Association between tea drinking and endometrial cancer risk: a meta-analysis

The meta-analysis on observational studies was conducted to explore the association of tea drinking with endometrial cancer (EC). The MEDLINE and EMBASE databases were searched until August 2018. Altogether 19 works on tea drinking that involved 6,797 EC patients and 858,780 normal controls, including 10 case control and 9 cohort studies, were enrolled. The pooled relative risk (RR) of EC for the greatest tea consumption compared with the lowest level was 0.99 (95% CI: 0.94-1.04; I2 = 53%, p for heterogeneity = 0.005). In terms of study design, pooled RRs were 0.83 (95% CI: 0.73-0.95) and 1.02 (95% CI: 0.96-1.08) for case-control and cohort studies, respectively. By study region, the pooled RRs were 1.01 (95% CI: 0.95-1.08) in Europe, 1.06 (95% CI: 0.94-1.20) in USA/Canada, and 0.80 (95% CI: 0.69-0.93) in Asia. By additional subgroup analysis, inverse association was shown in green tea (RR 0.73, 95% CI: 0.64-0.84) and black tea (RR 0.65, 95% CI: 0.46-0.92). No difference was detected in smoking status or body mass index. To sum up, although tea does not have obvious protective effect against endometrial cancer, either black tea or green tea protects against EC. Moreover, Asian studies show that tea drinking protects against EC.