title: Diabetes mellitus increases the risk of bladder cancer: an updated meta-analysis of observational studies.
abstract: BACKGROUND
  Increasing evidence suggests that diabetes mellitus (DM) may be associated with an increased risk of bladder cancer. We performed an updated meta-analysis to examine the association between DM and risk of bladder cancer.
  
  
  METHODS
  We systematically searched the EMBASE and Medline (PubMed) databases (from inception through February 1, 2013) and reviewed the reference lists of relevant publications to search for additional studies. Summary relative risks (RRs) with 95% confidence intervals (CIs) were calculated with random-effects models.
  
  
  RESULTS
  In total, 10 case-control and 14 cohort studies met the inclusion criteria. Analysis of all studies showed that DM was associated with an increased risk of bladder cancer (RR 1.30, 95% CI 1.18-1.43). There was heterogeneity among studies (Pheterogeneity <0.001, I(2)=81.5%). Cohort studies showed a lower risk (RR 1.23, 95% CI 1.09-1.37) than case-control studies (odds ratio 1.46, 95% CI 1.20-1.78). The positive association was significant only in women (RR 1.23, 95% CI 1.02-1.49), but not in men (RR 1.07, 95% CI 0.97-1.18). The combined RRs remained unchanged before and after the studies on type 1 diabetes were excluded from analysis. The association between DM and bladder cancer risk did not differ significantly by methods of DM ascertainment. The combined RRs were 1.17 (95% CI 1.03-1.34), 1.34 (95% CI 1.19-1.51), and 1.57 (95% CI 0.96-2.55), respectively, when restricting the analysis to the studies accounting for body mass index, cigarette smoking, or glucose-lowering drug use.
  
  
  CONCLUSIONS
  This meta-analysis indicates a positive association between DM and risk of bladder cancer. Further studies are warranted to determine whether DM prevention and control can reduce risk of bladder cancer.
authors.affiliation: Shanghai Minhang Center for Disease Control and Prevention , Shanghai, People's Republic of China .
authors.forename: Hong
authors.initials: H
authors.lastname: Fang
authors.forename: Baodong
authors.initials: B
authors.lastname: Yao
authors.forename: Yujie
authors.initials: Y
authors.lastname: Yan
authors.forename: Huilin
authors.initials: H
authors.lastname: Xu
authors.forename: Yinan
authors.initials: Y
authors.lastname: Liu
authors.forename: Hongmei
authors.initials: H
authors.lastname: Tang
authors.forename: Jie
authors.initials: J
authors.lastname: Zhou
authors.forename: Lili
authors.initials: L
authors.lastname: Cao
authors.forename: Weijie
authors.initials: W
authors.lastname: Wang
authors.forename: Jinling
authors.initials: J
authors.lastname: Zhang
authors.forename: Liyun
authors.initials: L
authors.lastname: Zhao
authors.forename: Xi
authors.initials: X
authors.lastname: Chen
authors.forename: Fen
authors.initials: F
authors.lastname: Zhang
authors.forename: Yanping
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D016022:Case-Control Studies; D015331:Cohort Studies; D003922:Diabetes Mellitus, Type 1 / Q000150:complications* / Q000453:epidemiology; D003924:Diabetes Mellitus, Type 2 / Q000150:complications* / Q000453:epidemiology; D005260:Female; D006801:Humans; D006943:Hyperglycemia / Q000150:complications* / Q000453:epidemiology; D007333:Insulin Resistance; D008297:Male; D016017:Odds Ratio; D012306:Risk; D012737:Sex Factors; D001749:Urinary Bladder Neoplasms / Q000453:epidemiology / Q000209:etiology*