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The 4 Stages of Sleep, REM & Why You Should Care

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The 4 Stages of Sleep, REM & Why You Should Care
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Sleep Basics

Before we dive into the nitty-gritty of sleep, let’s start with the basics.

The History of Sleep Science

Back in ancient times, people thought our brains completely shut off while we are sleeping. Little did we know that the complete opposite is true.

Based on this Harvard Medical Department’s timeline, here are some of the major scientific discoveries related to sleep throughout history:   

Dr. Nathaniel Kleitman, AKA the Father of Modern Sleep Research, opened the world’s first sleep laboratory at the University of Chicago.

His work spanned 70+ years and led to major findings that future researchers base their work on today.

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German Psychiatrist, Hans Berger invented the Electroencephalograms (EEG).

A device that measures and records electrical activity in the brain by hooking sensors up to a person’s head. The results are varying lengths of waves in graph form.

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With the help of the EEG and continuous research, the original five stages of sleep were established

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Rapid Eye Movement (REM) was coined by Dr. Kleitman and fellow researcher, Eugene Aserinsky.

While monitoring his own 8-year-old son, Aserinsky discovered that during the last stage of sleep our brains were highly active, contrary to popular belief.

Dr. William Dement, a student of Dr. Kleitman, established that sleep is cyclical.

For a healthy adult, a sleep cycle is typically 90 minutes long and repeats itself 4-5 times on average per night. 

This is where the 8 hours a night recommendation comes from:

90-minutes X 5 cycles = 450 minutes

450 minutes / 60 minutes = 7.5 hours

American Academy of Sleep merges two stages of sleep, resulting in only 4 stages of sleep instead of 5.

Anything that talks about 5 stages of sleep have been outdated for over a decade now. 

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Even though scientists have been researching sleep for years now, we still aren’t sure why we sleep! Of course, there are many speculations, but nothing is proven yet.

In the words of Dr. William Dement:

“We sleep in order to not be sleepy.” 

What is a Sleep Cycle?

There are two types of sleep that make up the 4 stages of a sleep cycle: Non-Rapid Eye Movement (NREM or “N” for short) and Rapid Eye Movement (REM)

We already learned that a typical cycle is 90 minutes long, but, according to Dr. Michael J Breus, the length of time a person needs to fully rest up is unique to that individual. This is why some people only need 6 hours of sleep per night, while others need much more.

I’ve noticed that I need 9 hours of sleep in order to wake up feeling refreshed, and that’s probably because I have a longer sleep cycle.

Bottom line:

Eight hours a night may be the general consensus, but there’s really no magic number. Everyone is different.

Sleep Cycles at Night

A healthy adult with no sleep disorders will cycle through the sleep stages on average 4-5 times a night. 

After the first cycle, your brain alternates between REM and NREM sleep in reverse order.

For example, after REM, you will transition back into N3, then N2, then back to N3, then REM. If you wake up, then you’ll start at N1 again.

Got it?

There’s a positive correlation between REM and N2 – the more REM sleep you have, the more N2 you’ll also get.

You may wake up during the transition period between N2 and REM, but probably won’t remember doing so in the morning.

REM has the opposite relationship with N3 – Deep Sleep. As the night progresses, the longer you’re in REM, the less N3 your body needs. 

So, what’s all this N1 and REM stuff?!

Let’s dig deeper, shall we?

Stage N1: Entering Sleep

You feel drowsy.

You crawl into your comfy bed, close your eyes and begin to drift off to sleep. I’m sure we’ve all experienced this before. 

For a healthy adult with no sleep disorder, the initial Stage 1 only lasts up to 1 – 7 minutes before you enter Stage 2. This makes up only 2 – 5% of the total sleep time.

Your Brain & Body

This first stage is considered more of a transition period.

You start to let go of the day’s tension and your thoughts begin to slow down yet you’re still aware of your surrounding.

Since your brain still registers sounds, so you can easily get pulled out of this stage by the closing of a door or by the hum of your fridge.

Your heartbeat and breathing recede. Your eyes roll to the back of your eyelids. You part your mouth slightly as your jaw relaxes. 

For some people, when they get woken up in this stage, they might even say they weren’t asleep at all.

Brainwaves

There are 5 main ones and they’re measured in frequency or cycles per second notated in Hertz (Hz). 

It might look like you’re only emitting one brainwave frequency at a time, but you’re actually emitting several at all times. One is just usually more dominant.

Let’s find out how each brainwave is different from one another. 

