Alcohol drinking and bladder cancer risk: a meta-analysis

Background: We aimed at investigating the risk of bladder cancer at different levels of alcohol consumption by conducting a meta-analysis of epidemiological studies. Patients and methods: In October 2010, we carried out a systematic literature search in the Medline database, using PubMed. We identified 16 case-control and 3 cohort studies, including a total of 11 219 cases of bladder cancer, satisfying the inclusion criteria for this meta-analysis. Moderate alcohol intake was defined as <3 drinks per day (i.e. <37.5 g of ethanol per day) and heavy intake as >= 3 drinks/day. Pooled estimates of the relative risks (RR) and the corresponding 95% confidence intervals (CI) were calculated using random effects models. Results: Compared with non-drinkers, the pooled RRs of bladder cancer were 1.00 (95% CI 0.92-1.09) for moderate and 1.02 (95% CI 0.78-1.33) for heavy alcohol drinkers. When we excluded four studies that did not adjust for tobacco smoking, the corresponding estimates were 0.98 (95% CI 0.89-1.07) and 0.97 (95% CI 0.72-1.31). Conclusions: This meta-analysis of epidemiological studies provides definite evidence on the absence of any material association between alcohol drinking and bladder cancer risk, even at high levels of consumption.