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What Is Sleep Architecture?

Updated on May 29, 2017
leahlefler profile image

Both of my children have sleep apnea. Over the last several years, they've completed about 10-12 sleep studies.

Sleep Architecture Changes with Age

Infants will spend as much as 50% of their total sleep time in REM sleep. REM sleep declines to approximately 20% by adulthood.
Infants will spend as much as 50% of their total sleep time in REM sleep. REM sleep declines to approximately 20% by adulthood. | Source

The Basics of Sleep Architecture

Sleep architecture is a reference to how an individual cycles through the stages of sleep. This is often measured during a sleep study, or polysomnogram (PSG). The percentage of time spent in each stage of sleep is calculated and reported to determine if a person is getting enough rapid-eye-movement (REM) sleep. Typically, the percentage is calculated either as a percentage of "time in bed" (TIB) or as a percentage of "total sleep time" (TST).

If a person has sleep apnea or other sleeping disorders causing frequent arousals, the sleep architecture will be affected. A lack of sufficient REM sleep can cause depression, mental confusion, high blood pressure, aggression, hand tremors, and a decrease in cognitive skills.

The amount of time spent in each stage of sleep varies by an individual's age, ethnicity, and genetic profile. There are general guidelines as to "normal" amounts of each sleep stage, however, so a person who only spends 5% of their total sleep time in REM sleep would be identified as having a problem with their sleep architecture.

Stage 1 Sleep EEG

Stage 1 sleep is marked by alpha waves, which indicate a very light phase of sleep.
Stage 1 sleep is marked by alpha waves, which indicate a very light phase of sleep. | Source

Stage 1 Sleep

The amount of time spent in Stage 1 sleep is minimal. This stage of sleep is extremely light, and if a person is woken they will often state they were not sleeping. This stage of sleep may be described as "drifting off," and electroencephalogram tracings will show a decrease in brain activity as a person transitions from wakefulness to Stage 1 sleep.

A unique phenomenon occurs during this stage of sleep: a person may feel as if they are suddenly falling and jerk awake. This is called hypnic myoclonia, or a hypnic jerk. These incidents are more common in children, and are also noted more frequently in people who have irregular sleep schedules.

Stage 2 Sleep EEG

Stage 2 sleep is marked by theta waves, sleep spindles, and K-complexes.
Stage 2 sleep is marked by theta waves, sleep spindles, and K-complexes. | Source

Stage 2 Sleep

As the body enters Stage 2 sleep, the heart rate slows and the body temperature begins to drop. The muscles may alternate between having tone and being completely at rest during this sleep stage. This is still classified as light sleep, and a person will wake fairly easily from this sleep stage. They will feel as if they were asleep if wakened.

The EEG tracings will show peaks and valleys, or "waves." The alpha waves of Stage 1 sleep show interruptions by spikes called "sleep spindles" and "K-Complexes." Theta brain wave activity is noted. This stage will be noted as "N2" or "NREM 2" sleep on a sleep study report.

Sleep spindles are brief bursts of brain activity, often followed by muscle twitching. The purpose of sleep spindles appears to be keeping the sleeper in a tranquil state: the spike in activity is generated between the thalamus and the cortex. One theory proposes that the muscle twitches allow a very young child's brain to learn about which nerves control specific muscles when the child is asleep. The sleep spindles allow an adult to sleep through a certain level of noise that would wake the sleeper in Stage 1 sleep. Interestingly, people with schizophrenia lack the normal pattern of fast and slow sleep spindles in sleep.

K-complexes engage the cortex and cerebral cortex, and are thought to be involved with processing of information during sleep. The complex often precedes a sleep spindle and shows a high voltage spike on an EEG. The complexes are spontaneous,but may be induced by touching a sleeping person in Stage 2 sleep.

