REM sleep behavior disorder is characterized by episodes of dream-enacting vigorous motor activity (i.e. punching, kicking, or crying out) and vocalizations during REM sleep. Normally in REM sleep the skeletal muscles are paralyzed. To an external observer, the only movement the sleeping body appears to make during REM are normal breathing and fluttering of the eyes. This period of paralysis is called atonia. Contrary to some popular belief, people do not typically "act out" their dreams, at least the dreams that occur during REM (as many, but not all dreams do.)
For people with the rare parasomnia REM behavior disorder (RBD), muscle atonia does not occur. These people move their bodies during REM sleep. At their worst, these behaviors can be violent or injurious to the sleeper and may disrupt sleep continuity. This playing out - called Dream Enactment Behavior - is experienced by most people diagnosed with RBD and is a primary reason for diagnosis. Occasionally people are diagnosed only on the basis of polysomnography results.
External observers see RBD patients sleep talking, yelling, and twitching and jerking their limbs during sleep. People typically do not remember RBD episodes. Some patients have a vivid memory of dream content, and the interesting thing about these dreams is that the memory of them remains. While most dreamers can recall details immediately upon awakening but forget dreams quickly, the dreams remembered from REM behavior disorder episodes can be recalled weeks or months later.
Studies have found that in half of RBD patients the condition has no discernable underlying cause, while half have a neurological condition that may be related to the RBD. RBD can be one of the first symptoms of childhood narcolepsy.
Conditions which may be linked include subarachnoid hemorrhage, dementia, Parkinson’s disease, cerebrovascular disease, multiple sclerosis, brain stem lesions, and tumors (both benign and cancerous). A doctor may wish to order a brain MRI for a patient diagnosed with RBD. The benzodiazapine anticonvulsant Klonopin (clonazepam) is the treatment of choice for RBD. Melatonin can also be used, with the clonzepem or alone, and Parkinson's Disease drugs are also used in some cases.
One of the most potentially dangerous parasomnias, RBD can be idiopathic (no known cause) or it can be a symptom or secondary disorder to a neurodegenerative disorder. Some experts feel there is no such thing as idopathic RBD, and if a patient has this parasomnia, it indicates another problem in the brain, even if that problem hasn't been found yet. However, if this is true, it can appears that decades can pass between the first episodes of RBD and full blown neurological diseases.
A study of hundreds of idiopathic RBD patients published in the journal Neurology in 2012 concluded that head injuries, pesticide exposure, and smoking are risk factors. Animal research has indicated that the GABA-A and GABA-B systems are part of what causes skeletal muscle paralysis in REM. By blocking molecular receptors, researchers were able to produce mice that demonstrate RBD symptoms.
Some scientific evidence suggests the antidepressant SSRI drugs may aggravate RBD. They are known to affect REM sleep. But experts are not sure about the connection.
The vast majority of patients afflicted by RBD are older men, over age 45, although women and children as young as 10 years old have been diagnosed. Patients with RBD have a physiological loss of normal skeletal muscle atonia most people experience during REM sleep. Furthermore RBD has been linked to a number of other neurological conditions.
REM sleep behavior disorder predominantly affects older people, with an estimated prevalence in adults of 0.4-0.5% . In a recent comparison study of the prevalence of parasomnias among a population of patients with diagnosed sleep disorders, REM sleep behavior disorder was found to be the least common with a frequency of 4.8%. This was the percentage of people with parasomnias who happened to have RBD. The percentage of all people with RBD is under 1%.
When diagnosing this parasomnia, doctors have to be sure they are not seeing another parasomnia with some similar symptoms (confusional arousals, sleepwalking) or panic attacks, dementia, or seizures.
In a substantial proportion of cases, RBD can occur before the development of Parkinson’s disease and Lewy body dementia. The prevalence of developing a neurodegenerative disease following up to 5 years of the RDB diagnosis is between 30%-45% according to recent studies .One researcher suggested that curing REM behavior disorder could be a way to prevent development of Parkinson’s Disease.
People with RBD who know about their behavior sometimes develop hypnophobia, especially when others are around (house guests) and they fear embarrassment. Therapists often recommend barriers around the bed to prevent destructive behavior on others. Patients have been known to constrain themselves by sleeping in sleeping bags or with oven mitts on their hands.
Comprehensive scientific article on RBD - by a doctor at the Mayo Clinic
Lighter side: An academic paper published in 2007 examined sleep disburbances in Disney animated films. The authors noticed a dog in Cinderella had dream-enactment that resembled RBD and other incidences of RBD were observed in Lady and the Tramp (1955) and The Fox and the Hound (1981), and Pluto’s Judgment Day (1935). The authors conclude "Disney screenwriters were astute observers of sleep and its disorders."