Alcohol intake and risk of nonmelanoma skin cancer: a systematic review and dose–response meta-analysis

Nonmelanoma skin cancer (NMSC) comprises mainly basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (cSCC). The association between alcohol intake and NMSC has been inconclusive; therefore the objective of this study is to quantify the relationship between alcohol intake and NMSC using meta-analyses. A systematic literature search of PubMed and Embase was performed on 30 October 2016. Eligible articles were case–control or cohort studies that examined alcohol intake and risk of BCC or cSCC and reported relative risks (RRs) with 95% confidence intervals (CIs). Of the 307 articles identified, 13 case–control and cohort studies were included in the systematic review, including 95 241 NMSC cases (91 942 BCC and 3299 cSCC cases). A random-effects model was used to obtain summary RRs and 95% CIs for dose–response meta-analyses. For every 10-gram increase in ethanol intake per day, a positive association was found for both BCC (summary RR of 1·07; 95% CI 1·04–1·09) and cSCC (summary RR of 1·11; 95% CI 1·06–1·16). While there was evidence suggesting a nonlinear association for BCC, it may be due to the sparse data at higher alcohol intake levels. This meta-analysis found evidence that alcohol drinking is positively associated with both BCC and cSCC risk in a dose-dependent manner. These results should be interpreted with caution due to potential residual confounding. Nonetheless, because alcohol drinking is a prevalent and modifiable behaviour, it could serve as an important public health target to reduce the global health burden of NMSC.