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You've probably heard the terms "REM sleep" and "non-REM sleep." REM stands for Rapid Eye Movement, and REM sleep is the state of sleep where your eyeballs move, while non-REM sleep is the state of sleep where your eyeballs do not move.
In normal sleep, you first enter non-REM sleep, then transition to REM sleep, and these cycles alternate. It is said that dreams occur about 80% of the time during REM sleep, and the content is often narrative and concrete. The dreams you remember when you wake up are those you had at the very end of REM sleep, just before waking. On the other hand, dreams seen during non-REM sleep are said to be vague.
The "REM sleep behavior disorder (RBD)" we are introducing today is a sleep disorder, one of the parasomnias, where the body moves in conjunction with dreams during REM sleep.
Overview of REM Sleep Behavior Disorder
Normally, during sleep, muscles relax and become immobile. During REM sleep, the motor nerve itself is active, but a function that inhibits nerve transmission in the motor system is at work, causing muscles to relax and become immobile. REM sleep behavior disorder occurs when this inhibitory function malfunctions, causing the body to move in response to dreams.
Actions can range from talking in one's sleep or slight movements of the limbs, to screaming, hitting or kicking nearby objects or people, or even sitting up, walking, or running. These are involuntary movements, unrelated to one's will.
Specific Symptoms of REM Sleep Behavior Disorder
So, what exactly happens?
For example, if you dream of playing basketball, you might shoot a ball while asleep. If you dream of being chased, you might run away. If you dream of boxing, you might punch. You might even hit the person sleeping next to you and cause injury.
Generally, these dreams are said to be nightmares accompanied by feelings of fear or discomfort. These abnormal behaviors are often brief, lasting only a few minutes. While these abnormal behaviors are more common in the latter half of sleep, they can occur at any time.
This situation can easily be mistaken for "delirium" (a psychiatric functional disorder characterized by impaired attention and cognitive ability, disorientation, impaired consciousness, hallucinations, etc.), but it differs in that if someone stimulates the person and wakes them up when symptoms appear, they wake up immediately and can recall the content of their dream.
In any case, the abnormal behaviors in REM sleep behavior disorder can harm not only the individual but also their bed partner, so early diagnosis and treatment are necessary.
Causes of REM Sleep Behavior Disorder
REM sleep behavior disorder is classified into "idiopathic REM sleep behavior disorder," where the cause is unknown, and "symptomatic REM sleep behavior disorder," which is associated with other underlying conditions.
It is believed that idiopathic cases, where the cause is unknown, account for more than half of all cases. On the other hand, the causes of symptomatic REM sleep behavior disorder include the following:
- Specific neurodegenerative diseases such as Parkinson's disease and Lewy body dementia
- Withdrawal from chronic alcohol or stimulant abuse
- Acute drug intoxication from tranquilizers, etc.
- Brainstem lesions such as multiple sclerosis, subarachnoid hemorrhage, or stroke at the brainstem level (medulla oblongata)
Is Age Related to REM Sleep Behavior Disorder?
Furthermore, it is said that aging and senescence are also related to REM sleep behavior disorder (in fact, it is more common in older men). Therefore, in this era of an aging population, it is quite possible that the incidence will increase.
