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Blood-thinning drugs appear to protect against dementia in AF patients

Protective effect seen in patients taking the drugs to reduce the risk of stroke

Ingrid Torjesen

Wednesday, 25 October 2017

Blood-thinning drugs not only reduce the risk of stroke in patients with atrial fibrillation (AF) but are also associated with a significant reduction in the risk of dementia, according to research* published in the European Heart Journal.

AF is known to carry an increased risk of stroke and dementia, and anticoagulants have been shown to reduce the likelihood of stroke, but until now it was not clear whether anticoagulants could also prevent dementia; 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.

For the study, the largest study ever to examine the link between anticoagulant treatment and dementia in AF patients, the 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 and followed the patients' progress.

At the start of the study, 54% of the 444,106 patients with atrial fibrillation 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, aging, Parkinson's disease and alcohol abuse.

Analysis showed that patients taking anticoagulant drugs to prevent blood clots at the start of the study had a 29% lower risk of developing dementia than patients who were not on anticoagulant treatment.

The researchers also found that the sooner oral anticoagulant treatment was started after a diagnosis of AF, the greater was the protective effect against dementia.

Over a cumulative 1.5 million years of follow-up, 26,210 patients were diagnosed with dementia. Over this period the protective effect against dementia of the drugs increased, with patients who continued to them experiencing a 48% reduction in the risk of dementia.

The researchers believe that the results strongly suggest that oral anticoagulants protect against dementia in AF patients. "In order to prove this assumption, randomised placebo controlled trials would be needed, but... such studies cannot be done because of ethical reasons," write Leif Friberg and Mårten Rosenqvist from the Karolinska Institute (Stockholm, Sweden) in their EHJ paper.

Dr Friberg, who is associate professor of cardiology at the Karolinska Institute, said the important implications from these findings were that patients should be started on oral anticoagulant drugs as soon as possible after diagnosis of AF and that they should continue to take the drugs.

"Doctors should not tell their patients to stop using oral anticoagulants without a really good reason. Explain to your patients how these drugs work and why they should use them. An informed patient who understands this is much more likely to comply and will be able to use the drugs safely and get better benefits. To patients I would say 'don't stop unless your doctor says so. Have your doctor explain why you should take the drug so that you feel you understand and agree'.

"Patients start on oral anticoagulation for stroke prevention but they stop after a few years at an alarmingly high rate. In the first year, approximately 15% stop taking the drugs, then approximately 10% each year. In this study we found that only 54% of patients were on oral anticoagulant treatment. If you know that AF eats away your brain at a slow but steady pace and that you can prevent it by staying on treatment, I think most AF patients would find this a very strong argument for continuing treatment.

"As a clinician I know there are AF patients who have a fatalistic view upon stroke. Either it happens or it does not. Few patients are fatalistic about dementia, which gradually makes you lose your mind. No brain can withstand a constant bombardment of microscopic clots in the long run. Patients probably want to hang on to as many of their little grey cells for as long as they can. In order to preserve what you´ve got, you should take care to use anticoagulants if you are diagnosed with AF, as they have been proved to protect against stroke and, which this study indicates, also appear to protect against dementia."

The study also found that there was no difference in dementia prevention between the older blood-thinning drug warfarin and the newer oral anticoagulants.

* Friberg L, Rosenqvist M. Less dementia with oral anticoagulation in atrial fibrillation. European Heart Journal, ehx579, 24 October 2017. DOI: 10.1093/eurheartj/ehx579

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