Chieti, Italy - A new analysis of the GISSI-Prevenzione trial shows that moderate coffee intake does not appear to have any effect on future cardiovascular events in patients who have already had an MI. Dr Maria Giuseppina Silletta (Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy) and colleagues report their results online December 3, 2007 in Circulation.
Silletta stressed to heartwire, however, that the findings can really be applied only to patients eating a Mediterranean diet who drink coffee prepared in the Italian way. Most of the participants in this study drank mocha or espresso coffee, which is unfilteredâ€”the ground coffee beans are in contact with hot water for only a very short time, Silletta explained.
â€œWe will tell patients that it is no problem for them to drink a moderate amount of coffee (two to four cups per day) after a heart attack, there is no cause for concern,â€ she said. But she noted that her team could not draw conclusions about very high coffee intake because of the small number of patients included in this category.
First to evaluate effects of coffee on a large prospective cohort of CHD patients
The Italian researchers explain that many studies have looked at the association between coffee consumption and risk of cardiovascular disease, but the issue remains controversial. Case-control studies suggest a harmful effect of coffee drinking on the risk of CHD, whereas prospective cohort studies show conflicting findings. And more recent studies have shown that coffee consumption may lower the risk of type 2 diabetes, they say.
But evidence is scarce on the association between coffee drinking and cardiovascular events among patients with documented CVD, they point out. Hence they decided to analyze data from a large cohort of patients who had had an MI and were enrolled in the GISSI-Prevenzione trial.
In their analysis, they included 11 231 patients with recent MI (within past three months), the majority of whom were male (n=9584). Usual dietary habits were assessed at baseline and updated at 0.5 and 1.5 years. Coffee consumption was categorized as never/almost never, low (less than two cups per day), moderate (two to four cups per day), or high (more than four cups per day).
The main outcome measure was the cumulative incidence of cardiovascular events (cardiovascular death, nonfatal MI, and nonfatal stroke). A total of 1167 events occurred during the three-and-a-half-year follow-up, with no significant differences found between the various categories of coffee drinker.
And when they analyzed stroke, MI, and sudden cardiac death separately, they also found no significant differences in CV events between the different levels of coffee drinkers. The findings on sudden death are of particular interest, they say, because there has been concern that drinking coffee might increase fatal arrhythmias.
The present study is the first to evaluate the effects of coffee consumption on a large prospective cohort of patients with established CHD. Ultimately, coffee consumption did not change the risk of CHD events, stroke, and sudden death,â€ the researchers note.
Coffee and CVD: A controversial issue Silletta et al go on to discuss why the issue of coffee and CVD is so controversial. For example, two recent studies showed, respectively, a J-shaped association between coffee intake and the risk of CHD and a U-shaped association, they note.
Can the discrepancies between the results from different studies ever be reconciled or explained? they wonder. They discuss several factors that may have affected the conclusions of various studies, particularly the earlier ones, such as recall and selection bias, inadequate adjustment for confounding factors, and publication bias.
Other difficulties in interpreting results include variations in cup size, brewing methods for coffee preparation, amount of caffeine contained in coffee beans, and the multitude of biologically active substances that are contained in coffee all could contribute to miss-classification of exposure and may in part explain some conflicting results.
In addition, the development of tolerance to the effects of caffeine among habitual drinkers adds to the complexity of the effects of coffee and may make it hard to extrapolate short-term metabolic studies to long-term use of coffee, they conclude.