When you’re awake, alert and moving. You could be focused on something complex or trying to make a decision.  

High brain activity as hundreds of thoughts are being filtered through your mind.

Most of the time, we’re in Beta. 

NREM Stage 1 – Our brains begin to slow down. 

You’re relaxed but barely conscious. You’re closing your eyes and ready to fall asleep.

We can daydream or be creative – we usually get our best ideas at this time. 

NREM Stage 2 – Unconscious or in deep meditation.

Your brain is processing the day’s activities, committing information to long-term memory and regulating emotion.

Your brain continues to slow down.

Stage NREM 3 – Unconscious in deep sleep. 

This is where healing on a cellular level takes place. It’s almost impossible to wake someone up in this stage. 

Your brain slows down even further. 

The latest brainwave to be discovered – not much is known about it.

You’re conscious and processing a lot of information or deeply focusing on something.

Hypnic Jerks

Stage NREM 1 is also when some involuntary body twitches happen, called ‘hypnic jerks’ or ‘sleep start’.

Why it happens is still a mystery but there are some theories.

Don’t worry about it too much because it’s perfectly normal and harmless. Sometimes, I jerk myself awake with my own twitches.

People with poor sleep quality may experience more hypnic jerks.

To reduce hypnic jerks, you can try:

  • Cutting out caffeine, alcohol or similar stimuli
  • Exercising during the day instead
  • Reducing your mental and emotional stress levels
  • Meditation or relaxation techniques

SAVVY FACT:

Stage 1 is essentially falling asleep, so it should only occur once if you don't wake up at all throughout the night!  

Stage N2: Light Sleep

Stage 1 and 2 are usually defined together as ‘light sleep.’ However, Stage 2 is actually when you enter sleep.

Your Brain

Harder to awaken, any movements or noises that would jolt you out of slumber in Stage 1 will show up on the EEG as a K complex, while bursts of brain activity will show up as sleep spindles.

NREM 2 typically lasts up to about 10 – 25 minutes, representing 45 – 55% of your total sleep time.

In this time, you’re less aware of your surrounding, your brain activity continues to slow down and you start to emit more Theta waves.

Your Body

Your entire body continues to relax.

Your breathing, heart rate, blood pressure, and all metabolic functions slow down even further.

Your eyes stop moving, your body temperature drops.

Most of the night is spent this Stage. For good reason too!

Stage 2 is essential for memory consolidation. According to one study, people who learned something new during the day will have a higher density of sleep spindles than those in a control group.  

You are now prepared to enter Stage 3 – the notorious Deep Sleep!

SAVVY FACT:

Like your naps? Did you know that different time spans are better for certain things?

  • 20 – 30 minutes fight fatigue with a power nap. You’ll feel refreshed because you haven’t entered Stage 3 yet!
  • 90 minutes – commit something to memory. One full sleep cycle allows your brain to process something new you just learned!

Stage N3: Deep Sleep

Our most restorative period during sleep.

The last (and also most popular) stage of NREM is deep sleep, also known as Delta sleep or Slow-Wave sleep. 

This last stage of NREM typically lasts 20 – 40 minutes, representing about 13 – 23% of your total sleep time.

The average person can transition from Stage 1 to 4 in about an hour. That is if there’s nothing keeping you up at night.

Your Brain

At this point, you’re giving off Delta waves – the lowest and slowest of brainwaves.

This usually occurs when you are in a deep but dreamless stage of sleep or meditation. In both cases, you’re no longer aware of your surrounding, as if you’re in a trance…

Speaking of trance, it’ll be super hard to wake you up during this time! Your mom would have to make a lot of noise or aggressively shake you back to life.

When you’re finally back to consciousness, you’ll feel completely discombobulated for a few minutes until you find your bearings. 

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Your Body

Enter self-repair mode.

Growth hormones are released for development, blood supply to muscles increases, immune system expel toxins. 

Most importantly, our energy recharges for the next day. 

SAVVY FACT:

Weirdly enough, even though your body is in repair mode, this is also when parasomnia - Eg. sleepwalking, sleeptalking, bedwetting - happens most often. 

Stage 4: REM Sleep

Ah, the dream stage.

Also called Rapid Eye Movement or Paradoxical Sleep

You enter this stage about 90 minutes after you go to bed.

The first time you enter REM is short-lived – around 10 minutes max.

REM has an inverse relationship with N3 – Deep Sleep; it will lengthen in time as your sleep cycle repeats itself. By your last sleep cycle, your REM state can last up to 60 minutes.

