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Blood-thinning drugs may not only prevent stroke in patients with abnormal heart rhythm, but also significantly reduce the risk of dementia, according to a study published today.
In the study, among 444,106 patients with atrial fibrillation (AF) or abnormal heart rhythm, those who were taking anticoagulant drugs to prevent blood clots at the start had a 29 per cent lower risk of developing dementia than those who were not on anticoagulant treatment.
When researchers at Karolinska Institute in Sweden looked at what happened during the period of time that the patients continued to take the drugs, they found an even bigger, 48 per cent reduction in the risk of dementia.
The study, published in the European Heart Journal, is the largest ever to examine the link between anticoagulant treatment and dementia in AF patients.
It looked at data from Swedish registries for patients between 2006 and 2014.
The results strongly suggest that oral anticoagulants protect against dementia in AF patients, researchers said.
"In order to prove this assumption, randomised placebo controlled trials would be needed, but such studies cannot be done because of ethical reasons. It is not possible to give placebo to AF patients and then wait for dementia or stroke to occur," they said.
AF is known to carry an increased risk of stroke and dementia, and anticoagulants have been shown to reduce the likelihood of stroke.
Until now it was not clear whether anticoagulants could also prevent dementia, researchers said.
However, it was thought possible because if the drugs can prevent the big blood clots that cause stroke, they might also protect against the small clots that can cause unnoticed microscopic strokes that eventually lead to cognitive deterioration, they said.
Researchers identified all patients in Sweden who had a diagnosis of AF between 2006-2014. They checked on what drugs had been prescribed and dispensed following the diagnosis.
The researchers followed the patients' progress and this provided them with 1.5 million years of follow-up, during which time 26,210 patients were diagnosed with dementia.
When they first joined the study, 54 per cent of patients were not taking oral anticoagulants such as warfarin, apixaban, dabigatran, edoxaban or rivaroxaban.
The researchers found that the strongest predictors for dementia were lack of oral anticoagulant treatment, ageing, Parkinson's disease and alcohol abuse.
They also found that the sooner oral anticoagulant treatment was started after a diagnosis of AF, the greater was the protective effect against dementia.