The association of alcohol, tea, and other modifiable lifestyle factors with myocardial infarction and stroke in Chinese men

Association between tea consumption and prevention of coronary artery disease: A systematic review and dose-response meta-analysis

Background

Evidence from previous studies reporting on the relationship between tea consumption and its preventive effect on coronary artery disease (CAD) has conflicting outcomes. With the accumulation of new clinical evidence, we conducted this meta-analysis to assess tea consumption and CAD risk.

Methods

We searched PubMed, EMBASE, Cochrane Library, and Medline databases for published observational studies from their inception to May 2022. A random-effects model was used to calculate risk ratios with 95% confidence intervals. We also conducted linear and non-linear dose-response meta-analyses to analyze the association. We regarded that one cup equals 237 mL. Subgroup analyses and univariate meta-regression were conducted to explore the source of heterogeneity.

Results

A total of 35 studies, including 24 on green tea and 11 on black tea consumption, were included in this meta-analysis. An inverse association for the risk of CAD was observed for black tea (RR: 0.85; 95% CI: 0.76, 0.96) and green tea (RR: 0.93; 95% CI: 0.88, 0.99). The dose-response meta-analysis showed that drinking less than four cups of black tea daily may effectively prevent CAD, while more than 4-6 cups/d will promote disease risk. Furthermore, the dose-response relationship between green tea consumption and the prevention of CAD showed that the risk of CAD gradually decreased as green tea consumption increased. We also demonstrated that the more cups of green tea consumed, the lower the risk of CAD. In the subgroup analysis by continent, a significant negative correlation between CAD risk and green tea consumption was observed in the Asian population (RR: 0.92; 95% CI: 0.85, 0.99) but not in the western population [North America (RR: 0.97; 95% CI: 0.92, 1.03), Europe/Oceana (RR: 0.91; 95% CI: 0.78, 1.07)].

Conclusions

Higher green tea consumption was associated with reduced CAD risk, but drinking more than 4-6 cups of black tea per day may increase the risk. This study offers new insight into the relationship between tea consumption and its preventive effect on CAD. However, further large prospective cohort studies are needed to validate these findings.

Systematic review registration

The protocol of this systematic review was registered in the International Prospective Register of Systematic Reviews (PROSPERO) system (CRD42022348069).

Tea consumption and the risk of abdominal aortic aneurysm

BACKGROUND

Tea has the potential to lower the risk of abdominal aortic aneurysm (AAA) owing to its high antioxidant capacity. AAA risk factors including smoking, hypertension, and hypercholesterolaemia, may modify this association.

METHODS

The study population included 45 047 men in the Cohort of Swedish Men (COSM) and 36 611 women in the Swedish Mammography Cohort (SMC), aged 45-83 years at baseline. The COSM was established in 1997 with all men who lived in two central Swedish counties (Västmanland and Örebro), and the SMC was established in 1987-1990 with women residing in Västmanland county. Tea consumption was assessed by means of food frequency questionnaires in 1997 and 2009.

RESULTS

During 17.5 years of follow-up, 1781 AAA cases (1496 men, 285 women; 1497 non-ruptured, 284 ruptured) were ascertained via Swedish registers. Tea consumption was inversely associated with total AAA incidence in men and women. Women had a 23 (95 per cent c.i. 8 to 36) per cent lower risk of AAA per each cup per day increment, whereas men had a 9 (0 to 17) per cent lower risk (Pinteraction = 0.029). Tea consumption was associated with a lower risk of both non-ruptured (hazard ratio (HR) 0.93, 95 per cent c.i. 0.85 to 1.01) and ruptured (HR 0.84, 0.71 to 0.98) AAA. Smoking status modified the association (Pinteraction < 0.001), whereby tea consumption was associated with lower risk of AAA in ex-smokers (per cup per day, HR 0.89, 0.80 to 0.98) and in never smokers (HR 0.88, 0.77 to 1.00), but not in current smokers (HR 0.95, 0.84 to 1.06). Tea consumption was associated with a lower risk in participants with (HR 0.88, 0.80 to 0.98) and without (HR 0.93, 0.88 to 1.00) hypertension, and in those with (HR 0.82, 0.67 to 1.01) and without (HR 0.92, 0.86 to 0.98) hypercholesterolaemia.

CONCLUSION

Tea consumption was associated with a reduced risk of AAA. The association was more pronounced for ruptured than non-ruptured AAA, and in patients with hypertension and hypercholesterolaemia than those without. The association was also observed in ex-smokers and never smokers, but not in current smokers.