Like deep sleep, as we get older, our REM time also gets cut short. For example, a baby spends about 50% in REM and adults spend only 20%.

Your Brain

This is where the paradox comes into play.

Your brain is highly active while your body is frozen, even though a lot of physiological changes are happening.

This is a GOOD thing!

Imagine how dangerous it is to be acting out whatever’s happening in your dream. Not only to yourself but others that are sleeping close to you.

At this point, you are exhibiting a combination of alpha, beta, and unequal waves, which is very similar to when you’re awake and conscious. There’s no dominate brain wave in REM

Your Body

You’re kind of paralyzed.

Except for quickened breathing, a faster heartbeat, and your eyes moving in all different directions, your torso and limbs don’t move at all.

This is REM Atonia doing its work. 

At this stage, you can be easily woken up and you’ll feel a bit groggy.

Sometimes, when you wake up during this phase, your body is still immobilized. This is called Sleep Paralysis – basically, REM is not done and still restricts your movements. 

This has only happened to me once when I was a teenager and it freaked me out. It didn’t help that my mom kept saying something about a demon…All I can say is that I know better now. 

SAVVY FACT:

Back in the ancient times, Chinese folklore tells a story about a ghost sitting on you while you sleep. That’s why you can’t move when you wake up. The Chinese term is 被鬼壓, which literally translated into “pressed by a ghost.”

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Your Dreams

You can enter some very intense dreams in this stage.

On multiple occasions, I’ve had dreams so vivid that my body overrode the REM Atonia.

For example, I’ve laughed myself awake too many times to count. That is the BEST way to wake up – you’re ecstatic, you’re hysterical, and you don’t care that you don’t remember why you’re so happy!

Your brain doesn’t really register your dreams. There are many theories as to why that is, but we still aren’t 100% sure.

What we do know is that we forget our dreams quickly because we didn’t have time to transfer them from short-term to long-term memory

Back in my college days, my dream recall ability was super weak, so I thought I didn’t dream at all. If I didn’t, then I’d go crazy! One study proved that not dreaming negatively impacts your memory – both object recognition and contextual fear. 

SAVVY FACT:

Want to improve your dream recall skills? Think about wanting to remember your dream before bed and jot down the details when you wake up!

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Sleep FAQs

Although there are still many mysteries in the study of sleep, there is a range of valuable information scientists have discovered already. 

There are 4 stages in total. 

Scroll up to learn about the details of each stage! 

  • N1 – Relaxed Stage – you’re falling asleep, easy to wake up and emitting alpha waves
  • N2 – Light Sleep – you just fell asleep, harder to wake up and sending out theta waves
  • N3 – Deep Sleep – you’re out cold, body in self-repair mode and transmitting delta waves
  • REM – Dream Stage – you’re dreaming, committing things to memory and exhibiting different brainwaves

According to the National Institutes of Health, the typical length of time to be in deep sleep for is 20-40 minutes for the initial cycle.

It should get longer as you cycle through the night.

With that said, it’s not really something that you can will yourself to do, unless you can control your unconscious.

If you’re at that level, please spill your secrets in the comments below!

For the rest of us regular folks, check out the tips below for better sleep, which can help you achieve deeper sleep.

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Stage N3 or Deep Sleep is the hardest stage to wake someone up from. This is during NREM – Non-Rapid Eye Movement.

People commonly get REM and Deep Sleep mixed up. It is NOT the same.

REM is when you typically dream and deep sleep is where your body repairs itself. It also takes a LOT of effort to wake you up in this stage.

On average, the FIRST sleep cycle will last 90 minutes. As the night progresses, our sleep cycle length will get longer, alternating between REM and N2.  

Remember that your sleep needs will be unique to you, so everyone’s sleep cycle length is slightly different. Here’s a typical breakdown:  

  • N1 = 7~ minutes
  • N2 = 25~ minutes
  • N3 = 40~ minutes
  • REM = 10~ minutes

Researched by National Institute of Neurological Disorders and Stroke, it’s possible to dream during NREM stages, but most vivid dreams occur in REM Sleep.

Again, REM (Stage 4) is NOT Deep Sleep (Stage 3). Learn more here! 

REM sleep is the last stage of the sleep cycle, where your brain is actively dreaming and emit brain waves similar to when you’re awake.

It’s important because it’s when all the good stuff happens! Your body is fixing itself on a cellular level, processing earlier events and transferring information into your long-term memory. Without it, your cognitive ability and memory will be affected.

