title: Diabetes mellitus and risk of bladder cancer: a meta-analysis of cohort studies.
abstract: OBJECTIVE
  Diabetes is associated with increased risk of cancer at several sites, but its association with risk of bladder cancer is still controversial. We examined this association by conducting a systematic review and meta-analysis of cohort studies.
  
  
  METHODS
  Studies were identified by searching PubMed, EMBASE, Scopus, Web of Science, Cochrane register, and Chinese National Knowledge Infrastructure (CNKI) databases through April 29, 2012. Summary relative risks (SRRs) with their corresponding 95% confidence intervals (CIs) were calculated using a random-effects model.
  
  
  RESULTS
  A total of fifteen cohort studies were included in this meta-analysis. Analysis of all studies showed that diabetes was associated with a borderline statistically significant increased risk of bladder cancer (RR 1.11, 95% CI 1.00-1.23; p<0.001 for heterogeneity; I(2) = 84%). When restricting the analysis to studies that had adjusted for cigarette smoking (n = 6) or more than three confounders (n = 7), the RRs were 1.32 (95% CI 1.18-1.49) and 1.20 (95% CI 1.02-1.42), respectively. There was no significant publication bias (p = 0.62 for Egger's regression asymmetry test).
  
  
  CONCLUSIONS
  Our findings support that diabetes was associated with an increased risk of bladder cancer. More future studies are warranted to get a better understanding of the association and to provide convincing evidence for clinical practice in bladder cancer prevention.
authors.affiliation: Department of Urology, First Affiliated Hospital, Zhejiang University, Hangzhou, Zhejiang Province, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Xu
authors.forename: Jian
authors.initials: J
authors.lastname: Wu
authors.forename: Yeqing
authors.initials: Y
authors.lastname: Mao
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhu
authors.forename: Zhenghui
authors.initials: Z
authors.lastname: Hu
authors.forename: Xianglai
authors.initials: X
authors.lastname: Xu
authors.forename: Yiwei
authors.initials: Y
authors.lastname: Lin
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
authors.forename: Xiangyi
authors.initials: X
authors.lastname: Zheng
authors.forename: Jie
authors.initials: J
authors.lastname: Qin
authors.forename: Liping
authors.initials: L
authors.lastname: Xie
mesh_terms: D015331:Cohort Studies; D015897:Comorbidity; D048909:Diabetes Complications / Q000209:etiology*; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D006801:Humans; D012044:Regression Analysis; D015203:Reproducibility of Results; D012307:Risk Factors; D012907:Smoking; D001749:Urinary Bladder Neoplasms / Q000209:etiology* / Q000517:prevention & control