FRIDAY, Oct. 15 (HealthDay News) -- People with fibromyalgia are 11 times more likely to have restless legs syndrome (RLS) than those in the general population, according to a new study.

Fibromyalgia is a condition that can cause significant pain and fatigue. Women account for 80 to 90 percent of patients diagnosed with fibromyalgia. Its cause is unknown.

The findings suggest that treating RLS -- which is characterized by an unpleasant urge to move the legs, usually at night -- may improve sleep and quality of life for people with fibromyalgia, the researchers said. RLS is often treated with drugs such as pramipexole or ropinirole.

In this study, U.S. researchers compared 172 fibromyalgia patients, average age 50, with a control group of 63 healthy people, average age 41. The prevalence of RLS was about 10 times higher in the fibromyalgia group (93 percent of whom were female) than in the control group -- 33 percent vs. 3.1 percent. After accounting for factors such as age, gender and ethnicity, the researchers calculated that fibromyalgia patients were 11 times more likely to have RLS.

As expected, major sleep problems were more common among the fibromyalgia patients, said the researchers.

"Sleep disruption is common in fibromyalgia, and often difficult to treat. It is apparent from our study that a substantial portion of sleep disruption in fibromyalgia is due to restless legs syndrome," contributing author Dr. Nathaniel F. Watson, an associate professor of neurology at the University of Washington in Seattle, said in an American Academy of Sleep Medicine news release.

The study appears Oct. 15 in the Journal of Clinical Sleep Medicine.

More information

The American College of Rheumatology has more about fibromyalgia.