NREM vs REM Sleep: What’s the difference?

Non-Rapid Eye Movement (NREM) and Rapid Eye Movement (REM) sleep cycles are two fascinating aspects of sleep. These different stages are crucial to our general health and cognitive function.

Understanding the intricacies of our sleep cycles and how they affect our health and everyday lives requires an understanding of the distinctions between NREM and REM sleep. 

We may learn how to optimize our sleep patterns and improve our general well-being in today’s fast-paced environment by investigating these intriguing areas of sleep.

What is sleep?

Our bodies and brains require sleep as a natural and necessary condition of rest if they are to operate at their best. It is a multi-stage, complicated process that takes place in cycles. 

Non-Rapid Eye Movement (NREM) sleep and Rapid Eye Movement (REM) sleep may be roughly divided into these phases.

The first stage of sleep is NREM sleep, sometimes referred to as calm sleep. It is further separated into four unique phases, each of which is distinguished by certain brainwave patterns and bodily alterations. 

We undergo a gradual change from waking to a condition of light sleep in the early phases of NREM sleep. 

Our brain activity decreases as we approach deeper stages of NREM sleep, and our body goes into a profound state of relaxation and repair.

The phase of sleep during which vivid dreams take place is known as REM sleep, sometimes known as active sleep. Our eyes move quickly beneath our closed eyelids and our brain activity rises during REM sleep [1]. 

Increased brain activity, emotional control, memory processing and learning are all characteristics of this period.

Each sleep cycle lasts around 90 minutes and is usually made up of many rounds of NREM and REM sleep. These cycles rotate throughout the night, with NREM sleep predominating in the early hours and REM sleep predominating in the later hours.

For overall health and well-being, getting enough NREM and REM sleep is essential. While REM sleep promotes cognitive function, emotional control and creative thinking, NREM sleep aids in physical restoration, development and memory consolidation.

what is NREM sleep?
Photograph: Rawpixel/Envato

What is NREM sleep?

The sleep stage known as NREM sleep, or non-rapid eye movement sleep, is characterized by significantly slower brainwave activity and less eye movement. 

NREM sleep is essential for memory consolidation, physical recovery, and development. 

Our bodies undergo physiological changes as we move through the stages of NREM sleep, such as a decline in metabolism, blood pressure and heart rate. 

Muscle development, hormone regulation and tissue regeneration are all possible in this relaxed state. 

Additionally, NREM sleep is crucial for memory consolidation since it makes it easier for freshly learned information to be incorporated into long-term memory storage [2].

Stages of NREM sleep

Non-Rapid Eye Movement, or NREM, sleep is broken down into four separate stages that increase in depth and relaxation. 

Specific brainwave patterns and physiological alterations characterize each level. 

Let’s examine the NREM sleep cycle:

• Stage 1 (Transition to sleep)

As soon as we begin to fall asleep, we enter this stage of NREM sleep, which is the lightest. 

We could experience drifting thoughts, fleeting feelings and a feeling of calm at this point. 

It acts as a bridge between the stages of consciousness and deeper sleep.

• Stage 2 (Light sleep)

Our brainwaves continue to slow down throughout this phase, and our sleep deepens. 

We experience a dip in body temperature, a slowed heartbeat and an absence of eye movement. 

The majority of our sleep cycles are spent in stage 2, which is essential for preserving the quality of our rest.

• Stage 3 (Deep sleep)

As we progress into deeper sleep, we enter stage 3. 

This stage is marked by a higher percentage of delta waves in the brain, which denotes a deeply relaxed state. 

Since it encourages muscular development, tissue regeneration and immune system strengthening, deep sleep is crucial for physical recovery.

• Stage 4 (Delta sleep)

The deepest stage of NREM sleep is often referred to as delta sleep. It is distinguished by the predominance of delta waves. 

As stage 4 sleep is essential for memory consolidation, learning and hormone control, it is also essential for general health. 

Growth hormone is secreted during this phase, aiding in physical growth and repair.

What is REM sleep?

The stage of sleep known as REM sleep, or rapid eye movement sleep, is interesting and essential. 

Due to the erratic and rapid movement of our eyes during this phase, REM sleep is appropriately titled. 

Despite being completely asleep, our brain activity is similar to waking during this active sleep phase. Normally, this phase follows a cycle of NREM sleep.

REM sleep is characterized by increased brain activity that is similar to awake, in contrast to the slower brainwave patterns seen during NREM sleep [3]. 

Various cognitive functions are supported by this increased activity. Dreaming and REM sleep are intimately related. This period is when we frequently have vivid dreams that stick with us. The nightmares can be vivid, creative and emotionally intense.

What are the key differences between NREM and REM sleep?

Our sleep cycles consist of two unique phases: REM (rapid eye movement) sleep and NREM (non-rapid eye movement) sleep. 

While both are necessary for our well-being, there are some significant differences between the two. Let’s examine how REM and NREM sleep differ from one another:

Brain activity and electrical patterns

The distinct levels of brain activity and cognitive activities that take place during NREM and REM sleep are reflected in the differing electrical patterns of both stages of sleep. 

