Restless leg syndrome is about 10 times more common in people with fibromyalgia than those without, which might be one reason people with fibromyalgia often report difficulty sleeping, according to research.

“Restless leg syndrome can be associated with a number of primary disorders, such as anemia and kidney failure. I think this study suggests we should add fibromyalgia to the potential associations of restless leg syndrome,” says Nathaniel F. Watson, MD, one of the study authors and an associate professor of neurology at the University of Washington in Seattle.

Fibromyalgia is a little understood arthritis-related condition characterized by widespread pain, fatigue, sleeping difficulties, and problems with memory or mental clarity. Restless leg syndrome is another condition doctors don’t totally understand; it causes people to want to move and stretch their legs constantly to relieve discomfort they feel deep in their thighs and calves.

In the Journal of Clinical Sleep Medicine, researchers at the University of Washington in Seattle describe their study of sleep quality in two groups. The first group consisted of 172 people, 93 percent of them women, with fibromyalgia and a mean age of 50. The control group consisted of 63 people without fibromyalgia, 56 percent of them women, with a mean age of 41. Both groups were asked a series of questions to assess their quality of sleep and level of insomnia. The results show restless leg syndrome in 33 percent of those with fibromyalgia and just 3.1 percent of those without fibromyalgia.

“I think this is likely going to be new information to many. Restless leg syndrome is somewhat of an esoteric diagnosis that many providers may not be aware of.  They may not be asking their patients the right questions to get to the right diagnosis, so it may be something people have been experiencing, but didn’t know it was a treatable disorder,” Dr. Watson says.

“We do have good treatments for it,” he adds, such as ropinirole, or Requip, and pramipexole, or Mirapex, which are approved to treat restless leg syndrome. “[Medication] can vastly improve it in some instances. It can go away completely. It just depends on the patient.”

Theodore Fields, MD, an attending physician in rheumatology at Hospital for Special Surgery in New York City, says data going back for years suggests that sleep and fibromyalgia are tightly connected. He believes restless leg syndrome could be a factor in a subset of people with fibromyalgia.

“It makes sense to me that any cause of insomnia can be related to fibromyalgia, which has been clearly shown to be related to lack of sleep. Periodic leg movements during sleep have been previously associated with fibromyalgia, and the results of this study are not unexpected,” Dr. Fields says.

He points out that the study used a self-administered questionnaire, which can be less accurate than a personal interview. He also says medications were not controlled for and researchers did not gather information on other medical issues or sleep problems, but he still believes the conclusion could be useful for patients and physicians.

“Restless leg syndrome is a condition that physicians may not routinely ask about, so this information may make it more likely they will begin to query patients about it.  Since it’s treatable, that’s an advantage for patients,” Dr. Fields says.

People with fibromyalgia who have leg discomfort that keeps them awake at night should mention it to their doctor to have it assessed and dealt with, says Dr. Watson.

“It’s reasonable to think that more continuous, longer, better quality sleep would have a positive impact on fibromyalgia, as it does on many medical disorders,” he says.