Aspirin may work to prevent a first heart attack or stroke in those at high risk, according to a fresh look at earlier aspirin studies.

Aspirin has been widely used for long-term protection in patients who have previously had a heart attack or stroke, but evidence suggests 40,000 extra lives could be saved each year if those with high-risk conditions received aspirin treatment.

Colin Baigent, a Medical Research Council (MRC) scientist who lead the research, said the study shows aspirin is beneficial in a wider range of conditions than previously believed, including high-risk conditions such as angina, peripheral arterial disease and diabetes.

Surveys conducted in the U.S. and U.K. reveal that less than half of patients with high-risk conditions are prescribed the drug. Lack of clear advice from some national guidelines is cited as one of the possible reasons aspirin is under used.

"Surveys in the UK show aspirin is currently prescribed to less than 25 per cent of people with high-risk diseases such as peripheral arterial disease – a condition which causes fatty deposits to build up in the arteries of the legs and in which heart attack and stroke are common," said Baigent.

He believes aspirin may help protect these high-risk patients, many of whom will die from their first heart attack.

More effective drugs may be available

Aspirin and other antiplatelet drugs act to stop platelets (a type of blood cell) from clumping into potentially harmful clots that can cause heart attacks and stroke.

But aspirin can also cause stomach problems such as bleeding and ulcers. As a preventative tool against heart attacks and stroke, aspirin should only be taken on the advice of a doctor.

For healthy people at slight risk, researchers aren't sure if the benefits of aspirin outweigh its risk.

For high-risk patients, however, wider use of aspirin may bring new hope to preventative treatment regiments.

Critics argue the researchers may overvalue aspirin's effectiveness and safety.

John Cleland, professor of cardiology at the University of Hull argues aspirin may change the nature of blood-related events, rather than prevent them. He adds that safety and the relationship between the costs and benefits of the treatment are inadequate in Baigent's study.

He believes more effective drugs may be available, and advocating aspirin as a preventative tool may divert attention from other treatment options.

The study appears in the Jan. 11 issue of the British Medical Journal .