"Aspirin is a really powerful drug but it can cause serious side effects," said ABC News chief health and medical editor Dr. Richard Besser. "It is very important that it only be used in those people for whom the benefits outweigh the risks."
Aspirin risks can include stroke caused by burst blood vessels and gastrointestinal bleeding, both of which can be fatal, cardiologists say. But the researchers in this study did not look at aspirin-related complications -- such as gastrointestinal bleeding or ischemia -- in people taking it inappropriately.
Simon said people can use online tools, such as the Framingham Risk Score, to determine their risk, or ask their doctors. Questions generally include age, gender, smoking status and family history.
The Journal of the American College of Cardiology study did not include people who had already had a heart attack, stroke or anything else that would warrant aspirin for prevention of a second cardiovascular problem. They also did have information on specific aspirin doses.
Researchers cautioned that their study could have underestimated inappropriate aspirin use in part because participants self-reported their aspirin use and aspirin is available without a prescription. They also noted that because they got their data from the PINNACLE cardiovascular patient registry, and PINNACLE practices are pushed for quality improvement, that non-PINNACLE practices might have even higher instances of inappropriate aspirin use.
Dr. Walter Clair, interim executive medical director of the Vanderbilt Heart and Vascular Institute, said he often sees patients who self-prescribe aspirin, but don't need it. This is because people who have hearts that skip beats, for instance, don't need to take aspirin.
"When I delve into why, they confuse the fact because they have an electrical problem, they have a plumbing problem," he said.
Still, some people need to be on aspirin and don't take it because they don't like the bruising.
The bottom line, Besser said, is that if patients are unsure, they should ask their doctors.
"Given that the recommendations for its use have been changing over time and that some people for whom it was once recommended should no longer be taking it, patients who are on aspirin should ask their doctors whether it is still the right drug for them," Besser said.