Long-term overtreatment with the anti-clotting drug warfarin, combined with antiplatelet therapy with aspirin or clopidigrel (Plavix) to prevent stroke, may raise the risk of dementia in people with atrial fibrillation.
The research was presented at the American Heart Association’s Scientific Sessions 2014, MedicalXpress reports.Atrial fibrillation, a common heart rhythm abnormality, raises the risk of stroke and all common forms of dementia. The mechanisms behind the association of the condition and dementia are unknown. “The dual drug regimen is often used to prevent strokes in people with coronary artery disease or peripheral vascular disease, but we have to consider that long-term exposure to anti-clotting drugs such as warfarin, if not well controlled, can significantly increase bleeding risk,” said Dr. T. Jared Bunch, lead author of the study. Bunch is director of electrophysiology at the Intermountain Medical Center Heart Institute in Murray, Utah. The combination drug therapy may result in “micro bleeds in the brain that don’t cause symptoms right away, but accumulate over time raising the risk of dementia,” according to MedicalXpress.
The research team studied 1,031 patients with no previous history of stroke or dementia for up to 10 years while they were on the drug combination, according to MedicalXpress. After adjusting for traditional stroke and bleeding risk factors, patients who had abnormally slow blood clotting times—International Normalized Ratio (INR) measurement above 3—on 25 percent or more of their monitoring tests were more than twice as likely to be diagnosed with dementia than patients whose tests showed overtreatment less than 10 percent of the time. Patients who had abnormally slow clotting times were considered to be receiving too much medication.
The researchers concluded that brain injury from both small bleeds and clots was important in the development of dementia in atrial fibrillation patients, MedicalXpress reports. “Even at skilled centers, it’s very common to have INR outside the ideal range up to 40 percent of the time, and over the years there may be an accumulative negative impact on cognitive ability,” Bunch said.
Since most of the patients in the study were Caucasian, the researchers are not sure their results would apply to other ethnic groups.