Doctors could save 40,000 lives every year if they were to prescribe aspirin to patients at risk from stroke or heart attack, according to new research.

Scientists in Oxford are urging GPs to pinpoint people at risk from circulatory disease and give them the drug before they become ill.

Although patients who have already suffered strokes or heart attacks are prescribed aspirin, researchers at Oxford University believe there are other people who would also benefit from the drug, as a preventative measure.

Dr Colin Baigent, who led the study at the Clinical Trial Service Unit at Oxford's Radcliffe Infirmary, said diabetics and people with angina were among those who should be assessed.

He said: "We should be identifying those at high risk, including people with angina, or bad circulation."

Previous research has shown that blood-thinning aspirin can help people who have already suffered from strokes and heart attacks, which are caused when red blood cells clot.

Dr Baigent's team reviewed 287 trials, involving 200,000 patients, and found the drug reduced the risk of heart attack by one third and stroke by one quarter.

Dr Baigent said: "These results clearly show that it should be considered routinely for all patients at high or intermediate risk of vascular disease."