Health reporter, BBC News
Aspirin makes it harder for blood clots to form
Men and women over a certain age should take aspirin daily to prevent heart attacks, experts say in Heart journal.
Nottingham and Sheffield universities' analysis of almost 12,000 patients found men from the age of 48 and women from 57 would benefit from the drug.
Heart attacks occur when a blood vessel is blocked by a clot, but aspirin makes it harder for blood clots to form.
The British Heart Foundation said more research was needed before "blanket prescribing" could be recommended.
Under existing recommendations, a GP will prescribe the drug if a person has already suffered a heart attack or a stroke.
It is also prescribed if factors such as high blood pressure put a patient at high risk of having such an "event" in the next few years.
But the researchers said, in reality, many people are not treated.
Some have speculated it may be easier to treat everyone over a specific age threshold such as 50 years.
An analysis of almost 12,000 patients aged between 30 and 75 showed that by the age of 47 in men and 58 in women, the 10-year coronary heart disease risk is 10% - a risk worth treating, the researchers said.
At that point, unless someone is at risk of dangerous side effects because they have a condition such as a stomach ulcer, the benefits outweigh the disadvantages, they concluded.
But this did not apply to people with diabetes or those at high risk of bleeding, the researchers said.
Although diabetics are likely to benefit from aspirin treatment because of their high heart disease risk, the evidence is not yet quite clear, they added.
And in anyone over the age of 75 years, the decision whether or not to take aspirin must be made on an individual basis, because they are more likely to suffer bleeding complications.
Study leader Dr Iskandar Idris, an honorary senior lecturer at Sheffield University, said routinely prescribing aspirin in these age groups was a feasible option.
But he added: "The final decision about use of aspirin must eventually be made after discussion with a healthcare provider."
Dr Mike Knapton, director of prevention and care at the British Heart Foundation, said: "Currently the recommendations in the UK are that aspirin is prescribed after a full risk assessment under medical supervision to those who have established cardiovascular disease.
"Further robust research is needed before aspirin should be considered as a blanket primary prevention measure in the UK.
"We would encourage everyone to examine their own individual risk and take steps to reduce it by adjusting their lifestyle."