title: Sleep duration and metabolic syndrome in adult populations: a meta-analysis of observational studies.
abstract: OBJECTIVE
  Epidemiological studies have repeatedly investigated the association between sleep duration and metabolic syndrome. However, the results have been inconsistent. This meta-analysis aimed to summarize the current evidence from cross-sectional and prospective cohort studies that evaluated this.
  
  
  METHODS
  Relevant studies were identified by systematically searching the PubMed, Cochrane CENTRAL, EMBASE and PsycINFO databases through November 2012 without language restriction.
  
  
  METHODS
  We identified 12 cross-sectional studies with 76 027 participants including 14 404 cases of metabolic syndrome, and 3 cohort studies with 2055 participants and 283 incident cases of metabolic syndrome.
  
  
  RESULTS
  For short sleep durations (<5 to 6 h), the odds ratios (OR) was 1.27 (95% confidence interval (CI)=1.10-1.48, I(2)=75.5%) in the 12 cross-sectional studies and 1.62 (95% CI=0.74-3.55, I(2)=71.4%) in the 3 cohort studies; for long sleep durations (>8 to 10 h), the OR was 1.23 (95% CI=1.02-1.49, I(2)=75.8%) in the 11 cross-sectional studies and 1.62 (95% CI=0.86-3.04, I(2)=0.0%) in the 2 cohort studies.
  
  
  CONCLUSIONS
  Short and long sleep durations are risky behaviors for increasing the risk of metabolic syndrome and thus have important public health implications, as sleep habits are amenable to behavioral interventions. The available data are sparse, and further studies, especially longitudinal studies, are needed to facilitate a better understanding of these associations.
authors.affiliation: Department of Family Medicine, Yeouido St Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: S-Y
authors.initials: SY
authors.lastname: Ju
authors.forename: W-S
authors.initials: WS
authors.lastname: Choi