Blood-thinning drugs are commonly used to reduce stroke risk in patients with atrial fibrillation (AF) but research from the Karolinska Institute suggests that anticoagulants may also protect patients from dementia.

Studies had previously pointed towards an association and researchers decided to examine 444,106 patients’ with AF’s records to determine if they could find a clear link. When compiled together, the research found that those taking anticoagulants to prevent blood clots had a 29% lowered risk of developing dementia compared to those who were not.

Beyond this, it was found that patient who continued to take the drugs over a longer period of time had 48% reduced risk of dementia.

The results are striking suggesting that the treatments, which extended to older forms of blood-thinners, such as warfarin, could perform a dual action – protecting against strokes and dementia.

It is speculated that preventing smaller blood clots in the brain prevents microscopic strokes in the brain that then lead to cognitive deterioration.

The only limitation to the study is that it proves the link between the two but would need to be verified by a clinical trial – something not possible, on ethical grounds.

"In order to prove this assumption, randomized 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," write Leif Friberg and Mårten Rosenqvist, of the Karolinska Institute, in their paper.

Despite the inability to prove the association, it is likely that the research will give doctors further impetus to ensure that patients with AF remain adherent to their medication.

Friberg commented further about patient’s propensity to stop taking the medication: "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".

This new information could provide doctors with a stark warning to patients that it is not simply the risk of stroke that increases when not taking the medication but also dementia risk.