Difference in REM and NREM sleep stage

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Why do we call them REM and NREM?

The full terms for these two stages are "rapid eye movement" and "non-rapid eye movement" and they describe the activity of our eyes during these phases. The observation of alternating eye movements and periods of rest was pivotal in the ground breaking discovery made by E. Aserinsky and N. Kleitman in sleep research This discovery led to the identification of the two alternating phases, now known as REM and NREM.

 

REM

What is REM sleep?

During REM sleep, our bodies experience complete paralysis, yet scientifically measured brain activity closely resembles that of wakefulness. In this stage, our brain experiences a phenomenon called “false awakening". Neurons in the brain get activated, giving rise to the vivid experiences characteristic of dreams.

Now, let's revisit the muscle paralysis for a moment. Why does the body decide to outlaw muscle activity during REM sleep? "During REM sleep, there’s a nonstop barrage of motor commands swirling around the brain, and they underlie the movement-rich experience of dreams. You can well imagine the calamitous upshot of falsely enacting a dream fight, or a frantic sprint from an approaching dream foe, while your eyes are closed and you have no comprehension of the world around you. The brain paralyzes the body so the mind can dream safely.” (M. Walker - Why we sleep? )

What is the function of dreaming?

Dreams serve a far more significant role than many people realize. They act as the bridge between consciousness and the unconscious mind. Through fake scenarios that unfold before us, we process emotions, traumatic events, and moments of joy.We navigate through recent experiences and feelings, integrating new knowledge with existing memories, ultimately updating our mental library and stabilizing our emotional intelligence.

It's no wonder people say "night brings counsel". During REM sleep the brain sifts through information and potential threats. Once emotions are stabilized and everything is properly sorted, solutions often present themselves with clarity.

 

NREM

What is NREM sleep?

The NREM stage, also known as deep sleep, can be divided into four levels: NREM 1, NREM 2, NREM 3, and NREM 4. The NREM 1 stage marks the transition between wakefulness and sleep. Typically lasting around 5-10 minutes, during this stage, all muscles relax, the body's internal temperature decreases, and brain waves slow down. It is common to experience muscle twitches or a sensation of falling or malaise during this stage.

Levels 3 and 4 are characterized as the deepest states, where the brain emits slow delta waves. It is notably challenging to awaken from this stage, and behaviours such as sleepwalking, sleep talking or night terrors may arise. During NREM 3 and 4, tissue repair occurs. This stage gives our bodies the strength to fight against diseases, infections and is important for muscle growth and overall organism development. Deep sleep is vital for the secretion of growth hormone and the replenishment of energy for the next day. Additionally, during this stage, information is transferred from short-term to long-term memory, where it undergoes further processing during REM sleep.

"Studies demonstrate that during delta rhythms, the brain exhibits activity that mirrors the memories acquired throughout the day.  Neurons activate in a precise sequence in which they were engaged during the daytime learning process This means that NREM sleep produces a significant learning-dependent performance boost." (J. K. Jarmar – Code of Life )

 

How do the sleep stages manifest?

Initially, you enter NREM 4 - the deepest sleep stage - typically at the beginning of the night. These two phases then alternate approximately every 90 minutes throughout sleep, with the ratio between them varying within each interval. During the first part of the night, the NREM phase, characterized by deep rest, predominates. In the latter part, the REM phase, associated with dreaming, becomes more prevalent and can last for up to an hour before awakening.

Because these phases alternate regularly but are not evenly distributed throughout sleep, it is crucial not only to get enough sleep but also to maintain a consistent sleep schedule. For example, if you retire to bed at 10 pm but wake up at 4 am, you have deprived yourself of 1-2 hours of sleep. While this may not significantly impact your functioning the next day, you would have lost the majority (approximately 60%) of your REM sleep (dreaming phase). Conversely, if you need to get up for work at 6 am but find yourself engaged in responsibilities until midnight, you have deprived yourself of a substantial portion of the NREM stage.

Neither scenario is without consequences. But is there a notable difference in their importance?

Which sleep do we need more?

The debate among scientists regarding the importance of the two sleep stages has been ongoing. An experiment has been conducted to shed light on this question:

The researchers kept the subject awake for one night. After 24 hours of wakefulness, the subject eventually fell asleep, and researchers monitored their brain waves. The findings revealed that following the day of wakefulness, the brain spent the majority of the night in the NREM phase. Researchers initially concluded that the NREM stage was more important, as its demand was notably higher following a period of sleep deprivation. However, upon repeating the experiment, researchers had to reconsider their stance. They observed that while the NREM stage dominated the first two nights after the day of wakefulness, on the third and fourth nights, it decreased significantly, with the REM stage predominating instead

Therefore, it cannot be definitively stated that one sleep stage is more important than the other. It can only be inferred that the body prioritizes NREM sleep initially, but subsequently reduces it to a minimum in favor of REM sleep.

This phenomenon can be illustrated with the example of information retention.  When we acquire new knowledge, such as a law of physics, NREM sleep facilitates the transfer of this information from short-term to long-term memory, while REM sleep ensures its retention. Hence, the two stages are complementary, and both are necessary for long-term memory retention.

 

How can you support both stages?

During the REM stage (dreaming), body temperature and room temperature play crucial roles. The onset and depth of REM sleep are closely tied to whether we feel warm or cold. Therefore, using a COOLER mattress protector can aid in achieving proper sleep, particularly during warmer months. You can read about how our sleep is affected by the ambient temperature in our article Temperature and sleep.

Additionally, the MAGNEREST protector significantly enhances the regularity of alternating between the two stages. In our case study, you can observe the effectiveness of the protector in extending both REM and NREM sleep.