[Tea consumption and cancer: a Mendelian randomization study].

Objective: A Mendelian randomization (MR) analysis was performed to assess the relationship between tea consumption and cancer. Methods: There were 100 639 participants with the information of gene sequencing of whole genome in the China Kadoorie Biobank. After excluding those with cancer at baseline survey, a total of 100 218 participants were included in this study. The baseline information about tea consumption were analyzed, including daily tea consumption or not, cups of daily tea consumption, and grams of daily tea consumption. We used the two-stage least square method to evaluate the associations between three tea consumption variables and incidence of cancer and some subtypes, including stomach cancer, liver and intrahepatic bile ducts cancer, colorectal cancer, tracheobronchial and lung cancer, and female breast cancer. Multivariable MR and analysis only among nondrinkers were used to control the impact of alcohol consumption. Sensitivity analyses were also performed, including inverse variance weighting, weighted median, and MR-Egger. Results: We used 54, 42, and 28 SNPs to construct non-weighted genetic risk scores as instrumental variables for daily tea consumption or not, cups of daily tea consumption, and grams of daily tea consumption, respectively. During an average of (11.4±3.0) years of follow-up, 6 886 cases of cancer were recorded. After adjusting for age, age2, sex, region, array type, and the first 12 genetic principal components, there were no significant associations of three tea consumption variables with the incidence of cancer and cancer subtypes. Compared with non-daily tea drinkers, the HR (95%CI) of daily tea drinkers for cancer and some subtypes, including stomach cancer, liver and intrahepatic bile ducts cancer, colorectal cancer, tracheobronchial and lung cancer, and female breast cancer, are respectively 0.99 (0.78-1.26), 1.17 (0.58-2.36), 0.86 (0.40-1.84), 0.85 (0.42-1.73), 1.39 (0.85-2.26) and 0.63 (0.28-1.38). After controlling the impact of alcohol consumption and performing multiple sensitivity analyses, the results were similar. Conclusion: There is no causal relationship between tea consumption and risk of cancer in population in China.

[Association between tea consumption and all-cause mortality in Chinese adults].

Objective: To investigate the association between tea consumption and the risk of all-cause and cause-specific mortality among Chinese adults. Methods: This study was based on China Kadoorie Biobank (CKB). Tea consumption information was self-reported by participants at baseline. Death was mainly identified by linkage to the death registry system. Cox proportional hazard regression models estimated HR and 95%CI. Results: With a median follow-up of 11.1 years, there were 34 661 deaths in 438 443 participants. Compared with those who never drink tea, all-cause mortality HR(95%CI) were 0.89(0.86-0.91) and 0.92(0.88-0.95) for non-daily tea drinkers and daily tea drinkers, respectively. A statistically significant difference was found in the association of tea consumption and the risk of all-cause mortality between men and women(interaction P<0.05). The protective effect was mainly seen in men. Compared with those who never drink tea, daily tea drinkers had a reduced risk of death from ischemic heart disease, ischemic stroke, hemorrhagic stroke, cancer, respiration diseases and other causes of death, and the corresponding HR(95%CI) were 0.83(0.76-0.92), 0.82(0.69-0.97), 0.86(0.78-0.94), 1.03(0.97-1.09), 1.00(0.87-1.16), 0.84(0.78-0.90). Among never smokers and non-excessive drinkers, there was no statistically significant association between daily tea drinking and the risk of death from cancer. While smokers and excessive drinkers had an increased risk of death from cancer (interaction P<0.001). Conclusions: Tea consumers had reduced risks of all-cause mortality and partial cause-specific mortality, but not for the risk of death from cancer. On the contrary, daily tea drinkers with smoking habits and excessive alcohol drinking had an increased risk of death from cancer.