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Stanford Report, July 12, 2000

Restless legs syndrome more common than thought  

BY MITCH LESLIE

Imagine that a platoon of furry spiders is slinking up your legs and you'll get a sense of what a person with restless legs syndrome endures every night as she tries to sleep. This sleep-robbing disorder may be much more common than previously recognized, affecting nearly 30 percent of the population, Stanford researchers report.

The hallmark of restless legs syndrome (RLS) is an "itching, creeping, crawling feeling in the legs that is relieved by leg movements," said Clete Kushida, MD, PhD, director of the Stanford Center for Human Sleep Research and co-author of the study. Sometimes patients notice a burning or painful sensation, while some feel nothing but still have a powerful urge to move their legs.

RLS is more than an annoyance. It steals sleep. The frequent leg movements needed to relieve discomfort prevent sufferers from dozing off, Kushida said. To make matters worse, people with RLS often have a related problem called periodic limb movement disorder, characterized by violent contractions of the limbs during sleep. These episodes can be extreme enough to wake the sleeper. Kushida said that because sleep is "chopped up," periodic limb movement disorder contributes to daytime fatigue.

The cause of RLS is unknown, but it appears to become more common with age, Kushida said. Previous studies have indicated that the incidence of the syndrome in adults lies somewhere between 2 percent and 15 percent. But last year Kushida and colleagues reported that 368 out of 1,254 patients (nearly 30 percent) surveyed at a primary care clinic in Moscow, Idaho, showed symptoms of RLS.

However, the diagnosis of RLS came not from sleep experts but from questionnaire data collected from all the patients who visited the clinic during a one-year period. So Kushida and colleagues decided to recheck the findings with a random sample of the patients. They had 15 patients fill out further questionnaires, undergo a structured RLS interview conducted by the primary care physicians, complete a sleep log and undergo sleep monitoring for two nights while hooked up to instruments that measure the number of leg movements. After the primary care physicians made their judgment, a sleep specialist who was unaware of the doctors' decision examined each case file and made an independent diagnosis.

As the researchers told a meeting of the Associated Professional Sleep Societies in Las Vegas on June 14, the expert and the primary care physicians using questionnaires reached the same diagnosis 87 percent of the time. The current sample is up to 76 patients, with a similar agreement rate. Though the sample size is small, Kushida said that the results suggest that the questionnaires provide an accurate way for non-experts to diagnose RLS. The results support the group's previous conclusion that the syndrome may be much more prevalent than even sleep experts imagined.

Doctors and patients need more education about the symptoms and treatments of RLS, Kushida said. In most cases, dopaminergic drugs like carbidopa/levodopa and pramipexole relieve symptoms, Kushida said. Side effects of these drugs, which elevate the levels of the neurotransmitter dopamine in the brain, are rare and usually consist of nausea or upset stomach. He recommends that people with symptoms of RLS contact their primary care physician or a sleep expert.

Kushida's Stanford collaborators are professor of psychiatry William Dement, MD, PhD, director of the Stanford Sleep Disorders Research Center; and Pam Hyde, administrative director of the Center. The primary co-author of the study is Deborah Nichols, the project director in Moscow, Idaho. The other participants in the study are Richard Allen of Johns Hopkins University; Terry Young of the University of Wisconsin-Madison; Richard Simon of the Kathryn Severyns Dement Sleep Disorders Center in Walla Walla, Washington; and John Grauke, J.B. Britzmann and John Brown of the Moscow Clinic. Pharmacia and Upjohn funded the research. SR