When you think about getting the sleep you need, it's normal to focus on how many hours of sleep you get. Sleep duration is undoubtedly essential, but it's not the only part of the equation. It's also important to think about the quality of your sleep and whether the time you sleep is actually restorative. A seamless transition through the four sleep stages is essential to receiving high-quality sleep. This article will focus on the different stages of sleep and how they affect the human body and your sleep cycle.
There are four stages of sleep, (though there is also an additional stage1 that is not regarded as a true sleeping stage because you are fully awake): Wake, N1, N2, N3, and REM sleep. Stages N1 to N3 are considered NREM sleep (non-rapid eye movement), and each stage is a progressively deeper sleep.
About 75% of sleep is spent in the NREM stages, most of which is spent in the N2 stage.
A typical night's sleep consists of 4 to 6 sleep cycles, with the sleep stages proceeding in the following order: N1, N2, N3, N2, REM.
A complete sleep cycle takes about 90 to 120 minutes. The first REM period is short, and as the night progresses, longer periods of REM sleep and less time in deep sleep (NREM) occur.
Awake/Alert - The first phase is the wakefulness phase or phase W(Wake), which also depends on whether the eyes are open or closed. During wakefulness, with eyes open, beta waves dominate. Alpha waves become the dominant pattern when people become drowsy and close their eyes.
If you count this as a genuine stage of sleep, you'll have what is commonly called "The 5 stages of sleep."
N1 (stage 1) - Light sleep (5% of total sleep)
This is the lightest stage of sleep. This short, drowsy phase is the transition to sleep when your breathing and heart rate slow down. The light sleep phase lasts about 1-5 minutes and makes up 5% of total sleep time.
N2 (stage 2) - Deeper sleep (45% of total sleep)
This phase represents a deeper sleep than stage 1, yet still considered light sleep. This is when your heart rate and body temperature drop. Stage 2 lasts approximately 25 minutes in the first cycle and lengthens with each subsequent cycle, eventually consisting of roughly 45% of total sleep. During this sleep stage, bruxism (teeth grinding) occurs.
N3 (stage 3) - Deep sleep (25% of total sleep)
N3 is also known as slow-wave sleep (SWS). This is considered to be the deepest stage of sleep.
This phase is the hardest to wake from; for some people, even loud noises (over 100 decibels) will not wake them.
As people get older, they tend to spend less time2 in this slow-wave sleep (deep sleep) and more time in sleep stage N2 (deeper sleep). Although this stage has the highest wakefulness threshold, a person awakened in this stage will have a temporary period of mental cloudiness, known as sleepiness.
Cognitive tests3 show that people awakened in this stage tend to have moderately impaired mental performance for 30 minutes to an hour. This is the stage when the body repairs and regrows tissues, builds bones and muscles, and strengthens the immune system. It is also the phase when sleepwalking, night terrors, and bedwetting occur.
REM sleep - (stage 4) (25% of total sleep)
REM sleep (rapid eye movement) is associated with dreaming and is not considered a restful sleep stage. This stage usually starts 90 minutes after you fall asleep, and each of your REM cycles gets longer during the night. The first period typically lasts 10 minutes, while the last period lasts up to an hour.
Sleep is an integral part of the human sleep cycle. It is a state of rest for the mind and body when the brain is inactive. During this time, we experience foggy dreams that are hard to recall.
The amount of sleep you should get varies from person to person. The key is to find out how much sleep you need and then take steps to ensure you get it.
Your age, genetics, lifestyle, and even the time of day determine the amount of sleep you need. For example, if you are a kid or a teenager, your body requires more sleep than someone who is an adult.
Many factors affect the amount of sleep you need. It's a good idea to consult your doctor to find out what's best for you.
Adults need a minimum of seven hours of sleep, but eight or nine hours is recommended.
The National Sleep Foundation recommends4 that adults get between 7-9 hours of sleep each night.
Recommended sleep by age:
A good night's sleep is essential for children's healthy development. It helps them grow, learn and stay healthy.
Sleep deprivation can lead to reduced cognitive function, reduced ability to concentrate, and increased irritability. Sleep also plays a crucial role in developing a child's immune system.
How much sleep children need is determined by their age and can range from 10-14 hours per night. A child's brain needs more deep sleep than an adult's brain to develop correctly, so they need more time in bed at night.
Recommended sleep by child age:
The human body needs sleep for several reasons. Sleep is essential for physical and mental health, memory, learning, and creativity.
Sleep is divided into two main stages: REM (rapid eye movement) and NREM (non rem sleep).
The first phase of sleep is NREM (Non-rapid eye movement sleep), which consists of three stages (N1, N2, and N3) that alternate with four sleep cycles per night.
