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 2007 to 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 (<= 4 h), short (5-6 h), and long (>= 9 h) versus average (7-8 h)]. Age was also evaluated continuously and categorically [adolescent (16-17 years), young adult (18-29 years), early middle age (30-49 years), late middle age (50-64 years), and older adult (>= 65 years)]. 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 was 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 became U-shaped in middle-age, and less of a relationship was 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.