Alcohol drinking and the risk of colorectal cancer death: a meta-analysis

A causal link between alcohol consumption and colorectal cancer (CRC) was established only recently by the International Agency for Research on Cancer. However, the quantitative association between alcohol drinking and CRC mortality is still an open question. We performed a systemic review and meta-analysis on epidemiological studies to quantify the risk for CRC mortality at different levels of alcohol consumption. A literature search was carried out in PubMed and Web of Science to identify all relevant studies published from January 1966 to June 2013. The pooled relative risk (RR) and the corresponding 95% confidence interval (CI) were estimated by categorical meta-analysis. A dose-risk relation was also analyzed. Nine cohort studies exploring the association between CRC mortality and alcohol drinking were identified. Compared with non/occasional drinkers, the pooled RR was 1.03 (95% CI, 0.93-1.15) for any, 0.97 (95% CI, 0.86-1.10) for light (12.5g/day of ethanol), 1.04 (95% CI, 0.94-1.16) for moderate (12.6-49.9g/day of ethanol), and 1.21 (1.01-1.46) for heavy drinkers (50g/day of ethanol). For heavy drinkers, the pooled estimate was apparently higher for men (RR=1.28; 95% CI, 1.13-1.46) than for women (RR=0.79; 95% CI, 0.40-1.54; P-heterogeneity=0.007). The dose-response analysis showed a J-shaped relationship between alcohol consumption and CRC mortality. The present meta-analysis provides the evidence for an association between heavy alcohol drinking (50g/day of ethanol) and CRC mortality.