Alcohol drinking and non-Hodgkin lymphoma risk: a systematic review and a meta-analysis.

Background: Whether an association between alcohol drinking and non-Hodgkin lymphoma (NHL) risk exists is an open question. In order to provide quantification of the issue, we carried out a meta-analysis of published data.
Methods: We identified 21 case-control and 8 cohort studies, including a total of 18,759 NHL cases. We derived meta-analytic estimates using random-effects models, taking into account correlation between estimates.
Results: The overall relative risk (RR) of NHL for drinkers versus non-drinkers was 0.85 [95% confidence interval (CI) 0.79-0.91]. Compared with non-drinkers, the pooled RRs were 0.88 for light (≤1 drink per day), 0.87 for moderate (1 to <4 drinks per day), and 0.84 for heavy (≥4 drinks per day) alcohol drinking. There was no association for light drinkers in cohort studies, whereas for moderate and heavy drinkers, the RRs were similar in case-control (0.85 for moderate, 0.92 for heavy) and cohort (0.89 for moderate, 0.79 for heavy) studies. The inverse relation with alcohol consumption (drinkers versus non-drinkers) was similar in men (RR = 0.83) and women (RR = 0.86), but apparently stronger in studies from Asia (RR = 0.69) than other world areas (RR = 0.88).
Conclusion: This meta-analysis provides quantitative evidence of a favourable role of alcohol drinking on NHL risk, though the lack of a biological explanation suggests caution in the interpretation of results.