Sleep Spindles in Stage 2 Sleep

Sleep spindles and K-complexes are common in Stage 2 sleep.
Sleep spindles and K-complexes are common in Stage 2 sleep. | Source

Stage 4 Sleep EEG

Slow wave sleep, as seen on this EEG, is indicative of a deep sleep. The sleeping person will be very difficult to rouse.
Slow wave sleep, as seen on this EEG, is indicative of a deep sleep. The sleeping person will be very difficult to rouse. | Source

Stage 3 and Stage 4 Sleep

Stage 3 and Stage 4 sleep are classified as "slow wave sleep" (SWS), characterized by delta waves on an EEG tracing. These stages used to be classified as different sleep stages, but are now considered a single sleep stage. This stage of sleep will be noted as "N3" or "NREM 3" sleep on a sleep study report.

In this phase of sleep, an individual is unresponsive to external stimuli. Noise, touch, or temperature changes will generally not wake the sleeper. This is the stage of "deep sleep" where muscle tissue regenerates, the immune system strengthens itself, and bone tissue grows.

Nighttime bed wetting occurs in this sleep stage, along with sleepwalking, night terrors, and talking while asleep. These sleep disorders are called parasomnias, and the majority of these problems decrease with age.

The amount of time spent in deep sleep decreases with age, and the elderly may spend little time (or even no time) in Stage 3/4 sleep.

REM Sleep EEG

REM sleep demonstrates an increase of brain activity (similar to wakefulness), while the body remains immobilized.
REM sleep demonstrates an increase of brain activity (similar to wakefulness), while the body remains immobilized. | Source

REM Sleep

REM sleep starts with the onset of high-frequency waves, similar in nature to the waves seen in people who are awake. The heart rate increases and the eyes move rapidly from side to side. This is the stage of sleep where dreaming occurs, and the brain is in an extremely active stage.The muscles are paralyzed in REM sleep, however, and a person cannot move while in this sleep state. This sleep stage is also called "paradoxical sleep," as the brain is highly active, but the body is paralyzed.

REM sleep is vital to the development of the brain. Very young infants spend as much as 50% of their total sleep time in REM sleep, and the amount of time spent in REM sleep decreases as a person ages. Adults spend approximately 20% of their total sleep time in REM sleep.

A lack of appropriate REM sleep will impair memory, cognition, and may cause attention deficit disorder in children.

Detecting Sleep Disorders in Children

A sleep study monitors brain wave activity, eye movement, leg movement, oxygen saturation, respiration, snoring, and heart rhythm to determine the source of potential sleep problems.
A sleep study monitors brain wave activity, eye movement, leg movement, oxygen saturation, respiration, snoring, and heart rhythm to determine the source of potential sleep problems. | Source

Sleep Architecture in Children

Sleep architecture is measured in children when they are sent for a sleep study. There are many sleeping disorders that may affect a child's sleep cycles—any problem that causes frequent arousals will disturb the normal distribution of sleep stages. Problems common to children include:

  • Periodic leg movements
  • Sleep-disordered breathing
  • Obstructive sleep apnea
  • Central sleep apnea
  • Parasomnias, such as sleep-walking or night terrors

Often, a sleep study will demonstrate a problem with sleep architecture and will also reveal the cause behind the disturbed sleep. In the case of sleep-disordered breathing, a physician will determine whether a child has apnea, and what type of apnea is present. In the case of obstructive apnea, a common course of action is to remove a child's tonsils and adenoids, as enlarged tonsils and adenoids are the single most common reason for obstructive apnea in children.

Each case must be evaluated by a physician and the appropriate therapy initiated - this may mean a tonsillectomy/adenoidectomy, evaluation by a neurologist, cardiologist, ear nose and throat doctor, or other specialist as indicated by the study. Once the underlying sleep disorder is treated, sleep architecture often improves dramatically.

Sleep Cycles in Children (Normal Values)

Stage
Definition
% of Total Sleep Time (%TST)
1
Very light sleep - easily aroused.
7.1%
2
Light sleep - heart rate slows and body temperature drops.
46.1%
3
Deep sleep - difficult to wake.
5.5%
4
Often combined with stage 3 sleep - deep sleep, very difficult to wake.
18.5%
REM
Rapid eye movement, dreaming, muscles immobilized.
22.6%
Data obtained from "Polysomnographic Characteristics in Normal Preschool and Early School-Aged Children," PEDIATRICS Vol. 117 No. 3 March 1, 2006 pp. 741 -753

The Biology of Sleep

Sleep Architecture in Adults

Adults spend less time in REM sleep than infants, but a significant percentage of the night is still spent in this stage. Adults typically spent 20-25% of their total sleep time in REM sleep, with the other 75-80% of the time distributed among the other NREM sleep stages.

