For people who have never had a heart attack or stroke, daily aspirin is no longer routinely advised. Three large trials published in 2018 found that it prevented few or no cardiovascular events in that group and clearly increased serious bleeding.
The picture is different if you already have heart or artery disease. Aspirin remains a well-established treatment after a heart attack, stroke or stent. If you take aspirin now, for any reason, do not stop it without asking the clinician who manages your care.
Key takeaways
- Aspirin to prevent a first heart attack is called primary prevention, and that is the use that fell out of favor.
- The ASPREE, ARRIVE and ASCEND trials found little or no heart benefit and more bleeding.
- The US Preventive Services Task Force advises against starting aspirin for primary prevention at age 60 or older.
- Aspirin for people with known cardiovascular disease is a separate question with stronger evidence.
- Stopping long-term aspirin has been linked to more cardiovascular events, so the decision belongs with your doctor.
Two different uses of the same pill
Aspirin makes platelets less sticky, so blood clots form less easily. That can stop a clot from blocking an artery. It also makes bleeding more likely, most often in the stomach and gut.
Doctors separate two situations:
- Secondary prevention means preventing another event in someone who already has cardiovascular disease.
- Primary prevention means preventing a first event in someone who has none.
In secondary prevention the risk of another clot is high, so the benefit outweighs the bleeding risk for most people. In primary prevention fewer events are on the way, and the bleeding risk is still there. Everything below is about primary prevention.
What the three 2018 trials found
| Trial | Who was studied | Result with aspirin |
|---|---|---|
| ASPREE | 19,114 healthy older adults, mostly 70 or older | No significant drop in cardiovascular disease; more major bleeding |
| ARRIVE | 12,546 adults at moderate estimated risk, without diabetes | No significant drop in cardiovascular events; more gut bleeding |
| ASCEND | 15,480 adults with diabetes and no known cardiovascular disease | Fewer serious vascular events; more major bleeding |
ASPREE. After a median of 4.7 years, the rate of cardiovascular disease was 10.7 events per 1,000 person-years with aspirin and 11.3 with placebo, a difference that was not statistically significant. Major bleeding was more frequent with aspirin: 8.6 versus 6.2 events per 1,000 person-years.1
ARRIVE. The main cardiovascular outcome occurred in 4.29% of the aspirin group and 4.48% of the placebo group over about five years, which was not a significant difference.2 Gut bleeding, mostly mild, roughly doubled.
ASCEND. In people with diabetes, serious vascular events occurred in 8.5% of the aspirin group and 9.6% of the placebo group over an average of 7.4 years. Major bleeding rose from 3.2% to 4.1%. The investigators concluded that the absolute benefits were largely counterbalanced by the bleeding hazard.3
Why the balance shifted
Older trials had suggested a modest benefit. A 2019 meta-analysis of 13 primary prevention trials with 164,225 participants still found one: aspirin was linked to fewer cardiovascular events, with about 265 people needing treatment to prevent one event. It was also linked to more major bleeding, with one extra major bleed for about every 210 people treated.4
When the benefit and the harm are that close in size, aspirin stops being an easy choice.
The ARRIVE authors offered one reason the benefit has shrunk. Far fewer events happened in their trial than expected, which they attributed to modern management of risk factors. When cholesterol, blood pressure and smoking are better controlled, there is less left for aspirin to prevent, while the bleeding risk remains.
What US guidance says now
The US Preventive Services Task Force updated its advice in 2022. It applies to adults without cardiovascular disease who are not at increased risk of bleeding.5
- Ages 40 to 59 with a 10-year cardiovascular risk of 10% or higher: the decision to start low-dose aspirin should be an individual one, and the net benefit is small.
- Age 60 or older: the Task Force recommends against starting low-dose aspirin for primary prevention.
Two things are easy to miss. The statement is about starting aspirin, not about people already taking it. And it leaves out anyone with a higher bleeding risk, such as people with a history of stomach ulcers, recent bleeding, or medications that raise bleeding risk.
Your 10-year risk figure comes from a calculator. Our PREVENT calculator guide explains what the percentage means.
If you already take aspirin
Do not start, stop or change aspirin without talking to the clinician who prescribed or recommended it. Aspirin is sold over the counter, but for heart protection it should be treated like a prescription.
There are two reasons for care. First, you may be taking it for a condition where it is clearly indicated, such as a previous heart attack, a stent or a stroke. Second, stopping may carry its own risk. In a Swedish study of more than 600,000 long-term users of low-dose aspirin, those who stopped had a 37% higher rate of cardiovascular events than those who continued.6 That study was observational and included people taking aspirin for both primary and secondary prevention, so it cannot prove that stopping caused the events. It is reason enough to ask before you stop.
Questions worth bringing to your doctor:
- Why was aspirin suggested for me in the first place?
- Do I have known cardiovascular disease, or was this for prevention only?
- What is my bleeding risk, given my age, history and other medications?
Next step: know which group you are in
The aspirin question turns on whether you have cardiovascular disease and how high your risk is. A structured risk evaluation can help frame that discussion with your own doctor. Both Cardio Res-Q assessments, the Comprehensive Assessment ($775) and the Enhanced Assessment ($999), include a clinical evaluation and advanced labs, and the Enhanced Assessment adds a calcium score and a CIMT ultrasound.
The Cardio Res-Q program page has the details. Cardio Res-Q does not replace your cardiologist or primary care doctor, and sharing results with your doctor explains how the two fit together. If you already take a statin, see Already on a Statin?.
Are You a Candidate for Cardio Res-Q?
Three quick questions about the risk factors we screen for. Your answers stay between you and the clinic.
Frequently asked questions
Should I take a baby aspirin every day to protect my heart?
That is a decision to make with your doctor, not from an article. For adults without cardiovascular disease, large trials found little or no reduction in events and more serious bleeding, and the US Preventive Services Task Force advises against starting at age 60 or older. For people with known cardiovascular disease the evidence is different.
I have taken aspirin for years. Should I stop?
Not by yourself. You may have a reason to be on it that still holds, and a large observational study linked stopping long-term aspirin to more cardiovascular events. Ask your doctor to review why you take it and whether the balance has changed.
What should I do if I think I am having a heart attack?
Call 911 right away. Emergency dispatchers and paramedics can tell you whether to take aspirin while you wait. Do not drive yourself to the hospital.
Related reading
This article is for general education and is not medical advice. Decisions about testing and medication should be made with your clinician. If you have chest pain or other symptoms of a heart attack, call 911.
