what is slow wave sleep

What is Slow Wave Sleep (and How To Get More of It)

What is Slow Wave Sleep? Slow wave sleep is often referred to as “deep sleep.” It occurs during the 3rd stage of the “non-rapid eye movement” (NREM) phase of sleep. It is during this phase that the brainwaves are classified as “delta waves.” Delta brainwaves are the slowest frequency of brainwave and also have the highest amplitude (wave height).

In oder to understand what is slow wave sleep, it helps to understand the basics of sleep. This article will explain the main axioms of sleep, how to sleep better, and how to increase slow wave sleep.

Slow Wave Sleep and Health

Sleep is one of the most important components of health, yet it is often overlooked by many.  Improving sleep can improve your physical and mental performance and overall well being. It is an understatement to say that improving your sleep will improve your life. 

Therefore, if you want to make yourself better (who doesn’t?) then optimizing your sleep can have a huge ROI on your quality of life. Specifically, getting more slow-wave sleep can help you have more restful sleep and better recovery. First, we will discuss some sleep basics and how our circadian rhythm affects our hormones throughout the day and while sleeping.

If you want to get right into the strategies and products that will improve your slow-wave sleep click here.

Why Do We Sleep?

Why do we sleep? While awake, we go about the day moving, working, eating, thinking, learning, etc. which breaks our bodies down and drains us mentally.  Sleep allows us to rejuvenate our immune, skeletal, muscular, and central nervous systems.  

The brain may be the organ that benefits the most from a good night’s sleep.  During sleep, the brain rewires neurons and cleans up metabolic waste products produced during the day.  In fact, neurons can only truly repair themselves when you are asleep.  Thus, for proper brain function, you need to get adequate sleep.

The body requires adequate sleep as well.  Growth hormone and testosterone are secreted at their highest amounts while you sleepThese hormones help the body to repair itself and take on the strain of tomorrow.  

Your immune system also needs to get enough sleep to perform properly.  Studies have shown that reduced sleep has a negative effect on the efficacy of the immune system. In particular, one study done on sleep-deprived rats showed a severe attenuation in their immune systems which resulted in multiple infections and eventually their death.

How much sleep is enough sleep?

Our demand for sleep changes as we age.  For example, newborns need 14-17 hours of sleep,  MIddle school children need 10-13 hours, high schoolers 8-10, adults 7-9, and seniors need 7-8 hours.  So for most readers of this article, it’s safe to say that 7+ hours is a healthy amount of sleep.

The Stages of Sleep

Sleep can be broken into a two major stages: REM sleep (rapid eye movement sleep) and NREM (non rapid eye movement sleep). 

REM Sleep

During REM sleep your eyes randomly move and your brain waves are comprised of low-level alpha and beta brain waves. What’s interesting about this stage of sleep is your brain demonstrates these same types of brain waves while you are awake.  In this stage of sleep you dream the most.

During an average night’s sleep, you can expect to get about  4 to 5 rounds of REM sleep. Each round of REM increases in length with the first round being the shortest and the last round being the longest.  The first round of REM occurs 70 minutes into sleep. It is during this first round where the majority of your testosterone is produced.  After the first cycle of REM is complete each subsequent REM cycle occurs about 1.5 hours apart from each other. 

REM sleep should consist of about 20-25% of your total sleep.  From personal experience, I try and shoot for 1.5 to 2 hours of REM sleep. 

Non-Rapid Eye Movement Sleep (NREM):

There are three different stages of NREM sleep: stage 1 (N1), stage 2 (N2), and stage 3 (N3)Stage 1 is also known as “drowsy” sleep and is the lightest stage of NREM. Brain activity in stage 1 sleep resembles brain activity while awake, but eventually begins to transition into lower frequency alpha brain and theta brain waves.  This stage only lasts about 10 minutes long.

During stage 2 sleep your muscles begin to fully relax and the brain demonstrates theta waves mostly with spurts of short bursts of higher frequency sigma waves.  Information and memory consolidation occurs during this stage. 45% of your sleep on average is classified as stage 2 sleep.  

Stage 3 sleep is also known as deep sleep or slow-wave sleep.  It’s called this because during this stage the brain demonstrates delta waves which are a low(slow) frequency of about .5-4 Hertz.  Heart rate, body temperature, blood pressure, and brain activity are at their lowest when in deep sleep. Another interesting fact is during slow wave sleep, your body produces its highest amount of growth hormone.  Therefore, slow wave sleep is extremely important for muscle recovery. 

Personally, each night I aim to get more than 1:45 of slow wave sleep. I probably average about 1.5 hours deep sleep although. A lot of deep sleep would be anything over 2:00 hours.  Overall, stage 3 sleep comprises about 20% of total sleep. You should expect your total slow wave sleep to be slightly less than total REM sleep.