Deep sleep (N3) helps to repair muscles, build bone density, and grow new cells in the brain. The second phase of sleep is REM (rapid eye movement), which takes up 25% of our time spent sleeping. This stage helps to consolidate memories from the day before and restore mental energy levels.
A sleep pattern, or sleep-wake pattern, is a circadian rhythm that instructs the body when to go to sleep and when to wake up.
The circadian rhythm is an internal clock that tells the body when to sleep and wake up. This cycle of sleep and wakefulness lasts about 24 hours.
A person's circadian rhythm is usually synchronized with the 24-hour day by external cues, such as daylight and nighttime. This is called a "circadian rhythm."
A person's sleep pattern (how long and when they sleep) is determined by their circadian rhythm and sleep-wake cycle.
Those who work rotating shifts or jobs that require them to be awake at odd hours have an increased risk of experiencing sleep disruptions and irregular sleep patterns.
These disruptions to one's natural sleep pattern and any deviations from it lead to fatigue and increase the risk of an accident.
There are 4 stages of sleep because all four stages of sleep have unique characteristics. However, the deep sleep stage, or N3 is sometimes further divided up into one more stage. This is technically correct, however, it´s not typically accepted as an additional true stage of sleep.
This is the first reason why sometimes you will hear that there are 5 stages of sleep.
What is the difference between these two deep sleep stages?
Stage 3 / N3 (first deep sleep stage)
In stage 3, the brain waves slow down and only a few bursts of activity can be seen.
When you are in a deep sleep, your muscles relax and your breathing slows down even more.
This stage of sleep is hard to wake up from, and you might feel confused if an alarm goes off or something else wakes you up.
Stage 4 / N3 (second deep sleep stage)
Stage 4 is a deeper sleep where the brain waves slow down even more and it is very hard to wake the person up. This is considered the deepest sleep of all the stages.
It is believed that during this stage of sleep, tissue repair occurs, as well as the release of hormones that aid in growth.
What is the second reason for hearing there are 5 stages of sleep?
The second reason is that some people regard the Wake/Alert stage as mentioned earlier in this article as a true sleep stage. As a gentle reminder is it the wakefulness phase, where you are not asleep.
This wakefulness phase can also be divided into one more stage, as we did with the N3 (deep sleep) stage.
This depends on whether the eyes are open or closed, yet still awake.
Awake/Alert - Eyes-open
Beta waves are the most common when you are awake with your eyes open, yet feeling drowsy.
Awake/Alert - Eyes-closed
Alpha waves become the dominant pattern when people feel tired and close their eyes, though not sleeping.
It is, however, quite rare you will hear people regarding both of these as individual sleeping stages.
So, if you count the Awake/Alert stage as a stage but disregard stage N3 (deep sleep) as two stages, there are 5 sleep stages again.
And if you count both Awake/Alert as a stage and both deep sleep stages, there will be 6 stages of sleep.
And if you are really bold, you will count Awake/Alert as two stages and still count deep sleep as two stages, there will be 7 stages of sleep.
Just to be clear, there are 4 uniquely characterized sleep stages, but 5 stages of sleep would also be accepted as true for some. Therefore, there are either 4 or 5 stages of sleep is true.
How many stages of sleep are there?
| 4 Sleep Stages | 5 Sleep Stages - VER 1 | 5 Sleep Stages - VER 2 | 6 Sleep Stages |
|---|---|---|---|
| Stage 1 / Light Sleep / N1 | Stage 1 / Light Sleep / N1 | Stage 1 / Awake/Alert | Stage 1 / Awake/Alert |
| Stage 2 / Deeper Sleep / N2 | Stage 2 / Deeper Sleep / N2 | Stage 2 / Light Sleep / N1 | Stage 2 / Light Sleep / N1 |
| Stage 3 / Deep Sleep / N3 / SWS | Stage 3 / Deep Sleep / N3 / SWS | Stage 3 / Deeper Sleep / N2 | Stage 3 / Deeper Sleep / N2 |
| Stage 4 / REM-Sleep / REM | Stage 4 / Deep Sleep / N3 / SWS | Stage 4 / Deep Sleep / N3 / SWS | Stage 4 / Deep Sleep / N3 / SWS |
| Stage 5 / REM-Sleep / REM | Stage 5 / REM-Sleep / REM | Stage 5 / Deep Sleep / N3 / SWS | |
| Stage 6 / REM-Sleep / REM |
Stage 1:
The first stage of sleep is called the "NREM 1" (Non-Rapid Eye Movement) or N1, or light sleep stage. The light sleep stage lasts from 1 to 10 minutes. Consisting of roughly 5% of total sleep.
