MONDAY, Jan. 12, 2015 (HealthDay News) -- Many Americans are likely using daily low-dose aspirin inappropriately in the hopes of preventing a first-time heart attack or stroke, a new study suggests.

Researchers found that of nearly 69,000 U.S. adults prescribed aspirin long-term, about 12 percent probably should not have been.

That's because their odds of suffering a heart attack or stroke were not high enough to outweigh the risks of daily aspirin use, said Dr. Ravi Hira, the lead researcher on the study and a cardiologist at Baylor College of Medicine in Houston.

Experts have long known that for people who've already had a heart attack or stroke, a daily low-dose aspirin can cut the risk of suffering those conditions again.

Things get more complicated, though, when it comes to preventing a first-time heart attack or stroke -- what doctors call "primary prevention." In general, the benefits of aspirin therapy are smaller, and for many people may not justify the downsides.

"Aspirin is not a medication that comes without risks," Hira said. He noted the drug can cause serious gastrointestinal bleeding or hemorrhagic stroke (bleeding in the brain).

Still, people sometimes dismiss the bleeding risks, Hira said, partly because aspirin is so familiar and readily available.

The idea of protecting the heart by simply taking a pill might appeal to some people, he said. "It's probably easier to take a pill than to change your lifestyle," Hira pointed out.

But based on the new findings, many Americans may be making the wrong choice, Hira's team reported Jan. 12 online in the Journal of the American College of Cardiology.

The results are based on medical records for more than 68,800 patients at 119 cardiology practices across the United States. The group included people with high blood pressure who had not yet developed heart disease.

Overall, Hira's team found, almost 12 percent of patients seemed to be prescribed aspirin unnecessarily -- their risks of heart trouble or stroke were not high enough to justify the risks of long-term aspirin use.

And what is "high enough"? For this study, it was defined as having at least a 6 percent chance of suffering a heart attack or stroke over the next decade.

Hira's team based that on recommendations from the American Heart Association and the U.S. Preventive Services Task Force.

Both groups say doctors should consider patients' risk factors for cardiovascular problems -- including age, diabetes, high blood pressure, high cholesterol and smoking -- and weigh those against the risk of bleeding.

People with a history of stomach ulcer, for instance, have up to three times the risk of gastrointestinal bleeding as people who've never had an ulcer, according to the task force.

"Often, the risk of bleeding is higher than the risk of heart attack or stroke," said Dr. Valentin Fuster, a cardiologist and professor of medicine at the Icahn School of Medicine at Mount Sinai in New York City.

Fuster, who was not involved in the study, agreed that the temptation to pop a pill can be great. And while some people need medication -- to control high blood pressure, diabetes or cholesterol, for instance -- pills alone do not cut it, Fuster said.

"The answer is to take care of yourself," he said. "That means exercise, watch your diet, don't smoke."

Women and younger patients were more likely than men and seniors to be using aspirin inappropriately, the study found. Also, the overall rate of misuse may be even higher than noted since many people may take daily aspirin without a doctor's recommendation, the researchers said.

The U.S. Food and Drug Administration recently weighed in on the issue, advising people against taking aspirin to prevent a first-time heart attack or stroke. But the agency also said it cannot make blanket recommendations that apply to everyone.

The important thing, Hira said, is to talk to your doctor before starting on low-dose aspirin -- even if you think your odds of a heart attack or stroke are high.

"Your doctor needs to assess not only your risk of cardiovascular disease," he said, "but also your risk of bleeding."

More information

The U.S. Department of Health has more on aspirin for preventing cardiovascular disease.