title: Sleep duration and risk of type 2 diabetes: a meta-analysis of prospective studies.
abstract: OBJECTIVE
  It remains unclear how many hours of sleep are associated with the lowest risk of type 2 diabetes. This meta-analysis was performed to assess the dose-response relationship between sleep duration and risk of type 2 diabetes.
  
  
  METHODS
  PubMed and Embase were searched up to 20 March 2014 for prospective observational studies that assessed the relationship of sleep duration and risk of type 2 diabetes. Both semiparametric and parametric methods were used.
  
  
  RESULTS
  Ten articles with 11 reports were eligible for inclusion in the meta-analysis. A total of 18,443 incident cases of type 2 diabetes were ascertained among 482,502 participants with follow-up periods ranging from 2.5 to 16 years. A U-shaped dose-response relationship was observed between sleep duration and risk of type 2 diabetes, with the lowest risk observed at a sleep duration category of 7-8 h per day. Compared with 7-h sleep duration per day, the pooled relative risks for type 2 diabetes were 1.09 (95% CI 1.04-1.15) for each 1-h shorter sleep duration among individuals who slept <7 h per day and 1.14 (1.03-1.26) for each 1-h increment of sleep duration among individuals with longer sleep duration.
  
  
  CONCLUSIONS
  Our dose-response meta-analysis of prospective studies shows a U-shaped relationship between sleep duration and risk of type 2 diabetes, with the lowest type 2 diabetes risk at 7-8 h per day of sleep duration. Both short and long sleep duration are associated with a significantly increased risk of type 2 diabetes, underscoring the importance of appropriate sleep duration in the delay or prevention of type 2 diabetes.
authors.affiliation: Department of Nutrition and Food Hygiene, Hubei Key Laboratory of Food Nutrition and Safety, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, People's Republic of China MOE Key Laboratory of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, People's Republic of China.
authors.forename: Zhilei
authors.initials: Z
authors.lastname: Shan
authors.affiliation: Department of Nutrition and Food Hygiene, Hubei Key Laboratory of Food Nutrition and Safety, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, People's Republic of China MOE Key Laboratory of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, People's Republic of China.
authors.forename: Hongfei
authors.initials: H
authors.lastname: Ma
authors.affiliation: Department of Nutrition and Food Hygiene, Hubei Key Laboratory of Food Nutrition and Safety, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, People's Republic of China MOE Key Laboratory of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, People's Republic of China.
authors.forename: Manling
authors.initials: M
authors.lastname: Xie
authors.affiliation: Department of Nutrition and Food Hygiene, Hubei Key Laboratory of Food Nutrition and Safety, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, People's Republic of China MOE Key Laboratory of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, People's Republic of China.
authors.forename: Peipei
authors.initials: P
authors.lastname: Yan
authors.affiliation: MOE Key Laboratory of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, People's Republic of China.
authors.forename: Yanjun
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Department of Nutrition and Food Hygiene, Hubei Key Laboratory of Food Nutrition and Safety, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, People's Republic of China MOE Key Laboratory of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Bao
authors.affiliation: Department of Nutrition and Food Hygiene, Hubei Key Laboratory of Food Nutrition and Safety, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, People's Republic of China MOE Key Laboratory of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, People's Republic of China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Rong
authors.affiliation: Harvard Medical School, Boston, MA.
authors.forename: Chandra L
authors.initials: CL
authors.lastname: Jackson
authors.affiliation: Departments of Nutrition and Epidemiology, Harvard School of Public Health, Boston, MA lgliu@mails.tjmu.edu.cn frank.hu@channing.harvard.edu.
authors.forename: Frank B
authors.initials: FB
authors.lastname: Hu
authors.affiliation: Department of Nutrition and Food Hygiene, Hubei Key Laboratory of Food Nutrition and Safety, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, People's Republic of China MOE Key Laboratory of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, People's Republic of China lgliu@mails.tjmu.edu.cn frank.hu@channing.harvard.edu.
authors.forename: Liegang
authors.initials: L
authors.lastname: Liu
mesh_terms: D000328:Adult; D000368:Aged; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D012890:Sleep / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult