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Aspirin for prevention: Know your risk of heart attack or stroke

In this installment of "Aspirin for prevention," physician-researcher Randall Stafford provides tips to calculate the risk of heart disease or stroke, to inform decisions about taking aspirin preventatively.

Editor's note: In March 2019, new guidelines were released that recommend more limited use of aspirin for prevention of cardiovascular disease. We have a revised blog series planned.

In the first post of this series, I discussed the possible benefits and harms of taking low-dose aspirin. While aspirin can prevent heart attacks, strokes and some cancers, it can cause stomach and brain bleeding. If someone is pre-disposed to having a heart attack or stroke, chances are they should take aspirin because the benefits for prevention will outweigh the potential for bad outcomes.

But how does someone like Fred, the slightly overweight 58-year-old we met last time, who is wondering whether he should take aspirin, determine his or her risk?

There are three alternatives:

  • If you have known disease of your arteries (see below), you are automatically at high risk.
  • If you're a women under 50 or a man under 40 you are likely to be low risk unless you smoke or have diabetes.
  • Otherwise you need to use an online risk estimator to determine your risk.

Known artery disease (atherosclerosis)

People known to have problems with cholesterol in their arteries (atherosclerosis) should take aspirin or an alternative anti-blood clotting medication. If you have had a history of heart attack, angina, bypass surgery or a stent, this indicates problems with the arteries providing blood to the heart muscle. If you have had a stroke or a mini-stroke (transient ischemic attack), this means that your brain arteries (cerebral arteries) are damaged. These problems or damage to other arteries in the body indicates that you should also take aspirin or an alternative.

No known artery disease

Except for smokers and those with diabetes, younger women (under 50) and men (under 40) are unlikely to benefit from aspirin.

If you're older, aspirin may or may not be beneficial. It depends on your future risk of having a heart attack or stroke. You can determine the chances of having problems in the next ten years using an online risk calculator (of the many available, I like this one from the American College of Cardiology). In addition to finding out whether aspirin is right for you, knowing this risk can be useful in treating high blood pressure and high cholesterol.

Let's use this calculator to figure out Fred's risk. To prepare for a doctor's visit to discuss aspirin, he had some blood tests performed. These showed a fasting blood glucose of 98, total cholesterol of 214, and high-density lipoprotein (HDL) of 44. His average home blood pressures are 138/86. He's on a blood pressure medication. And since his fasting blood sugar is under 126, we know he doesn't have diabetes.

Based on this information, we get back the number 11.4 percent from the calculator.

What does this mean? It indicates that in the next ten years, there's a 1 in 9 (11.4 percent) chance that Fred will have a stroke or heart attack in the next 10 years. While this number may not seem large, it should cause concern. By comparison, if Fred were 10 years younger and was a women, the risk would be only 2.4 percent.

Taking action based on the calculated risk

What do you do with the risk information?  A simple rule of thumb is that a risk above 10 percent indicates:

  • You're likely a good candidate for aspirin
  • You should be treated with a moderate to high-intensity dose of a statin medication for cholesterol
  • Your blood pressure should be treated through drugs or health behavior changes to less than 130/80.

In the next piece, we will talk about some additional, needed steps before you start aspirin, including having a discussion with your health care provider. Calculating your risk, however, is an incredibly important step in taking care of your health. What's yours?

This is the second in a series of three blog posts on aspirin for prevention. The first covered the benefits and potential harms of aspirin, while the next blog will cover how you and your health care provider can use your calculated risk to make decisions about aspirin and other prevention activities.

Randall Stafford, MD, PhD, a professor of medicine and director of the Program on Prevention Outcomes and Practices, is a primary care internal medicine physician at Stanford. He is developing practical strategies to improve how physicians and consumers approach chronic disease treatment and prevention. Additional information about the preventive use of aspirin is available at

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