AHA.14: Warfarin plus antiplatelet therapy may raise dementia risk

Patients with atrial fibrillation who often are over-anticoagulated on warfarin and receive antiplatelet therapy may be at increased risk of developing dementia, according to a study presented at the American Heart Association scientific session in Chicago on Nov. 16.

“Of all the variables in multivariate analysis, the only ones that truly predicted dementia risk in the population was over-anticoagulation percent time [of 25 percent of more] vs. over-anticoagulation that that was good, or less than 10 percent,” presenter Thomas Jared Bunch, MD, told Cardiovascular Business. “It is quite a strong marker for dementia risk.”

Bunch, director of electrophysiology research at the Intermountain Medical Center Heart Institute in Murray, Utah, and colleagues have been exploring the correlation between atrial fibrillation and dementia for many years. Repetitive cerebral injury from microbleeds or small clots from under- or over-anticoagulation may contribute to dementia, they have proposed.

In research published earlier this year, they found an incremental increased risk of dementia with every percentage point increase of under- or over-anticoagulation, based on time in the therapeutic range. “What was surprising in that study was that the risk of developing dementia was as high if you were under-anticoagulated as well as if you were over-anticoagulated,” Bunch said. “The latter finding is what prompted this second study.”

They focused on patients with no history of clinical dementia who received antiplatelet agents such as aspirin or clopidogrel (Plavix, Bristol-Myers Squibb/Sanofi-Aventis) in addition to warfarin, a group they speculated may be at even higher risk of developing dementia. The second study included 1,031 patients receiving antiplatelet therapy and warfarin at the center, with a follow-up of 4.5 years.

Patients with international normalized ratios (INRs) of 3 on 25 percent or more of their blood tests were more than twice as likely to be diagnosed with dementia as patients with INRs of 3 on 10 percent of tests, they determined.

Bunch estimated that in a typical practice 30 to 40 percent of atrial fibrillation patients who need anticoagulation therapy to reduce their risk of stroke may also be prescribed antiplatelet therapy for other coronary conditions. In addition, keeping patients in INR of 2 to 3 is challenging, even for good centers. His advice for lowering dementia risk in these patients?

“Don’t use aspirin with another anticoagulant unless it is needed,” he said. “We see a lot of patients who take aspirin because they assume there is a health benefit. We also see a lot of patients who are placed on aspirin and a new anticoagulant for warfarin and no one instructed them to stop taking the aspirin.”

He recommended physicians consider the long-term effects of anticoagulation therapy and be aware of increased bleeding risk with age. Alternative approaches such as novel oral anticoagulants may diminish dementia risks, although he cautioned that needed to be tested in a clinical trial.