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Aspirin to prevent cardiovascular disease: In one patient group, it may not work well

March 2, 2010 |  4:29 pm

For cardiovascular disease, the best time to intervene would ideally be before a heart attack or stroke ever happened. In at least one group of people, this doesn't seem to work very well, according to a study just published in the Journal of the American Medical Assn.

The researchers aren't entirely clear as to why: It could be that the study was just too small to identify a benefit.

The group in question was 3,350 women and men who had no cardiovascular disease diagnosis but a low score on a measure called an "ankle brachial index"--this is a ratio comparing systolic blood pressure at the ankle to systolic blood pressure at the arm. (Systolic pressure is the top number on a blood pressure reading, the one that corresponds to the pressure when the heart is contracting.) If the pressure is much lower in the ankle, that implies the leg arteries are partially blocked and thus delivering less blood -- a possible early sign of peripheral artery disease

Those 3,350 men and women in Scotland all had an ankle brachial index of 0.95 or less. To try and ward off progression of cardiovascular disease, the researchers gave some of them 100 milligrams of coated aspirin daily and some of them a placebo (by way of comparison).

But after an average of 8.2 years, the researchers (led by Gerald Fowkes at the University of Edinburgh) found no difference in rates of fatal or non-fatal heart attack, stroke or revascularization surgery between the aspirin and placebo group. They found no difference either in events such as angina or claudication (bad pain in the legs that occurs with peripheral artery disease).

Among other things, they conclude that "using the ABI [ankle brachi al index] in the community to screen individuals free of cardiovascular disease for an ABI of 0.95 or less is unlikely to be beneficial if aspirin is the intervention of choice."

That's especially the case, they add, given that taking aspirin has side effects that go along with its anti-blood-clotting action, such as ulcers and bleeding. The researchers didn't find a statistically significant increase of these side effects, but they did notice some trends there.

Again, it's possible that the study was too small to identify benefit: By their calculations, there would need to have been a 25% reduction in risk for them to detect anything. It didn't help, either, that the patients didn't adhere perfectly to their medication regimen --but if that happened in a study then it likely would happen in the real world too. 

A lot of qualifications in all of this: The scientists also suggest that other therapies such as statins might work well.

Jeffrey Berger of the New York University School of Medicine wrote a commentary accompanying the report, writing, among other things, that the benefits of aspirin therapy for people with peripheral artery disease "remains unproven."

-- Rosie Mestel