Alaska Sleep Education Center

The 4 Stages of Sleep

Posted by Jennifer Hines

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on Apr 6, 2022 9:24:54 PM

girl sleeping on a white bed.

An ordinary person spends a third of their life sleeping, and good sleep is one of the secrets to good health. A good night's sleep helps our bodies repair muscles, manage hormones, grow bones, and sort memories. Sleep can generally be segmented into REM (rapid eye movement) and non-REM.

The REM and the non-REM sleep categories are further divided into awake, light sleep, deep sleep, and Rapid eye movement (REM) stage. These stages are critical in maintaining both your physical and mental health. Then non- REM occurs first and includes the first three stages of awake, light, and deep sleep. In the last stage, one is usually deep asleep and cannot wake up when at this stage. The REM sleep stage happens an hour to an hour and a half after falling asleep, and it's the rapid eye movement stage. This stage plays a critical role between deep sleep and being awake.

Sleeping Cycles

The sleep stages take place in cycles, each lasting about 90- 120 minutes. A normal person undergoes about four to five cycles of sleep during the night. Normally throughout the night, the sleep stages keep shifting. In the first half of the night, a person experiences an increased percentage of NREM (non-rapid movement) sleep. In the second part of the night, a person experiences an increased percentage of rapid eye movement (REM) sleep.

What Happens In Each Stage Of Sleep

Awake Stage

This is the first stage or the non-REM, and it's typically the stage that transits a person from wakefulness to sleep. This stage lasts just a few minutes, and it's the lightest stage of sleep. When awakened during this stage of sleep, a person won't perceive as if they have fallen asleep. 


During this stage:

  • A person s breathing and heartbeat slow down
  • Their eye keeps rolling, and their movement slows
  • Their muscles begin to relax
  • The body produces low aptitude mixed frequencies waves with a theta range between 4 to 7 Hz

Light Sleep

This is the next non-REM sleep stage and consists of the largest percentage of a person's total sleep time. It is also considered the lighter stage of sleep. A person can also be awakened easily at this stage. This sleep stage prepares one and comes just before deep sleep. 


Characteristics of this stage include:

  • No eye movement
  • Drop-in body temperature
  • Breathing and heartbeat further slows down
  • K-complexes and sleep spindle brain waves appear for the first time in this sleep stage.

Deep Sleep

This is the non-REMs final sleep stage, and it's also the deepest sleep stage. The stage is also referred to as delta sleep or slow-wave. In this final non-REM, the person's body performs the critical health-promoting tasks. It is during this sleep stage that.

  • It would be difficult to arouse a person from sleep
  • Their heartbeat and their breathing is at their lowest
  • Eye movements are nil
  • A person's body is fully relaxed
  • The presence of delta brain waves is recognized
  • The body's immune system strengthens
  • Cell regeneration, tissue growth, and repair occur

REM Sleep Stage

The REM sleep stage comes in two phases the phasic and the tonic. The phasic REM sleep stage is characterized by rapid eye movement, while the tonic REM sleep phase does not have eye movements. This stage happens approximately 90 minutes after a person falls asleep, and it's where all the dreaming happens. The REM sleep stage only lasts for 10 minutes in the first sleep cycle, but it increases with every cycle. The REM sleep stage lasts between 30 to 60 minutes in the last cycle. 


During this sleep stage:

  • Rapid eye movement is experienced during phasic REM
  • There is an increase and a variance in both heart and breathing rates
  • Muscles paralyze with occasional twitches
  • There is increased brain activity

Tips for A Good Night's Sleep

Good sleep hygiene practices allow you to have good quality sleep. There are different ways you can improve your sleep hygiene practices, and they include.

  • Exposure to natural light. Spending some time outside during the day exposes your body to the sun's natural light. Natural light helps in maintaining a healthy circadian rhythm.
  • Move around or exercise. One of the easiest methods to improve your sleep quality is getting yourself into movement sessions or exercise.
  • Limited nap time. Napping for less than 30 minutes is very beneficial; however, when the nap exceeds 30 min, it becomes detrimental to your sleeping cycles and may leave you wide awake when bedtime finally comes.
  • Avoid certain foods and stimulants just before bed. Foods that cause stomach upsets and indigestion and alcohol, caffeine, and nicotine, when ingested before bed, can greatly impact your sleep quality.
  • Limit screen time before bed. Electronic devices such as phones and TVs emit blue light, which can interrupt the hormones that assist you in falling asleep. Screen time should be limited to an hour before sleeping.
  • Invest in a comfortable bedroom environment. Creating a comfy environment by investing in a high-quality mattress, blanket, pillow, and other bedroom accessories will help you relax, thus improving the quality of your sleep.

What Disturbs A Person's Quality Of Sleep

Sleep disorders affect a person's quality of sleep, leading to other health complications. The disorders include insomnia, sleep apnea, restless sleep syndrome, shift work disorder, narcolepsy, among others. If left untreated can lead to fatigue and a lot of daytime sleepiness.

Other factors that affect a person's sleep quality include older age, nocturia, pain, mood disorders, lifestyle habits, and other health conditions.

In A Nutshell

Every time one sleeps, the body goes through the four-stage sleep cycle. This affects your body's biological functioning through changes in your breathing, body temperature growth, replacement of cells, and muscle replenishing. All this time, the brain is working to form, organize and store memories. To get all the benefits of a good night's sleep, it's important to get at least 7 hours of uninterrupted sleep.

we have learned from this article the different stages of our sleep cycles as non-REM and REM cycles and how they affect our sleeping patterns and in turn our health. Various reasons affect the sleep cycles be it age, sleep habits, or any sleep-related illness as insomnia or sleep apnea.

Opting for a physician is one of the solutions to a better sleep cycle by curing the diseases while some healthy habits like consistent sleep schedule and noise and disruptions free sleep will also help improve sleep cycles.

If you’re struggling with getting enough sleep, or you’re feeling groggy and disorientated in the morning, you may have bigger issues than just understanding your sleep cycles.  The best thing you can do is visit your local sleep specialist.  If you live in Alaska, click on the link below to find a sleep specialist closest to you.


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