Many Americans are currently on a drug that could significantly raise their risk of getting dementia, an alarming new study has found.

The blood-thinning drug warfarin has been used ot prevent potentially life-threatening blood clots for many years, and many Americans have come to depend on it, but a study finds that it could also raise the risk of dementia, according to a Intermountain Medical Center statement.

Atrial fibrillation is a fairly common condition, especially with an aging population. An estimated 20 million Americans are currently taking warfarin.

Scientists examined data from more than 10,000 patients to see if there was a link between warfarin, dementia, and atrial fibrillation. All participants in the study were using warfarin over a long period of time, and none had a history of dementia. After 7 years, the research team found that dementia was much more prevalent in the group that had atrial fibrillation than those who did not, and by a wide margin — 5.8 percent to 1.6 percent.

“Our study results are the first to show that there are significant cognitive risk factors for patients treated with warfarin over a long period of time regardless of the indication for anticoagulation,” lead author T. Jared Bunch, MD, director of heart rhythm research at Intermountain Medical Center Heart Institute and medical director for heart rhythm services for the Intermountain Healthcare system, said in the statement, adding that the study was important for  a number of reasons. “First, as physicians we have to understand that although we need to use anticoagulants for many reasons including to prevent stroke in AF patients, at that same time there are risks that need to be considered some of which we are only right now beginning to understand. In this regard, only those that absolutely need blood thinners should be placed on them long-term. Second, other medications like aspirin that may increase the blood thinners effect should be avoided unless there is a specific medical need. Finally, in people that are on warfarin in which the levels are erratic or difficult to control, switching to newer agents that are more predictable may lower risk.”