Aspirin and Dementia: What the Research Says

Can a daily low-dose aspirin lower the risk of dementia? The largest trial in older adults found no overall benefit and more bleeding, and a newer genetic analysis hints that a small group might respond differently. Here's what is known and why you shouldn't start aspirin on your own.

By Jim Pavlish, Editor · Last updated: October 26, 2026 · Editorial policy

Low-dose aspirin is one of the most familiar medicines in the world. Because it thins the blood and calms some inflammation, and because problems with blood vessels play a part in many cases of dementia, people have long wondered whether a daily "baby aspirin" might protect the brain. The short answer today: for most older adults, it doesn't appear to, and it carries a real risk of bleeding. A newer study suggests the story may be more complicated for a small group of people, but that idea still needs to be tested.

This page is general information, not medical advice. Aspirin interacts with other medicines and health conditions, so any decision to start or stop it belongs with your doctor.

Why scientists thought aspirin might help

Several lines of reasoning made aspirin an appealing candidate:

• Blood vessels and the brain. Small strokes and damage to tiny blood vessels can cause or worsen dementia, especially Vascular Dementia and Mixed Dementia. Aspirin lowers the chance of clots forming in people who already have heart or vessel disease.
• Inflammation. Long-term inflammation may contribute to brain changes in Alzheimer's (see Inflammation and the Brain), and aspirin has anti-inflammatory effects.
• Platelets. Platelets, the small blood cells that help clots form, have been linked to dementia in earlier research. Aspirin makes platelets less sticky.

Older observational studies, which compare people who happen to take aspirin with people who don't, gave mixed results. Studies like that can't separate the effect of aspirin from everything else that differs between those groups, which is why a randomized trial was needed.

The big trial: ASPREE

The ASPREE trial (Aspirin in Reducing Events in the Elderly) enrolled more than 19,000 healthy older adults in Australia and the United States, mostly age 70 and up, who did not have heart disease, disability or diagnosed dementia. Half were randomly assigned to 100 mg of aspirin a day and half to a look-alike placebo, and they were followed for a median of about 4.7 years.

The results for the brain, published in Neurology in 2020, were clear:

• Dementia was about equally common in both groups.
• There was no difference in probable Alzheimer's disease, Mild Cognitive Impairment (MCI) or cognitive decline.
• Scores on memory and thinking tests changed at about the same rate in both groups.

The researchers concluded there was no evidence that aspirin reduced the risk of dementia, MCI or cognitive decline in healthy older people. Other reports from the same trial found that aspirin did not lower heart attacks and strokes enough in this group to outweigh a higher rate of serious bleeding.

The newer genetic analysis (2026)

In 2026, researchers at Monash University went back to the ASPREE participants who had genetic data, more than 13,500 people. They screened about 1,800 genetic "scores," each summing many small gene differences linked to a trait, to see whether any of them changed how aspirin affected dementia risk.

The strongest signal came from genetic scores linked to platelet count. Among people in the top 20% for one of these scores:

• About 1% of those taking aspirin developed dementia, compared with about 3.3% of those on placebo, roughly a 70% lower relative risk.
• But major bleeding was about twice as common with aspirin: 4.4% versus 2.1%.
• In the other 80% of people, aspirin showed no dementia benefit.

The authors call these findings "hypothesis-generating." That means they point to an idea worth testing, not a proven treatment. When researchers check hundreds or thousands of possibilities, some results can look strong by chance, so the finding needs to be confirmed in other groups of people and then tested in a trial designed for it. There is also no routine clinical test today that tells you whether you're in this genetic group. The lead author said people shouldn't start aspirin to prevent dementia based on this study without talking to their doctor, especially given the bleeding risk.

What the guidelines say

The U.S. Preventive Services Task Force, an independent panel that reviews prevention evidence, recommends that adults 60 and older not start daily aspirin to prevent a first heart attack or stroke, because the bleeding risk tends to outweigh the benefit at that age. For adults 40 to 59 with higher heart risk, it's an individual decision with a doctor. These guidelines are about the heart, not dementia, and they don't apply to people who already take aspirin because they've had a heart attack, stroke or stent. Those people should not stop aspirin without talking to their doctor, since stopping suddenly can raise the risk of a clot.

Practical takeaways

• Don't start aspirin on your own to protect your memory. The best evidence in older adults shows no overall brain benefit and a real bleeding risk.
• Don't stop prescribed aspirin on your own either. If you take it for your heart, ask your doctor whether it's still right for you.
• Bring all your medicines to your next appointment, including over-the-counter pills and supplements, and ask about bleeding risk if you also take blood thinners, pain relievers like ibuprofen, or certain supplements.
• Focus on proven steps for brain health: controlling blood pressure, staying active, protecting your hearing and not smoking. Our guide to Reducing Dementia Risk: The 14 Risk Factors covers what the evidence supports.
• Read headlines carefully. A "70% lower risk" in a small subgroup is not the same as a treatment for everyone. Our page on How to Read Health Research News explains how to tell the difference.

Sources

1. Ryan J et al. Randomized placebo-controlled trial of the effects of aspirin on dementia and cognitive decline. Neurology, 2020 (ASPREE)
2. Fransquet P et al. Platelet count polygenic scores may modify the effect of aspirin in primary prevention of dementia. Alzheimer's & Dementia, 2026
3. Monash University: Genetic analysis reveals potential benefit of aspirin for reducing dementia risk (October 2026)
4. U.S. Preventive Services Task Force: Aspirin Use to Prevent Cardiovascular Disease: Preventive Medication (2022)

Not medical advice. This article is general information, not a diagnosis or treatment plan for any individual. Talk with a doctor about your situation.

Related articles

• Reducing Dementia Risk: The 14 Risk Factors
• Vascular Dementia
• Blood Pressure and the Brain
• Prevention Trials
• How to Read Health Research News
• Genetic Testing and APOE4