Daily low dose aspirin increases brain bleeding risk by 38% in older adults

For the study, the researchers analyzed data from 19,114 adults with an average age of 74 years old.

Around 56% of participants were female, and none had a history of cardiovascular conditions such as:

The participants were randomly assigned one of two groups and given either a daily 100 mg dose of aspirin or a placebo. They were tracked for an average of 4.7 years.

The researchers found that low dose aspirin was linked to slight — but clinically insignificant — reductions in ischemic stroke incidence.

While 1.5% of those assigned aspirin (146 individuals) — experienced stroke, the same was true for 1.7% of those in the placebo group (166 individuals).

Aspirin did not lead to statistically significant reductions in hemorrhagic strokes either.

Whereas 0.5% of participants assigned aspirin (49 individuals) experienced a hemorrhagic stroke, the same was true for 0.4% of those in the placebo group (37 individuals).

The researchers also noted that individuals taking aspirin were significantly more likely to develop intracranial bleeding than those on a placebo.

Altogether, 1.1% of those taking aspirin (108 individuals) experienced intracranial bleeding, while the same was true for 0.8% of those taking a placebo (79 individuals).

Dr. Arun Manmadhan, assistant professor of medicine at the Vagelos College of Physicians and Surgeons at Columbia University, not involved in the study, told Medical News Today:

“This study adds to the growing body of evidence that the routine use of aspirin to prevent first-time cardiovascular events in the general adult population is of limited benefit and may cause harm due to excess bleeding, particularly in older adults. This study aligns with recent U.S. Preventive Services Task Force recommendations that advise against the routine use of aspirin to prevent cardiovascular disease in adults over the age of 60.”

MNT spoke with Dr. Hardik P. Amin, associate professor of neurology at Yale School of Medicine, not involved in the study, about how aspirin may reduce stroke risk.

He said that blood platelets — a type of blood cell that allows clotting — can form small clumps inside blood vessels in patients at risk of cardiovascular conditions.

“Aspirin prevents the clumping of platelets inside blood vessels, leading to its blood thinning effect, to reduce the risk of a heart attack or stroke,” Dr. Amin said.

MNT also asked Dr. Walavan Sivakumar, a board certified neurosurgeon, and director of neurosurgery at Pacific Neuroscience Institute-South Bay in Torrance, CA, not involved in the study, about how aspirin may increase the risk of intracranial bleeding.

Dr. Sivakumar noted that in the same way that aspirin decreases the chance of blood clots forming and being sent to the brain, it also may increase the risk of bleeding in the brain.

“Forming blood clots is also one of the ways that the body stops bleeding. As a result, aspirin also hinders the body’s ability to control bleeding once it occurs,” he said.

MNT spoke with Dr. Maria Parekh, stroke researcher and assistant professor of neurology with McGovern Medical School at UTHealth Houston, not involved in the study, about its limitations.

She noted that the number of strokes and intracranial bleeding cases were generally low in the study, so the findings may be susceptible to random and systematic errors.

Dr. Parekh added that aspirin is also known to benefit people who have had an ischemic stroke — when blood supply to the brain is interrupted or reduced — as it prevents clots from forming that could induce another stroke. This, she noted, is called “secondary prevention.”

“This trial, however, looked at the use of aspirin to prevent first-time ischemic stroke which is ‘primary stroke prevention’, specifically in healthy older adults “free of overt cardiovascular disease”. [It thereby excludes] those who were most likely to benefit from low dose aspirin,” she noted.

— Dr. Maria Parekh, stroke researcher

MNT also asked Dr. Ziad Hage, a board certified and fellowship-trained cerebrovascular and endovascular neurosurgeon at Novant Health in Charlotte, NC, not involved in the study, about the study.

He indicated that the findings may not apply to populations with a high stroke risk or to secondary stroke prevention. He added that as the participants in the study were predominantly older, white, and with easy access to blood pressure and lipid-lowering medications, the findings may also not apply to more diverse demographics.

“In healthy patients with no cardiovascular risk factors, these findings suggest that recommending aspirin use can cause more harm than good,” Dr. Sivakumar said.

“At that point, patients may opt for more conservative lifestyle modifications like [a] healthy diet and regular exercise.”

Dr. Hage agreed that aspirin should not be given to patients at a higher risk of cardiovascular conditions like stroke. He added that aspirin should also be avoided for patients with a higher risk of falling unless absolutely necessary.

“In summary, it is important for the community to understand that there is certainly a beneficial role for aspirin in certain cases, and therefore consultation with a specialist regarding this issue is paramount. Remember to seek medical care if developing stroke symptoms, such as sudden onset, face, arm or leg weakness, speech slurring or inability to speak, sudden loss of vision in one eye, and sudden loss of balance among other symptoms.”

— Dr. Ziad Hage, cerebrovascular and endovascular neurosurgeon