A meta-analysis of coffee and tea consumption and the risk of glioma in adults

Coffee contains many compounds, including antioxidants, which could prevent cancerogenesis, and coffee has been related with lower incidence of cancer at several sites. Tea is also rich in antioxidants, mainly polyphenols. To provide a quantitative overall estimate on the relation between coffee and tea consumption and glioma, we combined all published data, using a meta-analytic approach. In September 2012, a bibliography search was carried out in both PubMed and Embase to identify observational studies providing quantitative estimates on the issue. Pooled estimates of the relative risks (RR) and the corresponding 95 % confidence intervals (CI) were calculated using random-effects models. Six studies (four cohort and two case-control studies) were available for meta-analysis, for a total of about 2100 cases. The summary RRs and 95 % CIs of glioma for drinkers versus non/occasional drinkers were 0.96 (95 % CI: 0.81-1.13) for coffee and 0.86 (95 % CI: 0.78-0.94) for tea, with no heterogeneity between studies. When we compared the highest versus the lowest categories of consumption, the RRs were 1.01 (95 % CI: 0.83-1.22) for coffee, 0.88 (95 % CI: 0.69-1.12) for tea, and 0.75 (95 % CI: 0.54-1.05) for coffee plus tea. This meta-analysis, although based on few studies, suggests a lack of association between coffee intake and glioma risk, and a tendency, if any, to a lower risk for tea and coffee plus tea drinkers.