title: Type 2 diabetes mellitus and risk of gallbladder cancer: a systematic review and meta-analysis of observational studies.
abstract: OBJECTIVE
  Increasing evidence suggests that a history of type 2 diabetes mellitus (type 2 DM) may be involved in the development of various sites of cancer. However, the association with risk of gallbladder cancer remains unclear.
  
  
  METHODS
  We identified studies by a literature search of MEDLINE and EMBASE through 31 August 2014 and by searching the reference lists of pertinent articles. All data were independently extracted by two investigators using a standardized data abstraction tool. Summary relative risks (SRRs) with 95% confidence intervals (CIs) were calculated with a random effects model.
  
  
  RESULTS
  A total of 20 studies (eight case-control studies and 12 cohort studies) were included in this meta-analysis. Analysis of these 20 studies found that compared with non-diabetic individuals, diabetic individuals had an increased risk of gallbladder cancer (SRR = 1.56, 95% CI: 1.36-1.79). There was evidence of moderate heterogeneity among these studies (p = 0.010 and I(2)  = 43.5%). This increased risk relationship is independent of smoking, body mass index and a history of gallstones. However, whether or not controlled for, alcohol use may be one of the potential confounders that significantly affect the association between type 2 DM and the risk of gallbladder cancer. Diabetic women and men had a similarly increased risk of gallbladder cancer associated with type 2 DM.
  
  
  CONCLUSIONS
  These findings of this systematic review indicate that compared with non-diabetic individuals, both men and women with type 2 DM had an increased risk of gallbladder cancer. Copyright © 2015 John Wiley & Sons, Ltd.
authors.affiliation: Department of General Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Gu
authors.affiliation: Department of Gastroenterology, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
authors.forename: Shiyan
authors.initials: S
authors.lastname: Yan
authors.affiliation: Department of Gastroenterology, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
authors.forename: Baochan
authors.initials: B
authors.lastname: Wang
authors.affiliation: Department of Gastroenterology, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Shen
authors.affiliation: Department of Gastroenterology, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
authors.forename: Haixia
authors.initials: H
authors.lastname: Cao
authors.affiliation: Department of Gastroenterology, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
authors.forename: Jiangao
authors.initials: J
authors.lastname: Fan
authors.affiliation: Department of Gastroenterology, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
authors.forename: Yuqin
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000428:Alcohol Drinking / Q000009:adverse effects / Q000453:epidemiology; D016022:Case-Control Studies; D015986:Confounding Factors, Epidemiologic; D003924:Diabetes Mellitus, Type 2 / Q000150:complications*; D005706:Gallbladder Neoplasms / Q000150:complications* / Q000453:epidemiology; D006801:Humans; D064887:Observational Studies as Topic; D012307:Risk Factors
keywords: diabetes mellitus; gallbladder cancer; meta-analysis; observational study; relative risk