Aspirin: Making Sense of Changing Guidelines

For many people in their 50s, 60s, and 70s, taking a low-dose aspirin has been part of their daily routine for decades.

For people without cardiovascular disease, it has long been accepted that daily low-dose aspirin lowers the odds of having a first heart attack or stroke. The idea is so ingrained among the general public that millions take “baby” aspirin without consulting their physicians.

But a proposed update to the U.S. Preventive Services Task Force guidelines will likely pull back the task force's 2016 recommendations and limit daily aspirin for prevention to a more restricted group.

We spoke with internist Andrew Moran, MD, MPH, associate professor of medicine at Columbia University Vagelos College of Physicians and Surgeons, about the changes and what they mean for people considering or currently taking aspirin.

What’s changed with the new USPSTF proposal?

The 2021 proposal is a much more cautious and limited recommendation. In the Task Force’s 2016 guidelines, there was a relatively strong recommendation of low-dose aspirin in adults ages 50-59 years with a 10-year risk of cardiovascular disease 10% or higher and no risk of serious bleeding. A similar, but more conditional, recommendation was made for adults ages 60-69 years with the same cardiovascular risk. 

The Task Force now only conditionally recommends starting aspirin for cardiovascular disease prevention in adults ages 40-59 years old with a 10-year risk of cardiovascular disease 10% or higher who have no risk of serious bleeding. This means that preventive aspirin is not for everyone, and people should speak with their physician and decide together if starting aspirin is right for them.

People aged 40-59 years and with high blood pressure, high cholesterol, a smoking history, or a family history of heart disease are more likely to benefit from aspirin. People at lower cardiovascular disease risk and people with conditions or taking other medicines that increase bleeding risk should be cautioned against taking preventive aspirin.

And, in the new statement there is a clear recommendation against starting aspirin for cardiovascular disease prevention in adults ages 60 and older.

Why have they proposed these changes?

The Task Force reviewed the existing evidence on aspirin, including six new studies published since 2016. Adding these studies did not change what was known before about cardiovascular disease benefit or bleeding harms of aspirin—which is that the cardiovascular disease prevention benefit and major bleeding risk are roughly equivalent. 

The biggest change in 2021 is that the latest science casts doubt about aspirin’s ability to prevent colon cancer. A lot of people are unaware of this aspect of the guidelines, but the 2016 Task Force considered aspirin’s effect on colon cancer to get a more complete picture of aspirin’s potential benefits.

But the ASPREE trial, which enrolled people 70 years old or older, found during the five-year trial that colon cancer risk was higher with aspirin than without it. That said, the jury is still out regarding colon cancer—any benefits of aspirin in clinical trial participants will likely take 10 or 20 more years to come to light. This means that in the future, these guidelines may change again.

With the doubt about the benefit of aspirin for colon cancer prevention, the overall benefits of preventive aspirin are more evenly matched by the risks.

Why can taking low-dose aspirin be risky?

Throughout the 2021 USPSTF statement on aspirin for primary prevention, the main side effect worry is “major bleeding.” For the Task Force, major bleeding means bleeding from any site that was serious enough to require a visit to the hospital or a blood transfusion.

The most common type of bleeding due to aspirin use is from the gastrointestinal tract (esophagus, stomach, small intestine, large intestine) both because aspirin interferes with blood clotting and because aspirin can irritate the lining of the gastrointestinal tract and lead to bleeding. Gastrointestinal bleeding is almost always treatable and a transient problem. 

About five times less common than gastrointestinal bleeding, but much more serious, is bleeding within the brain—and aspirin increases that risk, too. To put things in perspective, for every thousand people on aspirin for 5-10 years, aspirin would be responsible for about 10 extra gastrointestinal bleeding events and about one extra intracranial bleeding event. Bleeding risks go up with age and with certain medical conditions or with taking other specific medications.

How many people in the United States are affected by these new guidelines?

About one quarter of Americans over 40 have intermediate risk of cardiovascular disease, so about 20 million people are still potentially eligible to take aspirin for preventing heart disease and stroke. 

Currently, 10 million adults 70 years old or older are taking aspirin for heart disease and stroke prevention. For this older age group, the U.S. Preventive Services Task Force has never made a recommendation for preventive aspirin, so many shouldn’t have been taking it. Given that the 2021 U.S. Preventive Services Task Force statement recommends that adults aged 60 years and older not be given aspirin for prevention, we expect that going forward, fewer older adults will take preventive aspirin.

What should I do if I’m currently taking aspirin but think I should stop based on these new guidelines?

The U.S. Preventive Services Task Force makes no clear recommendation about stopping aspirin for preventing heart disease and stroke in people already taking aspirin. Because most adverse bleeding occurs in the first year after starting aspirin, some health care providers will argue that patients who have tolerated aspirin well for years should continue it. Still, some patients may want to discontinue aspirin because of the weaker 2021 guideline recommendation. There is no known added risk of stopping aspirin after having taken it for prevention.

It is important to talk with your health care provider about your own individual profile. When risks and benefits are so closely balanced, the terms of the decision must be tailored to the individual patient: Is the risk for heart disease or stroke high enough to argue in favor of aspirin? Are there any risks for serious bleeding to argue against it? Together with your provider, you can weigh these pro and con factors and reach a decision that is best for you. 

What else can lower my risk of cardiovascular disease and colon cancer?

The best way for everyone to prevent cardiovascular disease is to exercise and eat a healthful diet. For people with high blood pressure, high cholesterol, or diabetes, standard daily medications other than aspirin go a long way to preventing heart disease and stroke.

These medications, such as blood-pressure-lowering medicines and statins, lower heart disease risk like aspirin but without aspirin’s potential side effects. In fact, many experts think that because effective cholesterol and blood-pressure lowering medicines are so common now, aspirin no longer contributes a benefit above and beyond them.

The best way to prevent colon cancer, for now, is to get screened for it. Colon cancer screening can identify and remove pre-cancerous polyps and early cancers before they become a problem. The same body—the U.S. Preventive Services Task Force—recommends regular colon cancer screening in all adults aged 45-75 years old.