title: Type 2 diabetes and risk of prostate cancer: a meta-analysis of observational studies.
abstract: BACKGROUND
  Emerging evidence suggests that diabetes may increase the risk of cancers. However, available evidence on prostate cancer is conflicting. We therefore examined the association between Type 2 diabetes and risk of prostate cancer by conducting a detailed meta-analysis of all studies published regarding this subject.
  
  
  METHODS
  PubMed database and bibliographies of retrieved articles were searched for epidemiological studies (published between 1970 and 2011), investigating the relationship between Type 2 diabetes and prostate cancer. Pooled risk ratio (RR) was calculated using random-effects model. Subgroup, sensitivity analysis and cumulative meta-analysis were also done.
  
  
  RESULTS
  Forty-five studies (29 cohort and 16 case-control studies) involving 8.1 million participants and 132 331 prostate cancer cases detected a significant inverse association between Type 2 diabetes and risk of prostate cancer (RR 0.86, 95% confidence interval (CI) 0.80-0.92). For cohort studies alone, the RR was 0.87 (95% CI 0.80-0.94), and for case-control studies alone, the RR was 0.85 (95% CI 0.74-0.96). Sensitivity analysis done by excluding one outlier further strengthened our negative association (RR 0.83, 95% CI 0.78-0.87). No evidence of publication bias was observed.
  
  
  CONCLUSIONS
  This meta-analysis provides strongest evidence supporting that Type 2 diabetes is significantly inversely associated with risk of developing prostate cancer.
authors.affiliation: Department of Pharmacy Practice, National Institute of Pharmaceutical Education and Research, Mohali, India.
authors.forename: D
authors.initials: D
authors.lastname: Bansal
authors.forename: A
authors.initials: A
authors.lastname: Bhansali
authors.forename: G
authors.initials: G
authors.lastname: Kapil
authors.forename: K
authors.initials: K
authors.lastname: Undela
authors.forename: P
authors.initials: P
authors.lastname: Tiwari
mesh_terms: D016022:Case-Control Studies; D003924:Diabetes Mellitus, Type 2 / Q000150:complications*; D006801:Humans; D008297:Male; D064887:Observational Studies as Topic; D016017:Odds Ratio; D011471:Prostatic Neoplasms / Q000209:etiology*; D012307:Risk Factors