Incorrect Blood Thinner Dose Ups Dementia Risk

A new study finds atrial fibrillation (AF) patients on blood-thinning medications are at greater risk of developing dementia if their drug doses are not in the optimal recommended range.

The findings contain “some good news” for primary care physicians managing AF patients with warfarin, says Jared Bunch, MD, director of electrophysiology research at the Intermountain Medical Center Heart Institute, and co-author of the study.
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Bunch and colleagues from Intermountain studied 2,693 AF patients, of whom 4% were diagnosed with dementia. Results were based on the percentage of time their blood-thinning medications were within the ideal range. The authors found patients were significantly more likely to develop dementia when using medicines such as warfarin to prevent blood clots, if the dosing is too high or too low for an extended period of time.

Specifically, patients within the therapeutic range less than 25% of the time were 4.5 times more likely to develop dementia. Patients within the range 25% to 50% of the time were 4.1 times more likely to develop dementia, while those within the therapeutic range 51% to 75% of the time were only at a 2.5% greater risk. The increased risk remained significant when adjusting for common risks of both stroke and bleeding, Bunch notes.

“The risk of dementia was very low when patients’ warfarin levels were well-controlled,” he says. Warfarin, however, is “a difficult drug to manage long-term, and I believe use of warfarin or Coumadin clinics can be helpful, particularly in the education of patients and the reinforcement of frequent follow-up.”

The study suggests that alternative methods for anticoagulation may be preferable as a means to reduce variability in patients for whom warfarin is difficult to manage due to genetics, drug-drug interactions, drug-food interactions, or poor compliance, he adds.

“It should be emphasized,” continues Bunch, “that the new anticoagulants have not been studied in this manner, but in general these novel agents have a much more predictable effect.”

Additionally, the researchers saw a risk of dementia with both over- and under-anticoagulation. This finding suggests that “both small bleeds and clots may be causing the cognitive decline,” he says.

“There are many non-pharmacologic products in development that may reduce clot risk and not result in a life-long need for anticoagulation. These will need to be studied as to their impact on dementia, but they are attractive alternatives to consider."

The findings are scheduled to be presented on Friday, May 9, at the 2014 Annual Heart Rhythm Society Scientific Session, held in San Francisco.

—Mark McGraw