According to the National Sleep Foundation, here are the recommended sleep durations by age:

  • 0-3 months = 14-17 hours 
  • 4-11 months = 12-15 hours
  • 1-2 years = 11-14 hours
  • 3-5 years =  10-13 hours 
  • 6-13 years = 9-11 hours 
  • 14-17 years = 8-10 hours 
  • 18-25 years =  7-9 hours 
  • 26-64 years = 7-9 hours
  • 65+ years = 7-8 hours 

Keep in mind that everyone’s needs are different, so it’s OK if you are slightly below or above the range.

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Actually, no at all. It’s quite easy to wake someone up during REM. People who do wake up at the tail end of their REM sleep tend to recall their dreams easily.

Only during deep sleep (Stage N3) is it hard to wake someone up from their slumber.   

No. We wake up by ourselves throughout the night all the time, we just don’t remember it.

Even if you wake someone up suddenly, it’s not dangerous. Other than risking their wrath.

They may feel disoriented for a few minutes, but they should appreciate you calling them to consciousness if it was for good reason. Just don’t flip their bed with them in it…

Yes, you can sleep too much.  

Dr. Michael J Breus‘ opinion is that oversleeping can lead to similar diseases and disorders as not getting enough sleep.

Your body should be able to regulate how much sleep you need unless you have a disorder.

How much is too much sleep? How much is not enough?

Your sleep needs are unique to you. It depends on so many factors like:

  • Genetics – What are you genetically predisposed to? 
  • Age – As you get older, you need less sleep
  • Fitness Level – The more active your lifestyle, the more your body needs to repair itself
  • Health – If you caught the flu, you’ll need more sleep too
  • Stress – What’s your life circumstances like – pressure from work or family?

Bottom line:

If you give yourself enough time to sleep (at least 8 hours) and you don’t have any sleeping disorders, your body will naturally get itself into a rhythm.

You probably didn’t wake up at the end of a sleep cycle. If you get woken up during deep sleep (Stage 3), then you’ll feel crappy.

Try setting an alarm so you don’t overextend your nap! 20 – 30 minutes to recover from fatigue OR 90 minutes to commit something to memory.

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Tips & Tricks to a Better Night Sleep

We’re always craving for a better night’s sleep, but would going to bed earlier do the trick? How do we do it exactly?

Besides the 12 essentials, here are some other things you can try:

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1 – Essential Oils

Dap some on your temples, inner wrist or elbow for fast absorption. Otherwise, you can use a diffuser.

We’ve all heard about the magic powers of lavender, but did you know that Sandalwood, Bergamot, and Valerian have similar effects?

 

2 – Journal

According to the University of Rochester’s Medical Department, writing out your thoughts, worries, goals or even just tomorrow’s to-do list can help you!

Try burning the piece of paper of worries – you might feel pretty satisfied!

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3 – Sleep Tracker

You can’t improve what you can’t measure, so start tracking your sleep journey!

Don’t want to shell out for a Fitbit or Apple Watch? Try these freemium mobile apps instead:

4 – Magnesium Supplement

A natural essential mineral that our body does not produce, Magnesium is consumed through food. It has many benefits, which includes relaxing our muscles.

Try taking a capsule before bed!

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5 – Meditation

There has been endless talk about the wonders of meditation but does it really work? Find out yourself!

Like sleep trackers, there are many mobile apps on the market that can guide you like: Headspace and Calm (iOS).

6 – Fast After 7PM

Too many people eat dinner at way too late.

Your body needs time to digest before you go to bed. Or else, it won’t be able to focus all its energy on self-repair when you shut down at night.

My advice? Stick to a 6PM dinner time. If you get hungry, drink water.

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7 – Set a Bedtime Routine

Last but not least, give yourself a night routine to follow. Steal the evening routine of Shawn Steveston – the sleep hacker expert!

Final Thoughts

So, what was new that you learned today?

Here are some brief highlights:

  • Humans sleep in cycles – one sleep cycle is typically 90 minutes
  • There are 4 different stages of a cycle, and you emit different brain waves in each stage
  • Deep Sleep and REM (dream state) are NOT the same things
  • Hypnic jerks are totally normal 
  • You got 7 tips on how to get better sleep
  • You got answers to 11 frequently asked questions about sleep 

Now that you know what you can do to get that oh-so-coveted deep sleep, go forth and slumber away!

But before you do, what kind of helpful hacks do you have to share with us?

Have you ever considered getting a waterbed?

They don’t have the same issues as before and are a lot better now.
Check out our best 5 waterbed mattress picks! 

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