Several epidemiological studies have examined the association between coffee drinking and risk of endometrial cancer. To provide a quantitative assessment of this association, we conducted a meta-analysis of observational studies published up to October 2011 through a search of MEDLINE and EMBASE databases and the reference lists of retrieved article. Pooled relative risks (RRs) with 95% confidence intervals (CIs) were calculated using a random-effects model, and generalized least square trend estimation was used to assess dose-response relationships. A total of 16 studies (10 case-control and six cohort studies) on coffee intake with 6,628 endometrial cancer cases were included in the meta-analysis. The pooled RR of endometrial cancer for the highest versus lowest categories of coffee intake was 0.71 (95% CI: 0.62-0.81; p for heterogeneity = 0.13). By study design, the pooled RRs were 0.69 (95% CI: 0.55-0.87) for case-control studies and 0.70 (95% CI: 0.61-0.80) for cohort studies. By geographic region, the inverse association was stronger for three Japanese studies (pooled RR = 0.40; 95% CI: 0.25-0.63) than five studies from USA/Canada (pooled RR = 0.69; 95% CI: 0.60-0.79) or eight studies from Europe (pooled RR = 0.79; 95% CI: 0.63-0.99). An increment of one cup per day of coffee intake conferred a pooled RR of 0.92 (95% CI: 0.90-0.95). In conclusion, our findings suggest that increased coffee intake is associated with a reduced risk of endometrial cancer, consistently observed for cohort and case-control studies. More large studies are needed to determine subgroups to obtain more benefits from coffee drinking in relation to endometrial cancer risk.
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