Aspirin for prevention: Should you take it?

Shreya Shah, MD

New research prompts a reconsideration

Recent studies have provided new information about when aspirin should be used to prevent disease. In general, they suggest that fewer people should use aspirin for cardiovascular disease prevention.

People with a history of heart attack, stroke or other types of cardiovascular disease are still strongly recommended to take a daily low-dose aspirin to reduce their risk of a future event. There is no question that aspirin has an important role after someone has already developed heart disease.

But new studies show that the risks of side effects from aspirin (such as bleeding) likely outweigh the potential benefits (such as prevention of a first heart attack or stroke). These findings have prompted a major shift in clinical practice.

However, there is still a role for aspirin in primary prevention for certain people (such as those with a high risk for cardiovascular disease and low bleeding risk), but this is not a simple decision.

People considering the use of aspirin for primary prevention should have a conversation with their health care provider to clarify the potential benefits and harms. Similarly, people already taking aspirin for primary prevention should have a discussion to see if they should continue or discontinue this medication.

How aspirin works

Aspirin interferes with small blood components known as platelets. By making platelets less sticky, aspirin can prevent blood clots, or clumps, from forming. When clots occur in critical blood vessels, such as the heart or brain, they can cause a heart attack or stroke. Aspirin can reduce the risk of heart attacks, strokes and several cancers — especially colon and rectal cancer.

However, the same process that makes aspirin beneficial can lead to problems.

When aspirin makes platelets less sticky, they cannot do their normal job of stopping abnormal bleeding. This can result in excessive bleeding in unexpected locations within the body, such as in the stomach or brain.

The key question with aspirin is which is greater — the possible preventive benefits or the chance of excessive bleeding?

Should you be on aspirin?

If you have known disease of your arteries or have a history of a heart attack, angina, stent, bypass surgery or stroke, then you should probably take aspirin or an alternative.

Randall Stafford, MD

If you have no known artery disease, then it depends on your risk of having a heart attack or stroke. Risk factors include high blood pressure, high cholesterol, diabetes and smoking history. If you are younger and have fewer risk factors, you are unlikely to benefit from aspirin. If you are older and have more risk factors, you may benefit from aspirin. You can determine the chances of a heart attack or stroke in the next 10 years using an online risk calculator, like one from the American College of Cardiology (called the ASCVD Risk Estimator Plus, available through an online search).

There are other factors that are important to consider when thinking about aspirin and discussing it with your health care provider:

Bleeding: If a person has a higher than average chance of bleeding (especially past bleeding), then aspirin should probably not be used unless the person is at a very high risk of a heart attack or stroke.

Colon cancer: Having a higher than normal chance of developing colon cancer might prompt use of aspirin even in someone at moderate risk of heart disease and stroke.

Aspirin dose: A low dose (81 mg) is just as effective for heart disease and stroke prevention as higher doses, which carry a greater chance of internal bleeding.  

Continuing aspirin: Once aspirin is started in a high-risk individual, it should be continued, unless major bleeding problems occur. If aspirin was previously started in someone at low risk, it is reasonable to consider stopping aspirin after a discussion with their health care provider. 

Other wellness strategies: Treating high blood pressure and high cholesterol can also lower the risk of a heart attack or stroke. Adopting healthier behaviors related to physical activity, diet, improved sleep, smoking cessation and stress reduction can further reduce the risk of heart attack, stroke and cancer. In fact, these health behavior changes can go a long way toward preventing heart disease and stroke, and may be even more effective than starting aspirin.

The decision to start, continue or discontinue aspirin for prevention requires a discussion between you and your health care provider to review the risks and potential benefits as well as your personal preferences. Your calculated risk may have implications for other disease prevention strategies.

Please take the time to find out if aspirin is or isn’t right for you. 

This piece was written by Shreya Shah, MD, assistant professor of primary care and population health, and Randall Stafford, MD, PhD, professor of medicine and director of the Program on Prevention Outcomes and Practices.