title: A prospective cohort study on the relationship of sleep duration with all-cause and disease-specific mortality in the Korean Multi-center Cancer Cohort study.
abstract: OBJECTIVE
  Emerging evidence indicates that sleep duration is associated with health outcomes. However, the relationship of sleep duration with long-term health is unclear. This study was designed to determine the relationship of sleep duration with mortality as a parameter for long-term health in a large prospective cohort study in Korea.
  
  
  METHODS
  The study population included 13 164 participants aged over 20 years from the Korean Multi-center Cancer Cohort study. Information on sleep duration was obtained through a structured questionnaire interview. The hazard ratios (HRs) and 95% confidence intervals (CIs) for mortality were estimated using a Cox regression model. The non-linear relationship between sleep duration and mortality was examined non-parametrically using restricted cubic splines.
  
  
  RESULTS
  The HRs for all-cause mortality showed a U-shape, with the lowest point at sleep duration of 7 to 8 hours. There was an increased risk of death among persons with sleep duration of ≤5 hours (HR, 1.21; 95% CI, 1.03 to 1.41) and of ≥10 hours (HR, 1.36; 95% CI, 1.07 to 1.72). In stratified analysis, this relationship of HR was seen in women and in participants aged ≥60 years. Risk of cardiovascular disease-specific mortality was associated with a sleep duration of ≤5 hours (HR, 1.40; 95% CI, 1.02 to 1.93). Risk of death from respiratory disease was associated with sleep duration at both extremes (≤5 and ≥10 hours).
  
  
  CONCLUSIONS
  Sleep durations of 7 to 8 hours may be recommended to the public for a general healthy lifestyle in Korea.
authors.affiliation: Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Yohwan
authors.initials: Y
authors.lastname: Yeo
authors.forename: Seung Hyun
authors.initials: SH
authors.lastname: Ma
authors.forename: Sue Kyung
authors.initials: SK
authors.lastname: Park
authors.forename: Soung-Hoon
authors.initials: SH
authors.lastname: Chang
authors.forename: Hai-Rim
authors.initials: HR
authors.lastname: Shin
authors.forename: Daehee
authors.initials: D
authors.lastname: Kang
authors.forename: Keun-Young
authors.initials: KY
authors.lastname: Yoo
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000401:mortality; D002423:Cause of Death; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007407:Interviews as Topic; D008875:Middle Aged; D009369:Neoplasms / Q000401:mortality*; D016016:Proportional Hazards Models; D011446:Prospective Studies; D056910:Republic of Korea; D012140:Respiratory Tract Diseases / Q000401:mortality; D012890:Sleep; D011795:Surveys and Questionnaires; D055105:Waist Circumference
keywords: Mortality; Prospective cohort; Sleep duration