Coffee Drinking and the Risk of Endometrial Cancer: An Updated Meta-Analysis of Observational Studies

Background: Several compounds contained in coffee have been found to suppress carcinogenesis in experimental studies. We conducted a dose-response meta-analysis to assess the impact of coffee consumption on the risk of endometrial cancer. Materials and methods: We searched MEDLINE and EMBASE databases for studies published up to August 2016. Using random effects models, we estimated summary relative risks (RR) for cohort studies and odds ratios (OR) for case-control studies with 95% confidence intervals (CI). Dose-response analyses were conducted by using generalized least square trend estimation. Results: We identified 12 cohort studies and 8 case-control studies eligible for inclusion, contributing with 11,663 and 2,746 endometrial cancer cases, respectively. The summary RR for highest compared with lowest coffee intake was 0.74 (95% CI: 0.68-0.81; p(heterogeneity) = 0.09, I-2 = 32%). The corresponding summary RR among cohort studies was 0.78 (95% CI: 0.71-0.85; p(heterogeneity) = 0.14, I-2 = 31.9%) and 0.63 (95% CI: 0.53-0.76; p(heterogeneity) = 0.57, I-2 = 0%) for case-control studies. One-cup increment per day was associated with 3% risk reduction (95% CI: 2-4%) in cohort studies and 12% (95% CI: 5-18%) in case-control studies. After pooling the results from 5 cohort studies, the association remained significant only in women with body mass index over 30 (RR = 0.71, 95% CI: 0.61-0.81). Conclusion: The results from our meta-analysis strengthen the evidence of a protective effect of coffee consumption on the risk of EC and further suggest that increased coffee intake might be particularly beneficial for women with obesity.