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Rapid Eye Movement Sleep: REM Disorders

Rapid eye movement (REM) sleep is an important, yet often misunderstood, stage of sleep. While sleep experts know the body is temporarily paralyzed during REM sleep (except in people with REM sleep disorders), some of the characteristics of REM sleep remain a mystery. For example, although researchers have determined that we dream during REM sleep, they have still not identified the exact benefits of rapid eye movement sleep.

REM

This sleep stage is known as the rapid eye movement stage because the eyes quickly move back and forth behind the eyelids during REM sleep. Rapid eye movement sleep differs so much from other sleep stages that other sleep stages are collectively referred to as non-REM sleep.

REM and Sleep Stages

REM is just one type of sleep stage. Altogether, sleep is characterized by five distinct stages, namely:

Stage 1: Five to ten minutes of drowsiness.
Stage 2: Light sleep.
Stages 3 and 4: Heavy, restful sleep.
Stage 5: REM sleep.

People with healthy sleeping patterns cycle through these five stages of sleep several times each night. As a person continues cycling through the sleep stages during the night, the REM sleep stages last longer and longer with each cycle. For instance, while the first REM stage lasts approximately ten minutes, the last period of REM sleep can last up to an hour.

REM Characteristics

While rapid eye movement sleep lasts longer as the night progresses, the physical and mental REM characteristics remain the same. Simply stated, all REM sleep is the same regardless of how long it lasts.

During REM sleep mental activity closely resembles that of the waking brain. Here are some of the physical characteristics associated with REM sleep:

Both heartbeat and breathing may be erratic.
Breathing quickens.
Erections may occur in men.
Heart rate increases.
The clitoris may enlarge in women.
The eyes move rapidly under the eyelids.
The face, hands and legs sometimes twitch.

The large muscles of the body are paralyzed during normal types of REM sleep. Paralysis prevents people from acting out dreams (a sensible precaution given the intense nature of many dreams). Along with rapid eye movement, this temporary paralysis is seen as one of the definitive REM characteristics.

Do We Need REM Sleep?

One theory suggests that REM sleep helps people consolidate memories and learning. In fact, studies indicate that REM sleep improves memory recall. However, it's also true that loss of REM sleep has no observable negative affects on memory.

If people are denied REM sleep, either in a laboratory setting or due to sleep deprivation, they experience an increase in rapid eye movement sleep the next time they sleep. This suggests that REM sleep fulfills some function, although what that function may be remains unclear.

REM Disorders: Abnormal Types of REM Sleep

Abnormal types of REM sleep include narcolepsy and REM sleep behavior disorder. In a normal sleep cycle, REM sleep occurs after the first four stages. Some abnormal types of REM can occur within fifteen minutes of falling asleep. REM occurring so early in the sleep cycle is one of the defining characteristics of narcolepsy.

In REM sleep behavior disorder, one of the most common REM disorders, a person lacks the muscle paralysis that is present in most types of REM sleep. As a result, people with REM disorders act out their dreams while they sleep.

Another characteristic of REM disorders is the occurrence of intense and violent dreams. Because a person who suffers from REM sleep behavior disorder acts out his dreams, he can be a danger to both himself and his bed partners.

People with REM sleep disorders may perform any of the following acts while sleeping:

flailing
grabbing
jumping or falling out of bed
punching and kicking
sitting up in bed
talking
thrashing
yelling and/or screaming.

The Causes of REM Sleep Behavior Disorders

Although 55 percent of REM disorders have no discernable cause, some factors that contribute to REM sleep disorders may include:

alcohol abuse
Lewy Body Dementia, a condition marked by features of both Alzheimer’s and Parkinson’s
multisystem atrophy, a degenerative condition similar to Parkinson’s
Parkinson's disease
shy-Drager syndrome, a degenerative disease characterized by a drop in blood pressure when standing
use of sedatives.

Although identifying the precise cause of REM sleep behavior disorders can be tricky, the medication clonazepan is an effective treatment for them. In the early stages of treatment, the patient may choose to sleep on a mattress on the floor, to minimize the risk of falling out of bed. Bed partners are advised to sleep in a different bed until treatment produces results.

Resources

eMedicine Health (2007). REM sleep behavior disorders. Retrieved July 25, 2007 from the eMedicine Health Web site:
www.emedicinehealth.com/rem_sleep_behavior_disorder/article

_em.htm.

Sleep Channel (2007). Sleep stages. Retrieved July 25, 2007 from the Sleep Channel Web site:
www.sleepdisorderchannel.com/stages/.

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