Tea consumption and the risk of biliary tract cancer: a systematic review and dose-response meta-analysis of observational studies

Abstract

Recent studies have shown that tea consumption is associated with the reduced incidence of some types of cancer, possibly including biliary tract cancer. However, the epidemiological evidences for the association with risk of biliary tract cancer are contradictory. Thus, we performed meta-analysis of published observational studies to assess the association between tea consumption and risk of biliary tract cancer. Relevant studies were identified by searching PubMed, EMBASE, and ISI Web of Science published before October 2016. The Newcastle-Ottawa Scale was used to evaluate the quality of included studies, and publication bias was evaluated using funnel plots, and Begg's and Egger's tests. This meta-analysis includes eight studies comprising 18 independent reports. The incidence of biliary tract cancer reduced about 34% (significantly) for tea intake group in comparison with never intake group (summary odds ratio [OR] = 0.66; 95% confidence interval [CI] = 0.48-0.85). Additionally, an inverse relationship between tea intake and risk of biliary tract cancer was statistically significant in women (OR = 0.65; 95 % CI = 0.47-0.83), but not in men (OR = 0.86; 95% CI = 0.58-1.13). Dose- response analysis indicated that the risk of biliary tract cancer decreased by 4% with each additional cup of tea one day (relative risk [RR] = 0.96, 95% CI = 0.93-0.98, p = 0.001). In summary, tea intake is associated with decreased risk of biliary tract cancer, especially for women.

Keywords: bile duct cancer; biliary tract cancer; cholangiocarcinoma; tea.

Figure 1. The process of selecting studies for the meta-analysis

Figure 2. Forrest plot showing the relationship between tea and the risk of biliary tract cancer

Points represent the risk estimate for each individual study. horizontal lines represent 95% confidence interval; diamonds represent the summary risk estimate with 95% confidence interval. CI, confidence interval. ES, effect size.

Figure 3

Dose-response relationship between tea intake and the risk of biliary tract cancer (A), gallbladder cancer (B), extra hepatic bile ducts cancer (C). The solid line and the long dash line represent the estimated relative risks and its 95% confidence interval. Short dash line represents the linear relationship.

Figure 4. Funnel plot for studies included in the meta-analysis of the relationship between tea intake and biliary tract cancer risk

LogOR: Log odds ratio. SE: standard error.