Busy nights

In some cases, nocturnal movements can herald Parkinson's disease, which can occur years later. When should you be concerned, and who should you consult? Valérie Cochen de Cock, researcher at the Euromov laboratory1 laboratory and neurologist at the sleep unit at the Clinique Beau Soleil.

While our days may be hectic, our sleep is supposed to be motionless. " When we sleep, we don't normally move," explains Valérie Cochen de Cock, a researcher at the Euromov laboratory. So why do we sometimes have the sensation of moving in our sleep? " In reality, these movements normally occur during the micro-awakening phases that punctuate sleep", explains the neurologist. Sleep may appear uniform, but it actually has many facets. "A cycle is made up of different stages that follow one another, cycles that are repeated throughout the night and are often interspersed with micro-awakenings, unconscious because too brief, or more prolonged awakenings that we can memorize." In particular, there are two important stages: slow wave sleep, which is first light and then deep, and which predominates at the start of the night, and REM sleep, which predominates at the end of the night. " It corresponds to a period during which brain activity is close to that of the waking phase, which is when we dream," explains Dr. Cochen De Cock, who sees his patients in a unit specialized in the treatment of sleep disorders at the Beau Soleil clinic.


And for some people, nights are not a smooth ride: they move around and display abnormal motor behaviors, known as parasomnias. Some of these disturbances occur during deep slow-wave sleep. These include sleepwalking, confusional arousals and night terrors. " These manifestations are quite frequent in children and tend to disappear in adults", explains the specialist.

But parasomnias can also occur during REM sleep phases, "in which case we speak of REM sleep behavior disorders," stresses the researcher. Normally, a latch system in the brainstem causes muscular atonia which prevents us from moving; it's as if we were paralyzed, but in these patients this latch malfunctions". A disorder that takes a form that is, to say the least, surprising. "Our typical patient is a man over the age of 50 who comes in for a consultation, telling us that his wife complains that he is violent with her while she is asleep." Sleepers who kick, scream, and may even go so far as to attempt to strangle their bed partner. "When we question the person, we find a dream story that explains the behavior: the sleeper dreams that his partner is being assaulted and that he defends her by attacking their assailant, when in reality it is she who is actually receiving the blows."

Parkinson's disease

These are stories that might make you smile, if they weren't harbingers of more worrying neurological disorders. " 80% of patients with REM sleep behavior disorders will develop Parkinson's disease within the next 10 years," explains Valérie Cochen de Cock.

Why does this sleep disorder precede the appearance of the first symptoms of this neurological disease? " During Parkinson's disease, a protein called alpha-synuclein aggregates, causing deposits called Lewy bodies", answers the neurologist. By analyzing the brains of deceased Parkinson's patients, scientists have discovered that the deposits build up progressively, starting in the brain stem, which is located in the lower part of the brain. "This is precisely the region responsible for atonia during sleep, our famous latch. This is why REM sleep movements are a sign that precedes the clinical manifestation of the disease by several years."


The neurologist invites sleepers who recognize themselves in this picture to consult a specialized service. There's nothing to be alarmed about," she says. "These nocturnal disorders can also be the manifestation of sleep apnea, which will mainly affect snoring and overweight patients. But in any case, it's always important to be able to make a diagnosis at an early stage, to ensure the best possible treatment." In the event of a diagnosis of REM sleep behaviour disorder, patients will be closely monitored to better identify the possible onset of Parkinson's disease. And perhaps prevent its onset. "For the moment, there is no preventive treatment, but studies show that physical activity is effective in slowing the onset of the disease."

The specialist, who is part of a group of around 100 researchers working on REM sleep behavior disorder, is taking part in a major national study to characterize sleep disorders in Parkinson's disease, due to start in September 2023. " If your partner complains of violent gestures while you sleep, or if you injure yourself at night by banging your head against a wall or falling out of bed, it's important to seek help," insists Valérie Cochen de Cock.

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  1. Euromov (UM, IMT Mines Ales)