Family history and iron deficiency appear to play important roles in childhood restless legs syndrome, according to a new study.

Restless legs syndrome (RLS) is a neurological condition that causes unpleasant sensations in the legs and an irresistible urge to move the limbs to relieve the discomfort, particularly at night. As a result, people with the condition often have sleep disturbances that make for daytime drowsiness.

Though family history and low iron stores in the body have been thought to play a role in at least some cases of restless legs syndrome, until now there has been little research on children with the disorder.

Traditionally, there’s been a tendency for pediatricians to describe children with leg discomfort as having “growing pains,” Dr. Suresh Kotagal, the lead author of the new study, told Reuters Health.

“But some may actually have restless legs,” said Kotagal, a pediatric neurologist at the Mayo Clinic in Rochester, Minnesota.

The new study, which included 32 children with RLS, is the largest of its kind to date, according to Kotagal. He and colleague Dr. Michael H. Silber report the findings in the Annals of Neurology.

The researchers evaluated the records of 538 children seen in their sleep disorders clinic between 2000 and 2004. Six percent were found to have RLS.

Of these 32 children, 72 percent had a parent with RLS, most often a mother.

In addition, blood iron levels were lower than expected among the children who were tested, according to the report. One-third of the children were near the bottom of the established norms for their age and sex, while three-quarters were in the bottom half of that range.

Iron deficiency has been found in adults with restless legs, Kotagal noted, but at a lower rate than was seen in these children. It’s unknown whether diet or a genetic predisposition to low iron is at work, he said.

Iron deficiency may contribute to RLS by way of its relationship with dopamine, a brain chemical that helps regulate movement. “Iron is a co-factor for the synthesis of dopamine in the brain,” Kotagal explained, and scientists believe that dopamine deficiency is involved in restless legs.

Medications that boost dopamine levels in the central nervous system are used as part of RLS treatment, though there is also some evidence that treating iron deficiency improves some patients’ symptoms, Kotagal noted.

It’s unclear, though, he said, whether preventing iron deficiency in children at risk of RLS due to family history can in turn prevent the syndrome from developing.

Restless legs can take a toll on a child’s quality of life and education, since the condition typically gets in the way of a good night’s sleep. Kotagal noted that research suggests some children with attention-deficit hyperactivity disorder, or ADHD, may also have restless legs syndrome - leading to the question, he said, of whether RLS-related sleep disturbances are causing those children’s attention problems.

In this study, 87 percent of the children with RLS had problems falling asleep or staying asleep.

SOURCE: Annals of Neurology, December 2004.