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Too many people take aspirin to prevent heart attacks, stroke, study says

Nearly 12% of people taking aspirin to avoid first heart attack or stroke should not do so, researchers say

Aspirin is a popular drug for people who’ve never had a heart attack or stroke and would like to keep it that way. But for more than one in 10 people who do so, aspirin could do more harm than good, a new study suggests.

Among 68,808 patients being treated by cardiologists around the U.S., 7,972 of them were taking aspirin despite having a very low risk of having a heart attack or stroke in the next 10 years. In other words, 11.6% of patients were taking the drug “inappropriately,” according to a study published Monday in the Journal of the American College of Cardiology.

Aspirin -- also known as acetylsalicylic acid -- averts heart attacks and strokes by preventing the formation of blood clots. Clots are made up of blood cells called platelets, which stick together with the help of an enzyme known as cyclo-oxygenase, or COX. But aspirin prevents COX from doing its job.

While that’s useful in the fight against cardivascular disease, it can be dangerous in other ways. When blood can’t clot easily, people run the risk of excessive bleeding. In the brain, that can lead to a hemorrhagic stroke. (A stroke caused by a clot is called an ischemic stroke.) Other kinds of internal bleeding can be life-threatening as well.  

That’s why experts recommend aspirin therapy only for people with a significant risk of a clot-related problem. That includes pretty much everyone who has already suffered an ischemic stroke or heart attack. It also includes people who have never had a heart attack or stroke but face at least a 6% to 10% risk of suffering one in the next 10 years, according to recent guidelines from the American Heart Assn., the American Stroke Assn. and the U.S. Preventive Services Task Force.

Researchers from the Baylor College of Medicine and their colleagues examined the medical records of  patients who were being tracked as part of the American College of Cardiology’s PINNACLE registry. They focused on patients who were taking aspirin to prevent their first heart attack or stroke.

The researchers used the Framingham general cardiovascular disease risk assessment tool to calculate the 10-year risk of the patients for whom data was available. Their analysis revealed that 11.6% of the patients had a risk below 6% -- too low to justify the potential side effects of the therapy.

Who were these people? In general, they were much younger (49.9 years old, on average) than people taking aspirin with good reason (average age 65.9 years). And 80% of them were women. In fact, 16.6% of the women analyzed were taking aspirin inappropriately, compared with only 5.3% of the men.

In some cardiology practices, as many as 72% of patients were taking aspirin even though their risk factors didn’t warrant it. But in other practices, that figure was 0%. Geography didn’t have much to do with this variation -- the rate of inappropriate asprin use was 11.4% in the Northeast, 12.2% in the Midwest, 11.3% in the South and 10.6% in the West.

It’s not clear whether all of the people taking aspirin inappropriately were doing so at the direction of their cardiologists. Aspirin doesn’t require a prescription, and some patients may be buying it of their own accord.

Either way, the study results make clear that doctors should do a better job of making sure patients are taking aspirin only when the cardiovascular benefits outweigh the risks, the study authors concluded.

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