Rare sleep disorder may be a harbinger of dementia

NEW YORK (Reuters Health) - More than half of people with a rare sleep disorder develop a neurodegenerative disease, such as Parkinson's disease, within 12 years of being diagnosed, results of a Canadian study published Wednesday indicate.

So-called "REM sleep behavior disorder" affects a small percentage of the population, Dr. Ronald B. Postuma, at McGill University in Montreal, Quebec, and colleagues explain in the journal Neurology. It is characterized by a loss of the normal muscle relaxation while dreaming and is seen most often in men aged 50 and older. REM sleep behavior disorder should not be confused with insomnia, night terrors, or confusional arousals.

Small studies have identified REM sleep behavior disorder as a risk factor for Parkinson's disease and dementia. To investigate further, Postuma's team conducted a follow-up study of 93 patients diagnosed with unexplained REM sleep behavior disorder between 1989 and 2006. The average time from diagnosis to last evaluation was 5.2 years.

During follow-up, 14 patients developed Parkinson's disease, 7 developed dementia, 4 developed Alzheimer's disease, and 1 developed a neurodegenerative disorder called multiple system atrophy (wasting).

The study showed that the chance a patient suffering from REM sleep behavior disorder will develop a neurodegenerative disease is 17.7 percent within 5 years of diagnosis, 40.6 percent within 10 years, and 52.4 percent within 12 years.

"These results establish a clear link and indicate that these sleep disorders could be a predictor of neurodegenerative disease," Postuma commented in a press statement.

"The results may help us better understand how these neurodegenerative diseases develop," Postuma added. "They also suggest that there may be an opportunity for protecting against the progression to disease, perhaps even preventing it before the symptoms can appear."

SOURCE: Neurology, online December 24, 2008.