Normal sleep has two distinct states: non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. NREM sleep is divided into three stages. During REM sleep, rapid eye movements occur, breathing becomes even, blood pressure rises, and there is a loss of muscle tone (paralysis). But the brain is highly active, and its electrical activity is similar to that during wakefulness. REM sleep is usually associated with dreaming. REM sleep makes up 20% to 25% of the sleep period.
In a person with REM sleep behavior disorder (RBD), the paralysis that normally happens during REM sleep is incomplete or absent, allowing the person to "act out" their dreams. RBD is marked by the acting out of dreams that are vivid, intense, and violent. Dream-enacting behaviors include talking, yelling, punching, kicking, sitting, jumping from bed, arm flailing, and grabbing. An acute form may occur during withdrawal from alcohol or sedative-hypnotic drugs.
The person may be awakened or wake spontaneously during the attack and vividly recall the dream that corresponds to the physical activity.
RBD is usually seen in middle-aged to elderly people and more often in men.
Causes of REM Sleep Disorder
The exact cause of RBD is unknown, but it may happen along with degenerative neurological conditions such as Parkinson's disease, multisystem atrophy (also known as Shy-Drager syndrome), and diffuse Lewy body dementia. In 55% of people, the cause is unknown, and in 45%, it’s linked with alcohol or sedative-hypnotic withdrawal, tricyclic antidepressant (such as imipramine), or serotonin reuptake inhibitor use (such as fluoxetine, sertraline, or paroxetine) or other types of antidepressants (mirtazapine).
RBD often happens several years before the development of these neurodegenerative diseases. In one study, 38% of people diagnosed with RBD developed Parkinson's disease within an average of 12 to 13 years after RBD symptoms began. Also, RBD is seen in 69% of those with Parkinson's disease and multisystem atrophy. The relationship between RBD and Parkinson disease is complex; not everyone with RBD will develop Parkinson's disease.
