for both continuous (P(interaction)=0.014) and categorical (P(interaction)=0.035) sleep duration. A pseudo-linear relationship is seen among the youngest respondents, with the highest BMI associated with the shortest sleepers and the lowest BMI associated with the longest sleepers. This relationship becomes U-shaped in middle-age, and less of a relationship is seen among the oldest respondents. CONCLUSIONS: These findings may provide insights for clinical recommendations and could help to guide mechanistic research regarding the sleep-obesity relationship.