Type 2 diabetes mellitus and risk of malignant melanoma: A systematic review and meta-analysis of cohort studies

Background: epidemiology studies have demonstrated inconsistent associations between type 2 diabetes mellitus and the risk of malignant melanoma. to this end,the aim was to perform a meta-analysis of cohort studies. method: medline,pubmed,embase and the cochrane library were searched up to february 2014. cohort studies addressing the relative risk of type 2 diabetes mellitus on malignant melanoma were included in this meta-analysis. the newcastle-ottawa scale was applied for quality evaluation. the pooled relative risks with the corresponding 95% confidence intervals (95% cis) were calculated by using random-effects or random-effects model. heterogeneity and publication bias were evaluated by i2 and funnel plot analysis,respectively. data was analyzed using stata 11.0. results: a total of 9 independent cohorts from 8 manuscripts were entered this meta-analysis. type 2 diabetes mellitus was slightly associated with an increased risk of malignant melanoma,and the pooled relative risk was 1.15 (95% ci,1.00-1.32) in diabetes compared with non-diabetes with significant evidence of heterogeneity among these studies (p=0.016,i2 =57.6%). for the studies adjusted for age,gender and obesity,the relative risks were 1.21 (95% ci,1.03-1.42),1.17 (95% ci,1.01-1.35) and 1.11 (95% ci,1.00-1.24),respectively. for the population-based studies in which case cohort established,the relative risk was 1.85 (95% ci,1.31-2.62). conclusion: type 2 diabetes might be an independent risk factor for malignant melanoma. further studies are needed to specifically test the effect,and fully elucidate the underlying pathophysiologic mechanisms.