Table of ContentsView AllTable of ContentsNREM Stage 1NREM Stage 2NREM Stage 3REM SleepSequence of Sleep StagesCycle InterruptionsImpact of Poor SleepSleep Tips
Table of ContentsView All
View All
Table of Contents
NREM Stage 1
NREM Stage 2
NREM Stage 3
REM Sleep
Sequence of Sleep Stages
Cycle Interruptions
Impact of Poor Sleep
Sleep Tips
As you sleep, your brain cycles through four stages of sleep. The first three are considerednon-rapid eye movement (NREM) sleep, also known as quiet sleep. The fourth israpid eye movement (REM) sleep, also known as active sleep.
Each sleep stage has a unique function and role in maintaining your brain’s overall cognitive performance. Some stages are also associated with physical repairs that keep you healthy and get you ready for the next day.
This article discusses the four stages of sleep. It also explains what happens during each sleep stage and what can hinder sleep.
Verywell / JR Bee
The first stage of the sleep cycle is a transition period between wakefulness and sleep.
If you awaken someone during this stage, they might report that they were not asleep.
During stage 1 sleep:
This brief period of sleep lasts for around five to 10 minutes. The brain is still relatively active and producing high amplitude theta waves, which are slow brainwaves occurring primarily in the brain’s frontal lobe.
People spend about half of their total sleep time during NREM stage 2, which lasts for about 20 minutes per cycle.
During stage 2 sleep:
The brain also begins to produce bursts of rapid, rhythmic brain wave activity, which are known as sleep spindles. They are thought to be a feature of memory consolidation—when your brain gathers, processes, and filters new memories you acquired the previous day.
While this is occurring, your body slows down in preparation for NREM stage 3 sleep and REM sleep—the deep sleep stages when the brain and body repair, restore, and reset for the coming day.
Deep, slow brain waves known as delta waves begin to emerge during NREM stage 3 sleep—a stage that is also referred to as delta sleep. This is a period ofdeep sleepwhere any environmental noises or activity may fail to wake the sleeping person.
Sleepwalkingtypically occurs during NREM stage 3 sleep. It is more common in the early part of your night’s sleep. Children and young adults are more likely to sleepwalk than older adults.
During NREM stage 3 sleep:
During this deep sleep stage, your body starts its physical repairs. Getting enough NREM stage 3 sleep makes you feel refreshed the next day.
Meanwhile, your brain consolidates declarative memories—for example, general knowledge, facts or statistics, personal experiences, and other things you have learned.
While your brain is aroused with mental activities during REM sleep, in this stage of sleep, your voluntary muscles become immobilized.
During REM sleep, your brain’s activity most closely resembles its activity during waking hours. However, your body is temporarily paralyzed—a good thing, as it prevents you from acting out your dreams.
REM sleep begins approximately 90 minutes after falling asleep. At this time:
Like stage 3, memory consolidation also happens during REM sleep. However, it is thought that REM sleep is when emotions and emotional memories are processed and stored.
Your brain also uses this time to cement information into memory, making it an important stage for learning.
Repair Work in ProgressDuring deep sleep (stage 3 and REM), your cells repair and rebuild, and hormones are secreted to promote bone and muscle growth. Your body also uses deep sleep to strengthen your immunity so you can fight off illness and infection.
Repair Work in Progress
During deep sleep (stage 3 and REM), your cells repair and rebuild, and hormones are secreted to promote bone and muscle growth. Your body also uses deep sleep to strengthen your immunity so you can fight off illness and infection.
Dreaming Sleep and Sleep Cycles
It’s important to realize that sleep does not progress through the four stages in perfect sequence.
When you have a full night of uninterrupted sleep, the stages progress as follows:
Once REM sleep is over, the body usually returns to NREM stage 2 before beginning the cycle.
Time spent in each stage changes throughout the night as the cycle repeats (about four to five times total).
How Long Is a Sleep Cycle?According to the National Sleep Foundation, a full sleep cycle is generally around 90 minutes long.
How Long Is a Sleep Cycle?
According to the National Sleep Foundation, a full sleep cycle is generally around 90 minutes long.
Factors That Affect Your Sleep Cycle
Any time you have trouble falling asleep or staying asleep at night, your sleep cycle will be affected.
Interrupted sleep is the term used to describe sleep that is not continuous throughout the night. When this happens, your sleep cycle can be disrupted. An in-progress sleep stage may be cut short, and a cycle may repeat before finishing.
Several issues can interrupt your sleep cycles. This may happen occasionally or chronically, depending on which one is at play.
Some factors that are associated with interrupted sleep and, therefore, may affect your sleep stages include:
Biphasic Sleep Schedule: Recommended or Disruptive?
What Happens When Sleep Stages Are Altered
Not spending enough time in each sleep stage or properly cycling through the stages of sleep can affect you in various ways, potentially having short-term and long-term consequences.
