For most people,dreamingis purely a “mental” activity: dreams occur in the mind while the body is at rest.But people who suffer from REM sleep behavior disorder (RBD) act out their dreams.They physically move limbs or even get up and engage in activities associated with waking. Some engage insleep talking,shouting, screaming, hittting or punching. Some even fly out of bed while sleeping! RBD is usually noticed when it causes danger to the sleeping person, their bed partner, or others they encounter. Sometimes ill effects such as injury to self or bed partner sustained while asleep trigger a diagnosis of RBD. The good news is that RBD can usually be treated successfully.
What we call “sleep” involves transitions between three different states: wakefulness, rapid eye movement (REM) sleep, which is associated with dreaming, and non rapid eye movement (N-REM) sleep. There are a variety of characteristics that define each state, but to understand REM sleep behavior disorder it is important to know that it occurs during REM sleep. During this state, the electrical activity of the brain, as recorded by an electroencephalogram, looks similar to the electrical activity that occurs during waking. Although neurons in the brain during REM sleep are functioning much as they do during waking, REM sleep is also characterized by temporary muscle paralysis.
In some sleep disorders such asnarcolepsyandparasomnias, like REM sleep behavior disorder, the distinctions between these different states breaks down; characteristics of one state carry over or “invade” the others. Sleep researchers believe thatneurological “barriers”that separate the states don’t function properly, though the cause of such occurrences is not entirely understood.
Thus, for most people, even when they are havingvivid dreamsin which they imagine they are active, their bodies are still. But, persons with RBD lack this muscle paralysis, which permits them to act out dramatic and/or violent dreams during the REM stage of sleep. Sometimes they begin by talking, twitching and jerking during dreaming for years before they fully act out their REM dreams.
In the course of “acting out their dreams,” people with RBD move their arms and legs in bed or talk in their sleep, or they might startsleepwalkingwithout waking or realizing they’re dreaming. The only sensations the sleeper experiences are what is occurring in their dream. And many of these dreams can be violent or frightening, causing injury to the sleeper and his bed partner.
Causes and Diagnosis
Studies of animals may explain REM sleep behavior disorder. Animals who have suffered lesions in the brain stem have exhibited symptoms similar to RBD. Cats with lesions affecting the part of the brain stem that involves the inhibition of locomotor activity will have motor activity during REM sleep: they will arch their backs, hiss and bare their teeth for no reason, while their brain waves register normal REM sleep.
REM behavior disorder underscores the importance of basic science research in animals,” says Mahowald, “because without the information obtained in basic science animal research, the disorder could never have been identified. Sleep is such a young field that we have the opportunity to take advantage of the fact that there is a close collaboration between basic science and clinicians.”
Diagnosis of REM Sleep Behavior Disorder
Because a number of parasomnias may be confused with RBD, it is necessary to conduct formal sleep studies performed at sleep centers that areexperienced in evaluating parasomniasin order to establish a diagnosis. In RBD, a single night of extensive monitoring of sleep, brain, and muscle activity will almost always reveal the lack of muscle paralysis during REM sleep, and it will also eliminate other causes of parasomnias.
The first series of cases of REM sleep behavior disorder was described in 1985 by Mark Mahowald, MD, and Carlos Schenck, MD, of the University of Minnesota. In Principles and Practice of Sleep Medicine (W.B. Saunders Company, 2000), they outlined several case histories of people with RBD:
A 77-year old minister had been behaving violently in his sleep for 20 years, sometimes even injuring his wife.
A 60-year old surgeon would jump out of bed during nightmares of being attacked by “criminals, terrorists and monsters.”
A 62-year old industrial plant manager who was a war veteran dreamt of being attacked by enemy soldiers and fights back in his sleep, sometimes injuring himself.
A 57-year old retired school principal was inadvertently punching and kicking his wife for two years during vivid nightmares of protecting himself and family from aggressive people and snakes.
“Past history and current neurological and psychiatric evaluations were unremarkable, apart from the findings reported,” the authors noted. “All four men were known by day to be calm and friendly individuals.”
Drs. Mahowald and Schenck and others have found that more than 90% of RBD patients are male, and that the disorder usually strikes after the age of 50, although some patients are as young as nine years old. Most RBD patients are placid and good-natured when awake; however, many of them display rhythmic movements in their legs during non-REM and slow-wave sleep.
A telephone survey of more than 4,900 individuals between the ages of 15 and 100 indicated that about two percent of those surveyed experience violent behaviors during sleep; Mahowald and Schenck estimate that one-quarter of them were probably due to RBD, which means it may be experienced by 0.5% of the population.