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NEW YORK (Reuters Health) - Women with heart disease who down a few cups of coffee each day tend to live as long as those who avoid the beverage, a large study finds.
The results, reported in the American Journal of Clinical Nutrition, add to a mixed bag of research on whether caffeinated coffee is a hazard for people at high risk of heart problems.
In theory, coffee could be problematic because it has caffeine and other compounds that can raise blood pressure or have other negative effects on the cardiovascular system.
But some studies have found that coffee drinkers have no increased risk of a second heart attack or premature death. A few others have even hinted at protective effects from coffee.
In the new study, which followed nearly 12,000 U.S. nurses with a history of heart disease or stroke, those who regularly drank caffeinated coffee were no more likely to die than non-coffee-drinkers during the study period - which for some was more than 20 years.
Researchers found no link between a woman's coffee intake and her risk of death from heart attack, stroke or any other cause. And that was true even of women who downed four or more cups per day.
"Our results suggest that coffee drinking is OK for patients with cardiovascular disease, but it would be desirable to replicate our results in other populations," lead researcher Dr. Esther Lopez-Garcia, of Universidad Autonoma de Madrid in Spain, told Reuters Health in an email.
One problem with generalizing the current results, she explained, is that all the women in the study were nurses -- so they might not be representative of women with heart disease in general.
Nor can the study discount coffee as a possible cause of cardiovascular problems, at least in some people.
"What this study shows is that, in a general population, there's no obvious harm, or benefit, to consuming coffee after a heart attack," said Ahmed El-Sohemy, an associate professor at the University of Toronto who has studied coffee intake and heart health.
The problem is that certain individuals may benefit from some caffeine, while others may be harmed, according to El-Sohemy, who was not involved in the new study.
Recent studies have pointed to the importance of genetics, El-Sohemy told Reuters Health in an email.
Some research, for example, has linked coffee drinking to increased risks of high blood pressure in people who are naturally "slow metabolizes" of caffeine. But the reverse pattern has been seen in people who quickly process caffeine: more coffee, lower heart risks.
"What this study doesn't tell us is who might coffee be harmful to, and who might benefit from it," El-Sohemy said.
The findings come from the long-running Nurses' Health Study, which began tracking more than 100,000 female nurses in 1976. The researchers focused on 11,697 women who developed heart disease or had a stroke sometime between 1976 and 2002.
Of those women, 62 percent continued to drink caffeinated coffee after their diagnosis.
Overall, 1,159 women had died by 2004. That risk was no greater among coffee drinkers than non-drinkers, including women who drank at least four cups of java per day.
One possibility is that women in relatively worse health would choose to avoid caffeinated coffee, the study authors note. But they found no evidence that changes in women's coffee intake after their heart complication or stroke explained the findings.
They also accounted for factors like age, weight, high blood pressure and diabetes, and still found no association between coffee consumption and risk of death.
The findings, Lopez-Garcia said, "support the idea" that people with heart disease who already drink coffee do not have to give it up.
But she also advised checking with your doctor, particularly if you have uncontrolled high blood pressure or other conditions that could be aggravated by caffeine -- like sleep problems or anxiety.
El-Sohemy was even more cautious. It is hard to make individual recommendations on safe coffee intake, according to the researcher, because of genetic variations in people's caffeine metabolism.
"I don't see how any results can be interpreted from studies that don't take this genetic difference into account," El-Sohemy said.
Tests for genetic variations in the enzyme that processes caffeine are not routinely available, he noted.
SOURCE: bit.ly/kUXi5R American Journal of Clinical Nutrition, online May 11, 2011.