title: Diabetes and risk of bladder cancer among postmenopausal women in the Iowa Women's Health Study.
abstract: OBJECTIVE
  Studies have indicated that diabetes is a risk factor for bladder cancer; however, many failed to adjust for confounding variables. An earlier publication from the Iowa Women's Health Study reported a positive association of baseline diabetes with bladder cancer risk between 1986 and 1998, although the number of cases was small (n = 112). We re-examined the diabetes-bladder cancer risk association by accounting for 12 more years of follow-up and assessed whether the association varied by diabetes duration, body mass index, or waist-to-hip ratio (WHR).
  
  
  METHODS
  Proportional hazards regression was used to estimate the hazard ratio (HR) of bladder cancer (n = 277) in relation to diabetes (before enrollment and during follow-up) and diabetes duration using a time-dependent approach.
  
  
  RESULTS
  In a multivariate time-dependent analysis, the HR for bladder cancer was 1.69 (95 % CI 1.40-2.41) in relation to diabetes among 37,327 postmenopausal women initially free of cancer. There was an interaction between diabetes and WHR (p = 0.01). Bladder cancer HR in diabetic women with WHR > 0.9 was 2.5 times higher than expected. There was no dose-response relation of bladder cancer risk with diabetes duration. Compared to no diabetes, HRs were 1.77, 2.03, and 1.55 for diabetes durations of ≤5, 6-10, and >10 years, respectively.
  
  
  CONCLUSIONS
  We confirmed a positive association between diabetes and bladder cancer risk among white postmenopausal women. We also observed a synergistic interaction between diabetes and high WHR in bladder cancer development that might be explained by increased insulin resistance and inflammation related to abdominal obesity.
authors.affiliation: Division of Epidemiology and Community Health, School of Public Health, University of Minnesota, 1300 S. Second Street, Suite 300, Minneapolis, MN 55454-1015, USA. prizm001@umn.edu
authors.forename: Anna E
authors.initials: AE
authors.lastname: Prizment
authors.forename: Kristin E
authors.initials: KE
authors.lastname: Anderson
authors.forename: Jian-Min
authors.initials: JM
authors.lastname: Yuan
authors.forename: Aaron R
authors.initials: AR
authors.lastname: Folsom
mesh_terms: D000368:Aged; D015331:Cohort Studies; D048909:Diabetes Complications / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007484:Iowa / Q000453:epidemiology; D008875:Middle Aged; D017698:Postmenopause; D011446:Prospective Studies; D012307:Risk Factors; D014481:United States; D001749:Urinary Bladder Neoplasms / Q000175:diagnosis / Q000453:epidemiology*; D016387:Women's Health