People with irregular heartbeats who have a stroke are 35% less likely to have a second stroke if they are given blood-thinning drugs earlier than currently recommended, research has found. There are more than 1.6 million people in the UK with atrial fibrillation – an irregular heartbeat. The condition can lead to a clot forming inside the heart, which can travel to the brain, blocking the blood supply and causing a stroke. In the UK, more than 100,000 people have a stroke each year, and atrial fibrillation patients are five times more likely to have a stroke than those without the condition. People with atrial fibrillation who have had a stroke also have an increased risk of having another, but this risk can be reduced by taking anticoagulants. However, anticoagulants can cause brain bleeds. UK guidelines suggest that patients with irregular heartbeats who have had a moderate or severe stroke should wait at least five days before starting blood-thinning drugs. Now two new studies, presented at the World Stroke Congress 2024, suggest that people with atrial fibrillation who have a stroke, and take blood-thinning drugs earlier than currently recommended, are not only less likely to have a second stroke but have no increased risk of a brain bleed than those who take them later. An international team of researchers conducted a meta analysis of four randomised controlled trials looking at the safety and efficacy of starting anticoagulants early, compared with later, in people with acute stroke and atrial fibrillation. The academics compared more than 5,000 patients given blood thinners within four days of a stroke with those who started anticoagulants the fifth day or later. They found that 2.12% of patients given anticoagulants within four days went on to have another stroke within 30 days, compared with 3.02% of those who started them later – a 35% difference. A second study presented at the conference, funded by the British Heart Foundation and published in the Lancet, found that giving anticoagulants within four days of a stroke – rather than delaying treatment – did not increase the risk of a brain bleed, even for those who had a more severe stroke. The team analysed data from 3,621 patients with atrial fibrillation who had had a stroke between 2019 and 2024, across 100 UK hospitals. Half of the participants began anticoagulant treatment within four days of their stroke (early), and the other half started treatment seven to 14 days after having a stroke (delayed). Early treatment was found to be as effective as delayed treatment and did not increase the risk of a bleed into the brain. David Werring, a professor of clinical neurology at University College London and a lead author of both studies, said: “It’s not like a magic bullet, but at a population level, it’s really important. If we can give anticoagulants earlier, to 20,000 people a year – the approximate number of people with atrial fibrillation who have a stroke in the UK each year – that means we could stop up to 200 strokes potentially. And crucially, there appears to be no increased risk of a brain bleed from starting this treatment earlier.” Responding to the findings, Prof Bryan Williams, the chief scientific and medical officer at the British Heart Foundation, said: “These results could be transformative, making the case for earlier treatment that could help more people with atrial fibrillation avoid having another stroke, and the associated complications.”