People with severe cases of restless leg syndrome have a greater risk of stroke, a new study finds.

It is estimated that 10 percent of Americans suffer from restless leg syndrome, (RLS) and two-to-three percent have a severe form of the neurological disorder, which is characterized by throbbing, pulling, creeping, or other unpleasant sensations in the legs and an uncontrollable, and sometimes overwhelming, urge to move them.

Pennsylvania State University researchers looked at 72,916 women enrolled in the Nurse’s Health Study. They ranged in age from 41 to 58 and had not suffered stroke when the study began. They were also not diabetic or pregnant, two factors that raise stroke risk. After six years, 161 of the women had suffered a stroke.

The investigators found that the women who had severe RLS were at increased risk of stroke.

The study was presented at Sleep 2015, the annual meeting of the Associated Professional Sleep Societies LLC.