It's possible that a person who sleeps through the night without interruption won't spend much more time in stage 1 as the night goes on and they progress through subsequent sleep cycles.
Stage 2:
The second stage of sleep is called "NREM 2" (Non-Rapid Eye Movement) or N2 or the deeper sleep stage. The deeper sleep stage lasts from 10 to 60 minutes. It lengthens with each subsequent cycle, eventually consisting of roughly 45% of total sleep.
Stage 3:
The third stage of sleep is called "NREM 3" (Non-Rapid Eye Movement) or N3, Slow-Wave Sleep (SWS), Delta Sleep, or the deep sleep stage.
The N3 stages, which occur in the early stages of sleep, typically last anywhere from 20 to 40 minutes. Stage 3 consists of roughly 25% of total sleep.
As you sleep through the night, the deep sleep stages become shorter, and you spend more time in REM sleep.
Stage 4:
The fourth stage of sleep is known as REM (Rapid Eye Movement). It is not as deep as stage 3; however, it is still considered deep sleep.
On average, it takes around 90 minutes of sleep before you begin to experience REM sleep.
REM periods last longer as the night goes on, particularly in the night's second part.
The initial stage of REM sleep may only last 5 minutes, while subsequent stages might endure for up 60 minutes, during which people have difficulty waking up when they need to in the morning.
REM sleep consists of roughly 25% of total sleep in adults.
Summary of a normal sleep cycle and the different stages of sleep:
A typical night's sleep consists of four to six sleep cycles, with sleep phases progressing in the following order: N1, N2, N3, N2, and REM.
The sleep-wake cycle is a vital function of our physical and mental health.
It aids in regulating our hormones and body temperature, which regulates our metabolism.
Some of the considerable impacts of sleep deprivation on comprehension5, emotions, and physical health may be explained by the inability to achieve sufficient amounts of deep sleep and REM sleep.
People who are often awakened during the earlier stages of sleep, such as those who suffer from a sleep disorder, have a higher risk of not progressing through these deeper stages of sleep in the proper manner.
Insomniacs frequently do not get enough overall sleep to spend the required time in each stage.
We all know that a good night's sleep is vital for our health, but not all know the benefits of sleeping well. A good night's sleep can help you to be more productive, recover from illness faster and stay healthy.
Sleep deprivation can cause many health problems such as obesity, diabetes, heart disease, and depression.
We should get 7-9 hours of sleep every night to maintain a healthy lifestyle.
The majority of people awaken once or twice during the night.
Caffeine or alcohol consumption late in the day, a bad sleep environment, a sleep problem, or another health issue are all possible causes.
If you can't fall back asleep, you won't get enough quality sleep to keep you refreshed and healthy.
It's vital to figure out what's keeping you awake so you can remedy the problem and get some sleep.
Furthermore, it is critical to understand what influences sleep stages.
Age often has an effect on the sleep stages.
The younger an individual is, the more likely they are to sleep well.
This indicates that they will likely enter rapid eye movement (REM) and deep sleep more quickly and frequently.
Less REM and deep sleep will be experienced with increasing age.
The duration of these stages is also affected by age. Younger people might spend up to 25% of their time in REM, while older people might spend as little as 5%.
During the first few months of life, infants may spend up to 50% of their sleep time in REM sleep.
Consuming alcohol can have different effects6 on the sleeping stages.
Because of its sedative characteristics, alcohol may help with sleep onset, helping you to fall asleep more quickly. However, alcohol has been found to cause a person to wake up more often than normal during the night. This is because it negatively alters the natural sleep cycle, which promotes deep sleep and REM sleep.
On the other hand, people who drink before bed frequently experience interruptions in their sleep cycle as liver enzymes digest alcohol.
This can also result in increased daytime drowsiness and complications the next day.
Sleep disorders are a problem that affects many people.
Some of the most common sleep disorders affecting the sleep cycle are insomnia, restless leg syndrome, and sleep apnea.
These and other diseases that induce repeated awakenings may disrupt a healthy sleep cycle.
Wake/Alert is a phase that can be seen as the opposite of sleep. It is a state where the person is not sleeping yet.
This stage is the wakefulness stage, also called stage W, and it depends on whether or not the eyes are open.
Beta waves are the most common when you wake up with your eyes open.
Alpha waves become the main pattern when people feel tired and close their eyes.
The wake/alert stage is not considered a true sleep stage because you are not asleep.
However, it is essential for the sleep cycle and plays a vital role in falling asleep.
Light sleep is the stage of sleep where we do not sleep completely. It is also classified as stage 1 or NREM stage 1.
