Photo courtesy of American Stroke Association
November 16, 2014 — Long-term overtreatment with the anti-clotting drug warfarin, combined with antiplatelet therapy of aspirin or clopidigrel to prevent stroke, may raise the risk of dementia in people with atrial fibrillation, according to research presented at the American Heart Association’s Scientific Sessions 2014.
Researchers studied 1,031 patients with no previous history of stroke or dementia for up to 10 years while on the drug combination. 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. The increase is higher than what researchers found in a previous study of warfarin alone.
Patients who had abnormally slow clotting times were considered to be receiving too much medication.
Researchers previously found that atrial fibrillation patients taking warfarin were more likely to develop dementia if lab measurements of their clotting time were frequently too slow or too fast. From those results they concluded that brain injury from both small bleeds and clots was important in the development of dementia in atrial fibrillation patients.
If you’re taking warfarin and an antiplatelet drug such as aspirin or clopidgrel, check with your doctor to make sure you need one or both of the long-term antiplatelet medications, Bunch said.
Most patients in the study were Caucasian; researchers aren’t sure results would apply to other ethnic groups.
For more information: www.heart.org
November 12, 2025 
