title: The Risk of Developing Diabetes in Association With Long Working Hours Differs by Shift Work Schedules.
abstract: BACKGROUND
  The impact of long working hours on diabetes is controversial; however, shift work is known to increase the risk of diabetes. This study aimed to investigate the association between long working hours and diabetes among civil servants in Japan separately by shift work schedules.
  
  
  METHODS
  A prospective cohort study was conducted from April 2003 to March 2009. A total of 3195 men aged ≥35 years who underwent an annual health checkup at baseline were analyzed by shift work schedules (2371 non-shift workers and 824 shift workers). Self-reported working hours were categorized as 35-44 and ≥45 hours per week. The incidence of diabetes was confirmed by fasting plasma glucose concentration ≥126 mg/dL and/or self-reported medical diagnosis of diabetes at the annual checkup. A Cox proportional model was used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for developing diabetes associated with long working hours.
  
  
  RESULTS
  The median follow-up period of non-shift and shift workers was 5.0 and 4.9 years, respectively. During this period, 138 non-shift workers and 46 shift workers developed diabetes. A decreased HR was found among non-shift workers working ≥45 hours per week (HR 0.84; 95% CI, 0.57-1.24); however, shift workers working ≥45 hours per week had a significantly increased risk of diabetes (HR 2.43; 95% CI, 1.21-5.10) compared with those working 35-44 hours per week. An analysis restricted to non-clerical workers also showed similar results.
  
  
  CONCLUSIONS
  The risk of diabetes associated with long working hours differed by shift work schedules.
authors.affiliation: Department of Public Health, Hokkaido University Graduate School of Medicine.
authors.forename: Akira
authors.initials: A
authors.lastname: Bannai
authors.forename: Eiji
authors.initials: E
authors.lastname: Yoshioka
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Saijo
authors.forename: Sachiko
authors.initials: S
authors.lastname: Sasaki
authors.forename: Reiko
authors.initials: R
authors.lastname: Kishi
authors.forename: Akiko
authors.initials: A
authors.lastname: Tamakoshi
mesh_terms: D000328:Adult; D003920:Diabetes Mellitus / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D010561:Personnel Staffing and Scheduling / Q000706:statistics & numerical data*; D011446:Prospective Studies; D012306:Risk; D013997:Time Factors; D014940:Work Schedule Tolerance