aspirin to prevent heart attack

Aspirin helps prevent heart attacks by stopping the formation of clots that block blood flow to the heart. Aspirin is used to prevent a first heart attack in people with heart disease risk factors, such as diabetes and high cholesterol. It's also taken to prevent a second heart attack.

But this "blood-thinning" effect sets aspirin therapy up for some potentially serious side effects.

Serious Bleeding 5 Times More Common

The new study shows that taking more than 100 mg of aspirin a day increases the risk of bleeding -- from nose bleeds to bleeding in the brain.

For example, Serebruany says serious bleeding -- like bleeding in the brain or in the stomach -- occurs in just more than 1% of heart disease patients taking a baby aspirin (80 mg of aspirin). But serious bleeding occurs in 5% of heart disease patients taking 200 mg or more of aspirin daily.

When all bleeding was considered -- including minor instances, such as nosebleeds -- 100 to 200 mg of daily aspirin led to bleeding in 11% of patients. Bleeding occurred in just more than 3% of patients taking a baby aspirin.

Serebruany says his study does not address how well different doses of aspirin prevent heart attacks. "I think it is very probable that low-dose aspirin is as effective as higher doses to prevent second heart attacks."

Heart Specialists Disagree on Aspirin Dose

Serebruany says he decided to investigate the relationship between aspirin dose and bleeding risk because there was a difference of opinion among heart specialists. "Cardiologists all like aspirin, but they disagree about how much aspirin should be used."

He analyzed data from 31 published studies that included information from 200,000 heart disease patients. All the patients were on daily aspirin therapy at doses ranging from 30 mg daily to 1,300 mg daily.

Robert Bonow, MD, who is chief of cardiology at Northwestern University Feinberg School of Medicine in Chicago, tells WebMD that, "I think it's fairly clear from these data that low-dose aspirin is probably the best choice for prevention -- certainly it is the best choice for [preventing first heart attacks]."

But Bonow, who was not involved in the study, says most cardiologists "have individual preferences about using aspirin. For example, if you've just opened some arteries with stents, you might want to start the patient off on a high dose because stents do increase the risk of blood clots."

Stents are tiny, flexible coils that are used to prop open blocked arteries, but stents also increase the risk of blood clots. "I think doctors worry about this," says Serebruany. "But I still maintain that lower-dose aspirin is better and most likely just as effective as higher-dose aspirin."