April 16, 2008 / 9:37 PM / in 10 years

Sleep disorder may precede Parkinson's disease

NEW YORK (Reuters Health) - Individuals who exhibit behaviors related to the loss of normal eye movements associated with rapid eye movement (REM) sleep are at increased risk of Parkinson’s disease and mild dementia, a Mayo Clinic researcher reported at the 60th annual meeting of the American Academy of Neurology, being held this week in Chicago.

The findings come from a series of studies conducted by Dr. Bradley Boeve and colleagues involving 765 residents of Olmstead County who were between the ages of 70 and 89. The subjects were assessed for anxiety, depression, apathy and probable REM sleep behavior disorders based on a series of questionnaires.

REM is the sleep phase in which dreams occur. Periods of REM are variable in length, but normally represent about 20 percent of a typical night’s sleep. Interruption or lack of REM sleep can cause a variety of symptoms such as frequent nocturnal wakening, daytime sleepiness, and restless movement.

The overall prevalence of REM sleep behavior disorders in this population was 8.0 percent. “These are ostensibly cognitively normal older people in the community” and a prevalence of 8.0 percent is high, Boeve told Reuters Health, “especially if it is a risk factor for dementia.”

There was a significant relationship between REM sleep behavior disorders and anxiety and apathy, but no significant link was found between REM sleep behavior disorders and depression.

“We see some nice supporting data of an ascending disease,” Boeve noted.

“REM sleep behavior disorders appear to start at the south end of the brain stem and appear to ascend,” he explained. “The next site higher in the brain stem is the emotions, and this component of the syndrome appears to come later, after there has been a history of violent nightmares. Next is the motor movement center, and the highest is the cerebral cortex and cognitive defects.”

Boeve pointed out that REM sleep behavior disorders appear to be associated with Parkinson’s disease and dementia.

Some patients will respond to treatment with levodopa, he said. Clonazepam can also be effective for a large number of patients and over-the-counter melatonin works about half of the time. “Patients still dream, but they have fewer violent nightmares.”

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