What are the 4 sleep stages?

Michael Rosenberg
Michael Rosenberg

Specializes in translating complex information into readable, engaging content. Michael@top10us.com

sleep stages

Sleep is a much more complex phenomenon than most of us realize. Apart from relaxing and restoring our bodies, sleep performs many vital functions in keeping us healthy, revitalized and productive. However, many people are still unaware of the complexities involved in the sleep process, including the sleep stages. 

What are sleep stages?

Sleeping is a unique body function that passes through different stages or phases to complete fully. Each sleep stage has a specific function during our sleep and involves different ways our body works during the stage. Missing out on a single stage constantly for many days can lead to cognitive performance and brain function problems. Additionally, you face other health issues to develop over time as well. After all the sleep stages are complete, we consider it one complete sleep cycle. To be certain, our body passes through many sleep cycles every night, considering the eight sleep cycles or similar progressions.

The main division of the sleep stages are as follows:

  • The first three stages are called the non-rapid eye movement or NREM sleep stages. In general terms, you may consider it the quiet sleep phase.
  • The last stage, or Stage 4, is the rapid eye movement (REM) sleep stage. This stage is more formally known as active or paradoxical sleep.

How Our Brain Enters Sleep?

Generally, sleep does not occur instantly for our body. Instead, after considerable tests with the electroencephalogram (EEG), scientists have discovered that our brain slowly enters sleep. We are still considerably awake in the earliest phases and usually very alert. The main reason is that the production of beta waves is still intact at this stage. These small and fast waves are the reason a person stays alert.

However, once the brain slows down and relaxes, it faces vivid hypnagogic hallucinations sensations. For example, considering that someone either called your name or facing a myoclonic jerk: thinking that you are falling from someplace when you are still in your bed.

NERM Stage 1

This stage is the transitional stage between your sleep and wakefulness. Here, the brain slows down, and every other major body function starts to rest as well. From your eye movements to your heartbeat, most body functions start to enter sleep mode. In some cases, your muscles may twitch during this phase as well.

NREM Stage 2

This stage lasts for 20 minutes in every sleep cycle. Here, a person loses awareness of his surroundings and faces a fall in body temperature. All eye movements stop completely. However, the heartbeat and breathing start to normalize during this phase.

In these phases, bursts of rapid and rhythmic wave activity occur, called sleep spindles. Here, memory consolidation occurs as well. Usually, the previous day’s memories started to consolidate in your brain.

NREM Stage 3

Here, the brain begins to produce delta waves in a slow pattern. Therefore, sleep during this stage is also called delta sleep. During this period, any activity or noises in the surroundings may not cause a person to wake up from sleep. The main features of this phase include complete relaxation of the muscles and a sharp drop in blood pressure. Furthermore, this phase takes you further into the deepest time of your sleep. All defective memories start to consolidate in your mind, from knowledge to personal experiences, thoughts, and learning.

REM Sleep

The last stage of your sleep is the REM stage. Here, your muscles start to become immobilized. During this stage, your brain almost mimics how it performs during the day and in waking hours. However, you face temporary sleep paralysis during this stage as well. Without this paralysis, people may start acting whatever they see during their dreams. Here, the brain starts to think about different activities. Breathing can be fast and irregular, and your eyes may move more rapidly than before.

This is the only phase, according to most scientists, during which a person dreams. Basically, the memory consolidation during the previous phase starts to act out during the fourth stage. During these last two stages, your cells build and repair. Similarly, all the hormones are produced and maintained by the body.

What Interrupts the Sleep Cycle?

Older age and nocturia are some of the important factors that can damage the sleep cycle of a person. Similarly, mood disorders, pain, and lifestyle choices like caffeine and nicotine intake can disturb sleep as well.


Having a great night’s sleep means you pass most sleep cycles properly. Similarly, having the right progression between different phases and enjoying deep sleep is essential for productivity. Let us know in the comments section if our article was helpful.

Related Articles:

Sleep Calculator: How much sleep do you need?

How to treat sleep apnea?


Sign up our newsletter to get article update about health mental and psychologist therapy.