Long-term use of the anti-clotting drug warfarin (Coumadin) and an antiplatelet medication, such as aspirin or clopidogrel (Plavix), may raise the risk of dementia in people with atrial fibrillation (AF). A study presented at the American Heart Association Scientific Sessions suggests that the threat may be due to abnormal effects on blood circulation in the brain caused by improper warfarin dosing. Patients who take warfarin to prevent blood clot formation must undergo frequent testing to make sure the medication isnt making their blood clot too quickly or too slowly. Researchers say that its not uncommon for warfarin patients to be outside the ideal clotting range as much as 40 percent of the time. They also suggest that over the years, the cumulative effects of that unhealthy circulation could lead to dementia. One contributing factor could be overmedication caused by a combination of warfarin and antiplatelet therapy. If you have AF and youre taking warfarin and antiplatelet medications, talk with your doctor about whether you could reduce your medication intake.