In April, a special bed developed at ETH Zurich – the Somnomat – was used in a study with children suffering from sleep-related rhythmic movement disorder. The children came all the way from the UK as part of an international collaboration.

Except for the small red light of the 3-D camera, it is pitch-black in the sleep laboratory. Basil has no problem with that; in fact, he likes it. The 14-year-old from Somerset is often tired during the day. He has even fallen asleep in class. The reason for this is his sleep-related rhythmic movement disorder (RMD). It started when he was 18 months old. Since then, he has been rocking his body back and forth forcefully on all fours at periods during the night. His mother Denise says that it took years for him to be diagnosed and referred to a specialist at the University Hospital in Southampton. Thanks to Dr Cathy Hill, Basil is now in Zurich lying in an automated bed – the Somnomat – as a participant in a study by the ETH Sensory-Motor Systems Lab.

Study leader Rachel van Sluijs, a doctoral student of ETH Professor Robert Riener, works with Basil to determine the frequency and direction of rocking he likes best. This is easier with Basil than with the other study participants, the youngest of whom is only five years old. “First we practiced with some of our laboratory colleagues’ children, since it’s quite different to explain something to a child than to an adult,” says van Sluijs. She also got her sister, a graphic designer, on board because she needed a rating scale with smiley faces: This way also the youngest participants that could not read were able to evaluate the rocking movement of the bed.

Little research, rarely diagnosed

Cathy Hill has been working for many years with children suffering from RMD. So far, the disorder has not been studied extensively, but it is a major burden for children and parents. “I have seen children pushing their beds all over the room due to their uncontrolled movements. The body movements can really be very violent. They can harm children, not only in terms of sleep quality,” Hill explains.

When she saw a BBC report about the Somnomat on TV, she immediately thought it might be an interesting method to treat RMD and decided to contact the researchers at ETH Zurich. Initially the idea was to carry out the study with Swiss children. However, in Switzerland patients are told that symptoms disappear with age and general practitioners do not refer them to specialists. That made it difficult to recruit Swiss participants – so Hill has now come to Zurich with six of her patients from the UK.

Little sleep for the study leaders

For van Sluijs and her colleagues Quincy Rondei and Elisabeth Wilhelm, the two-week study means little sleep. Each of the children spends three consecutive nights in the sleep laboratory. First, they sleep in a normal bed to get used to their surroundings. The second and third night they spend in the Somnomat: one night with and one night without rocking movement.

Rocking in your sleep

A self-drawn evaluation table with smiley faces. (c) ETH Zürich / Stefan Schneller

During the three nights, they are under the watchful eyes of van Sluijs, Rondei and Wilhelm. As an engineer, Wilhelm is responsible for the technical aspects. She has a lot of experience from other projects. The best-known one uses the Somnomat as an anti-snoring bed, a project that is already close to becoming a product. There, however, they use a mechanical system which is already commercially available. In the current study, the bed is much more a prototype. The moving parts, which are built at ETH, are fully exposed. Dangerous in a study with children. This is why there are mats around the bed that immediately trigger an emergency stop as soon as a child gets out of bed and might touch the mechanics or a parent goes to the bed.

According to Wilhelm, the technical challenge is to make the system as quiet as possible so that it does not interfere with sleep. The bed can swing at different speeds either sideways or in the direction of the sleeping person, depending on the participants’ wishes.

Now with 3-D camera

The current study also offers researchers from the Austrian Institute for Technology (AIT) the possibility of testing a new 3-D camera procedure that registers the movements of the sleepers. The advantage: no wiring of the test participants. This is often a critical aspect in sleep studies, as it influences normal sleep behaviour. Rachel van Sluijs is optimistic that the data they collected during the study will advance the development of the Somnomat as well as research into sleep-related RMD.

Rhythmic movement disorder

Sleep-related (RMD takes different forms. Some patients move their heads violently back and forth, others go on all fours at night and hit their heads against the bed post or the wall. The disorder usually appears in children before their first birthday and should not be confused with the gentle rhythmic movements like head rolling that some children engage in when falling asleep. When parents observe the behaviour and seek medical advice, doctors usually tell them that the children grow out of this behaviour by the age of five. Whether this is really the case cannot be reliably determined, since there are no large studies with significant numbers of people affected. Standardised treatment options do not yet exist; trial and error is the only option. Some children find it helpful to sleep in a hammock, while others respond to medication supplements such as melatonin.

Source: ETH Zurich