Writing in the Lancet, the team said that immediate self-treatment when patients experience stroke-like symptoms would considerably reduce the risk of major stroke over the next few days.

Aspirin is already given to people who have had a stroke or transient ischemic attack (TIA -- often called a 'mini-stroke') to prevent further strokes after they have been assessed in hospital and in the longer-term, reducing the subsequent stroke risk by about 15%. However, based on a previous study in Oxford (the EXPRESS Study) the team suspected that the benefits of more immediate treatment with aspirin could be much greater.

Lead researcher Professor Peter Rothwell, a stroke expert from the University of Oxford, explained, “'The risk of a major stroke is very high immediately after a TIA or a minor stroke (about 1000 times higher than the background rate), but only for a few days. We showed previously in the 'EXPRESS Study' that urgent medical treatment with a 'cocktail' of different drugs could reduce the one-week risk of stroke from about 10% to about 2%, but we didn't know which component of the 'cocktail' was most important.”

“One of the treatments that we used was aspirin, but we know from other trials that the long-term benefit of aspirin in preventing stroke is relatively modest. We suspected that the early benefit might be much greater. If so, taking aspirin as soon as possible after 'warning symptoms' event could be very worthwhile,” he added.