The influence of sex and age on the relationship between sleep duration and metabolic syndrome in Korean adults

Aims: To investigate the influence of sex and age on the relationship between sleep duration and metabolic syndrome in a nationally representative population. Methods: We used data from the Korea National Health and Nutrition Examination Survey (2001-2010) and enrolled 24,511 participants aged 20-79 years. Sleep duration was categorized into five groups: <= 5, 6, 7 (referent), 8, and >= 9 h/day. Age was categorized into three groups: younger (20-39 y), middle-aged (40-59 y), and older (60-79 y). The association between sleep duration and metabolic syndrome was assessed in the total, separately in men and women, then in six groups based on sex and age. Results: The prevalence of metabolic syndrome by sleep category demonstrated a U-shaped pattern in the total population. However, after adjusting for age, education, occupation, exercise, smoking, alcohol, and body mass index, the prevalence of metabolic syndrome increased in long sleepers (OR 1.31; 95% CI 1.14-1.51) but not in short sleepers (OR 1.00; 95% CI 0.89-1.11). The relationship between sleep duration and metabolic syndrome varied by sex and age-long sleep (>= 9 h/day) was positively associated with metabolic syndrome only in younger (OR 2.13; 95% CI 1.38-3.28) and middle-aged (OR 1.63; 95% CI 1.21-2.21) women. Short sleep (<= 5 h/day) was not associated with metabolic syndrome in any sex and age groups. However, extremely short sleep (<= 4 h/day) was associated with metabolic syndrome in middle-aged men (OR 1.76, 95% CI 1.05-2.96). Conclusion: These data suggest that sex and age significantly modify the relationship between sleep duration and metabolic syndrome. (C) 2013 Elsevier Ireland Ltd. All rights reserved.