People with irregular heartbeat, also known as atrial fibrillation, should take blood thinners to prevent stroke, according to an updated guideline from the American Academy of Neurology. About one in 20 people with untreated atrial fibrillation will likely have a stroke in the next year.

The uneven heart rhythm of atrial fibrillation allows blood to remain in the heart’s upper chambers. Blood can form clots within the atria of the heart and travel to the brain, a major risk factor for stroke. Atrial fibrillation, which affects about 2.7 million Americans, also can lead to heart failure and other heart-related complications.

“The American Heart Association applauds the American Academy of Neurology’s new guidelines addressing the important clinical problem of atrial fibrillation and the attendant risk of stroke,” said AHA President Mariell Jessup, M.D., professor of medicine at the University of Pennsylvania School of Medicine and medical director of Penn’s Heart and Vascular Center. “These guidelines detail the potential benefit of anticoagulants to reduce the risk of stroke, contributing to our goal of making stroke largely preventable.”

While oral anticoagulants (blood thinners) are highly effective in preventing stroke, they also carry a risk of bleeding. There are currently no approved treatments to reverse the bleeding in the newer anticoagulants, but they’re under development, according to the AHA.