Stages Of Sleep

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written by sleep expert Lauren Hall

Stages Of Sleep: Everything You Need To Know:

Every night our body goes through a sleep cycle. So when getting a good night’s sleep, it’s not all about how many hours you get but how long you spend in the deep sleep stages. A lot goes on while you rest, and that’s no secret; to have the most restorative rest, you need to go through all the sleep stages.

But what is the sleep cycle, and what are the sleep stages?

Our body goes through a sleep cycle consisting of five sleep stages. Light sleep in the first two stages, then deeper sleep stages in three and four, then REM sleep in the fifth stage which is associated with dreaming. These stages occur across a 90-120 minute cycle, and we tend to have 4-6 sleep cycles a night.

We tend to experience rapid eye movements (REM) more in the second half of the night. With the first REM experience lasting 10 minutes and as the cycles go on, the period increases. Sounds pretty cool so far, right? Well, I am going to talk about this in more detail with you in this full guide.

Our sleep cycle is known as an ultradian biological rhythm as it occurs multiple times throughout the night. It goes hand in hand with circadian rhythms and the sleep-wake cycle in particular, but that is a whole other guide, so be sure to check that out.

In this article, I will be covering all the juicy details of our sleep stages and why they are so important for our health.

sleep on your side

What Is A Sleep Cycle?

Everyone knows sleep is not uniform; we don’t just fall asleep and then wake up feeling revived. Our body goes through multiple sleep stages to help restore and rejuvenate our body as well as make brain connections throughout the night. After all, our mind is most active when we sleep.

Our body goes through four or five sleep stages multiple times during the night for around four to six sleep cycles. Not all sleep cycles are the same length, but they vary between 90-120 minutes per cycle.

Sleep cycles are part of our internal biological clock, which causes patterns of brain waves that occur when we sleep. Each of these stages is characterized by a different level of brainwave activity which can be monitored using an EEG monitor. It changes from slow-wave sleep to REM sleep which we experience dreams.

Are All Sleep Cycles the Same?

To put this simply, no. As you progress through your nightly sleep, your sleep cycles tend to get longer. Your first sleep cycle when you start falling asleep tends to be the shortest of them all, ranging from as little as 70 minutes to 100 minutes.

But how long does the sleep cycle last?

As you progress through the night, your REM sleep stages tend to become longer and so do the deep sleep stages, so each sleep cycle is more likely to fall in between 90 and 120 minutes. As you spend more and more time in the deep sleep stages and REM stages, the cycles become longer.

Sleep cycles vary from person and from night to night; there are many factors that go into the sleep stages, such as age, recent sleep patterns along with alcohol consumption.

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What Are The Stages Of Sleep?

Some psychologists say that there are only four sleep stages while others say there are five, but to make things easier I am going to talk about the four sleep stages. These are determined based on the analysis of brain activity and brain waves while you rest.

You start with light sleep and as you reach the deeper sleep stages you reach the rapid eye movement stage (REM) which is best characterized by dreams. Each stage has been determined with an EEG monitor which tracks brain waves and activity.

 

Sleep Stages Type Of Sleep Other Names For This Stage Typical Length 
Stage One NREM N1, Light Sleep  1-5 minutes
Stage Two NREM N2, Light Sleep 10-60 minutes
Stage Three NREM N3, Slow-Wave Sleep, Delta Sleep, Deep Sleep 20-40 minutes
Stage Four REM REM Sleep, Dreaming 10-60 minutes

NREM Sleep Patterns:

So let’s talk about these stages of sleep in more detail; they can be broken down into non-REM sleep and REM sleep. So as you get deeper into the stages of sleep, your sleep becomes deeper and more restorative. Let’s start with the non-REM stages.

Stage One/ N1:

The first stage is a very light stage of sleep. It is when you first start dozing off and only usually lasts around 5 minutes. Your body’s brain activities start to slow down in this stage with brief movements/ twitches, and they become more rhythmic (alpha waves) and then turn into beta waves as they progress into stage two.

There are small changes in brain activity during this stage. This stage is a form of light sleep where the person can be easily woken, but if undisturbed, the person can easily move into stage two and progress deeper into the sleep cycle. Many people only spend a minute or two in the first stage.

