Association between sleep duration, fat mass, lean mass and obesity in Korean adults: the fourth and fifth Korea National Health and Nutrition Examination Surveys.

This study investigated the association between sleep duration, fat mass, lean mass and obesity. Participants of this cross-sectional study were 16 905 adults included into the 4th and 5th Korea National Health and Nutrition Examination Surveys. Sleep duration was assessed by self-reported survey and categorized into ≤ 5, 6, 7, 8 and ≥ 9 h per day. The group reporting 7 h of sleep per day (comprised of those sleeping 7-8 h per day) was used as the reference group. Body composition was measured by dual X-ray absorptiometry (DEXA). Obesity was defined based on the criteria from the Korean Society for the Study of Obesity. Least-squares means of fat mass index (FMI) and lean mass index (LMI) adjusted for age, employment status, comorbidities and physical activity were used to assess the relation between sleep duration and body composition. Multivariable logistic regression was used to calculate the adjusted odds ratios (aOR) and 95% confidence intervals (95% CI) of obesity according to sleep duration after adjusting for sociodemographic and health-related factors. After adjustment, FMI increased with fewer hours of sleep (P for trend: < 0.001) and LMI decreased with more hours of sleep (P for trend: 0.011). Compared to the reference group, sleep-deprived individuals were 1.22 times more likely to have general obesity (aOR: 1.22; 95% CI: 1.03-1.45) and 1.32 times more likely to have abdominal obesity (aOR: 1.32; 95% CI: 1.10-1.58). Our findings suggest that sleep deprivation might be related to an increase of fat mass and obesity, while oversleeping could be linked to a reduction of lean mass.