Should You Take Aspirin to Prevent a Heart Attack or Stroke?

Cardiovascular disease is the leading cause of death in the United States, killing about 700,000 Americans annually. For decades, physicians recommended that healthy older adults take a low dose of aspirin daily to help prevent the disease.

But after a series of clinical trials challenged long-held beliefs about the benefits of aspirin in certain groups, the American Heart Association (AHA), American College of Cardiology (ACC), and United States Preventive Services Task Force (USPSTF) changed their guidelines to advise most older patients against taking daily aspirin if they have no prior history of cardiovascular disease, because of its potentially dangerous side effects.

Yet, despite these updated guidelines, research from 2019 estimates that approximately 29 million Americans without a history of cardiovascular disease still take aspirin preventatively, and 6.6 million do so without a recommendation from a health care provider.

So, should you still take aspirin to prevent cardiovascular disease?

"It's a complicated and nuanced topic,” says Yale Medicine cardiologist Michael Nanna, MD, who says this is one of the most common questions he gets from patients. There isn’t a simple “yes” or “no” answer to the question of whether to use low-dose aspirin to prevent CVD (cardiovascular disease), he adds. “It depends on a variety of factors, including a person’s age, risk factors, and medical history.”

We asked Dr. Nanna to explain the changing guidelines and offer advice on who should and should not take aspirin to prevent cardiovascular disease.

Cardiovascular disease is an umbrella term for diseases or events involving the heart or blood vessels.

It includes a wide range of conditions, such as coronary artery disease (when the coronary arteries that supply blood to the heart muscle become narrowed or blocked by plaque), arrhythmias (irregular heartbeats), high blood pressure, and peripheral artery disease (where the arteries that supply blood to the limbs become narrowed or blocked), among others.

It also includes cardiovascular events, such as heart attack (when the coronary artery becomes completely blocked, preventing blood from reaching a part of the heart muscle), heart failure (in which the heart is unable to pump sufficient blood to meet the body’s needs), or stroke (when the blood supply to part of the brain is interrupted or reduced, preventing brain tissue from getting oxygen and nutrients). A stroke can be caused by a blocked artery (ischemic stroke) or the leaking or bursting of a blood vessel (hemorrhagic stroke).

Risk factors for CVD include high cholesterol, smoking, diabetes, obesity, poor diet, physical inactivity, and excessive alcohol use.

Aspirin is a nonsteroidal anti-inflammatory drug (NSAID) that treats headaches, fever, and pain. It’s also a blood thinner, which means it prevents small blood cells (platelets) from clumping together and forming clots.

Blood clots are a leading cause of heart attack and stroke. That’s why, for many decades, doctors recommended that people in their 50s start taking daily low-dose (or baby) aspirin (around 81 milligrams) to protect against these events, which become more common as people get older. This is called "primary prevention"—to prevent the disease.

It was also thought—and is still true—that the pills would be beneficial to patients who already had a history of cardiovascular disease, including events like a heart attack or stroke, or those who had undergone bypass surgery or had a placement of a coronary artery stent, to prevent future events—also known as "secondary prevention."

The guideline changes were largely because of the increased risk of bleeding from aspirin use coupled with limited CVD benefit.

Because of its blood-thinning capabilities, aspirin can increase the risk of bleeding in the gastrointestinal (GI) tract and the risk of hemorrhagic stroke (caused by bleeding inside or on the surface of the brain). Older adults are already more susceptible to GI bleeding, hemorrhagic stroke, and bleeding in the brain from head trauma, so aspirin may exacerbate these conditions.

“Twenty years ago, before the guidelines changed, many people 60 and older were taking aspirin as a primary prevention medication even though they were at low risk for cardiovascular disease,” Dr. Nanna says. “And then in 2018, three landmark studies were published, each looking at slightly different populations.”

Collectively, those studies (ASPREE, ASCEND, and ARRIVE) showed the benefits and risks of daily aspirin use for preventing CVD. Two of them indicated no significant reduction in heart attack or stroke but an increased risk of bleeding. One of them showed a very small reduction in cardiovascular events but with higher bleeding risk.

“Older people do have a higher risk for cardiovascular events but also an increased bleeding risk as they age,” says Dr. Nanna. “So, if you add additional bleeding risk from aspirin use, which may only provide a mild CVD benefit, the potential risk for a significant bleeding complication starts to outweigh the benefits.”

Critically, all three studies only looked at patients who were taking aspirin as a preventative measure against developing cardiovascular disease. For patients who have already experienced a cardiovascular event, or who have undergone bypass surgery or have had a placement of a coronary artery stent, there continues to be "strong evidence" that aspirin helps prevent another event, according to The Journal of the American Medical Association (JAMA).

"There is a common misconception among patients, and even among some health care workers, that we should be stopping aspirin in everybody. And that's definitely not the case," Dr. Nanna explains. "Patients shouldn't just stop taking their aspirin if they've had a history of a cardiovascular event unless directed to by their cardiologist for a specific reason. And that's important to emphasize."

Because of these studies, the ACC and AHA updated their guidelines in 2019 to recommend that preventative aspirin be considered for certain high-risk individuals ages 40 to 70 but that it should be avoided for patients over 70.

The USPSTF updated its guidelines in 2022 to "recommend against initiating low-dose aspirin use for the primary prevention of CVD in adults 60 years or older." It also recommends that patients ages 40 to 59 with a 10% or greater 10-year CVD risk be assessed on an individual basis.

“A person in this age group has a low baseline risk of bleeding,” Dr. Nanna says. “So, if you’re in that age bracket and have a high risk for cardiovascular events, then the net benefit may lean toward taking baby aspirin because the bleeding risk from the therapy is low and the potential benefit is higher.”

For people who have had a heart attack or stroke, the guidelines from the ACC, AHA, and USPSTF maintain that taking daily aspirin might be beneficial to prevent future events.

The nuanced piece, he adds, is figuring out what to recommend to people who have asymptomatic nonobstructive atherosclerotic vascular disease, which is a buildup of fatty deposits (plaque) in the artery walls. This buildup can lead to serious health complications, including progressive coronary artery disease, heart attack, stroke, and peripheral artery disease. But these patients are not quite as high risk as those who have had a prior cardiovascular event, he says.

“In people who have subclinical atherosclerotic CVD but who have not had a thrombotic event, such as a heart attack or stroke, we are often still using aspirin, but I don’t think they fit neatly into a primary or secondary prevention category,” says Dr. Nanna. “They are more like prevention 1.5, and that is the next area that needs to be studied in terms of benefits and risks associated with aspirin therapy.”

Read the full recommendations from the AHA/ACC and USPSTF.

For most healthy older adults, daily aspirin should not be used to prevent first-time cardiovascular events. This recommendation applies even to patients who have been taking aspirin preventatively for years, Dr. Nanna adds.

"There can be a reluctance to stop the aspirin, but we have data, especially in the older adult population, that if it is being used for primary prevention—meaning not for atherosclerotic vascular disease—then it probably should be stopped," Dr. Nanna says.

Ultimately, the decision to start taking daily aspirin should be made on an individual basis with a health care provider who can evaluate your co-occurring conditions, age, family history, and other risk factors, he adds.

"This is about personalized medicine and shared decision-making," Dr. Nanna says. "I take it on a case-by-case basis, where I'm weighing what I can estimate as a patient's risk for heart attack and stroke and deciding whether that risk threshold is high enough that it would outweigh the bleeding risk associated with starting low-dose aspirin. And then I present the patient with that information, and we make a decision together.”