title: Shift work and diabetes mellitus: a meta-analysis of observational studies.
abstract: BACKGROUND
  Observational studies suggest that shift work may be associated with diabetes mellitus (DM). However, the results are inconsistent. No systematic reviews have applied quantitative techniques to compute summary risk estimates.
  
  
  OBJECTIVE
  To conduct a meta-analysis of observational studies assessing the association between shift work and the risk of DM.
  
  
  METHODS
  Relevant studies were identified by a search of PubMed, Embase, Web of Science and ProQuest Dissertation and Theses databases to April 2014. We also reviewed reference lists from retrieved articles. We included observational studies that reported OR with 95% CIs for the association between shift work and the risk of DM. Two authors independently extracted data and assessed the study quality.
  
  
  RESULTS
  Twelve studies with 28 independent reports involving 226 652 participants and 14 595 patients with DM were included. A pooled adjusted OR for the association between ever exposure to shift work and DM risk was 1.09 (95% CI 1.05 to 1.12; p=0.014; I(2)=40.9%). Subgroup analyses suggested a stronger association between shift work and DM for men (OR=1.37, 95% CI 1.20 to 1.56) than for women (OR=1.09, 95% CI 1.04 to 1.14) (p for interaction=0.01). All shift work schedules with the exception of mixed shifts and evening shifts were associated with a statistically higher risk of DM than normal daytime schedules, and the difference among those shift work schedules was significant (p for interaction=0.04).
  
  
  CONCLUSIONS
  Shift work is associated with an increased risk of DM. The increase was significantly higher among men and the rotating shift group, which warrants further studies.
authors.affiliation: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Gan
authors.affiliation: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Yang
authors.affiliation: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Xinyue
authors.initials: X
authors.lastname: Tong
authors.affiliation: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Huilian
authors.initials: H
authors.lastname: Sun
authors.affiliation: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Cong
authors.affiliation: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Xiaoxu
authors.initials: X
authors.lastname: Yin
authors.affiliation: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China School of Economics and Management, Jiangxi Science and Technology Normal University, Nanchang, Jiangxi, China.
authors.forename: Liqing
authors.initials: L
authors.lastname: Li
authors.affiliation: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Shiyi
authors.initials: S
authors.lastname: Cao
authors.affiliation: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Xiaoxin
authors.initials: X
authors.lastname: Dong
authors.affiliation: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Gong
authors.affiliation: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Oumin
authors.initials: O
authors.lastname: Shi
authors.affiliation: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Deng
authors.affiliation: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Huashan
authors.initials: H
authors.lastname: Bi
authors.affiliation: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Zuxun
authors.initials: Z
authors.lastname: Lu
mesh_terms: D003920:Diabetes Mellitus / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D064887:Observational Studies as Topic; D012307:Risk Factors; D012737:Sex Factors; D014940:Work Schedule Tolerance; D017132:Workplace / Q000458:organization & administration