The Science of REM Sleep: What You Should Know

We experience our first REM (Rapid Eye Movement) sleep 90 minutes after falling asleep, with each subsequent REM cycle getting longer.

REM Sleep: What You Should Know

Human beings spend an average of six to ten hours of sleep per night. That’s generally between a quarter and a third of our 24-hour day. Considering the large portion of our lives that we spend devoted to sleep, even the best scientists admit to understanding very little about it and why it’s necessary, though it clearly is essential to our physical and emotional well-being. Sleep has an effect on every body system, and studies have shown that a lack of sleep not only has a detrimental effect on mood, it can also cause cardiovascular disease, obesity, diabetes, and high blood pressure.

To understand the REM (Rapid Eye Movement) portion of sleep we must first look at all the cycles of sleep. Our ancestors probably were not aware that not all sleep is the same, and that while we are tucked in at night, we actually spend the hours cycling through several different stages of sleep, each of which seem to benefit us in different ways.

Stages of sleep

Until around the 1950s, people believed that sleep was nothing more than a long period of unconsciousness meant to give us rest. We now know that there is much more going on behind the closed eyes of a sleeper, and sleeping changes throughout the night. Instead, sleep is divided into five unique stages and we cycle through each of these stages four to six times per night, typically spending around 90 minutes per cycle.

Stage One: This is what we often call “twilight sleep.” We may drift in and out between sleep and wakefulness. Our conscious thoughts may take a sudden turn into the nonsensical, and then back, when we have an inward chuckle of wonderment at the weird turn of our thoughts, before quickly going off again into something equally strange. Then we drift into a light sleep; one from which we may easily be wakened. You may also make weird, twitchy muscle movements and occasionally experience a sudden jolt as though you were falling. After a few minutes of light sleep you drift into stage two.

Stage Two: We spend about half of our night in this non-REM stage. Our body temperatures drop and heart rate begins to slow. Muscles alternate between being toned and relaxed as we get ready for deep sleep.

Stage Three: During this deep sleep stage our bodies are still, and we have no eye movement. Blood pressure drops and breathing is slow and regular. This is the sleep stage that most rejuvenates our muscles, regrows bone, and builds our immune system. This stage of sleep is necessary in order to feel refreshed in the morning.

Stage Four, REM Sleep: We experience our first REM (Rapid Eye Movement) sleep around 90 minutes after falling asleep, with each subsequent REM cycle getting longer, and the final REM stage of our night generally lasting about an hour. Unlike the other sleep stages, during REM sleep our brain is very active. During non-REM sleep, our minds rest while our body rejuvenates, but during REM our minds become energized while our limbs are temporarily paralyzed.

This is in order to keep us from acting out our dreams, as this is the stage where most dreaming occurs, and our brain activity closely resembles that of wakefulness. Eyes move rapidly beneath our closed eyelids, heart rate and blood pressure rises. If awakened during this phase of sleep, people recall and report their most vivid, detailed, and emotional dreams. Dreams in earlier stages are vague and less clear and emotional.

According to studies, 65 percent of dreams during REM sleep are reported to be either sad, full of anxiety or angst, or even anger; with only 20 percent being happy, and 1 percent being sexual. There has been much speculation for generations about the purpose of dreaming, but science has yet to reach a consensus on the many theories.

REM sleep is less understood than the other sleep stages, though most scientists believe it may be important in rejuvenating the brain. Infants spend nearly 50 percent of their sleeping time in REM sleep, and adults spend 20 percent in REM, with that time lessening as we age.

Adding to the uncertainty about the purpose of REM sleep, is the fact that research has shown that individuals can be awakened and robbed of their REM sleeps for up to two weeks with no known adverse effects. However it is also noted that when allowed to return to having REM sleep, those individuals may rebound by having longer and more frequent periods of REM as though to make up for what was lost, indicating that REM is important to our well-being in some way that is still unclear.

Resources—WebMD, Cleveland Clinic, National Sleep Foundation