Alcohol, alcoholic beverages, and melanoma risk: a systematic literature review and dose-response meta-analysis

Several studies in recent years have investigated the relationship between alcohol intake and melanoma risk, with conflicting results. To help clarify this issue, we conducted a literature review and dose-response meta-analysis of studies published until June 30th, 2017, that examined the association between alcohol intake (overall and by beverage type) and melanoma risk. We used random effect models with maximum likelihood estimation to calculate summary relative risk (SRR) and 95% confidence intervals (95%CI). We included 20 independent studies (encompassing 10,555 melanoma cases and over 1.6 million non-cases/controls) published during 1986-2016, of which six had a prospective cohort study design. Adjustment for phenotypic characteristics and sunlight exposure was performed in 11 and nine studies, respectively. Alcohol intake was moderately associated with melanoma risk: the SRR were 1.29 (95% CI 1.14-1.45) for those in the highest vs. lowest category of current alcohol intake, and 1.96 (95% CI 1.02-3.76, I (2) = 0%) for cumulative intake. In the dose-response analysis, the increase in risk associated with a 10 g increment in daily alcohol intake was 1.07 (95% CI 1.03-1.11). Risk estimates did not differ by gender, study design and adjustment for confounders; between-studies heterogeneity was acceptable, and there was no evidence of publication bias. Our findings suggest that alcohol drinking may be moderately associated with increased melanoma risk, although residual confounding and bias cannot be ruled out. Further research is needed to confirm these findings, clarify the role of the different alcohol sources, and investigate the interaction with known melanoma risk factors.