THURSDAY, Oct. 16, 2008 (HealthDay News) -- Contradicting current recommendations, a new trial finds that aspirin does not reduce the risk of heart attack and stroke for people with diabetes or peripheral arterial disease.
Aspirin clearly is effective in secondary prevention, reducing the risk for people who already have had a heart attack or stroke, said study author Dr. Jill Belch, a professor of vascular medicine at the University of Dundee in Scotland. Her report was published in the online issue of the BMJ.
However, in the study of 1,276 people who had not yet suffered a heart attack or stroke but were at high risk because they had diabetes or peripheral arterial disease (partial blockage of leg arteries), "we found that they did not benefit from daily aspirin," Belch said. The study showed that aspirin is ineffective in primary prevention, she noted.
"The number of heart attacks and strokes was exactly the same over eight years for those taking aspirin and those taking placebo," Belch said.
The same was true of the antioxidants given in the trial, she said, which was no surprise. "All the antioxidant studies over the past 10 years have been negative," Belch said.
Both the American Heart Association and the U.S. government recommend aspirin for people who have not had heart attacks or strokes but are at high risk for cardiovascular trouble because of conditions such as diabetes.
Those recommendations probably should be changed, said Dr. William R. Hiatt, a professor of medicine at the University of Colorado, who wrote an accompanying editorial.
The newly reported study "is consistent with six other studies on primary prevention, and all those studies were negative," Hiatt said.
The current recommendations are based on analysis of studies that found some primary prevention benefit in subgroups, he said. "Overall, if you do not have heart disease, the risk of bleeding outweighs any benefit you get from aspirin," Hiatt said.
The U.S. Preventive Services Task Force recommendation for use of aspirin in people at high risk of heart disease cited five studies that included 50,000 people. But its report noted that "no trial showed a significant all-cause mortality difference between aspirin-treated and control groups."
Hiatt said that he served on an advisory committee of the U.S. Food and Drug Administration that reviewed a request in 2003 by Bayer to extending the labeling of aspirin to include primary prevention in heart disease. "We couldn't support that request," he said.
Advertisements urging people to take aspirin to benefit the heart are accurate for those who already have had an event, both Belch and Hiatt said.
"It works if you've already had a heart attack," Belch said. "But there is no proof for primary prevention, no proof at all."
"The evidence is solid that aspirin should be given to people with known heart disease," Hiatt said. "But the evidence for people who have risk factors for heart disease is different."
Risks and possible benefits of aspirin for the heart are reviewed by the U.S. Food and Drug Administration.