Circadian rhythm- From Sunrise to Sunset:

If you want to understand sleep, than you’ll need to understand the 24 hour circadian rhythm.


-6 am: Cortisol levels begin to rise.  Cortisol increases your heart rate and increases glucose uptake in the brain. It breaks down liver glycogen to elevate blood sugar as well.  This results in more blood, oxygen, and nutrients to muscles and brain to get you going for the day.   

-Within a few hours of waking, the hunger hormone ghrelin is secreted which enhances your craving to eat.  Eating a meal within the first two hours of waking has been shown in studies to optimize hormonal levels. This advice violates most intermittent fasting protocols, but it may be a better routine for hormone optimization.  

Photoreceptors in your eyes send electrical signals to your brain which further wake you up.  Getting morning sunlight is a great way to enhance energy levels and suppress melatonin levels.

-At around 11 am, sex hormones peak. Males under 40 produce the most of their testosterone during the first REM cycle and maintain a high production rate until waking.  After waking, testosterone levels begin to decline every 90 mins. At the end of the day testosterone levels reach their lowest point.


Around 2:30 your reaction time and muscle coordination are at their highest. Later, around 5:30 PM, protein synthesis, recovery capacity peakand cardiovascular efficiency peak. This makes the afternoon and earlier evenings good times to do heavy, intense lifting/workouts.


-A setting sun hits your optic nerves in your eyes which then sends a signal to something called the suprachiasmatic nucleus which amplifies chemical messages to the rest of the body like melatonin.

Leptin and adiponectin are released in the body from sunset to bedtime which work synergistically to burn fat while you sleep.  Blue light can prevent your body from secreting these hormones, so putting away your computer and/or iPhone an hour or more before bedtime are good strategies to prevent this from happening.  However, most of us either watch TV or continue working on our computers well into the night. At night I like to use blue light blocker glasses. Here’s a cheap pair I bought off of amazon that I currently use. 

Melatonin secretion begins around 10 pm.  Once again, this can be disrupted by any type of blue light that you are exposed to at night.  Melatonin helps to down-regulate brain activity. As melatonin peaks, so does the hormone prolactin.  Healthy prolactin levels help to secret healthy levels of growth hormone. Thus, making sure that you are not exposed to unnatural blue light sources at night is essential for proper growth hormone secretion during sleep. 

At midnight more leptin is secreted and it enters the hypothalamus.  Leptin stimulates the mitochondria to produce heat while you are asleep which results in fat burning.  Therefore, having have adequate leptin levels is essential for good sleep and for fat loss. For example, if your leptin levels are low at night a protein called agouti can increase appetite. An increase in appetite can lead to late-night snacking and blood sugar variability. Blood sugar swings disrupt sleep and can throw your hormones out of whack for the next night’s sleep.  It can become quite the vicious cycle.   

Strategies to Increase Slow-Wave Sleep

We have discussed a few strategies already on how to improve your sleep, and if you are looking specifically to improve your slow wave sleep then following all/some of these protocols is sure to help.

Strategy #1:

Avoid blue light after sunset.  As discussed previously this can disrupt melatonin secretion which can have a deleterious effect on your sleep and other hormones. In fact, most strategies to help improve your sleep involve increasing melatonin production at night.  

Strategy #2:

Get natural sunlight in the morning upon waking.  It will help to “sync” up your natural circadian rhythms with sunrise and sunset.  This will also help you to start producing vitamin D which further syncs your circadian rhythm.

Strategy #3:

Eat your carbs at night.  A study conducted by Israeli scientists took two groups: an experimental group that ate all their carbs at night and a control group which ate their carbs throughout the day, they found that the experimental group that ate their carbs at night not only lost more weight but showed higher leptin (“I’m full” hormone) levels and lower ghrelin (hunger hormone) levels at night. 

This piece of advice can be somewhat tricky because too many carbs at night, especially right before bed, can increase blood sugar levels which can be detrimental to sleep and recovery. That’s why its best to save your workouts for afternoon/evenings and follow up your workout with a nice meal full of protein and moderate carbohydrates. This way you are more insulin sensitive and able to store the sugars consumed in your muscle rather than in your fat stores.

Strategy #4:

Eat a healthy portion of protein.  Proteins are made up of 20 different amino acids.  Tryptophan is one of those amino acids.  Neurotransmitters like serotonin are derived from tryptophan and melatonin is also produced from it. Melatonin is one of the main hormones that signal to our body’s that it’s time to sleep. Therefore, consuming a healthy amount of protein can drastically improve sleep quality.  

