Alcohol drinking and multiple myeloma risk--a systematic review and meta-analysis of the dose-risk relationship.

The role of alcohol intake in the risk for multiple myeloma (MM) is unclear, although some recent findings suggest an inverse relationship. To summarize the information on the topic, we carried out a systematic review and a dose-risk meta-analysis of published data. Through the literature search until August 2013, we identified 18 studies, eight case-control and 10 cohort studies, carried out in a total of 5694 MM patients. We derived pooled meta-analytic estimates using random-effects models, taking into account the correlation between estimates, and we carried out a dose-risk analysis using a class of nonlinear random-effects meta-regression models. The relative risk for alcohol drinkers versus non/occasional drinkers was 0.97 [95% confidence interval (CI), 0.85-1.10] overall, 0.96 (95% CI, 0.74-1.24) among case-control studies, and 1.00 (95% CI, 0.89-1.13) among cohort studies. Compared with nondrinkers, the pooled relative risks were 0.96 (95% CI, 0.81-1.13) for light (i.e. ≤ 1 drink/day) and 0.89 (95% CI, 0.74-1.07) for moderate-to-heavy (i.e. >1 drink/day) alcohol drinkers. The dose-risk analysis revealed a model-based MM risk reduction of about 15% at two to four drinks/day (i.e. 25-50 g of ethanol). The present meta-analysis of published data found no strong association between alcohol drinking and MM risk, although a modest favorable effect emerged for moderate-to-heavy alcohol drinkers.