Thousands of people at risk of heart attacks and strokes are not being given aspirin, despite the fact the drug could save their lives, according to a study published todayin the British Medical Journal.

At least 3,000 people in Britain and 40,000 worldwide could survive if there was "more appropriate" use of the drug, whose crucial property is its ability to thin the blood, preventing the clotting that triggers strokes and serious heart attacks. The figure is in addition to the 7,000 Britons and 100,000 people worldwide whose lives are calculated to be saved by being prescribed aspirin following a sudden heart attack or angina – the pain caused by too little blood reaching the heart muscle.

Dr Colin Baigent of the Medical Research Council, who led the research, said: "This study shows that aspirin is beneficial in an even wider range of conditions than previously believed. What we now need is to ensure that aspirin, or some other anti-platelet drug, is routinely considered for patients who might need it."

The research reviewed the results of 300 clinical trials involving more than 200,000 patients. Co-ordinated by scientists at Oxford University, it was the largest international study of disease treatment.

Aspirin has been identified for at least a decade as a potential weapon against heart attacks and strokes. A number of doctors have recommended the drug for long-distance fliers as a precaution against deep-vein thrombosis.

In some cases, adding a second anti-platelet drug to aspirin appeared to provide extra protection. Platelets are small spherical bodies which play an important role in blood clotting.

Dr Baigent said aspirin was prescribed to less than a quarter of people with artery diseases that can cause heart attacks and strokes.