A few examples of issues that can arise from a disrupted sleep cycle include problems with:
People with a disrupted sleep cycle are also at greater risk for:
Tips For a Healthier Sleep Cycle
According to the Centers for Disease Control and Prevention, 1 in 3 adults in the US reports not getting enough sleep.There are things everyone can try to help improve the quality and quantity of sleep.
If you practice goodsleep hygiene, you can often improve the quantity and quality of your sleep. If you still are not getting sufficient sleep after trying the above tips for at least a week, see a healthcare professional to assess if you need other assistance, such as medication or asleep apnea device.
Summary
As your body progresses through the four sleep cycle stages—stages 1 through 3 (non-rapid eye movement, or NREM) and rapid eye movement sleep, or REM sleep, it transitions through different biological processes that affect your temperature, breathing, cells, and muscles. All the while, your brain is busy forming, organizing, and storing memories.
The sleep cycle follows a specific pattern, but that can be interrupted because of various habits, health conditions, and even older age.
Over time, not getting enough sleep and not cycling through the four stages can cause physical and mentalhealth issues.
A Word From VerywellAdequate and restful sleep is the cornerstone of overall well-being. Aim for seven to nine hours of uninterrupted sleep each night, allowing your body to traverse the essential stages of NREM and REM sleep. Create a conducive sleep environment, maintain a consistent sleep schedule, and heed the signals of your body and mind. Quality sleep is not a luxury but a vital prescription for optimal health—nourishing both your physical vitality and mental resilience.—SMITA PATEL, DO, MEDICAL EXPERT BOARD
A Word From Verywell
Adequate and restful sleep is the cornerstone of overall well-being. Aim for seven to nine hours of uninterrupted sleep each night, allowing your body to traverse the essential stages of NREM and REM sleep. Create a conducive sleep environment, maintain a consistent sleep schedule, and heed the signals of your body and mind. Quality sleep is not a luxury but a vital prescription for optimal health—nourishing both your physical vitality and mental resilience.—SMITA PATEL, DO, MEDICAL EXPERT BOARD
Adequate and restful sleep is the cornerstone of overall well-being. Aim for seven to nine hours of uninterrupted sleep each night, allowing your body to traverse the essential stages of NREM and REM sleep. Create a conducive sleep environment, maintain a consistent sleep schedule, and heed the signals of your body and mind. Quality sleep is not a luxury but a vital prescription for optimal health—nourishing both your physical vitality and mental resilience.
—SMITA PATEL, DO, MEDICAL EXPERT BOARD
13 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.National Institute of Neurological Disorders and Stroke.Brain basics: understanding sleep.Vijayan S, Lepage KQ, Kopell NJ, Cash SS.Frontal beta-theta network during REM sleep.Elife. 2017;6(1):e18894. doi:10.7554/eLife.18894Yetton BD, McDevitt EA, Cellini N, Shelton C, Mednick SC.Quantifying sleep architecture dynamics and individual differences using big data and Bayesian networks.PLoS One. 2018;13(4):e0194604. doi:10.1371/journal.pone.0194604Feld GB , Diekelmann S.Sleep smart—optimizing sleep for declarative learning and memory.Front Psychol. 2015;6(1):622. doi:10.3389/fpsyg.2015.00622National Library of Medicine: MedlinePlus.Sleepwalking.Glosemeyer RW, Diekelmann S, Cassel W, et al.Selective suppression of rapid eye movement sleep increases next-day negative affect and amygdala responses to social exclusion.Sci Rep. 2020;10(1):17325. doi:10.1038/s41598-020-74169-8Johns Hopkins Medicine.The science of sleep: understanding what happens when you sleep.National Sleep Foundation.What are the sleep stages?.Tatineny P, Shafi F, Gohar A, Bhat A.Sleep in the elderly.Mo Med. 2020;117(5):490-495.Medic G, Wille M, Hemels ME.Short- and long-term health consequences of sleep disruption.Nat Sci Sleep. 2017;9:151-161. doi:10.2147/NSS.S134864Liu Y, Wheaton AG, Chapman DP, Cunningham TJ, Lu H, Croft JB.Prevalence of healthy sleep duration among adults—United States, 2014.MMWR Morb Mortal Wkly Rep. 2016;65(6):137-141. doi:10.15585/mmwr.mm6506a1National Institutes for Health.Good sleep for good health.National Library of Medicine: MedlinePlus.Healthy sleep.
