Restless legs syndrome affects nearly 2 percent of US/UK children

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"This study suggests that restless legs syndrome is common and troublesome in children and adolescents, occurring more frequently than diabetes and epilepsy," said principal investigator Daniel Picchietti, a professor of pediatrics in the University of Illinois College of Medicine and a pediatrician and sleep medicine specialist with the Carle Clinic Association and Carle Foundation Hospital in Urbana, Ill.

Restless legs syndrome (RLS) is a neurological sleep disorder characterized by sensations in the legs that create an urge to move. Symptoms are typically worse at night and during rest. RLS is closely associated with another condition, periodic limb movement disorder, in which a person's legs jerk during sleep. Some people with periodic limb movement disorder also have RLS. Others lack the sensations in the legs that typify RLS.

Most of what is known about restless legs syndrome comes from research on adults. The new analysis is the first population-based prevalence study of RLS in children, and it is the first to use specific pediatric diagnostic criteria. The research team collected detailed data from 10,523 families in the U.S. and U.K.

The new study affirmed that there is a strong genetic component to RLS, Picchietti said. More than 70 percent of the children with RLS had at least one parent with the condition. In 16 percent of the affected children, both parents had RLS symptoms.

Two recent studies - appearing in July in the New England Journal of Medicine and in Nature Genetics - found genes associated with RLS.

"Restless legs syndrome runs in families. That is one of the major points of our study, and the discovery of associated genes really supports it," Picchietti said.

Awareness of RLS in adults is increasing (depictions of - and jokes about - RLS are appearing more frequently in popular culture). It is less recognized in children, however, and parents and clinicians sometimes dismiss children's complaints about unusual sensations in their legs as nothing more than "growing pains," Picchietti said.

Many adults diagnosed with RLS report that their symptoms began in childhood. In the early 1990s, Picchietti began to notice that some children who came to his office because they had trouble sleeping or paying attention in school had symptoms of RLS. But there was scant research on the prevalence of RLS in children.

The new study included a rigorous analysis of participants' reported symptoms, and excluded those who did not meet all of the National Institutes of Health criteria for diagnosing children with RLS. A child who had periodic limb movements during sleep and no other symptoms of RLS would not be counted, for example. A child who reported leg cramps or growing pains would not be included unless he or she met all of the other diagnostic criteria for RLS.

Some parents are surprised to learn that conditions such as attention deficit hyperactivity disorder and depression appear to be more common in those diagnosed with RLS. Sleep disturbance, by itself, is known to aggravate ADHD and depression, which may explain the association, Picchietti said. But there may also be other reasons for the association.

Picchietti described the new findings as a major step forward in understanding how many children are affected by RLS. "But this is not the final answer," he said. "While some children with RLS had significant sleep disturbance and daytime symptoms, others did not. Which children would benefit from treatment and what those treatments should be are important issues to be addressed. Much more study is needed."

University of Illinois at Urbana-Champaign