Warfarin Use Can Increase Dementia Risk in AF Patients

A new study shows that atrial fibrillation (AF) patients treated over a long period of time with Warfarin experience higher rates of dementia than their counterparts.

Researchers at Intermountain Medical Center (IMC; Salt Lake City, UT, USA) enrolled 10,537 patients with no prior history of dementia who were treated with warfarin for both AF and other, non-AF conditions (such as valvular heart disease and thromboembolism) on a long-term basis. The researchers also examined other variables, such as age, hypertension, diabetes, hyperlipidemia, renal failure, smoking history, prior myocardial infarction (MI) or cerebral vascular accident, and heart failure. Participants were aged 18 years and older.

The results showed that during a follow-up of approximately seven years, dementia was more prevalent in the AF group (5.8%) than the non-AF group (1.6%). In both groups the risk of dementia increased as time in therapeutic range decreased, or became erratic; when warfarin levels were consistently too high or too low, dementia rates increased. Regardless of the adequacy of anticoagulation, the AF patients consistently experienced higher rates of all forms of dementia. The study was presented at the 37th annual scientific sessions of the Heart Rhythm Society, held during May 2016 in San Francisco (CA, USA).

“As physicians we have to understand that although we need to use anticoagulants for many reasons, including to prevent stroke in AF patients, at that same time there are risks that need to be considered, some of which we are only right now beginning to understand,” said lead author T. Jared Bunch, MD, director of heart rhythm research at IMC. “In this regard, only those that absolutely need blood thinners should be placed on them long-term. In people that are on warfarin in which the levels are erratic or difficult to control, switching to newer agents that are more predictable may lower risk.”

Warfarin decrease blood coagulation by inhibiting vitamin K epoxide reductase, an enzyme that recycles oxidized vitamin K to its reduced form after it has participated in the carboxylation of several blood coagulation proteins, mainly prothrombin and factor VII. It was initially introduced in 1948 as a pesticide against rats and mice and is still popular for this purpose. In the early 1950's warfarin was found to be effective and relatively safe for preventing thrombosis and embolism in many disorders. It is the most widely prescribed oral anticoagulant drug in North America.

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