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Long-term overtreatment with warfarin raised risk for dementia
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CHICAGO — In patients with atrial fibrillation receiving antiplatelet and anticoagulant therapies, those who were overtreated with warfarin more than 25% of the time had an increased risk for dementia, researchers reported at the American Heart Association Scientific Sessions.
T. Jared Bunch, MD, and colleagues studied 1,031 patients managed by the Intermountain Healthcare Clinical Pharmacist Anticoagulation Service who were receiving warfarin for AF, who were taking antiplatelet therapy, and who had no history of dementia, stroke or transient ischemic attack. The researchers hypothesized that patients receiving antiplatelet and anticoagulant therapies would display higher rates of dementia if they were exposed to overtreatment of anticoagulation for a high percentage of the time, and that the mechanism might be exposure to chronic microbleeds resulting in repetitive cerebral injury.
T. Jared Bunch
The primary outcome was presence of dementia. Patients were followed for up to 10 years and were stratified by percent time of International Normalized Ratio (INR) above 3; the target range was 2 to 3.
Patients with an INR >3 on more than 25% of lab measurements were more likely to have valvular heart disease, renal failure, a high CHADS2 score and a prior bleed compared with patients with lower INR values. Dementia was diagnosed in 5.8% of those patients, and they remained at increased risk for dementia throughout follow-up, according to the researchers.
After multivariate adjustment, Bunch and colleagues found that patients with an INR >3 on more than 25% of lab measurements had a higher rate of dementia compared with those with an INR >3 on less than 10% of lab measurements (HR=2.4; P=.04). Overanticoagulation time was the single strongest predictor of dementia risk amongst the patients studied, according to the researchers.
“There are several take-home points from this research,” Bunch, director of electrophysiology at Intermountain Medical Center Heart Institute, Murray, Utah, told Cardiology Today.
“First, many people who are on warfarin take aspirin for reasons that are not completely clear. Some take warfarin as they feel it can benefit their heart. In these people, aspirin should be stopped, as it has the potential to harm. Next, in people who are consistently overanticoagulated who require aspirin for the presence of [CAD] or vascular disease, switching to a newer anticoagulant that has more predictable effect may lower risk. However, these newer drugs need to be studied to see if this is true. Finally, patients often live with [AF] for decades. Their risks and benefits of using anticoagulation over this long timeframe will change. Physicians need to constantly evaluate patients to determine if the potential benefits outweigh the risk for continued use of anticoagulants, and if changes in their stroke prevention approach are needed,” he said. – by Erik Swain
For more information:
Bunch TJ. Abstract #13426. Presented at: American Heart Association Scientific Sessions; Nov. 15-19, 2014; Chicago.
Disclosure: Bunch reports no relevant financial disclosures.