This stage of sleep is characterized by a low level of brain activity. However, it still has some characteristics that are different from the rest of the stages in a night's sleep cycle.
The duration of light sleep can last anywhere from 1 to 10 minutes, which means that it represents about 5% of the total sleep time of the night.
Knowing about this stage is important because it can affect your mood and cognitive abilities during the day.
The second stage, also known as N2 or deeper sleep, is a phase of sleep characterized by a slower heart rate and lower body temperature. This stage lasts around 25 minutes in the first cycle. It grows with each subsequent cycle, eventually accounting for 45% of total slumber. Bruxism (tooth grinding) occurs during this sleep stage.
This stage of sleep is essential because it helps the body to recover and heal from the day. You may also experience muscle twitches while preparing for slow-wave sleep during this sleep phase.
Deeper sleep, or NREM stage two, usually happens right after you fall asleep. You spend more time in this stage as the night goes on. This is a restful sleep phase where your breathing and heart rate are regular.
You're not easily awakened during this sleep phase, but you may feel groggy if you are. You may also experience some muscle twitches during stage 2 sleep. Deeper sleep helps to restore your energy and vitality so you can function optimally during the day. Deeper sleep is important for optimal daytime functioning.
Deep sleep is the most critical stage of sleep because it allows the brain to recover and repair itself. It helps people to wake up feeling more refreshed and energetic. Deep sleep is a state of the human brain that is characterized by slow-wave sleep.
There are two types of deep sleep: slow-wave sleep and paradoxical sleep. Slow-wave sleep is the deepest form of deep sleep, and it occurs in stage 3 (deep sleep). Paradoxical sleep, on the other hand, occurs in the REM stage.
Deep sleep is the most relaxing form of sleep that our body gets. It is also called the non-REM (non-rapid eye movement) stage of sleep.
Benefits of deep sleep:
REM sleep is a deep sleep stage characterized by rapid eye movements. This stage of sleep is believed to be crucial for the consolidation of memories and brain function.
REM stands for Rapid Eye Movement, which is a state of sleep that occurs during the fourth stage of the sleep cycle. REM is also called paradoxical sleep because it has features in common with wakefulness, including rapid eye movements and muscle activity. Still, it has many features in common with non-REM stage 3 (deep sleep).
The amount of REM sleep a person experience varies from one night to another and over time within an individual's lifetime. In general, children experience more REM than adults do.
Sleep cycles are intervals during which we pass through various stages of sleep.
A typical night's sleep consists of 4 to 6 sleep cycles, with the sleep stages proceeding in the following order: N1, N2, N3, N2, REM.
Throughout the night, we will repeat these stages in a cycle that will last anywhere from 70-120 minutes before starting again.
It is typical for sleep cycles to fluctuate throughout a night's sleep.
The initial sleep cycle is typically the shortest, ranging from 70 to 100 minutes, and subsequent cycles usually range7 from 90 to 120 minutes.
The proportion of the night spent in each stage of sleep also shifts.
Factors such as age, past sleep patterns, and alcohol use contribute to individual and nightly variations in sleep cycles.
A normal sleep cycle includes all four stages of sleep: NREM stage one, NREM stage two, NREM stage three, and REM sleep.
We will move through these stages several times during a typical night's sleep. The first sleep cycle of the night usually lasts 70-100 minutes, and each subsequent sleep cycle usually lasts 90-120 minutes.
After completing a full sleep cycle, your body will restart from either NREM stage 1 or NREM stage 2 until the final cycle is completed, at which point you should wake up rested.
The amount of time spent in each stage varies depending on age and other factors. For example, infants spend 50% of their sleep in REM sleep, while adults only spend 25% of their total sleep time in REM sleep.
Most people experience four to six sleep cycles per night.
There is some individual variation, but the average sleep cycle length is 90-120 minutes.
There are a few things you can do to ensure that you have a healthy sleep cycle:
By following these tips, you can help ensure that you get the high-quality sleep your body needs to function at its best. Sleep is essential for good health, so make it a priority!
The recommended amount of sleep for adults is 7 to 9 hours. However, this number can vary depending on the person's age and health.
There are many factors that affect the quality of your sleep. For example, your stress levels, how well you slept the previous night, and how much caffeine you had during the day.
Understanding the role of the four sleep stages is important for getting the high-quality sleep your body needs. Each stage serves a specific purpose and is crucial for rest and rejuvenation. By understanding the different sleep stages, you can create a bedtime routine that helps you fall asleep and stay asleep throughout the night.
There are many things you can do to promote a healthy sleep cycle, such as getting enough sleep, avoiding caffeine before bed, and establishing a regular sleep schedule. By following these tips, you can help ensure that you get the restful sleep your body needs.