A systematic review of quantitative bias analysis applied to epidemiological research

BACKGROUND

Quantitative bias analysis (QBA) measures study errors in terms of direction, magnitude and uncertainty. This systematic review aimed to describe how QBA has been applied in epidemiological research in 2006-19.

METHODS

We searched PubMed for English peer-reviewed studies applying QBA to real-data applications. We also included studies citing selected sources or which were identified in a previous QBA review in pharmacoepidemiology. For each study, we extracted the rationale, methodology, bias-adjusted results and interpretation and assessed factors associated with reproducibility.

RESULTS

Of the 238 studies, the majority were embedded within papers whose main inferences were drawn from conventional approaches as secondary (sensitivity) analyses to quantity-specific biases (52%) or to assess the extent of bias required to shift the point estimate to the null (25%); 10% were standalone papers. The most common approach was probabilistic (57%). Misclassification was modelled in 57%, uncontrolled confounder(s) in 40% and selection bias in 17%. Most did not consider multiple biases or correlations between errors. When specified, bias parameters came from the literature (48%) more often than internal validation studies (29%). The majority (60%) of analyses resulted in >10% change from the conventional point estimate; however, most investigators (63%) did not alter their original interpretation. Degree of reproducibility related to inclusion of code, formulas, sensitivity analyses and supplementary materials, as well as the QBA rationale.

CONCLUSIONS

QBA applications were rare though increased over time. Future investigators should reference good practices and include details to promote transparency and to serve as a reference for other researchers.

Tea consumption and the risk of atherosclerotic cardiovascular disease and all-cause mortality: The China-PAR project

Aims

The role of tea consumption in the primary prevention of atherosclerotic cardiovascular disease remains unclear in cohort studies. This prospective cohort study aimed to investigate the associations of tea consumption with the risk of atherosclerotic cardiovascular disease and all-cause mortality.

Methods

We included 100,902 general Chinese adults from the project of Prediction for ASCVD Risk in China (China-PAR) in 15 provinces across China since 1998. Information on tea consumption was collected through standardized questionnaires. Outcomes were identified by interviewing study participants or their proxies, and checking hospital records and/or death certificates. Cox proportional hazard regression models were used to calculate hazard ratios and their corresponding 95% confidence intervals related to tea consumption.

Results

During a median follow-up of 7.3 years, 3683 atherosclerotic cardiovascular disease events, 1477 atherosclerotic cardiovascular disease deaths, and 5479 all-cause deaths were recorded. Compared with never or non-habitual tea drinkers, the hazard ratio and 95% confidence interval among habitual tea drinkers was 0.80 (0.75–0.87), 0.78 (0.69–0.88), and 0.85 (0.79–0.90) for atherosclerotic cardiovascular disease incidence, atherosclerotic cardiovascular disease mortality, and all-cause mortality, respectively. Habitual tea drinkers had 1.41 years longer of atherosclerotic cardiovascular disease-free years and 1.26 years longer of life expectancy at the index age of 50 years. The observed inverse associations were strengthened among participants who kept the habit during the follow-up period.

Conclusion

Tea consumption was associated with reduced risks of atherosclerotic cardiovascular disease and all-cause mortality, especially among those consistent habitual tea drinkers.

Pharmacological values and therapeutic properties of black tea (Camellia sinensis): A comprehensive overview

Medicinal plants are essential parts of traditional medicine due to their phytochemical constituents having pharmacological values and therapeutic applications. Black tea have thousands of various biological compounds such as flavonoids (Thearubigins (TRs) and theaflavins (TFs) and catechins), amino acids (L.theanine), vitamins (A, C, K), phenolic acids (caffeic acid (CA), gallic acid (GA), chlorogenic acids (CGA) and cauramic acid), lipids, proteins, volatile compounds carbohydrates, β-carotene and fluoride that illustrated many promising pharmacological effects regarded as growth promoter, cardioprotector, potent cholesterol-lowering effect, antioxidant and antimicrobial, etc inhuman. Although there is an exponential growth in molecular evidence of cholesterol-lowering and antioxidant effect in human, there is still a lack of information of the pharmacological effects of black tea. To fill this information gap, therefore, this review article underscores broadening the new insight pertaining to black tea that could be used as safe food additive. This article also illuminates the interesting role of black tea as an herbal medicine that is the future demand to get rid of synthetic health promoters in the human health practice. Moreover, this information would be useful in terms of the low-cost practice of natural medicines with no residual effects, and a natural protection of the human being. In addition, further studies at a molecular level are needed to reveal its mechanism of action particularly for the hypocholesterolemic effect of black tea to overcome the heart-related diseases, fewer side effects and being a natural safeguard of human health.