13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.National Institute of Neurological Disorders and Stroke.Brain basics: understanding sleep.Vijayan S, Lepage KQ, Kopell NJ, Cash SS.Frontal beta-theta network during REM sleep.Elife. 2017;6(1):e18894. doi:10.7554/eLife.18894Yetton BD, McDevitt EA, Cellini N, Shelton C, Mednick SC.Quantifying sleep architecture dynamics and individual differences using big data and Bayesian networks.PLoS One. 2018;13(4):e0194604. doi:10.1371/journal.pone.0194604Feld GB , Diekelmann S.Sleep smart—optimizing sleep for declarative learning and memory.Front Psychol. 2015;6(1):622. doi:10.3389/fpsyg.2015.00622National Library of Medicine: MedlinePlus.Sleepwalking.Glosemeyer RW, Diekelmann S, Cassel W, et al.Selective suppression of rapid eye movement sleep increases next-day negative affect and amygdala responses to social exclusion.Sci Rep. 2020;10(1):17325. doi:10.1038/s41598-020-74169-8Johns Hopkins Medicine.The science of sleep: understanding what happens when you sleep.National Sleep Foundation.What are the sleep stages?.Tatineny P, Shafi F, Gohar A, Bhat A.Sleep in the elderly.Mo Med. 2020;117(5):490-495.Medic G, Wille M, Hemels ME.Short- and long-term health consequences of sleep disruption.Nat Sci Sleep. 2017;9:151-161. doi:10.2147/NSS.S134864Liu Y, Wheaton AG, Chapman DP, Cunningham TJ, Lu H, Croft JB.Prevalence of healthy sleep duration among adults—United States, 2014.MMWR Morb Mortal Wkly Rep. 2016;65(6):137-141. doi:10.15585/mmwr.mm6506a1National Institutes for Health.Good sleep for good health.National Library of Medicine: MedlinePlus.Healthy sleep.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
National Institute of Neurological Disorders and Stroke.Brain basics: understanding sleep.Vijayan S, Lepage KQ, Kopell NJ, Cash SS.Frontal beta-theta network during REM sleep.Elife. 2017;6(1):e18894. doi:10.7554/eLife.18894Yetton BD, McDevitt EA, Cellini N, Shelton C, Mednick SC.Quantifying sleep architecture dynamics and individual differences using big data and Bayesian networks.PLoS One. 2018;13(4):e0194604. doi:10.1371/journal.pone.0194604Feld GB , Diekelmann S.Sleep smart—optimizing sleep for declarative learning and memory.Front Psychol. 2015;6(1):622. doi:10.3389/fpsyg.2015.00622National Library of Medicine: MedlinePlus.Sleepwalking.Glosemeyer RW, Diekelmann S, Cassel W, et al.Selective suppression of rapid eye movement sleep increases next-day negative affect and amygdala responses to social exclusion.Sci Rep. 2020;10(1):17325. doi:10.1038/s41598-020-74169-8Johns Hopkins Medicine.The science of sleep: understanding what happens when you sleep.National Sleep Foundation.What are the sleep stages?.Tatineny P, Shafi F, Gohar A, Bhat A.Sleep in the elderly.Mo Med. 2020;117(5):490-495.Medic G, Wille M, Hemels ME.Short- and long-term health consequences of sleep disruption.Nat Sci Sleep. 2017;9:151-161. doi:10.2147/NSS.S134864Liu Y, Wheaton AG, Chapman DP, Cunningham TJ, Lu H, Croft JB.Prevalence of healthy sleep duration among adults—United States, 2014.MMWR Morb Mortal Wkly Rep. 2016;65(6):137-141. doi:10.15585/mmwr.mm6506a1National Institutes for Health.Good sleep for good health.National Library of Medicine: MedlinePlus.Healthy sleep.
National Institute of Neurological Disorders and Stroke.Brain basics: understanding sleep.
Vijayan S, Lepage KQ, Kopell NJ, Cash SS.Frontal beta-theta network during REM sleep.Elife. 2017;6(1):e18894. doi:10.7554/eLife.18894
Yetton BD, McDevitt EA, Cellini N, Shelton C, Mednick SC.Quantifying sleep architecture dynamics and individual differences using big data and Bayesian networks.PLoS One. 2018;13(4):e0194604. doi:10.1371/journal.pone.0194604
Feld GB , Diekelmann S.Sleep smart—optimizing sleep for declarative learning and memory.Front Psychol. 2015;6(1):622. doi:10.3389/fpsyg.2015.00622
National Library of Medicine: MedlinePlus.Sleepwalking.
Glosemeyer RW, Diekelmann S, Cassel W, et al.Selective suppression of rapid eye movement sleep increases next-day negative affect and amygdala responses to social exclusion.Sci Rep. 2020;10(1):17325. doi:10.1038/s41598-020-74169-8
Johns Hopkins Medicine.The science of sleep: understanding what happens when you sleep.
National Sleep Foundation.What are the sleep stages?.
Tatineny P, Shafi F, Gohar A, Bhat A.Sleep in the elderly.Mo Med. 2020;117(5):490-495.
Medic G, Wille M, Hemels ME.Short- and long-term health consequences of sleep disruption.Nat Sci Sleep. 2017;9:151-161. doi:10.2147/NSS.S134864
Liu Y, Wheaton AG, Chapman DP, Cunningham TJ, Lu H, Croft JB.Prevalence of healthy sleep duration among adults—United States, 2014.MMWR Morb Mortal Wkly Rep. 2016;65(6):137-141. doi:10.15585/mmwr.mm6506a1
National Institutes for Health.Good sleep for good health.
National Library of Medicine: MedlinePlus.Healthy sleep.
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