Update on aspirin

People with heart disease should take aspirin; the decision is trickier for those without it.

For survivors of a heart attack or a clot-caused (ischemic) stroke, and for almost everyone else with coronary artery disease, there's an across-the-board recommendation to take an aspirin a day. But what about folks who haven't been diagnosed with heart disease? Can an aspirin a day help them, too?

Aspirin reduces the risk of having a first or repeat heart attack or ischemic stroke. It does this by making platelets less likely to form blood clots. How much it can help depends on your cardiovascular health. The worse it is, the more aspirin can do for you; the healthier your arteries, the less it can do.

The chances that aspirin can cause a problem are about the same no matter where you are on the cardiovascular health spectrum. Aspirin can upset the stomach, contribute to the formation of ulcers, and cause bleeding in the stomach and intestines — sometimes serious enough to require hospitalization and a blood transfusion. Aspirin use also increases the risk of having a hemorrhagic (bleeding) stroke.

For women and men without heart disease, current national recommendations on aspirin use from the United States Preventive Services Task Force, published in 2009, recommend aspirin on a sliding scale based on age and cardiovascular risk (see table).

Aspirin prevents:

Heart attack
Ischemic stroke

Aspirin causes:

Gastrointestinal bleeding
Hemorrhagic (bleeding) stroke

Aspirin recommended if 10-year risk is greater than


under age 45




80 years and above

Aspirin not recommended





Aspirin recommended if 10-year risk is greater than


under age 55




80 years and above

Aspirin not recommended





Health guidelines are constantly evolving. Three studies could someday influence the aspirin guidelines, and for now offer some guidance in knowing if aspirin can help you.

Refining recommendations. Calculating your risk is an essential step in determining if you should take aspirin. We've listed several calculators at www.health.harvard.edu/147. These calculators give you a percentage. Say yours is 8%. That means for every 100 people like you, 8 will have a heart attack or stroke over the next 10 years.

A new model suggests that taking aspirin offers a substantial benefit if your 10-year risk is above 10.6%. If it is below 6%, the benefits of aspirin are small. Between 6% and 10.6%, your preference for or against aspirin should guide the decision you make (Circulation: Cardiovascular Quality and Outcomes, May 2011). Talking with your doctor about aspirin is the most important part of the decision-making process.

Minimizing bleeding risk. Using information on aspirin use by almost 88,000 women over a 24-year period, researchers found that the dose of aspirin had a greater effect on bleeding problems than did the duration of use (American Journal of Medicine, May 2011). Low-dose aspirin (81 milligrams) provided sufficient action against platelets with few effects on gastrointestinal bleeding. Minimizing the use of other nonsteroidal anti-inflammatory drugs, such as ibuprofen or naproxen, while taking aspirin can also help avoid gastrointestinal bleeding.

Survival benefit. The individual clinical trials testing aspirin in people without known cardiovascular disease haven't given a solid signal on whether aspirin prevents premature deaths in addition to preventing a first heart attack or ischemic stroke. The two don't have to go hand-in-hand. If aspirin helped prevent some fatal heart attacks but caused some fatal strokes or stomach bleeds, its effect on all-cause death would be nil. An Australian analysis of nine trials that included a total of 100,000 participants showed fewer deaths among those taking aspirin than among those taking placebo (American Journal of Medicine, published online May 17, 2011).

Aspirin: not for do-it-yourselfers

Some people who take aspirin for their hearts' sake shouldn't. For them, aspirin is more likely to cause problems than it is to prevent a heart attack or ischemic stroke. At the same time, some of the millions of Americans who have been diagnosed with heart disease don't take aspirin but should.

Deciding to take aspirin isn't a do-it-yourself task. If your heart and arteries are in good shape, talk with your doctor before embarking on daily aspirin. If you have had a heart attack or stroke, or have been diagnosed with another form of heart disease, and you aren't taking aspirin, ask your doctor why not.