A Double-Blind, Randomized, Placebo-Controlled Study to Evaluate the Efficacy and Safety of STA-2 (Green Tea Polyphenols) in Patients with Chronic Stable Angina

BACKGROUND

Green tea intake has been shown to improve endurance capacity in animal studies, but whether it has a similar effect on humans remains unclear. A randomized, double-blinded, parallel-controlled study was conducted to evaluate the short-term effect of STA-2, a pharmaceutical preparation of green tea polyphenols, in patients with effort-induced angina and documented positive exercise tolerance test.

METHODS

A total of 79 patients recruited from three medical centers were randomly assigned to receive 2 STA-2 250 mg capsules, each containing 100 mg green tea polyphenols, three times daily, or placebo for six weeks after two consecutive symptom-limited treadmill exercise tests to ascertain the reproducibility of exercise tolerance.

RESULTS

There was no difference in total exercise tolerance time from baseline to Week 6 between two groups (p = 0.639). There were also no observed improvements in subgroup analyses stratified by age, gender, and BMI categories. However, a significant reduction in low-density lipoprotein levels was shown in patients in the STA-2 group (-8.99 ± 19.18 mg/dL) versus the placebo group (0.57 ± 19.77 mg/dL), p = 0.037, with greater benefits in patients not taking antihyperlipidemic drugs (STA-2: -9.10 ± 19.96 mg/dL vs. placebo: 4.42 ± 15.08 mg/dL, p = 0.037).

CONCLUSIONS

STA-2 treatment for 6 weeks did not increase exercise time as measured on a treadmill. However, this study also indicated that STA-2 treatment could have potential beneficial effects on LDL-cholesterol concentrations.

The association between smoking quantity and hypertension mediated by inflammation in Chinese current smokers

OBJECTIVES

Previous studies indicated that cigarette smokers were more likely to develop hypertension, and both smoking and hypertension were associated with inflammation. Whether inflammation mediates the relationship of them is unclear. This study aims to examine whether inflammation mediates the association between smoking and hypertension.

METHODS

Nine hundred and eighty-four Chinese current smokers from a community-based chronic diseases survey in Guangzhou and Zhuhai were interviewed about sociodemographics, smoking, chronic conditions, and other health-related variables. Hypertension was defined according to 2007 European Society of Hypertension and European Society of Cardiology (ESH-ESC) Practice Guidelines. Inflammatory markers including C-reactive protein (CRP), interleukin (IL)-6, IL-1β, monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), and vascular cell adhesion molecule-1 (VCAM-1) were measured by flow cytometry. Logistic regressions were performed to assess the mediation of inflammation on the relationship between smoking quantity and hypertension.

RESULTS

We observed a positive association between smoking quantity and hypertension (P<0.05). After controlling for potential confounders, daily cigarette consumption was significantly associated with higher level of CRP and VCAM-1 and lower level of TNF-α among six measured inflammatory markers, and the current smokers with hypertension had significantly higher level of MCP-1 and CRP than those smokers who were normotensive. Furthermore, the association between smoking quantity and hypertension was mediated by CRP, which accounted for 58.59% of the estimated causal effect of smoking on hypertension.

CONCLUSION

We have confirmed previous observations that smoking quantity was positively associated with hypertension, and the results of our study suggested that the association between smoking and hypertension was probably mediated by CRP.

Influence of tea consumption on acute myocardial infarction in China population: the INTERHEART China study

We assessed the association between tea consumption and acute myocardial infarction (AMI) using INTERHEART China data. Cases (n = 2909) and controls (n = 2947) were randomly selected and frequency matched by age and sex. Participants who drank tea ≥4 cups/d had a significantly higher risk of AMI than tea nondrinkers; odds ratio (OR) was 1.29 (95% confidence interval [CI]: 1.03-1.61) compared with tea nondrinkers. A similar trend was found in green tea drinkers; OR was 1.52 (95% CI: 1.13-2.05) in the participants who drank 3 cups/d and 1.73 (95% CI: 1.35-2.22) in the participants who drank ≥4 cups/d compared with tea nondrinkers. We also found that green tea consumption had a greater effect on females; OR was 2.80 (95% CI: 1.43-5.50) in females. In conclusion, we found that the risk of AMI increases as tea consumption increases. Further studies are needed to confirm this association.

