The sleep disorder is called REM sleep behavior disorder. People with the disorder do not have the normal lack of muscle tone that occurs during REM sleep, often known as the dream stage of sleep. Instead, they have excessive muscle activity such as punching, kicking, or crying out, essentially acting out their dreams.

REM sleep behavior disorder appears to be a predictor of neurodegenerative disease in more than 50 percent of cases.

According to the latest study by Dr. Ronald Postuma from the Research Institute of the MUHC and Dr. Jacques Montplaisir from the Université de Montréal and the Hôpital du Sacré-Cœur de Montréal, 52.4 per cent of patients with REM sleep behaviour disorder develop a neurodegenerative disease within 12 years following their initial diagnosis.

These results were published on December 24, 2008 in the journal Neurology.

High risk of neurodegenerative disease

The study showed that the chance a patient suffering from an REM sleep behaviour disorder will develop a neurodegenerative disease is 17.7 per cent within five years of diagnosis, 40.6 per cent within 10 years, and 52.4 per cent within 12 years. "These results establish a clear link and indicate that these sleep disorders could be a predictor of neurodegenerative disease," explained Dr. Postuma.

The 93 patients who participated in this study were recruited and assessed at the Hôpital du Sacré-Coeur de Montréal by Dr Jacques Montplaisir.

Impact on future research

"Doctors should pay close attention when following these patients, as their observations could help define the precursors of diseases such as Parkinson's, Alzheimer's, Lewy body dementia, or multiple system atrophy," stated Dr. Montplaisir, principal investigator of the study. Currently, it is difficult to diagnose these diseases with certainty before an advanced stage, as doctors lack data on warning signs. Understanding how to detect these diseases early would be of great value to clinical practice.

Although effective treatments against REM sleep behaviour disorder do exist, these medications do not postpone the onset of neurodegenerative disease. As research is very active in this field, these patients could represent a viable target population in the relatively near future to test the effectiveness of new innovative treatments to fight neuronal degeneration.

A rare pathology

REM sleep behaviour disorder affects a small percentage of the population. It is characterized by a loss of the normal muscle relaxation while dreaming and is seen most often in men fifty and older. This is a specific pathology that should not be confused with insomnia, night terrors, or confusional arousals.

This study was funded by the Canadian Institutes of Health Research (CIHR) and the Fonds de la recherche en santé du Québec (FRSQ).

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