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People should consider taking aspirin immediately after a minor stroke to prevent or limit the harm caused by further strokes, researchers say.

Oxford University scientists say though doctors are already advised to give the drug, the benefits of taking it early on have been "hugely underestimated" and treatment is sometimes delayed.

Writing in the Lancet, they call for clearer medical and public guidelines.

NHS England says it will carefully consider the findings of the study.

Crucial hours

Minor strokes and TIAs (transient ischaemic attacks or mini-strokes) occur when there is an interruption of blood flow to the brain - they can cause weakness to the limbs or problems with speech or vision and symptoms usually disappear within days.

But the chance of going on to have a major stroke - with more permanent symptoms - is higher in the days after an attack.

Previous studies have suggested aspirin plays some part in reducing this, particularly in the long-term, by reducing the risk of blood clots forming, or thinning the blood.

But the team of scientists say their findings show most of the benefit lies in the first crucial hours and days after a minor stroke or TIA.

They estimate taking early aspirin treatment at this point could reduce the risk of having a major stroke from one in 20 people per day to one in 100.

Lead researcher Prof Peter Rothwell said the benefits of immediate aspirin therapy had been "hugely underestimated".

He added: "We need to encourage people, if they think they've had some neurological symptoms that might be a minor stroke or TIA, to take aspirin immediately, as well as ideally seeking medical attention."

How to recognise a stroke

F ace - has their face fallen on one side? Can they smile?

ace - has their face fallen on one side? Can they smile? A rms - can they raise both their arms and keep them there?

rms - can they raise both their arms and keep them there? S peech - is their speech slurred? If you notice any of these symptoms it is...

peech - is their speech slurred? If you notice any of these symptoms it is... Time - time to call 999 if you see any single one of these signs

Additional symptoms of stroke and mini-stroke can include:

Sudden loss of vision or blurred vision in one or both eyes

Sudden weakness or numbness on one side of the body

Sudden memory loss or confusion

Sudden dizziness, unsteadiness or a sudden fall, especially with any of the other symptoms

Source: Stroke Association

Researchers now call for medical services - including paramedics and NHS helplines - to recommend the drug as soon as possible if a TIA is suspected.

Meanwhile they say it is essential that patients who have a minor stroke are not just sent home from the emergency department with advice to add aspirin on to their next prescription.

The team reviewed data from 15 trials, involving thousands of people who had taken aspirin immediately after a stroke or as long-term treatment to prevent a second one.

Dr Dale Webb, at the Stroke Association charity, described the trial as an exciting development.

He added: "However, it's important to note that taking aspirin is not an alternative to seeking medical attention. Anyone who thinks they are having a TIA should always call 999 immediately.

"And the findings suggest that anyone who has stroke symptoms, which are improving while they are awaiting urgent medical attention can, if they are able, take aspirin."

Strokes - the definitions

Transient ischaemic attacks (also known as mini-strokes) - symptoms resolve within 24 hours but the majority resolve within 10-60 minutes.

Minor stroke - symptoms last more than 24 hours but often resolve within a few days - and are usually relatively mild

Major stroke - usually taken to mean some permanent symptoms remain

Source: Peter Rothwell, University of Oxford

Meanwhile Tony Rudd, National Clinical Director for Stroke at NHS England, said:"This report contains important data that will need to be carefully considered and then, if needed, appropriate changes made to guidelines for the management of acute stroke and transient ischemic attack."

Health experts suggest in general aspirin should not be taken without medical advice if people have bleeding disorders or swallowing problems and should be considered with caution if someone has asthma, for example.

New stroke guidelines for doctors are due out in the autumn.