Daily Aspirin: Who Should Take It and Who Should Stop

For years, many adults took a "baby aspirin" each day to protect their heart. Then the advice changed. Maybe you take aspirin now and wonder if you still should. Maybe a friend told you to start. This guide explains what the evidence shows and why the answer depends on your own history.

How aspirin works

Aspirin makes platelets less sticky. Platelets are small blood cells that help form clots. Most heart attacks and many strokes happen when a clot forms on plaque inside an artery. Less sticky platelets mean fewer of these clots.

The same effect also makes bleeding more likely. This includes bleeding in the stomach and bowel, and, rarely, in the brain. Every decision about aspirin weighs fewer clots against more bleeding.

Low-dose aspirin is usually 81 mg in North America.

Two very different groups

People who already have heart or artery disease

This is secondary prevention. It applies if you had a heart attack, a stent, bypass surgery, most types of stroke or mini-stroke, or artery disease in the legs.

For these people, the benefit is clear. A large analysis of trials found that aspirin lowered serious vascular events from 8.2% to 6.7% per year [2]. That is about 15 fewer events per 1,000 people each year. The benefit was much bigger than the extra bleeding [2].

People without heart or artery disease

This is primary prevention. Here, the balance is much closer. In the same analysis, aspirin lowered serious vascular events from 0.57% to 0.51% per year [2]. That is about 6 fewer events per 10,000 people each year. Major bleeding outside the brain rose from 0.07% to 0.10% per year, or about 3 more per 10,000 [2].

Later trials made the case weaker. The ASPREE trial enrolled about 19,000 healthy older adults, most aged 70 or older [3]. After about 5 years, aspirin did not help people live longer free of dementia or disability. Major bleeding was higher, at 3.8% compared with 2.8% on placebo [3].

What your doctor looks at

US guidance

The US Preventive Services Task Force (USPSTF) updated its advice in 2022 for adults without heart disease [1]:

• Adults 40 to 59 with a 10-year heart risk of 10% or higher: the decision to start low-dose aspirin should be individual. The net benefit is small. People with low bleeding risk who are willing to take it every day are more likely to benefit.
• Adults 60 or older: the USPSTF recommends against starting aspirin to prevent a first heart attack or stroke.

These recommendations are about starting aspirin. They do not apply to people who take it because they already have heart disease [1].

Canadian guidance

The Canadian Task Force on Preventive Health Care has not issued a recommendation on aspirin for primary prevention. Canadian clinicians generally weigh the same trial evidence described above. For atrial fibrillation, the Canadian Cardiovascular Society says aspirin alone should not be used to prevent stroke [4].

Things that raise bleeding risk

Your clinician will think twice about aspirin if you have:

• A past stomach ulcer or bleeding from the gut
• Use of other drugs that raise bleeding risk, such as anticoagulants, steroids, or anti-inflammatory pain pills like ibuprofen
• Low platelet counts or a bleeding disorder
• Chronic kidney or liver disease
• Older age
• Uncontrolled high blood pressure

Why you should not stop on your own

If you take aspirin because of a heart attack, stent, or stroke, stopping can raise your risk of a clot. This risk is highest soon after a stent is placed. Some people take aspirin with a second antiplatelet drug for a set time.

If you take aspirin only for prevention, it may be reasonable to stop. But this should be a planned decision with your clinician. Tell your clinician or dentist that you take aspirin before any surgery or procedure. Do not stop it for a procedure unless the team that prescribed it agrees.

Other reasons people take aspirin

Aspirin is also used for reasons other than first-time heart prevention. These follow different rules.

• Colorectal cancer: an earlier USPSTF statement listed colorectal cancer prevention as a possible benefit. In 2022, the USPSTF found the evidence was not strong enough to support taking aspirin for this reason [1].
• Pregnancy: low-dose aspirin is advised for some pregnant people at high risk of preeclampsia. This is a separate decision made with a prenatal care provider.
• Pain and fever: higher, short-term doses of aspirin are used for pain. Children and teens should not take aspirin for viral illness, because of a rare but serious condition called Reye syndrome.

If you are not sure why you take aspirin, bring the bottle to your next visit and ask.

Questions to ask your clinician

• Why am I taking aspirin: for prevention, or because of a past heart or brain event?
• What is my 10-year heart risk?
• What is my bleeding risk?
• Do the benefits still outweigh the risks for me at my age?
• Do any of my other medicines raise my bleeding risk with aspirin?
• If I stop, how should I do it, and what should I watch for?
• Should I take something to protect my stomach?

When to get care quickly

Call 911 for chest pain or pressure, signs of stroke, or sudden severe shortness of breath. A 911 dispatcher may tell you to chew an aspirin during a possible heart attack, if you are not allergic and have no reason to avoid it.

Get urgent care if you take aspirin and have black or bloody stools, vomit blood or material like coffee grounds, or have a sudden severe headache.

Bottom line

Daily aspirin is a strong tool for people who already have heart or artery disease. For people without it, the benefit is small and close to the bleeding risk, so most should not start, especially at age 60 or older. If you already take aspirin, review the reason with your clinician before you change anything.

Primary AI can show you the guideline and study sources behind this topic in plain language, so you can bring better questions to your appointment.