The specific functions and experiences connected with each stage of sleep are influenced by these distinctive brainwave patterns.

  • NREM sleep

Our brain produces slower, more coordinated brainwave patterns during NREM sleep, such as theta and delta waves. These slower waves represent a relaxed, sleepy mood. The degree of brain activity during NREM sleep is lower than it is during awake.

  • REM sleep

The heightened brain activity that characterizes REM sleep, on the other hand, is similar to awake. 

Brainwave patterns in the brain are quicker and less coordinated than those observed during conscious times of activity. 

It is thought that this increased brain activity during REM sleep promotes cognitive functions including memory consolidation and emotional control [4].

Eye movement and muscle tone

The contrasts between REM (rapid eye movement) and NREM (non-rapid eye movement) sleep are further highlighted by the unique features of eye movement and muscular tone throughout each stage:

  • NREM sleep

During NREM sleep, there are hardly any eye movements. Large-scale body motions are often absent, and the muscles are normally relaxed. 

However, throughout this phase, there can be a few little muscular twitches and movements.

  • REM sleep

The fast and erratic movement of the eyes during this phase of sleep gives REM sleep its name. Vivid dreams are linked to these eye movements. 

Additionally, during REM sleep, muscular tone is significantly decreased, which might occasionally result in temporary muscle paralysis to prevent acting out dreams. 

This muscle atonia serves as a safeguard to keep the body motionless during active dream activity.

Dreaming and cognitive activity

Between REM (rapid eye movement) and NREM (non-rapid eye movement) sleep, there is a considerable difference in dreaming and cognitive activity, which reflects the distinctive procedures and experiences connected to each stage:

  • NREM sleep

While dreams can happen during NREM sleep, they are often less vivid and remembered than during REM sleep. 

NREM dreams often have less vivid imagery and more fragmented narratives. Common experiences and uninteresting ideas frequently appear in NREM dreams.

  • REM sleep

Dreaming is closely related to REM sleep. REM dreams are frequently vivid, intensely emotional and visually engaging. 

This stage is marked by an increase in cognitive activity, which includes memory integration, emotional processing and original thought. 

Dreams during REM can be imaginative, strange and have narratives that appear disconnected from reality.

REM Sleep
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Physiological changes in the body

Our bodies experience incredible physiological changes when we sleep, which improves our overall well-being. 

Both REM (rapid eye movement) and NREM (non-rapid eye movement) sleep cause significant changes in our physical processes. 

The following list highlights the different functions and impacts on general well-being:

  • NREM sleep

Physical healing and development are linked to NREM sleep. It encourages growth hormone secretion, muscular development, and tissue healing. 

This phase is essential for bodily restoration and renewal. The body’s cells, tissues, and organs depend heavily on NREM sleep for recovery and repair.

  • REM sleep

The processes of cognition and emotion are significantly influenced by REM sleep. 

It promotes learning, emotional control, and memory enlargement. Increased brain activity in the memory and emotional areas of the brain occurs during REM sleep. 

Integration of knowledge, creativity and problem-solving skills must occur at this level.

Sleep disorders and their impact on NREM and REM sleep

Various sleep disorders can disrupt the balance between NREM and REM sleep, affecting their respective functions:

  • Sleep apnea

NREM sleep is frequently impacted by sleep apnea, which causes fragmented sleep and delays in the regular development of sleep phases.

  • REM sleep behavior disorder

In this condition, REM sleep is not accompanied by muscular paralysis, which causes dream-acting. 

It interferes with the typical muscular atonia seen during REM sleep, which might result in harm or sleep difficulties.


The two phases of sleep, Non-Rapid Eye Movement (NREM) and REM (Rapid Eye Movement) sleep, are essential to our sleep cycles and general health. 

While REM sleep supports cognitive functions, emotional control and vivid dreaming, NREM sleep fosters physical restoration, development and memory consolidation. 

The different traits of various stages of sleep, such as brain activity, eye movement, muscle tone, dreaming and physiological changes, emphasize how difficult it is to strike a good balance between NREM and REM sleep and how crucial it is to do so. 

Improved sleep patterns and improved physical and cognitive performance in everyday life can result from prioritizing quality sleep and learning the subtle differences between various sleep phases.


Is NREM and REM the same?

The two types of sleep, REM (rapid eye movement) and NREM (non-rapid eye movement)—are not equivalent. They are two separate sleep phases with distinct features. While REM sleep involves fast eye movements, higher brain activity and vivid dreaming, NREM sleep is linked with slower brainwave activity and physical relaxation.

Can you dream in NREM?

Yes, it is possible to dream during non-rapid eye movement (NREM) sleep, although these dreams are often less vivid and fragmented than those that occur during rapid eye movement (REM) sleep. NREM dreams frequently center on commonplace events, uninteresting ideas or random recollections.

Is Nightmare a REM or NREM?

Nightmares typically occur during REM (Rapid Eye Movement) sleep. REM sleep is associated with vivid dreaming, including intense and often frightening dreams. Nightmares can be characterized by vividness.


Photograph: Rawpixel/Envato
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