Sleep Stages, Cycles, And Why We Sleep

May 08, 2024
Fact Checked
Sleep is important for your physical and mental health. Learn about the sleep cycles your body goes through at night and how they can impact your health.

Key Takeaways

Getting quality sleep can be challenging. And as we age, older adults often experience less total time sleeping, along with more disruptions to their sleep. Additionally, many sleep issues become more common for older adults, such as insomnia, sleep apnea, restless leg syndrome, sleep disorders, and stress.

How much sleep do you need each night? Adults between the ages of 18 to 64 need approximately 7 to 9 hours of sleep, while adults age 64 and older need about 7 to 8 hours per night. [1]Centers for Disease Control and Prevention. How much sleep do I need? Found on the internet at https://www.cdc.gov/sleep/about_sleep/how_much_sleep.html Lack of adequate sleep affects mood, thinking, and ability to learn and function. A good night’s sleep depends on the sleep cycle, which is made up of four sleep stages. Understanding the sleep cycle stages may be one way to help you catch more Zzzzs.

Why we sleep

Sleep is essential to good physical and mental health. While experts still don’t know exactly why humans need sleep, they do agree on its specific benefits, including:

Understanding the cycles of sleep may help you figure out why your sleep may not be optimal and provides a way to help you improve your sleep hygieneSleep hygiene refers to your sleep environment and behaviors that can affect your quality and quantity of sleep.

What are the sleep stages that make up a sleep cycle?

A sleep cycle is the period when your brain and body rotate through the four sleep stages. Typically, a full night of rest allows for four to six sleep cycles. To achieve highly restorative sleep, you need to progress easily through the four stages of sleep, as each plays an important role in maintaining your physical and cognitive health. The average sleep cycle lasts 80 to 100 minutes, at which point it starts over. [2]National Institutes of Health. Sleep Phases and Stages. Found on the internet at https://www.nhlbi.nih.gov/health/sleep/stages-of-sleep

The four stages of sleep

The four stages of sleep fall into one of two phases, non-rapid eye movement (NREM) sleep and rapid eye movement (REM). NREM sleep accounts for 75 to 80% of the sleep cycle. [3]What Happens During Sleep? National Institute of Child Health and Human Development. April 29, 2019. Found on the internet at https://www.nichd.nih.gov/health/topics/sleep/conditioninfo/what-happens

An infographic showing the four stages of sleep: light sleep, deeper sleep, deepest sleep, and rapid eye movement.

Each sleep cycle is made of four sleep stages and typically lasts 80 to 100 minutes.

The first stage of sleep, stage 1, lasts only one to seven minutes, beginning when you first relax to the point of drifting off to sleep. By stage 2, your body adapts by slowing down your breathing and heart rate, and your body temperature drops. In stage 3, your body, breathing, and mind are the most still, and you get the deepest sleep. These first three stages of NREM sleep take approximately 90 minutes to complete.

Stage 4 is the REM sleep stage, where your body is still while your mind is active. The REM stage is the dream stage and one that occurs before the cycle starts over. It can last anywhere from 10 minutes up to an hour before transitioning back to stage 1. [4]How sleep works. March 24, 2022. National Institutes of Health. Found on the internet at https://www.nhlbi.nih.gov/health/sleep/why-sleep-important

Table 1 Comparison table of the 4 stages of sleep

Sleep stages vary, but generally, this is what most people experience during their nighttime slumber.

Sleep stage

Type

Length

Purpose

Stage 1NREM1–7 minutesThis is a light sleep stage, during which you move into a calm, relaxed state.
Stage 2NREM10–25 minutesDuring this deeper sleep stage, your body temperature drops and your vital signs slow down. Your brain is organizing memories.
Stage 3NREM20–40 minutesThis is the deepest sleep stage, during which you become very still. Your body and mind are healing and recovering from physical and mental stress.
Stage 4REM10–60 minutesThis active sleep stage is when you dream, and your eyes dart back and forth.

What affects sleep stages?

Sleep patterns change through the course of our lives. Even though we need just as much sleep as before, getting a full night’s sleep can be challenging for those experiencing physical, psychological, or lifestyle changes.

How to get better sleep

Understanding the importance of sleep serves as a great first step in improving your sleep quality. Throughout your day, there are practices you can use to promote better sleep at night. Here are some tips to improve your sleep hygiene: [14]Centers for Disease Control and Prevention. Tips for Better Sleep. Found on the internet at https://www.cdc.gov/sleep/about_sleep/sleep_hygiene.html

“As easy as it may be to justify staying out a few hours later than usual, you should aim to go to bed at the same time every night. In the morning, try to wake up at the same time, even on weekends,” said Chad Denman, MD, a sleep medicine specialist in Austin, Texas.

