The underlying cause of sleep problems in many children with autism could be connected to the neurological condition restless legs syndrome.
By Lisa Spear
Sleep issues, common in children with autism,1 are often written off as behavioral problems, but emerging science is unraveling a more complex picture of the root cause of insomnia in this patient population.
New research, published in the Journal of Clinical Sleep Medicine, reveals a significant connection between sleep troubles in pediatric autism patients and restless legs syndrome (RLS).2 Often diagnosed with insomnia, even when there are telltale signs of restless legs, a child might experience a delay in getting a complete diagnosis, which can in turn postpone appropriate treatment.
“It is a reminder to all of us to not necessarily take things at face value and to ask the right questions,” says Judith Owens, MD, MPH, professor of neurology and director of the Center for Pediatric Sleep Disorders at Harvard Medical School in Boston, who was not involved in the study.
“It is very common that parents will come in and one of their chief complaints is that the child is all over the bed, they are moving constantly, they are falling out of bed, and tossing and turning.” Owens encourages providers to dig deeper when they encounter these cases. “Everything that looks like ‘insomnia’ in that population could very well have an underlying, organic etiology. That is a very important message,” she says.
The retrospective research, led by scientists at Emory University in Georgia in partnership with Nox Health, found that restless legs could be the underlying cause behind bedtime resistance and motor restlessness in pediatric autism patients.
The scientists looked at data from patients’ charts from a three-year period to investigate the prevalence of RLS symptoms in children with autism spectrum disorder (ASD) and chronic insomnia.
Out of a sample of 103 children treated at a sleep clinic in Atlanta, 39% met the criteria for an RLS diagnosis. This is far more than the approximately 2% of children in the general population who have an RLS diagnosis.3 Those with a history of obstructive sleep apnea were excluded from the study.
“What we found is that a very large number of these kids coming in with insomnia fill the criteria for pediatric RLS and, unbeknownst to the parents, unbeknownst to their physicians, RLS is probably the cause,” says coauthor Jeffrey Durmer, MD, PhD, a neurologist and sleep specialist who works as the chief medical officer for Nox Health.
Data from overnight polysomnography (PSG)—available in about half of the study participants—showed that those with RLS had significantly higher rates of periodic limb movements throughout the night compared to the control group. Both leg kicking and body rocking were observed more commonly in those with RLS. The majority, 77%, had periodic limb movements during sleep, compared to none in the control group.
Since the diagnosis of RLS relies on the patient explaining the symptoms they are experiencing in their own words, many pediatric patients with autism may not receive a diagnosis because they have language or cognitive delays.
Instead of not making the diagnosis, Durmer says clinicians should have a high degree of suspicion of RLS when evaluating these patients. He encourages healthcare providers to seek out biological evidence in lieu of self-reported descriptions, to look at periodic limb movements during in-lab sleep testing, evaluate ferritin levels, family histories, and reports of bedtime resistance from parents.
When a child rocks back and forth, slaps their legs, knocks their feet against the side of a crib, or rubs at their ankles during the night, these could all be clues to an underlying nighttime movement disorder.
“When these behaviors are displayed at night they are likely misconstrued as being related to the autism. This may account for a lot of missed diagnostic opportunities,” the authors write. “Evaluation of children with ASD requires a more thorough teasing apart of bedtime behaviors, with specific probing for the presence of motor behaviors that cluster in an evening circadian pattern, as this is classic signaling for RLS.”
A sleep specialist in California at the Stanford Center for Sleep Sciences and Medicine, Mark J. Buchfuhrer, MD, who is not affiliated with the study, says he hopes this research will spread awareness about this little-known association.
“Although the link between ADHD and RLS has been well-described and known for many years, sleep and RLS physicians have had little to no knowledge of the association of RLS and ASD,” says Buchfuhrer.
Why might children with autism have a higher prevalence of RLS? Diet is one likely factor.
Many of these children are picky eaters and have extremely restricted diets, which put them at risk for iron deficiency. The pathophysiology of RLS is tied to iron deficiency and dopaminergic dysfunction.4
“It makes perfect sense that this would be a population that would be more vulnerable to these particular movement disorders,” says Boston-based pediatric sleep specialist Owens.
In the Emory study, 89% of RLS patients had low serum ferritin, indicating that their body’s iron stores were low. Many then responded favorably to oral iron treatment. Those who did not improve after iron therapy were prescribed the medication gabapentin, which is regularly prescribed off-label to control RLS symptoms in children.
“Lo and behold, the therapies provided for RLS, like iron therapy and gabapentin or a combination of the two, were remarkably effective at treating this group of kids,” says Durmer.
The study, the researchers acknowledged, did have limitations due to missing PSG data or ferritin values for a decent number of patients in the sample. This missing data also highlights the many obstacles in evaluating patients with autism for RLS, the authors note.
“Many caregivers declined testing outright because they did not think their child would tolerate the procedure, and a few studies were aborted because the child became overly agitated,” the study says. “Limited tolerance for procedures is a common issue and a real barrier in the assessment of RLS in children with ASD.”
These obstacles to diagnosis mean that it is all the more important to put in extra work to understand sleep issues in patients with autism spectrum disorder. It’s easy to assume a child with autism is having trouble falling asleep because of a behavioral issue, or due to an inappropriately early bedtime, Owens says, but clinicians should go the extra mile to investigate nighttime movement disorders.
While melatonin can be helpful in some circumstances, she encourages clinicians who treat the pediatric autism population to think beyond the “knee-jerk approach” of using melatonin before first dialing in the reasons behind a child’s sleep struggles.
She says, “In a child with autism who is not able to verbalize their symptoms, you might have to ask: What type of movements is this child displaying as they are trying to fall asleep? That’s a very important question.”
Lisa Spear is associate editor of Sleep Review.
1. Malow BA, Katz T, Reynolds AM, et al. Sleep difficulties and medications in children with autism spectrum disorders: a registry study. Pediatrics. 2016; 137(suppl 2):S98–104.
2. Kanney ML, Durmer JS, Trotti LM, Leu R. Rethinking bedtime resistance in children with autism: is restless legs syndrome to blame? J Clin Sleep Med. 2020;16(12):2029–35.
3. Picchietti D, Allen RP, Walters AS, Davidson JE, Myers A, Ferini-Strambi L. Restless legs syndrome: prevalence and impact in children and adolescents–the Peds REST study. Pediatrics. 2007 Aug;120(2):253-66. doi: 10.1542/peds.2006-2767.
4. DelRosso L, Bruni O. Treatment of pediatric restless legs syndrome. Adv Pharmacol. 2019;84:237–53.