Tea and health: studies in humans

Tea, next to water is the cheapest beverage humans consume. Drinking the beverage tea has been considered a healthpromoting habit since ancient times. The modern medicinal research is providing a scientific basis for this belief. The evidence supporting the health benefits of tea drinking grows stronger with each new study that is published in the scientific literature. Tea plant Camellia sinensis has been cultivated for thousands of years and its leaves have been used for medicinal purposes. Tea is used as a popular beverage worldwide and its ingredients are now finding medicinal benefits. Encouraging data showing cancer-preventive effects of green tea from cell-culture, animal and human studies have emerged. Evidence is accumulating that black tea may have similar beneficial effects. Tea consumption has also been shown to be useful for prevention of many debilitating human diseases that include maintenance of cardiovascular and metabolic health. Various studies suggest that polyphenolic compounds present in green and black tea are associated with beneficial effects in prevention of cardiovascular diseases, particularly of atherosclerosis and coronary heart disease. In addition, anti-aging, antidiabetic and many other health beneficial effects associated with tea consumption are described. Evidence is accumulating that catechins and theaflavins, which are the main polyphenolic compounds of green and black tea, respectively, are responsible for most of the physiological effects of tea. This article describes the evidences from clinical and epidemiological studies in the prevention of chronic diseases like cancer and cardiovascular diseases and general health promotion associated with tea consumption.

Mediation role of C-reactive protein on the association between smoking quantity and type 2 diabetes in current Chinese smokers

OBJECTIVE

Previous studies have indicated that cigarette smokers are more likely to develop type 2 diabetes and that both smoking and type 2 diabetes are associated with C-reactive protein (CRP). This study examined whether CRP mediates the association between smoking quantity and type 2 diabetes.

METHODS

Nine hundred and eighty-four current Chinese smokers were selected from a community-based chronic disease survey conducted in Guangzhou and Zhuhai. Type 2 diabetes was defined according to the WHO 1999 criteria. CRP was measured with flow cytometry. Binary logistic regression was performed to assess the mediation.

RESULTS

A positive association was observed between smoking quantity and type 2 diabetes (P < 0.05). After controlling for potential confounders, daily cigarette consumption was significantly associated with higher CRP levels. Current smokers with type 2 diabetes had higher CRP levels than smokers without type 2 diabetes. The association between the smoking quantity and type 2 diabetes was mediated by CRP, which accounted for 50.77% of the association.

CONCLUSIONS

This study provides further evidence that smoking quantity is positively associated with type 2 diabetes and suggests that the association between smoking and type 2 diabetes might be mediated by CRP.

Tea consumption and cardiovascular disease risk

BACKGROUND

The present analysis was conducted in response to inconsistent epidemiologic studies on the relation between consumption of tea and cardiovascular diseases.

OBJECTIVE

We undertook a literature review of the consistency and strength of the associations between tea and cardiovascular diseases on the basis of published observational studies and meta-analyses addressing tea or tea flavonoids and cardiovascular disease risk.

DESIGN

We performed a search in 3 databases for meta-analyses and compared them with studies they subsumed. We performed an additional search for subsequent studies to determine whether the conclusions were consistent.

RESULTS

Many epidemiologic studies have been conducted and summarized in 5 meta-analyses on either tea consumption or flavonoid consumption and cardiovascular disease or the subset of stroke. Heterogeneity of effect was seen when the outcome included all cardiovascular diseases. In the case of stroke, a consistent, dose-response association with tea consumption on both incidence and mortality was noted with RRs of 0.80 (95% CI: 0.65, 0.98) for flavonoids and 0.79 (95% CI: 0.73, 0.85) for tea when high and low intakes were compared or the addition of 3 cups/d was estimated.

CONCLUSION

Thus, the strength of this evidence supports the hypothesis that tea consumption might lower the risk of stroke.

Relationship between amounts of daily cigarette consumption and abdominal obesity moderated by CYP2A6 genotypes in Chinese male current smokers

BACKGROUND

Cigarette smoking is an important risk factor for abdominal obesity. However, the degree to which the CYP2A6 genotype moderates the relationship between smoking and abdominal obesity has not been established.

