THURSDAY, May 19, 2005 (HealthDay News) -- Every day, millions of older Americans take low-dose aspirin to lower their cardiovascular risk.
But a new study questions the wisdom of that practice. Australian researchers say the benefits of giving older people aspirin to prevent heart disease and stroke might not outweigh risks for hemorrhage linked to chronic use of the drug -- on paper, at least.
It's a purely theoretical calculation, extrapolating data from large-scale population studies, explained Dr. Mark Nelson, chairman, discipline of general practice at the University of Tasmania and lead author of a report published online this week by the British Medical Journal.
Nelson believes the mathematical finding could warrant a large-scale, real-life trial to see if the concerns are justified.
The study doesn't question the reduction in cardiovascular problems such as heart attack and stroke that come from small daily doses of aspirin, Nelson stressed. A number of studies have shown "that if you live long enough, it will almost certainly give you a benefit from the point of view of cardiovascular intervention."
But the very property that enables aspirin to reduce those risks -- its ability to reduce blood clotting -- can increase risks for hemorrhages, some of which can be fatal, he explained.
The study postulated a population of 10,000 men and 10,000 women age 70 to 74 with no cardiovascular disease. Data from Australian studies (which Nelson said almost certainly apply to Americans) indicate that low-dose aspirin would prevent 389 heart attacks and 19 strokes among the men and 321 heart attacks and 35 strokes among the women, the calculations indicated.
On the other hand, there would be 499 men and 572 women who would experience excessive, potentially life-threatening bleeding in the gastrointestinal tract, with 76 men and 54 women experiencing similar bleeds in the brain, the study predicted.
Thus, "the results in health-adjusted years of life lived (which take into account length and quality of life) are equivocal for aspirin causing net harm or net benefit," the report concluded.
The question applies strictly to older people, Nelson said, "because there is a far greater risk of hemorrhage than in the younger age group."
And he added another major caveat: the cardiovascular benefits of low-dose aspirin would clearly outweigh any potential harm in people with major cardiovascular risk factors such as diabetes, high cholesterol or high blood pressure.
"If there are multiple risk factors, it is reasonable to assume that the benefits for the younger age group apply," Nelson said. "But we should be developing the evidence for that through a large-scale controlled trial."
The Australian research prompted a quick, skeptical response from Dr. Donald W. LaVan, clinical associate professor of medicine at the University of Pennsylvania, and spokesman for the American Heart Association.
"This is like a handicapper who has a formula for picking winners in horseracing," LaVan said. "It is a hypothetical kind of guesswork, not the kind of thing I need to take care of my patients."
In practice, very few older people are entirely free of cardiovascular risk factors, LaVan pointed out. "There is evidence that low-dose aspirin carries a very low risk, and the benefits I've seen thus far outweigh the risk," he said.
And in practice, "I would carefully weed out people who have other problems that might put them at risk," LaVan said. "If someone has had a prior adverse reaction to aspirin, a prior gastrointestinal bleed or evidence of capillary weakness such as easy bruising, the use of aspirin would be undertaken with advisability about possible problems."
Nelson agreed that physicians and patients should decide together whether or not to use daily aspirin, regardless of his team's theoretical findings. "Each physician must make his own decision on the basis of the patient sitting in front of him," he said.
Current recommendations on aspirin therapy to prevent cardiovascular problems are available from the American Heart Association.