“While sleeping in might feel nice from time to time, it can be disruptive to your natural sleep cycle,” Denman added.

Bottom line

Getting a good night’s sleep is essential for our physical and mental health. Understanding the stages of your sleep cycles can help you manage your quality of sleep. A sleep cycle is the period of time your brain and body go through during four sleep stages. The circadian rhythm, the body’s internal sleep-wake cycle, may not be as effective as you age. A lack of sleep can have adverse effects on mood and body, and make existing conditions worse. Luckily, there are good habits you can practice to promote healthy sleep.

Frequently asked questions

REM, short for rapid eye movement, is the last stage of the sleep cycle, where your brain waves are active and dreaming occurs. Your mind goes through several REM cycles throughout the night and can last anywhere from 10 minutes to 1 hour.

Stage 1: Light sleep. Your brain, heart rate, and breathing slow.

Stage 2: Deeper sleep. Your body temperature drops, and your vital signs slow down.

Stage 3: Deepest sleep. Your body becomes very still and your brain activity slows down.

Stage 4/REM Sleep: Your brain becomes active, and your eyes dart back and forth.

We dream during stage 4, also called REM sleep, but sleepers can dream during other stages, too. This dream stage varies anywhere from 10 minutes to 1 hour long. Some people remember their dreams, while others do not.

Sleep debt occurs when you do not get enough sleep over consecutive nights. For example, if you are used to sleeping 8 hours but only get 6 per night, you are in debt by 2 hours per night. Catching up on the weekends may feel good, but your best bet is to get back on a sleep schedule to feel the most rested.

Adults between the ages of 18 to 64 need approximately 7 to 9 hours of sleep. Adults age 64 and older need about 7 to 8 hours per night.

Have questions about this review? Email us at reviewsteam@ncoa.org.

Sources

  1. Centers for Disease Control and Prevention. How much sleep do I need? Found on the internet at https://www.cdc.gov/sleep/about_sleep/how_much_sleep.html
  2. National Institutes of Health. Sleep Phases and Stages. Found on the internet at https://www.nhlbi.nih.gov/health/sleep/stages-of-sleep
  3. What Happens During Sleep? National Institute of Child Health and Human Development. April 29, 2019. Found on the internet at https://www.nichd.nih.gov/health/topics/sleep/conditioninfo/what-happens
  4. How sleep works. March 24, 2022. National Institutes of Health. Found on the internet at https://www.nhlbi.nih.gov/health/sleep/why-sleep-important
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  8. Yeghiazarians Y, et al. Obstructive Sleep Apnea and Cardiovascular Disease: A Scientific Statement From the American Heart Association. Circulation. July 20, 2021. Found on the internet at https://www.ahajournals.org/doi/10.1161/CIR.0000000000000988
  9. Craig S, et al. Investigation and management of residual sleepiness in CPAP-treated patients with obstructive sleep apnoea: the European view. European Respiratory Review. May 25, 2022. Found on the internet at https://err.ersjournals.com/content/31/164/210230
  10. Dong L, et al. Association between sleep duration and depression in US adults: A cross-sectional study. Journal of Affective Disorders. January 2022 Jan. Found on the internet at https://www.sciencedirect.com/science/article/pii/S016503272101034X?via%3Dihub
  11. Brupbacher G, et al. The effects of exercise on sleep in unipolar depression: A systematic review and network meta-analysis. Sleep Medicine Reviews. 2021. Found on the internet at https://www.sciencedirect.com/science/article/pii/S108707922100037X?via%3Dihub
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  13. Daghlas I, et al. Sleep Duration and Myocardial Infarction. Journals of the American College of Cardiology. Sept. 10, 2019. Found on the internet at https://www.sciencedirect.com/science/article/pii/S0735109719359492?via%3Dihub
  14. Centers for Disease Control and Prevention. Tips for Better Sleep. Found on the internet at https://www.cdc.gov/sleep/about_sleep/sleep_hygiene.html
Lauren Evoy Davis is a health journalist with expertise in cancer and other chronic conditions. Lauren holds an MA in Journalism from American University and a BA in English from Elon University. Her work has been published by the American Society of Clinical Oncology, Legacy, Health Central, WebMD, Verywell Health, Patient Power, and Verizon.
Dr Chester Wu
Chester Wu Medical Reviewer
Dr. Chester Wu is board certified in Psychiatry and Sleep Medicine, training at Baylor College of Medicine and Stanford University School of Medicine, respectively. He has since established his own private practice in Houston, TX where he provides psychiatric and sleep medicine services.
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