A Monash University-led study has found that the risk of brain bleeding outweighs any potential benefit of reducing the risk of strokes in healthy older adults who take daily low dose aspirin.

Published in JAMA Network Open, this is the first major investigation into the risk/benefit of aspirin as a primary prevention measure in older people, who are often exposed to head trauma through falls and other knocks to the head. Bleeding is a known side effect of aspirin.

Researchers drew on data from ASPREE (ASPirin in Reducing Events in the Elderly), a primary prevention aspirin trial involving more than 19,000 initially healthy older adults, mostly over the age of 70, the vast majority in Australia and the rest in the U.S.

Primary prevention involves actions to preserve health and prevent adverse health events. Secondary prevention interventions are taken after a health event to avoid it happening again.

The participants, who did not have known cardiovascular disease when they entered the study, were randomly assigned 100 mg daily aspirin or placebo tablet for an average of five years.

The secondary analysis study found no statistically significant difference in the incidence of ischemic stroke—the most common type of stroke, caused by a blockage in vessels carrying blood to the brain—between the aspirin and placebo group.

Overall, strokes were reported in 4.6% of the aspirin group and 4.7% in the placebo group. While the number of brain bleeds was small, bleeding events were 38% higher in those who took aspirin compared to placebo.

The researchers concluded that the risk of brain bleeding outweighed any potential benefit in reducing strokes. This included bleeds into the brain, and bleeds on the brain surface which are commonly associated with head trauma.

"These findings suggest that low-dose aspirin may have no role for the primary prevention of stroke and that caution should be taken with use of aspirin in older persons prone to head trauma e.g. from falls," the researchers wrote.

Senior Author Professor John McNeil said the study underlined possible risks for some, but older people taking aspirin should not stop doing so without consulting with their GP.

"Although the overall incidence of bleeding was not common, it highlighted another risk of low-dose aspirin, especially relevant to older people susceptible to head trauma," Professor McNeil said.

"These findings do not apply to older adults taking aspirin on medical advice, such as after a heart attack and ischemic stroke. In secondary prevention, the balance of risks and benefits generally favours aspirin. It's important to consult with your GP before making any changes to your medicine intake."

First author and Director of Stroke Services at Alfred Health, Professor Geoffrey Cloud, said people could reduce their risk of stroke by living a healthy lifestyle.

"Older people concerned about reducing their risk of having their first stroke should not take daily aspirin without their doctor's advice but instead concentrate on modification of lifestyle risk factors and blood pressure control," he said.