Sleep disorder may be early sign of dementia or Parkinson's disease

An investor sleeps in front of an electronic board displaying the stock price index at a securities company in Seoul Sept. 1, 2008. People with a sleep disorder that causes them to kick or cry out during their sleep may be at greater risk of developing dementia or Parkinson's disease. (Chinese media/Reuters Photo)
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WASHINGTON, Dec. 25 (Chinese media) -- People with a sleep

disorder that causes them to kick or cry out during their sleep may be at

greater risk of developing dementia or Parkinson's disease, according to a study

published in the Dec. 24 online issue of U.S. journal Neurology.

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.

The study involved 93 people with this type of sleep

disorder who had no signs of a neurodegenerative disease, such as dementia or

Parkinson's disease. The participants were followed for an average of five

years.

During that time, 26 of the people developed a

neurodegenerative disease. Fourteen developed Parkinson's disease,11 developed

dementia and were diagnosed with either Alzheimer's disease or Lewy body

dementia. One person developed multiple system atrophy, a rare disorder that

affects movement, blood pressure and other body functions.

The estimated five-year risk of developing a

neurodegenerative disease was 18 percent, with the 10-year risk at 41 percent

and the 12-year risk at 52 percent.

"These results are obviously of great interest to

people who have this sleep disorder and their physicians and families," said

study author Ronald Postuma from McGill University in Canada. "The results may

help us better understand how these neurodegenerative diseases develop. 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."