American Sleep Association

Deep Sleep: How to Get More of It

Woman in deep sleep while wearing a sleep mask

We’ve all heard of deep sleep (also known as slow-wave sleep) and how our bodies need it to function properly, but what exactly is it? There is an abundant amount of research on deep sleep, but we have all of the essential information you need to know on what it is, its function, and how you can get more of it.

What is Deep Sleep?

Deep sleep is the sleep stage that is associated with the slowest brain waves during sleep. Because the EEG activity is synchronized, this period of sleep is known as slow-wave sleep: it produces slow waves with a relatively high amplitude and a frequency of less than 1 Hz. The initial section of the wave is indicated by a down state; an inhibition period whereby the neurons in the neocortex are silent. It’s during this period that the neocortical neurons are able to rest. The next section of the wave is indicated by an upstate; an excitation period whereby the neurons fire briefly at a rapid rate. This state is a depolarizing phase, whereas the former state is a hyperpolarizing phase. In contrast with Rapid Eye Movement sleep (REM sleep cycle), the main characteristics of slow-wave sleep are absent or slow eye movement, moderate muscle tone, and lack of genital activity.

Research Behind Sleep Stages and Deep Sleep

According to the Rechtschaffen & Kales (R & K) Standard of 1968, deep sleep can be described as stage three of non-rapid eye movement sleep and is often referred to as “slow-wave sleep”. There’s no clear difference between stages three and four; however, stage three has 20 to 50 percent delta activity while stage four has over 50 percent. Since the year 2008, the American Academy of Sleep Medicine no longer refers to stage four, and stages three and four have combined to create stage three. Therefore, a period of 30 seconds’ sleep, consisting of 20% or more slow-wave sleep, is now considered to be stage three. Slow-wave sleep (deep sleep) is one of the Stages of Sleep.

EEG graph measuring brain activity during deep sleep

Features of Deep Sleep

  • Electroencephalograph (EEG) demonstrates delta waves (high amplitude, low frequency)
  • Consolidation of memories
  • High arousal threshold
  • Presumed restoration of body and brain

Why Is Deep Sleep Important?

Deep sleep is important for consolidation of new memories, and is often referred to as “sleep-dependent memory processing.” Thus, individuals with primary insomnia will have impaired memory consolidation and won’t perform as efficiently as normal patients when completing memory tasks following a period of sleep. In addition, declarative memory is improved with slow-wave sleep, and this includes both semantic and episodic memory.

A central model has been created on the assumption that long-term memory storage is promoted by interaction between the hippocampal and neocortical networks. Several studies have shown that, once subjects have been trained to learn a declarative memory task, there was a significantly higher density of human sleep spindles when compared to the non-learning control task. This occurs due to unconscious wave oscillations that make up the intracellular recordings from cortical and thalamic neurons.

X-ray of brain

Function of Deep Sleep

Human sleep deprivation studies seem to suggest that the principal function of deep sleep may be to give the brain time to restore itself from its daily activeness. An increase of glucose metabolism in the brain occurs as a result of tasks that require mental activity. Yet another function affected by slow-wave sleep is growth hormone secretion, which is always greatest at this stage. Plus, it also creates both an increase in parasympathetic neural activity and a decrease in sympathetic neural activity.

In deep sleep, the highest arousal thresholds are observed, such as the difficulty of awakening by the sound of a particular volume. When a person awakens from slow-wave sleep, they generally feel quite groggy. Cognitive tests after awakening do indicate that mental performance can be impaired for periods of up to 30 minutes when compared to awakenings from other stages. This phenomenon is known as “sleep inertia.

There is always a sharp rebound of slow-wave sleep after sleep deprivation, meaning that the next bout of sleep will not only include more slow-wave sleep than normal, but deeper slow-wave sleep. The previous duration of this stage, in addition to the duration of prior wakefulness, will determine the duration of slow-wave sleep. When determining the amount of slow-wave sleep in any given sleep period, the major factor to note is the duration of preceding wakefulness, which is typically related to the build-up of sleep-inducing substances in the brain.

Sleep Disorders During Deep Sleep

There are several sleep disorders and parasomnias that occur predominantly during slow-wave sleep. Sleepwalking (Somnambulism), night terrors (sleep terrors), bed-wetting (Enuresis), sexsomnia, and sleep eating are all associated with slow-wave sleep. Individuals with narcolepsy often have fragmented deep sleep.

Factors that Increase Slow-Wave Deep Sleep

Factors that have shown to increase slow-wave sleep in the sleep period that follows them include intense prolonged exercise and body heating, such as immersion in a sauna or hot tub.

