Child sleeping restlessly

PhD graduate and co-chair of World Sleep Day, Lourdes DelRosso, describes a new sleep disorder

  • 17 March 2022
  • 3 min read

Sleep is an important contributor to health. During the last decades, research has demonstrated that insufficient sleep can adversely affect blood pressure, hormone levels, response to infection, and metabolism, among other health aspects.

Recently, sleep has been implicated in memory, mood, and healthy decision making. This year, World Sleep Day emphasises the importance of sleep for good mental health with the slogan “Quality sleep, sound mind, happy world.”

The 3 dimensions of sleep quality

But the question immediately arises: what constitutes quality sleep? The World Sleep Society defines three elements of sleep quality: duration, continuity, and depth. 

For many years we have known that sleep duration is important, and that insufficient sleep adversely affects us. Unfortunately, we are all familiar with the news headlines highlighting an accident caused by a sleepy driver. We are also somewhat familiar with the concept of sleep depth. We know that when we wake up with the minimal noise or disturbance we must not be in a deep stage of sleep and therefore not achieving an adequate sleep. But the concept of sleep continuity is somewhat obscure. 

Restless sleep as sleep disrupter 

In simple terms, sleep continuity refers to sleep that is solid through the night. When we go to sleep at 10.00pm and wake up at 7.00am without waking up through the night, we can say that sleep was solid. But was it?

Sleep experts use methods to study sleep disorders and sleep continuity in the laboratory. The most accurate method, called polysomnography (poly=many, somno=sleep, graphy=graphs) provides information on the brain waves during sleep and can assess accurately whether a person has brief nocturnal awakenings even if not remembered in the morning. 

RSD in PSG

Polysomnographic image taken during a sleep study. All lines represent sleep sensors, and in the centre you see movement that shows disrupted sleep.

The concept of sleep continuity assessment in polysomnography is the basis for my research. For the past 5 years, I saw in my medical practice, children that despite sleeping an adequate amount of time for their age and with good sleep depth, were having daytime symptoms of fatigue, difficulty concentrating, or not able to pay attention in school. The parents noticed that the children moved constantly through the night. In fact, one parent once told me “It is impossible my child is getting good sleep quality moving like a helicopter at night.” 

With the help of experts in sleep movement disorders I put together the first study on children with what we called “restless sleep disorder” or RSD. We found that children with RSD moved more than children without it and moved more through the night than children with another common sleep movement disorder “restless legs syndrome” or RLS. In fact, the group of children with RSD moved at least 5 times per hour of sleep. In our sleep laboratory, 7.7% of children referred with a sleep complaint, had the diagnosis of RSD.

Movements at night histogram

Histogram representing hourly night distribution of all movements collected from the RSD group during sleep.

Iron supplementation can improve sleep quality

What causes children to move so much during their sleep? We found out that iron levels were low in all children diagnosed with RSD. 

Iron is an important mineral that is needed for adequate production of oxygen carrying cells in our blood as well as in the production of substances in our brain called “neurotransmitters.” These neurotransmitters have various roles, but one of them is control and regulation of movement. It was the logical first step to supplement iron in our children diagnosed with RSD. Most of the children experienced improvement in daytime symptoms and sleep quality after iron supplementation, particularly sleep seemed more restful, there were less nocturnal movements, more energy, attention and better mood during the day.

After 12 peer reviewed publications on the characteristics and treatment of RSD, the international sleep medicine community has recognized RSD as a new paediatric sleep disorder. The prompt recognition of RSD in children and identification of iron deficiency, will lead to prompt treatment, improving sleep quality, providing a sound mind during the day, and contributing to a happy world. 


Lourdes DelRosso's PhD thesis is titled “Restless Sleep Disorder: A new sleep disorder in children”. She is co-chair of World Sleep Day and the World Sleep Society.