Strategy #5

Maintain “sleep consistency.” The more variable the times are that you go to sleep and wake the less consistent your sleep is.  Therefore, by going to bed and waking at the same time each day you can achieve good sleep consistency. Check out the picture below.  As you can see, slow-wave sleep increases with increased sleep consistency. Not only will your sleep be better, but your body will feel more rested because it is during this stage where 95% of the body’s growth hormone is secreted.  

Sleeping in a room that is mid to upper 60s is the optimal temperature to sleep at.

what is slow wave sleep
slow-wave sleep

Strategy #6

Stay cool. When it comes to increasing slow-wave sleep or deep sleep, sleeping in a cold environment is paramount. Studies show that sleeping in a hot environment adversely effects slow-wave sleep and REM sleep.

Supplements that help increase Slow-Wave Sleep

Whey Protein– contains protein and amino acids like tryptophan which cross the blood-brain barrier and help raise melatonin levels and enhance sleep.

Vitamin D: Low levels of vitamin D are associated with poor sleep quality.  That’s why supplementing with vitamin D is a good way to get better sleep when you don’t have much access to sunlight (like during the winter).  Here is my vitamin D of choice. It’s not as pricey as some others and it also has vitamin K2 in it which is important for health calcium absorption.  

Melatonin: Researchers at MIT have shown that melatonin has positive effects on sleep.  In fact, they have shown that doses as low as 0.3mg are enough to have a beneficial effect on sleep.  If you go to the drug store and look at the shelf you’ll find melatonin supplements with very large dosages in the range of 3-5mg.  My personal sleep data supports that supplementing with melatonin increases both REM and SWS sleep. I have also soon better HRV scores when supplementing with melatonin.  

Zinc: If you’re a male, adequate zinc supplementation is key for proper testosterone levels.  It turns out getting zinc in your diet can also be beneficial for your sleep. A deficiency in zinc can lead to poor melatonin production which will adversely affect sleep quality.  

Magnesium: Magnesium helps convert tryptophan into melatonin, therefore, taking magnesium in the PM can enhance your sleep.  Magnesium has also been shown to enhance GABA activation in the brain (more on GABA next) which helps to put you in a more restful state. When buying magnesium supplements, be sure to stay away from the cheaper forms such as magnesium carbonate, oxide, sulfate, and gluconate.  These forms don’t absorb well in the body. Magnesium citrate is the most bioavailable form.  

GABA: GABA is your brain’s main inhibitory neurotransmitter. It calms your neurons and prevents them from getting overexcited. Too much GABA can prevent your sleep from getting deep enough to reach the more deep and restful stages of sleep (stage 3).  But just the right amount can help improve sleep quality.  Try this supplement 

L-Theanine: L-theanine is an amino acid that is naturally found in green tea.  It enhances the production of GABA in the brain.  This explains the relaxing effects that are felt after drinking green tea.  Use L-theanine to help you relax before going to sleep. 

Spirulina: This is a food that is good for you in so many different ways.  That’s why it is often deemed a “superfood.” It’s a good source of tryptophan which enhances melatonin and serotonin production.  Besides spirulina, almonds and pumpkin seeds also give the body a healthy supply of tryptophan.

Products Slow-Wave Sleep:

The Chili Pad

Chili Pad

My number #1 product to help increase slow-wave sleep is…The Chili Pad. The Chili Pad circulates cool water underneath your body while you’re asleep to help lower your core body temperature. I have seen some great results after using if for just a few weeks. Not only does it help get you better and more restful sleep, it helps increase HRV (heart rate variability). My personal sleep and recovery data has backed this claim up!

Click Here and use these promo codes to get a large discount off your desired Chili Technologies products

Chilipad20 (20% off a full chiliPAD sleep system)
OOLER15 (15% off a full OOLER sleep system)
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Sleep mask

Not all of us can completely black out our rooms. There is usually always some sort of light pollution that manages to creep its way into my room. Thats why I will usually sleep with a quality sleep mask like the one pictured below.

I posted my personal WHOOP sleep data below. You can see that on average, I personally increased my slow-wave sleep by about 45 minutes when wearing a sleep mask. This is huge! It’s hard to find a product as cheap as a sleep mask that can make such a difference in sleep quality.

whoop slow wave sleep data
whoop sleep data

Blackout curtains

I do not have the data on hand that verifies this claim, but I personally tracked my HRV and deep sleep when I moved into a new apartment and purchased black out curtains. It makes a huge difference. If you live in a metropolitan area, purchasing black out curtains might be the only way to eliminate light pollution in your bedroom.

Blue Light Blocking Glasses

These glasses are critical if you work on the computer often and if you watch/stream tv at night. Blocking blue light before sleep allows your body to secret melatonin levels. If this process gets interrupted your sleep will be disrupted.

That its for my products, supplements, and strategies to enhance slow-wave sleep and overall sleep. If you have any more suggestions, please feel free to leave comments!

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