As adults age, less time is spent in deep sleep. Stage 4 sleep may entirely disappear in the elderly. As a person ages, sleep becomes more fragmented and the circadian rhythm becomes disturbed, causing insomnia and nighttime waking. Parasomnias like restless leg syndrome become more common. The reduced quality (and quantity) of sleep at night leads to an increase of daytime sleeping, which can further compound the problems of getting sufficient rest at night.

Sleep Cycles in Adults (Normal Values)

Stage
Definition
Time Spent in Stage
1
Very light sleep - easily aroused.
2-5%
2
Light sleep - heart rate slows and body temperature drops.
45-55%
3
Deep sleep - difficult to wake
5-8%
4
Often combined with Stage 3 sleep. Very deep sleep, difficult to wake.
10-15%
REM
Rapid eye movement, dreaming, muscles immobilized.
20-25%
From M.H. Kryger, T. Roth, & W.C. Dement (Eds.), Principles and Practice of Sleep Medicine, 5th edition, (pp. 16-26). St. Louis, Elsevier Saunders.

Sleep Architecture Disturbance: A Case Study

Timothy is a bright and slender seven year old boy, who experiences difficulty with bed wetting, occasional snoring, and mouth breathing. He is often moody at the end of the day and is a very "active" sleeper. His teacher at school reports he is often daydreaming, and has difficulty maintaining focus.

His pediatrician ordered a sleep study to determine if a cause could be found for his tiredness, mouth breathing, bed wetting, and moodiness. The sleep study was extremely helpful in identifying sleep related disorders, including interrupted sleep architecture, in Timothy. His sleep architecture is located in the table below:

Case Study: Abnormal Sleep Architecture

Sleep Stage
Normal % TST
Timothy's % TST
1
7.1%
1.2%
2
46.1%
57%
3
5.5%
32.6%
4
18.5%
0%
REM
22.6%
9.2%
A case study: 7 year old boy with sleep-disordered breathing and abnormal sleep architecture.

The Importance of Sleep in Children

Case Study: Abnormal Sleep Architecture Causes

Currently, Timothy is only experiencing less than half of the normal quantity of REM sleep expected in a child of his age. In addition, there is no Stage 4 sleep noted, though a significant amount of Stage 3 sleep could be observed.

Timothy's sleep study noted the presence of periodic leg movements, sleep-disordered breathing with obstructive sleep apnea and central apnea events, and frequent arousals due to oxygen desaturations (lowest oxygen level recorded was 83%).

Timothy was referred for evaluation by an otolaryngologist to determine if removing his tonsils and adenoids would be indicated, as the obstructive apnea is the main cause of his nighttime desaturations. Referrals to a cardiologist and a neurologist were also indicated due to the presence of central apnea associated with desaturation.

The Science of Sleep: Part 1

The Science of Sleep Part 2

The Science of Sleep Part 3

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    • Kristen Howe profile image

      Kristen Howe 19 months ago from Northeast Ohio

      Leah, this was very interesting to know about the sleep arc throughout the ages. Thanks for sharing!

    • leahlefler profile image
      Author

      leahlefler 4 years ago from Western New York

      Thanks, DIYmommy! I hope your little one gets into a good sleep pattern soon, so that Mommy can get some sleep! Babies have double the REM sleep of adults - their brains are growing so quickly!

    • DIYmommy profile image

      Julie 4 years ago

      With a newborn (3 months old now!) asleep next to me right now, I found your article to be particularly interesting. I also found it be very informative and well structured. Thank you for the great hub!

    • leahlefler profile image
      Author

      leahlefler 4 years ago from Western New York

      Following a normal architecture pattern is important, teaches12345 - sleep is so vital to health! Here's to a full night's sleep for everyone - with all the proper sleep cycles!

