[A dose-response meta-analysis on the relationship between daily tea intake and cardiovascular mortality based on the...

Objective: To explore the relationship between daily tea intake and cardiovascular disease (CVD) mortality. Methods: PubMed, EMbase, The Cochrane, Chinese Biomedical Literature Database, CNKI, and Wanfang Database were searched to collect research on tea intake and CVD mortality. The search period was from the establishment of the database to June 2020. Two researchers independently screened and extracted literature. The risk of bias was evaluated in the included studies, a dose-response meta-analysis was conducted, sensitivity analysis and publication bias analysis of the research results, and quality evaluation of the included literature and GRADE classification of the evidence body were performed. Results: A total of 21 cohort or case-control studies were included, including 1 304 978 subjects. Among them, 38 222 deaths from CVD were reported. The quality scores of the included studies were all ≥ 6 points. The dose-response meta-analysis showed that for every additional cup of tea intake per day, the mortality rate of CVD decreased by about 3% (95%CI 0.95-0.98, P<0.05), and there was a non-linear dose-response relationship (P<0.05). Compared with people who do not drink tea, people who drink 1 to 8 cups of tea a day have 8% lower CVD mortality (RR=0.92, 95%CI 0.89-0.95), 13% (RR=0.87, 95 %CI 0.84-0.91), 15% (RR=0.85, 95%CI 0.82-0.89), 15% (RR=0.85, 95%CI 0.81-0.89), 16% (RR=0.84, 95%CI 0.80-0.89), 16% (RR=0.84, 95%CI 0.81-0.88), 16% (RR=0.84, 95%CI 0.81-0.87), 16% (RR=0.84, 95%CI 0.80-0.88), respectively. The results of traditional meta-analysis showed that compared with people who do not drink tea, people who drink more than 1 cup of tea a day are associated with 14% lower CVD mortality rate (RR=0.86, 95%CI 0.81-0.91, I²=73.2%, P<0.05). The results of subgroup analysis showed that compared with the corresponding people who did not drink tea, men who drank more than 1 cup of tea a day reduced the CVD mortality rate by 24%, women by 14%, European and American populations by 12%, and Asian populations by 15%. The population who consumed green tea decreased CVD mortality by 15%, and the population of non-smokers decreased CVD mortality by 20% (all P<0.05). The population who consumed black tea decreased CVD mortality by 8%, and the smoking population who consumed black tea decreased CVD mortality by 3%, and the difference was not statistically significant (all P>0.05). The results of the bias analysis showed that Begg=0.42 and Egger=0.62, indicating that the distribution on both sides of the funnel chart is symmetrical, suggesting that there is no publication bias. The results of sensitivity analysis showed that the effect size of the outcome index did not change significantly after excluding any article, indicating that the results are robust and credible. The GRADE evaluation showed that the evidence grades of the outcome indicators were all low grade. Conclusions: Daily tea consumption is related to reduced CVD mortality. It is therefore recommended to drink an appropriate amount of tea daily.