More than 10 percent of patients who take low-dose aspirin to prevent heart attack or stroke may not need it. In some cases, it may even do some harm.

In a new study published in the Journal of the American College of Cardiology, researchers from Baylor College of Medicine in Texas found that nearly 12 percent of patients who had been prescribed aspirin should not be taking the medicine. And because aspirin is available over-the-counter, the team suggests this number may be even higher when considering the number of patients who have self-prescribed a daily dose. Aspirin helps to thin the blood and can be used to prevent blood clots, but researchers believe that for many patients, an aspirin a day could do more harm than good. 

Researchers looked at the medical records for 68,000 patients and calculated each one's risk for developing heart disease or having a stroke over the next decade. They considered factors such as age, gender and blood pressure. Researchers excluded patients with a history of cardiovascular disease, since previous studies clearly show that a daily dose of aspirin can help prevent heart attacks in this group. But they found that there were a number of low-risk patients taking aspirin who probably shouldn't be.

The team found that inappropriate use of aspirin occurred more frequently in women — around 17 percent — than in men, where it was closer to 5 percent. In these cases, researchers concluded that their risk for heart disease and stroke was not great enough to warrant a daily dose of aspirin. And previous studies have shown that the risks of aspirin therapy could outweigh the benefits, particularly in women. 

In one study, published in the journal Heart, 28,000 healthy women age 45 and older, were given either a placebo or 100 milligrams of aspirin every other day. After 15 years, researchers noted that the daily aspirin use reduced the risk for cardiovascular disease by a small amount; however, a large number of the women in the study suffered from long-term gastrointestinal bleeding.

Bottom line: For those whose risk of heart attack and stroke is low, the risk of developing complications from daily aspirin use may be too great. Talk to your doctor about if you should (or shouldn't) be taking a daily dose of aspirin. 

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