However, based on a previous study, the team suspected that the benefits of more immediate treatment with aspirin could be much greater.
“The risk of a major stroke is very high immediately after a TIA or a minor stroke (about 1,000 times higher than the background rate), but only for a few days,” said lead researcher Peter Rothwell, stroke expert from the University of Oxford.
The team revisited the individual patient data from twelve trials (about 16,000 people) of aspirin for long-term secondary prevention — that is, to prevent a further stroke — and data on about 40,000 people from three trials of aspirin in treatment of acute stroke.
They found that almost all of the benefit of aspirin in reducing the risk of another stroke was in the first few weeks, and that aspirin also reduced the severity of these early strokes.
Rather than the 15 percent overall reduction in longer-term risk reported previously in these trials, aspirin reduced the early risk of a fatal or disabling stroke by about 70-80 percent over the first few days and weeks.