title: Short sleep duration and health outcomes: a systematic review, meta-analysis, and meta-regression.
abstract: OBJECTIVE
  The dose-response of short sleep duration in mortality has been studied, in addition to the incidences of notable health complications and diseases such as diabetes mellitus, hypertension, cardiovascular diseases, stroke, coronary heart diseases, obesity, depression, and dyslipidemia.
  
  
  METHODS
  We collected data from prospective cohort studies with follow-ups of one year or more on associations between short sleep duration and the outcomes. For the independent variable, we divided participants at baseline into short sleepers and normal sleepers. The primary outcomes were defined as mortality and an incident of each health outcome in the long-term follow-up. Risk ratios (RRs) for each outcome were calculated through meta-analyses of adjusted data from individual studies. Sub-group and meta-regression analyses were performed to investigate the association between each outcome and the duration of short sleep.
  
  
  RESULTS
  Data from a cumulative total of 5,172,710 participants were collected from 153 studies. Short sleep was significantly associated with the mortality outcome (RR, 1.12; 95% CI, 1.08-1.16). Similar significant results were observed in diabetes mellitus (1.37, 1.22-1.53), hypertension (1.17, 1.09-1.26), cardiovascular diseases (1.16, 1.10-1.23), coronary heart diseases (1.26, 1.15-1.38), and obesity (1.38, 1.25-1.53). There was no sufficient usable evidence for meta-analyses in depression and dyslipidemia. Meta-regression analyses found a linear association between a statistically significant increase in mortality and sleep duration at less than six hours. No dose-response was identified in the other outcomes.
  
  
  CONCLUSIONS
  Based on our findings, future studies should examine the effectiveness of psychosocial interventions to improve sleep on reducing these health outcomes in general community settings.
authors.affiliation: Department of Public Health and Epidemiology, Faculty of Medicine, Oita University, Oita, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Itani
authors.affiliation: Division of Public Health, Department of Social Medicine, Nihon University School of Medicine, Tokyo, Japan.
authors.forename: Maki
authors.initials: M
authors.lastname: Jike
authors.affiliation: Department of Health Promotion and Human Behavior, Department of Clinical Epidemiology, Kyoto University Graduate School of Medicine/School of Public Health, Kyoto, Japan. Electronic address: noriowncu@gmail.com.
authors.forename: Norio
authors.initials: N
authors.lastname: Watanabe
authors.affiliation: Department of Public Health and Epidemiology, Faculty of Medicine, Oita University, Oita, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Kaneita
mesh_terms: D002318:Cardiovascular Diseases / Q000453:epidemiology; D006801:Humans; D009765:Obesity / Q000453:epidemiology; D012890:Sleep
keywords: Diabetes mellitus; Hypertension; Meta-regression; Mortality; Sleep deprivation; Vascular disease