title: Sleep duration and obesity among adults: a meta-analysis of prospective studies.
abstract: BACKGROUND
  Results from longitudinal studies on sleep duration and incidence of obesity remain controversial.
  
  
  METHODS
  PubMed and Web of Science updated on 20 February 2014 were searched for eligible publications. Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated using a random-effects model.
  
  
  RESULTS
  Eleven published articles were included, involving 197,906 participants for short sleep duration and 164,016 participants for long sleep duration. Compared with the normal sleep duration, the pooled OR for obesity was 1.45 (95% CI, 1.25-1.67) for the short sleep duration overall. After removing the three studies that had strong effects on heterogeneity, the pooled OR was 1.25 (95% CI, 1.14-1.38). The positive association was consistent among all subgroups analysis except in the European group (OR, 1.45; 95% CI, 0.79-2.64). No significant association was found between long sleep duration and risk of obesity overall (OR, 1.06; 95% CI, 0.98-1.15) and in subgroup analysis.
  
  
  CONCLUSIONS
  This meta-analysis indicated that short sleep duration was significantly associated with incidence of obesity, whereas long sleep duration had no effect on future obesity among adults.
authors.affiliation: Department of Epidemiology and Health Statistics, Qingdao University Medical College, Qingdao, China. Electronic address: yiliwu79@163.com.
authors.forename: Yili
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Department of Epidemiology and Health Statistics, Qingdao University Medical College, Qingdao, China.
authors.forename: Long
authors.initials: L
authors.lastname: Zhai
authors.affiliation: Department of Epidemiology and Health Statistics, Qingdao University Medical College, Qingdao, China.
authors.forename: Dongfeng
authors.initials: D
authors.lastname: Zhang
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D009765:Obesity / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D011446:Prospective Studies; D012890:Sleep / Q000502:physiology; D012892:Sleep Deprivation / Q000150:complications* / Q000503:physiopathology
keywords: Adults; Epidemiology; Long sleep duration; Meta-analysis; Obesity; Short sleep duration