17 mars 2023
To what extent do sleep disorders announce a risk of developing Alzheimer’s disease? To find out, researchers are observing REM sleep in the elderly… as well as the presence of neurotoxic deposits. Close-up on their discoveries, on the occasion of the International Day of Sleep organized on March 17.
Before the first signs of Alzheimer’s disease are expressed, many patients report sleep disturbances. Thus, difficulty falling asleep, phases of insomnia or episodes of recurring nightmares can increase before dementia occurs.
These sleep disorders are they caused by the very first stages of the disease, or are they on the contrary a risk factor, which promotes neurodegeneration? ». Et « is there a link between sleep disorders and the presence of neurotoxic deposits characteristic of Alzheimer’s disease? “: researchers from the GIP Cyceron in Caen asked themselves these questions in their study, published in January in the journal Annals of Neurology.
Early detection of affected neurons
To answer this, they scanned the brains of elderly people without cognitive impairment, during the paradoxical sleep phase, characterized by the occurrence of dreams. To detect the presence of deposits of amyloid plaques, significant of the onset of Alzheimer’s, the scientists also carried out imaging examinations (PET scan and MRI). The opportunity, moreover, assess their brain structure and functioning “, describes the team of Dr Géraldine Rauchs*, at the origin of this study.
Main interest of the study of paradoxical sleep: this phase ” involves neurons (…) early affected in Alzheimer’s disease, cholinergic-type neurons ». Et « changes in REM sleep are observed in the early stages of the disease, before those affecting slow-wave sleep », continues Dr. Rauchs.
Until now, the work carried out concerned precisely the study of slow-wave sleep, ” because it corresponds to an intense recovery period, and because it is during this period that the toxic waste produced by our neurons would be eliminated “. Observations that have also confirmed the link between “ accumulation of amyloid proteins and slow-moving sleep disorders ».
The power of brain waves for proof
What did the researchers learn from these observations? First point : ” the power of the cerebral waves which characterize paradoxical sleep, the theta waves, is all the weaker as the amyloid deposits in the cortex are numerous. A correlation completely absent during observations carried out in the slow phases of sleep. What to reinforce therefore “ the hypothesis of a link between early changes in REM sleep and the risk of progression to dementiae “emphasizes the researcher.
And following ?
To be sure of this, the teams will have to study in the same volunteers the evolution of sleep disorders, cognitive disorders and amyloid aggregation over time “. And in a second step open the search to people in ” good cognitive health, but also with volunteers who suffer from cognitive disorders of varying severity ».
To finish, « identification of sleep disorders might make it possible to identify people at risk and offer them preventive approaches », concludes Dr. Rauchs.
* Researcher within the team Neuropresagein the Physiopathology and Imaging of Neurological Diseases Unit (unit 1237 Inserm/University of Caen-Normandy) at the GIP Cyceron, in Caen
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Source : Inserm, March 9, 2023 – Annals of Neurology, January 15, 2023
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Written by : Laura Bourgault – Edited by: Emmanuel Ducreuzet
