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A black-and-white image of a sleeping research participant punching the air.

A sleeping patient throws a punch while dreaming he is fighting off an attacker. His behavior was the first documented case of REM Sleep Behavior Disorder.

The sleep link

Exploring the connection between a sleep disorder and neurodegenerative diseases

By Nicole Christiansen

From eNews, May 19, 2005

For Mark Mahowald and Carlos Schenck, working at the Minnesota Regional Sleep Disorders Center in the Hennepin County Medical Center is no snooze. The two medical doctors have been researching sleep disorders together since 1982, and they've always had plenty to discover. Recently, they've found that a rare sleep disorder in which people act out their dreams is strongly linked to Parkinson's disease. When a patient came into their clinic in the mid-1980s complaining of "violent moving nightmares," the doctors watched him sleep and observed him kicking and punching in bed. The man had dreamed he was fighting off an attacker. Schenck, an associate professor of psychiatry at the University and a senior researcher at the sleep center, noticed that the patient's violent behavior was happening during periods of rapid eye movement sleep (REM), a stage in which the mind shows an electrical activity pattern similar to being awake but the body normally is paralyzed. Suddenly, a subject that at first seemed a curiosity became "extraordinarily interesting," says Mahowald, director of the sleep center and a neurology professor at the University. What they also discovered was that the disorder, REM Sleep Behavior Disorder or RBD, was an early warning sign of a serious neurodegenerative disease for most patients. In the 20 years of studying RBD, Mahowald and Schenck have found that 70 percent of otherwise healthy patients with the sleep disorder have gone on to develop Parkinson's disease or a related disease--usually within 10 to 15 years of RBD's onset. Schenck and Mahowald documented the first human cases of RBD in a 1986 report that explained the basics of the disorder. While most people are paralyzed during the REM sleep cycle, people with RBD are not. So instead of lying still, people with RBD often act out their dreams, thrashing, yelling, running out of bed, and sometimes hurting others around them. They might get out of bed and move around, but the only sensations they feel are those occurring in their dreams.

While 70 percent of people with the sleep disorder develop a Parkinsonian disease, only 25 percent of those with Parkinson's disease have REM Sleep Behavior Disorder.

It's a little like sleepwalking. Sleepwalkers, however, walk around in non-REM sleep and are hard to wake up, says Mahowald. When they do awaken, they're confused and disoriented. People with RBD are immediately alert after being awakened and often can give detailed accounts of what they were dreaming. One patient remembered dreaming he was a running back heading for a touchdown. He had gotten out of bed and ran hard into his bedroom dresser. Another patient dreamed he was about to break a suffering deer's neck, but in reality he nearly broke his wife's neck. RBD is a nonpsychiatric disorder that affects mostly older men. More than 90 percent of RBD patients are male, and the disorder usually becomes apparent after age 50, although some patients have been as young as 9. People with RBD may act out violent dreams when they're asleep, but most are good-natured when they're awake. The underlying abnormality is not known. Antidepressants such as Prozac, Zoloft, and Effexor can induce or aggravate RBD in some people. The connection between RBD and neurodegenerative diseases is equally cloudy. While 70 percent of people with the sleep disorder develop a Parkinsonian disease, only 25 percent of those with Parkinson's disease have RBD. An average of 13 years pass between development of the sleep problem and development of the Parkinsonian disease. The good news for RBD patients is that the sleep disorder is easily diagnosed and easily treated. An anticonvulsant medication suppresses RBD behaviors in 90 percent of patients. For the majority of RBD patients who will eventually develop Parkinson's, the bad news is that there's currently no drug to stop the progression of the disease. There's still much to learn about the connection between the sleep disorder and neurodegenerative diseases. The early appearance of RBD in Parkinson's will be valuable when researchers develop medications that alter the disease's progression, Mahowald says. He believes that what researchers discover about Parkinson's in the next 10 years with new technologies will be greater than everything they've learned up to this point. "It's going to blow the lid off what we know," he says.