Individuals with a deep-sleep disorder are more likely to develop neurodegenerative diseases such as Parkinson's or dementia, a new Canadian study reports.

The study, by Dr. Ronald Postuma from the Research Institute of the McGill University Health Centre and Dr. Jacques Montplaisir from the University of Montreal, suggests 52.4 per cent of patients with rapid eye movement (REM) sleep disorder will develop a neurodegenerative disease within 12 years of the initial diagnosis.

The researchers followed all the sleep-disorder patients at Montreal's Hôpital du Sacré Coeur who had been diagnosed with the disorder.

Of 93 patients studied, 26 developed a neurodegenerative disorder, including:

• Fourteen with Parkinson's.
• Seven with Lewy body dementia, a common cause of dementia among the elderly.
• Four with clinical dementia.
• One with multiple system atrophy, which affects movement, blood pressure and other body functions.

"The estimated five-year risk of neurodegenerative disease was 17.7 per cent, the 10-year risk was 40.6 per cent and the 12-year risk was 52.4," the reseatchers said in an abstract of their paper published online.

"These results establish a clear link and indicate that these sleep disorders could be a predictor of neurodegenerative disease," Postuma said in a news release.

The participants averaged 65.4 years old, and four out of five were men.

During REM sleep, also known as the dream stage of sleep, the muscles don't relax, as happens normally. Instead, those with the disorder may punch, kick and cry out.

Preliminary U.S. estimates suggest one of every 200 people may suffer from the disorder.

Postuma said the study involved only people with no known cause for the problem.

The study, supported by grants from the Canadian Institutes of Health Research and the Fonds de la recherche en santé du Québec was published Wednesday in Neurology, the journal of the American Academy of Neurology.