Doctors have long recommended daily low-dose aspirin for older people at risk for heart attacks and strokes. More recently, aspirin was also thought to reduce the risk of colorectal cancer. But new evidence shows that, for many people, the risk of side effects outweighs the benefits.

Aspirin is best known as a pain reliever, but it also has anti-inflammatory properties and acts as a blood thinner to prevent clots. While taking aspirin occasionally to relieve pain or reduce fever is safe for most adults, taking it every day can lead to gastrointestinal bleeding and bleeding in the brain.

In October 2021, the U.S. Preventive Services Task Force (USPSTF) released draft guidelines that call into question the widespread use of daily aspirin for cardiovascular and colorectal cancer prevention.

For years, doctors have recommended aspirin therapy for people who have already had a heart attack or stroke, known as secondary prevention. The protective benefits are well established, and that advice has not changed. But guidelines for people who have not yet had a heart attack or stroke, known as primary prevention, have shifted.

In its 2016 guidelines, the USPSTF recommended daily low-dose aspirin (equivalent to a baby aspirin) for people in their 50s who have at least a 10% risk for cardiovascular events over 10 years. The new draft advises these individuals to consult their doctor to evaluate their risk-benefit balance.

The previous guidelines advised at-risk people in their 60s who have not yet had a heart attack or stroke to consult their doctor to evaluate their individual risks and benefits. The new draft says daily aspirin is not recommended for this group, as the potential benefits do not outweigh the risk of bleeding, which rises with age.

The old guidelines said there wasn’t enough evidence to assess the balance of benefits and harms for people older than 70 or younger than 50. That’s still the case for those over 70, but the new draft says some at-risk people in their 40s may see a small benefit from daily aspirin.

Randomized trials have shown that daily aspirin therapy for primary prevention may reduce the risk for heart attacks and strokes by as much as 10% to 20%. But the management of people at risk for cardiovascular disease has improved in recent years thanks to lifestyle changes, better blood pressure control and the use of cholesterol-lowering statin medications. This means the benefits of aspirin have diminished relative to its risks.

The new draft brings the USPSTF guidelines more in line with those of other medical organizations. The American College of Cardiology and American Heart Association recommend that aspirin therapy for primary prevention should be prescribed selectively for people ages 40 to 70 who have an elevated risk for cardiovascular disease and no increased risk of bleeding.

Some studies suggest daily aspirin therapy may also help lower the risk for colorectal cancer, liver cancer and ovarian cancer. The USPTF recommended daily low-dose aspirin for colorectal cancer prevention in its previous guidelines, but the new draft says more evidence is needed.

The new guidelines do not apply to people of any age who are currently on daily aspirin. Such individuals should consult their doctor before they stop taking aspirin therapy.

In summary, the benefits and harms of low-dose daily aspirin for primary prevention of cardiovascular disease and colorectal cancer depend on individual risk factors. Consult your doctor to discuss whether aspirin therapy is right for you.