    • leahlefler profile image
      Author

      leahlefler 4 years ago from Western New York

      Sleep is so important for children and adults - memory problems and type II diabetes have been linked to a lack of sufficient REM sleep and slow wave sleep. I hope we get Matt's (my older son's) sleep issues sorted out soon, too, AliciaC. My younger son uses a C-Pap so that helps him for the time being.

    • teaches12345 profile image

      Dianna Mendez 4 years ago

      Quite an interesting article and so educational on sleep patterns. From your chart, I believe I follow a pretty normal sleep architecture. Good to know. I know many who suffer from sleep deprivation will find this so useful. Voted up.

    • AliciaC profile image

      Linda Crampton 4 years ago from British Columbia, Canada

      This is a very useful article, Leah! It contains a lot of interesting information to think about. I hope your children's sleep problems are solved soon.

    • leahlefler profile image
      Author

      leahlefler 4 years ago from Western New York

      Thanks, mperrottet - sleep is fascinating and is vital for both children and adults. My older son has disrupted sleep architecture and desaturations to the low 80% level in sleep - so we have to find a solution for him. In children, the cause is often large tonsils and/or adenoids, which are a fairly easy "fix." I'll have to check out your article!

    • leahlefler profile image
      Author

      leahlefler 4 years ago from Western New York

      I have periods where I remember my dreams vividly, then go through a "dry spell" where I seem not to remember my dreams as well. We see our ENT on the 18th of February, so we will get a plan in place for my older son. My younger son has had several failed airway surgeries and we may attempt another, but we have to weight the benefits vs. risks. He is currently using a C-Pap machine to splint his airway open at night. I hope you have sweet dreams, Peggy!

    • mperrottet profile image

      Margaret Perrottet 4 years ago from Pennsauken, NJ

      This is such a well-done thorough hub. I find the study of sleep fascinating, and so important. I wrote an article on sleep as well, and will add a link to this excellent hub. It's good that you're getting help for your boys, and I hope that their sleep problems are remedied. Voted up, useful, and interesting, and I will be sharing as well.

    • Peggy W profile image

      Peggy Woods 4 years ago from Houston, Texas

      Hi Leah,

      What an interesting article regarding sleep. Hope your boys sleep problems are soon solved and remedied. I found the charts very interesting. I do a lot of dreaming and often remember my dreams. My husband rarely remembers his dreams. I heard or read one time that if one wakes up soon after dreaming, one is more likely to remember it. I am a light sleeper compared to my husband. Perhaps that is why I remember them so readily? UUI votes and will share.

    • leahlefler profile image
      Author

      leahlefler 4 years ago from Western New York

      I sometimes have insomnia, Om, but fortunately it is only occasionally. My boys both have significant sleep apnea and require intervention. Sometimes large tonsils cause a real problem for kids (and my younger son has an airway condition called laryngomalacia). In adults, the cause is usually an obstruction higher up, with the tongue and palate causing the obstruction. Thankfully, it is treatable so people with apnea don't build up a sleep debt!

    • Om Paramapoonya profile image

      Om Paramapoonya 4 years ago

      I do have sleeping problems sometimes but not too often. All this info is really interesting. It was a great read!

    • leahlefler profile image
      Author

      leahlefler 4 years ago from Western New York

      Thanks, PaisleeGal - sleep disorders are commonly under diagnosed, and can precipitate several health conditions (including type II diabetes). A good night's rest is vital for your health!

    • PaisleeGal profile image

      Pat Materna 4 years ago from Memphis, Tennessee, USA

      Very Interesting article!

    • leahlefler profile image
      Author

      leahlefler 4 years ago from Western New York

      Thanks, Dirt Farmer. Both of my children have sleep apnea - one is currently using a C-Pap machine and the other is seeing an ENT shortly (he'll probably just need a tonsillectomy and adenoidectomy). We've done about 10-12 sleep studies with our kids in the past 3 years!

    • The Dirt Farmer profile image

      Jill Spencer 4 years ago from United States

      I found this really interesting & shared it. Good one!

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