Researchers have discovered that stroke survivors with irregular heartbeats could significantly reduce their chances of experiencing a second stroke by starting blood-thinning medications earlier than current guidelines recommend.

According to a study presented at the World Stroke Congress 2024, individuals with atrial fibrillation—an irregular heartbeat condition affecting over 1.6 million people in the UK—are five times more likely to suffer a stroke compared to those without the condition. Each year, more than 100,000 people in the UK experience a stroke, and for those with a history of stroke and atrial fibrillation, the risk of having another one increases.

Current UK guidelines recommend waiting at least five days after a moderate or severe stroke before initiating anticoagulant therapy due to the risk of brain bleeds. However, the new studies indicate that starting blood-thinning drugs within four days can reduce the risk of a second stroke without increasing the likelihood of bleeding.

The research team, comprising international experts, conducted a meta-analysis of four randomized controlled trials that compared the outcomes of over 5,000 patients who received anticoagulants within four days of a stroke to those who began treatment on the fifth day or later. They found a notable difference: 2.12% of patients on early treatment had a second stroke within 30 days, compared to 3.02% in the delayed treatment group—marking a significant 35% reduction.

In a second study funded by the British Heart Foundation and published in The Lancet, researchers analyzed data from 3,621 patients with atrial fibrillation who suffered a stroke between 2019 and 2024 across 100 UK hospitals. The findings showed no increased risk of brain bleeds among patients who started anticoagulants within four days post-stroke, regardless of the severity of their condition.

David Werring, a professor of clinical neurology at University College London and lead author of both studies, emphasized the importance of these findings, stating, “It’s not like a magic bullet, but at a population level, it’s really significant. If we could administer anticoagulants earlier to the estimated 20,000 individuals with atrial fibrillation who experience a stroke in the UK each year, we could potentially prevent up to 200 additional strokes, and importantly, there seems to be no increased risk of brain bleeds from this early intervention.”

In response to the results, Professor Bryan Williams, chief scientific and medical officer at the British Heart Foundation, remarked, “These findings could be transformative, supporting the argument for earlier treatment, which could help many individuals with atrial fibrillation avoid subsequent strokes and their related complications.”