title: Relationship between hepatitis C virus infection and type 2 diabetes mellitus: meta-analysis.
abstract: OBJECTIVE
  To investigate the association between hepatitis C infection and type 2 diabetes mellitus.
  
  
  METHODS
  Observational studies assessing the relationship between hepatitis C infection and type 2 diabetes mellitus were identified via electronic and hand searches. Studies published between 1988 to March 2011 were screened, according to the inclusion criteria set for the present analysis. Authors performed separate analyses for the comparisons between hepatitis C virus (HCV) infected and not infected, and HCV infected and hepatitis B virus infected. The included studies were further subgrouped according to the study design. Heterogenity was assessed using I(2) statistics. The summary odds ratios with their corresponding 95% CIs were calculated based on a random-effects model. The included studies were subgrouped according to the study design. To assess any factor that could potentially affect the outcome, results were further stratified by age group (proportion of ≥ 40 years), gender (proportion of male gender), body mass index (BMI) (proportion of BMI ≥ 27), and family history of diabetes (i.e., self reported). For stability of results, a sensitivity analysis was conducted including only prospective studies.
  
  
  RESULTS
  Combining the electronic database and hand searches, a total of 35 observational studies (in 31 articles) were identified for the final analysis. Based on random-effects model, 17 studies (n = 286,084) compared hepatitis C-infected patients with those who were uninfected [summary odds ratio (OR): 1.68, 95% CI: 1.15-2.45]. Of these 17 studies, 7 were both a cross-sectional design (41.2%) and cohort design (41.2%), while 3 were case-control studies (17.6%). Nineteen studies (n = 51,156) compared hepatitis C-infected participants with hepatitis B-infected (summary OR: 1.92, 95% CI: 1.41-2.62). Of these 19 studies, 4 (21.1%), 6 (31.6%) and 9 (47.4%) were cross-sectional, cohort and case-control studies, respectively. A sensitivity analysis with 3 prospective studies indicated that hepatitis C-infected patients had a higher risk of developing type 2 diabetes compared with uninfected controls (summary odds ratio: 1.41, 95% CI: 1.17-1.7; I(2) = 0%). Among hepatitis C-infected patients, male patients (OR: 1.26, 95% CI: 1.03-1.54) with age over 40 years (summary OR: 7.39, 95% CI: 3.82-9.38) had an increased frequency of type 2 diabetes. Some caution must be taken in the interpretation of these results because there may be unmeasured confounding factors which may introduce bias.
  
  
  CONCLUSIONS
  The findings support the association between hepatitis C infection and type 2 diabetes mellitus. The direction of association remains to be determined, however. Prospective studies with adequate sample sizes are recommended.
authors.affiliation: Faculty of Medicine and Health, International Medical University, Kuala Lumpur 57000, Malaysia. cho3699@gmail.com
authors.forename: Cho
authors.initials: C
authors.lastname: Naing
authors.forename: Joon Wah
authors.initials: JW
authors.lastname: Mak
authors.forename: Syed Imran
authors.initials: SI
authors.lastname: Ahmed
authors.forename: Mala
authors.initials: M
authors.lastname: Maung
mesh_terms: D003924:Diabetes Mellitus, Type 2 / Q000150:complications*; D006509:Hepatitis B / Q000150:complications; D006526:Hepatitis C / Q000150:complications*; D006801:Humans; D012307:Risk Factors