Systematic review with meta-analysis: Alcohol consumption and the risk of colorectal adenoma

Background Studies on the relation between alcohol consumption and risk of colorectal adenoma (CRA), a precursor of colorectal cancer, have been inconsistent. Aim A systematic review with meta-analysis was conducted to investigate the association and the dose-response of alcohol with CRA. Methods A literature search was performed on PubMed to identify relevant studies published up to January 2014. A fixed or random effects model was used to estimate summarised relative risks (RRs) and 95% confidence intervals (CIs) for the association between alcohol intake and CRA risk. Statistical heterogeneity between studies was assessed with the χ2 statistic and quantified by I. Results Twenty-three case-control studies and two cohort studies were included in the meta-analysis. All drinkers were associated with 17% increased risk for CRA, compared with nondrinkers or occasional alcohol drinkers. The dose-response analysis demonstrated that for drinkers of 10, 25, 50 and 100 g/day alcohol consumption, the estimated RRs of CRA were 1.02 (95% CI 0.89-1.16), 1.06 (95% CI 0.92-1.20), 1.16 (95% CI 1.02-1.33) and 1.61 (95% CI 1.42-1.84) respectively, in comparison with non-/occasional drinkers. The risks were consistent in the subgroup analyses of gender and site of adenoma, while it was stronger in European studies than the studies in the US and Asia. Conclusions This study suggests that alcohol intake is related to a significant increase of risk for colrectal adenoma.