Stage Two/ N2:

The second stage is when your body starts to drop in body temperature; in order to fall asleep, your body must drop a degree in temperature in order to delve deep into those deeper sleep stages. In this stage, muscles also begin to relax, and your breathing begins to slow down.

Beta waves are often found in the second stage; the brain activity is slow with short bursts of activity which helps prevent you from being woken up by external stimuli.

The second stage of sleep tends to last around 10-60 minutes but on average around 10-25 minutes with the first cycle. As the night progresses, this stage tends to get longer and longer. On average, you spend around half of your sleep in the second sleep stage.

When people have trouble falling asleep, it is because they are bouncing between the first and second sleep stages. This causes sleep deprivation as you are not reaching the deeper sleep stages, which are the most restoring and rejuvenating. This can also lead to certain sleep disorders.

Stage Three/ N3:

The third stage of sleep is also known as deep sleep; it involves delta waves that are slower still but have greater amplitude than earlier wave patterns. When someone is in deep sleep or slow-wave sleep stage, they are very difficult to wake up as their body is relaxed and almost paralyzed.

Muscle tone, pulse, and breathing rate decrease in N3 sleep, and the body relax even further. The brain activity during this period. These delta waves have an identifiable pattern. Experts believe that his sleep stage is most critical to achieving restorative sleep, allowing for body recovery and growth.

Even though brain activity is reduced, it can help bolster the immune system and make cognitive connections that contribute to insightful thinking, creativity, and memory. We spend most of our time in a deep sleep for the first part of the night, with roughly 20-40 minutes per cycle.

But as the night progresses, the third sleep stage tends to be shorter, and we spend more time in the rapid eye movement (REM)stage. On average, to achieve healthy, quality sleep, you should spend 1-2 hours in this stage per eight hours of sleep.

Rapid Eye Movement (REM) Stage:

During the REM sleep stage, brain activity tends to become more rapid and mimics similar waves to when you are awake. Your body experiences atonia during this stage, which is a temporary paralysis of the muscles, with two exceptions being your eyes and breathing muscles.

You can notice when someone is in this sleep stage as, despite their eyes being shut, you can notice their eyes moving rapidly under the eyelids. This is where the rapid eye movement (REM) name came from.

REM sleep is essential to cognitive functions like memory, learning, and creativity. It is known for the most vivid dreams and lucid dreams occur because of the increase in brain activity. So this stage is highly correlated with dreaming. Dreams can still occur at any stage but are most common and intense in the REM sleep stage.

In total, the REM sleep stage should take up around 25% of your sleep on average for adults.

What Is The Deepest Stage Of Sleep?

This is often debated between stage three sleep and stage four/ REM sleep, and you can argue that they are both the deepest stages of sleep because of their different characteristics. Stage three is the deepest stage of Non-REM sleep; it performs a variety of important health-promoting tasks and body renewing.

Stage three is known as deep sleep or slow-wave sleep, and it is when your body makes cognitive connections, makes repairs across your body, and helps the brain create and store new memories, improving the ability to collect and recall information.

REM sleep or stage four sleep is also considered the deepest sleep because our body produces delta waves while in this sleep. It is considered the deepest stage of sleep because your body is almost paralyzed, and it is impossible for you to wake up. It is also the sleep stage associated with dreaming.

Your brain uses REM sleep to cement information into memory, making it crucial for learning and decision making, so arguably, you can say both are the deepest stages of sleep, and those with sleep disorders cannot reach these deep sleep stages, which lead to sleep deprivation.

back sleeper

Why Do The Sleep Stages Matter?

Sleep stages are super crucial for both your mind and your body; during the night, your body goes through these sleep stages is vital for neurological and body repair as it allows your brain and body to recuperate and develop. The deep sleep and REM sleep stages are the most important of them all.

If you do not reach those deep sleep stages, then there are profound consequences such as fragmented sleep and consequences on thinking, emotions, and physical health. Those with sleep apnea related sleep disorders may struggle to make it through a full cycle and reach these deeper sleep stages/

While those with insomnia sleep disorders may not spend enough time in these deeper sleep stages, insomnia is a sleep disorder where you struggle to fall asleep and stay asleep at night this can also lead to hypersomnia which is excessive daytime sleepiness.

What Affects The Sleep Stages?

