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Sleep has had a bad rap for years.
In the eyes of society, diet and fitness were coveted while sleep was valued the least. Back in the day, those who slumbered on for too long were deemed lazy.
Now that sleep is finally recognized to be essential to our well-being, why not understand more about the stages of sleep so you can get better rest?!
- Sleep Basics
- Stage N1: Entering Sleep
- Stage N2: Light Sleep
- Stage N3: Deep Sleep
- Stage 4: REM Sleep
- Stages of Sleep FAQs
- 7 Tips for Better Sleep
- Final Thoughts
Typically, we all move through 4 stages of sleep: 3 Non-REM stages and then REM (rapid eye movement).
These stages repeat themselves in what is called a ‘sleep cycle’ throughout the night. It takes about 90~ minutes to complete a cycle. More information about this below!
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.
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.
With the help of the EEG and continuous research, the original five stages of sleep were established.
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
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?
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.
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.
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.
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.
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
Stage N2: Light Sleep
Stage 1 and 2 are usually defined together as ‘light sleep.’ However, Stage 2 is actually when you enter sleep.
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 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!
- 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.
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.
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%.
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.
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.
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.
Stages of Sleep FAQs
Although there are still many mysteries in the study of sleep, there is a range of valuable information scientists have discovered already.
The different stages of sleep are:
- 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
The deepest stage of sleep is Stage N3. It’s the hardest stage to wake someone up from.
People commonly get REM and Deep Sleep mixed up – they’re NOT the same. REM is when you typically dream and deep sleep is where your body repairs itself.
This is how long each sleep stage is on average:
- N1 = 10~ minutes
- N2 = 25~ minutes
- N3 = 45~ minutes
- REM = 10~ minutes
The FIRST sleep cycle lasts about 90 minutes.
As the night goes on, our sleep cycle length will get longer and the duration of each stage will change. Typically, you will alternate between REM and N2 the most.
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.
REM sleep is 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 will be affected.
According to the National Sleep Foundation, This is much sleep you need 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.
No, it’s not hard to wake someone in REM sleep – quite easy, actually.
People who do wake up at the tail end of their REM sleep tend to recall their dreams easily.
It’s only hard to wake someone during deep sleep (Stage N3).
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.
4 or 7 hours of sleep COULD be 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?
If you give yourself enough time to sleep and you don’t have any sleeping disorders, your body will naturally get itself into a rhythm.
You feel worse after taking a nap because you probably didn’t wake up at the end of a sleep cycle.
This is especially true if you wake up during deep sleep (Stage 3).
Try setting an alarm so you don’t overextend your nap!
Remember 20 – 30 minutes to recover from fatigue (before you enter Stage 3) OR 90 minutes to commit something to memory (to complete 1 sleep cycle).
7 Tips for Better 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?
Here are some things you can try:
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!
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!
6. No Food 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.
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 sleep, 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, you can either a) go forth and slumber away, or b) learn more sleep secrets here!
But before you do, what kind of helpful hacks do you have to share with us?
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