Does tea affect cardiovascular disease? A meta-analysis

This meta-analysis of tea consumption in relation to stroke, myocardial inf arction, and all coronary heart disease is based on 10 cohort studies and s even case-control studies. The study-specific effect estimates for stroke a nd coronary heart disease were too heterogeneous to be summarized (homogene ity p < 0.02 for stroke, p < 0.001 for coronary heart disease). Only the re lative risk estimates for myocardial infarction (seven studies) appeared re asonably homogeneous (homogeneity p = 0.20). The incidence rate of myocardi al infarction is estimated to decrease by 11% with an increase in tea consu mption of 3 cups per day (fixed-effects relative risk estimate = 0.89, 95% confidence interval: 0.79, 1.01) (1 cup = 237 ml). However, evidence of bia s toward preferential publication of smaller studies that suggest protectiv e effects urges caution in interpreting this result. The geographic region where the studies were conducted appeared to explain much of the heterogene ity among coronary heart disease, myocardial infarction, and probably strok e results. With increasing tea consumption, the risk increased for coronary heart disease in the United Kingdom and for stroke in Australia, whereas t he risk decreased in other regions, particularly in continental Europe.