There are a few things that can actually affect how much sleep you get in a typical night and the quality of this sleep. Some factors can stop you from progressing through the sleep stages and gaining the most enriching night’s sleep in the deeper sleep stages.

Here are some of the factors that can affect your sleep quality and stop you from getting enough sleep.

Age: As we get older, our body produces less and less melatonin, which is the hormone that induces sleep. Time spent in each sleep stage dramatically changes as a result of getting older; older adults tend to spend less time in the enriching deep sleep stages and REM sleep stage and tend to experience fragmented sleep.

Whereas a newborn, on the other hand, will spend as much as 50% of their sleep in the REM sleep stage as they enter the REM sleep stage as soon as they fall asleep. But as they reach the age of five, their sleep stages become similar to an adult’s sleep stages.

Sleep Patterns: If someone’s sleep pattern has become very irregular and fragmented for a period of days, this can cause a knock-on effect on your sleep cycle; those with sleep or neurological disorders struggle to get that good sleep quality because they are bouncing between the first two stages.

This is also why promoting healthy sleep habits before and during sleep hygiene is super important.

Alcohol: For many of this may be a shock; you may be reading this and thinking, “but I fall asleep super easy after a drink,” and while this may be the case, your body cannot reach those deep sleep stages after inducing alcohol. This is also why we suffer from a hangover the next day as sleep is fragmented along with alcohol leaving our system.

Alcohol decreases REM sleep earlier on in the night, but as the alcohol wears off, there is a REM sleep rebound which means you spend prolonged periods in the REM stages, which detriments sleep quality. So while you may be getting enough sleep, the quality is poor.

Sleep Disorders: Sleep disorders are the top culprit for poor quality sleep as our body cannot reach the deep sleep stages throughout the night if constantly being disturbed by a sleep disorder. For example, Sleep apnea, Restless Leg Syndrome, and other conditions cause multiple awakenings in the night.

This can interrupt the healthy sleep cycle; while you can take sleep medicine to help make falling asleep much easier, those with these sleep disorders will always suffer from fragmented sleep in comparison to healthy adults.

relaxing hot bath

How To Create A Healthier Sleep Cycle:

While it is impossible to have control over your sleep cycle, there are a few ways you can promote a healthy progression through each sleep stage. The best thing you should do is firstly improve your sleep hygiene and sleep environment– such as the room temperature, sleeping on the right mattress, sleeping with the right pillows, etc.

Reading before bed is also recommended as research shows that it is a brilliant way to relax your mind for going to sleep. Reading can distract and relax your mind and even reduce stress levels by up to 70% so you can fall asleep faster and reach those deep sleep and dreaming stages easier.

When reading at night I would recommend that you invest in a book light for reading at night, it is an ideal choice to prevent you from disrupting your partner. Plus if you buy one with a warm light it will help you fall asleep much easier as it will help your body to start producing melatonin. 

Setting a consistent sleep schedule will actually make a world of difference for improving your quality of sleep, for example, falling asleep and waking up at a similar time both on weekdays and weekends, and setting half a sleep routine before bed can improve sleep quality massively.

Try to limit alcohol before bedtime, and eliminating noise and light disruptions can allow you to achieve an uninterrupted sleep and promote the natural cycle of your circadian rhythm and ultradian rhythms (sleep cycle).

If you struggle to fall asleep on day to day basis and think you might suffer from a sleep disorder like sleep apnea, it is important to talk to a sleep specialist or doctor who can recommend a treatment plan such as sleep medicine to help promote your natural sleep cycle.

Just creating a sleep routine and understanding sleep can help promote a healthy sleep cycle, allowing you to sleep deeply and achieve the most nourishing and rejuvenating night’s rest.

sleeping on your side

Final Thoughts:

So there you have it, everything you need to know about the stages of sleep; the first three Non-REM sleep stages work together to repair and rejuvenate your body, especially the third sleep stage. Non-REM sleep helps your body wind down and fall into a deep sleep, helping you feel well-rested in the morning.

While REM sleep is crucial for stimulating parts of your brain that are essential in learning, making, and retaining memories, getting enough sleep in all sleep stages will provide you with the most refreshing night’s rest and most restorative.

Your sleep cycle is more important than you think!

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