Taking aspirin regularly does not significantly reduce the risk of heart attacks or stroke, a study has found.
It had previously been thought by many that a low daily dose of the blood-thinning medicine benefits older people.
But a study involving more than 19,000 participants has found that there is no significant advantage and that taking aspirin regularly can instead lead to a slightly increased risk of serious bleeding.
Lead researcher Professor John McNeil, of Monash University, Australia, said the study proves many older people may be taking the medicine “unnecessarily”.
“Despite the fact that aspirin has been around for more than 100 years, we have not known whether healthy older people should take it as a preventive measure to keep them healthy for longer.
“Aspirin is the most widely used of all preventive drugs and an answer to this question is long overdue.
“[The study] has provided this answer.”
He added: “It means millions of healthy older people around the world who are taking low-dose aspirin without a medical reason may be doing so unnecessarily, because the study showed no overall benefit to offset the risk of bleeding.”
Professor McNeil did warn, however, that the results do not apply to people with existing conditions, including a previous heart attack, angina or stroke, for which aspirin can be recommended to prevent further problems.
The study involved 19,114 people, mostly over the age of 70.
It was called the Aspirin In Reducing Events In The Elderly (ASPREE) trial and the results have been published in three papers in the New England Journal of Medicine.
Around half of the participants took a 100mg low dose of aspirin daily, while the others were given a placebo.
Their health was re-examined after around five years.
Rates of cardiovascular events, such as coronary heart disease, non-fatal heart attacks and strokes, were similar across both groups, the study found.
But 3.8% of the aspirin takers experienced serious bleeding, compared with 2.8% of the placebo group. And 5.9% of those taking aspirin died during the study, compared to 5.2% of the placebo-takers.
The small increase in deaths, mostly from cancer, may be coincidental and needs more study, the authors said.