PURPOSE

This study aims to investigate whether or not the relationship between smoking quantity and abdominal obesity is influenced by CYP2A6 genotypes.

METHODS

Nine hundred fifty-four male current smokers were selected. A venous specimen was collected to test serum cotinine and CYP2A6 genotype, and all smokers were divided into heavy (>15 cigarettes/day) and light smokers (≤15 cigarettes/day).

RESULTS

Heavy smoking increased the risk of abdominal obesity (odds ratio (OR) = 1.57; 95% CI, 1.13-2.19) compared with light smoking. Furthermore, heavy smoking had a positive interactive effect with CYP2A6 poor metabolizer genotype on abdominal obesity (OR = 3.90; 95% CI, 1.25-12.18). Moreover, CYP2A6 poor metabolizer genotypes were associated with slower nicotine metabolism.

CONCLUSIONS

Heavy smoking may increase the risk of abdominal obesity-particularly in smokers with CYP2A6 poor metabolizer genotypes.

Association between daily cigarette consumption and hypertension moderated by CYP2A6 genotypes in Chinese male current smokers

The purpose of this study was to assess whether cytochrome P450 enzyme 2A6 (CYP2A6) genotypes moderate the association between smoking and hypertension. In this study, 954 Chinese male current smokers from a community-based chronic disease screening project in Guangzhou were interviewed with a structured questionnaire about socio-demographic status, smoking and other health-related behaviors. Blood was collected for DNA extraction and CYP2A6 genotyping. Hypertension was defined according to 2007 ESH-ESC Practice Guidelines. A multivariate logistic regression was performed to examine the interaction between smoking quantity and CYP2A6 genotypes on hypertension after adjusting for age, education level and other potential confounders. Multivariate analyses indicated that smoking more than 15 cigarettes per day significantly increased the risk of hypertension (odds ratio (OR)=1.59, 95% confidence interval (CI)=1.21-2.10) compared with smoking 1-15 cigarettes per day, and further suggested that smoking interacted with normal CYP2A6 metabolizer genotype to increase the risk of hypertension. Smokers consuming more than 15 cigarettes per day with normal CYP2A6 metabolizer genotypes had the highest risk of hypertension (OR=2.04, 95% CI=1.11-3.75) compared with those consuming 1-15 cigarettes per day with slower CYP2A6 metabolizer genotypes. These findings demonstrated that smoking quantity was positively associated with hypertension and that CYP2A6 genotypes may moderate this relationship.

Interaction between heavy smoking and CYP2A6 genotypes on type 2 diabetes and its possible pathways

OBJECTIVE

To explore the interactions between smoking and CYP2A6 genotypes on type 2 diabetes (T2DM) as well as potential pathways for smoking in causing T2DM.

DESIGN

Cross-sectional study.

METHODS

A total of 1344 smokers with complete data from a community-based T2DM survey in Guangzhou and Zhuhai of China from July 2006 to June 2007 were interviewed with a structured questionnaire about socio-demographic status and daily cigarette consumption. Serum glucose, insulin, and cotinine were measured after an overnight fast. Subjects were genotyped for CYP2A6 and classified, according to genotype, into normal, intermediate, slow, or poor nicotine metabolizers based on prior knowledge of CYP2A6 allele associations with nicotine C-oxidation rate. Abdominal obesity was defined as a waist-to-hip ratio ≥0.90 for males or ≥0.85 for females. Type 2 diabetic patients (n=154) were diagnosed according to WHO 1999 criteria. Chi-square tests, multivariate logistic regression models, and a structural equation model were used in this study.

RESULTS

Multivariate analysis indicated that, compared with light smoking, heavy smoking significantly increased the risk of T2DM (odds ratio (OR)=1.75, 95% CI=1.01-3.05). There were significant interactions between heavy smoking and slow CYP2A6 (OR=5.12, 95% CI=1.08-24.23) and poor CYP2A6 metabolizer genotypes (OR=8.54, 95% CI=1.28-57.02) on T2DM. Structural equation modeling indicated that CYP2A6 moderation of smoking quantity risk on T2DM was mediated by the effects on serum cotinine, abdominal obesity, insulin resistance, and insulin secretion.

CONCLUSIONS

Heavy smoking was significantly associated with T2DM, and this association was moderated by CYP2A6 genotype and mediated by serum cotinine, abdominal obesity, insulin resistance, and insulin secretion.