Aspirin taken immediately after minor stroke or TIA greatly reduces risk of second stroke

Aspirin reduces the risk of a second stroke by as much as 80% in the first few weeks after a transient ischemic attack (TIA) or minor ischemic stroke—an effect that has been greatly underestimated in previous trials, according to a study published online May 18, 2016 in The Lancet.

“Immediate treatment with aspirin [after TIA or minor stroke] can substantially reduce the risk and severity of early recurrent stroke,” said lead researcher Peter Rothwell, MD, PhD, Head of the Centre for the Prevention of Stroke and Dementia, and Professor of Clinical Neurology at the University of Oxford, in Oxford, United Kingdom.

The risk of recurrent stroke can be as high as 10% in the week after a TIA or minor stroke.

“This finding has implications for doctors, who should give aspirin immediately if a TIA or minor stroke is suspected, rather than waiting for specialist assessment and investigations,” Dr. Rothwell added.

Previous randomized clinical trials have already shown that aspirin can reduce the risk of a second stroke—but these trials showed only a modest risk reduction of 13% and were performed on a long-term basis.

“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,” Dr. Rothwell said. This suggested to the researchers that aspirin might indeed have a meaningful effect—but only in the short term, not the long term.

“We suspected that the early benefit might be much greater,” Dr. Rothwell explained. “If so, taking aspirin as soon as possible after a ‘warning symptoms’ event could be very worthwhile.”

Non-randomized observational studies back up this idea, and have shown that aspirin has substantially greater benefits—in reducing risk and possibly severity of stroke—as early treatment in the acute phase.

“We hypothesized that the short-term benefits of early aspirin have been underestimated,” the researchers wrote.

For this study, the researchers reviewed data on about 16,000 people from 12 trials of aspirin for the prevention of secondary stroke, as well as data on nearly 40,000 people from 3 trials of aspirin for the treatment of acute stroke.

The researchers found that aspirin reduced the risk of recurrent ischemic stroke by about 60% and disabling or fatal ischemic stroke by about 70% in the first few weeks. But the greatest benefit occurred in patients with TIA or minor stroke, largely in the first 2 weeks.

For the longer term, aspirin continued to reduce the risk of ischemic stroke after 6 weeks. But it provided no benefit after 12 weeks.

Aspirin’s effect on early recurrent stroke was due partly to a substantial reduction in severity, the authors noted. This effect was independent of dose, patient characteristics, or etiology of TIA or stroke.

“It is essential that aspirin is given to patients with suspected TIA or minor stroke immediately,” the authors concluded. “Indeed, a case can be made for public education about self-administration after transient unfamiliar neurological symptoms.”

“The findings suggest that anyone who has stroke symptoms, which are improving while they are awaiting urgent medical attention, can take 1 dose of 300 mg aspirin, if they are able,” said Dale Webb, DPhil, Director of Research and Information at the Stroke Association, in London, UK.

“The research findings are also timely, as the stroke community is currently working to develop a new set of national clinical guidelines on stroke,” he added.