title: The influence of sex and age on the relationship between sleep duration and metabolic syndrome in Korean adults.
abstract: OBJECTIVE
  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 ≥9h/day. Age was categorized into three groups: younger (20-39y), middle-aged (40-59y), and older (60-79y). 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 (≥9h/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 (≤5h/day) was not associated with metabolic syndrome in any sex and age groups. However, extremely short sleep (≤4h/day) was associated with metabolic syndrome in middle-aged men (OR 1.76, 95% CI 1.05-2.96).
  
  
  CONCLUSIONS
  These data suggest that sex and age significantly modify the relationship between sleep duration and metabolic syndrome.
authors.affiliation: Department of Public Health, Yonsei University Graduate School, Seoul, Republic of Korea.
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Stefani
authors.forename: Hyeon Chang
authors.initials: HC
authors.lastname: Kim
authors.forename: Jieun
authors.initials: J
authors.lastname: Kim
authors.forename: Kyungwon
authors.initials: K
authors.lastname: Oh
authors.forename: Il
authors.initials: I
authors.lastname: Suh
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008297:Male; D024821:Metabolic Syndrome / Q000503:physiopathology*; D008875:Middle Aged; D009749:Nutrition Surveys; D015995:Prevalence; D056910:Republic of Korea; D012307:Risk Factors; D012737:Sex Factors; D012890:Sleep / Q000502:physiology*; D012892:Sleep Deprivation / Q000503:physiopathology*; D012907:Smoking; D013997:Time Factors; D055815:Young Adult
keywords: Age; Effect modification; Metabolic syndrome; Sex; Sleep