Studies have shown that slow-wave sleep is facilitated when brain temperature exceeds a certain threshold. It’s believed that circadian rhythm and homeostatic processes regulate this threshold. An unusually low, short-term carbohydrate diet in healthy sleepers promotes an increase in the percentage of slow-wave sleep. This includes a production in the percentage of dreaming sleep (REM sleep), when compared to the control with a mixed diet. It’s believed that these sleep changes could very well be linked to the metabolism of the fat content of the low carbohydrate diet. In addition, the ingestion of antidepressants and certain SSRI’s can increase the duration of slow-wave sleep periods; however, the effects of THC on slow-wave sleep remain controversial. Total sleep time in these instances is often unaffected due to a person’s alarm clock, circadian rhythms, or early morning obligations.

Woman getting deep sleep before alarm clock rings

How to Get More Deep Sleep

The most important thing that you can do to increase your amount of deep sleep is to allow yourself adequate total sleep time. Often, individuals will deprive themselves of adequate total sleep. In addition to reducing deep sleep, REM sleep is also shortened.

There is some data to suggest that vigorous exercise can increase or consolidate deep sleep. Some sleep specialists recommend aerobic activities like jogging, running, and swimming. For those who are prone to insomnia, it is best to exercise earlier in the day and not before bedtime.

In Summary

Stage three of the sleep cycle stages, slow-wave sleep (deep sleep), is a crucial part of your cognitive functioning. It plays a major role in memory consolidation and brain restoration. Because of its importance for your overall health, you must increase your amount of deep sleep by allowing yourself to have enough total sleep time each night. Additionally, exercise and a healthy diet are a couple of different methods you can try to help increase your slow-wave sleep.

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39 comments on “Deep Sleep: How to Get More of It”

  1. I found using Twitter (not just at night) caused a generalised low level stress that significantly reduced my deep sleep (FitBit data) and heart rate variability (HRV4Training app). My suggestion would be reducing or eliminating it, and not taking your phone into the bedroom ...

  2. I have had about 4 sleep studies in the last couple years. No one can seem to believe that just because I'm heavier, I don't have sleep apnea. It's been proven I don't with the tests. What does seem to be happening is I don't get deep enough sleep. No one seems to know how to treat that. I have Fibromyalgia & Arthritis & that makes sleep difficult, especially if the restless leg thing gets going. I also have an autistic child who wakes me frequently at night. There's not much I can do about these but I sure would love to try & get a decent sleep for once in my life!!! Is there a chance?

  3. I have a problem my daughter is about 13 years with bulky body structure when goes to sleep lies down with no response v shouts and carry outs different methods for awaiting her after sometime in some of the cases she e response with an anger and in some cases v we lose our temper end leave her please suggest the best course for her

  4. This is tricky. Eating well, exercise, weight loss, daily routine, blackout curtains, melatonin and theanine, cpap all helped me at age 51. My resting heartbeat gets as low as 48 from improved exercise but despite sleeping as much as 10 hours, Before and after improved fitness over several years, my scores never really get above 90 on Fitbit. There is almost always a proportion of restlessness equal to REM and Deep that I’m at a loss to reduce. It’s confounding because the bed and environment are great.

    I do take medicines but I have a hard time believing they contribute to that. Any ideas?

  5. I have been researching deep sleep because lately I have been exhausted, red-eyed, and foggy despite the amount of time I spend asleep. About three weeks ago I invested in a Galaxy smartwatch and while averaging 7-7.5 hours of time sleeping I consistently get 0-7% deep sleep. This is curious because I am only 38 and I thought it only decreased significantly for 60+ folks. I have no issues falling or staying asleep and am fit, regular weight, and I don't do anything of those things that would hinder my deep sleep. I believe I have good sleep hygiene. I considered that it might be my new smartwatch so I checked my last Fitbit from a year ago and it wasn't much better then. Is it more likely that the exhaustion is from stress rather than deep sleep? I'm trying to figure out if there anything I should be doing to fix this.

    1. I have the same issue - there are just too many nights after which I wake up in the morning feeling like I slept about 5 min - even if it was 8 hrs. I constantly felt tired. After a sleep study, I was told that I wasn't getting almost any deep sleep, a condition considered a form of insomnia. Would like to learn more about how to get the deep sleep I need.

      1. I'm interested in hearing what you found out, if anything. I suffer from the same issue--my fitbit is telling me I get very little deep sleep most nights, and although I sleep for 8-9 hours most nights, I still feel so tired during the day. I have a sleep study scheduled, but I'm nervous they won't be able to do anything to help. Have you found anything to help you get more deep sleep?

  6. Hey Melly,
    I have spent my life being hypersomnic. Coffee is helpful, but I am wondering if espresso might be better. I usually only have a couple cups in the morning (I get up between 5 & 6). I don't have any caffeine after 2:30 or so. Some of the other comments were interesting. I might give the elimination of carbs after a certain amount of time.

  7. The Oura ring is the best sleep tracker I have seen. Safe (it has an "airplane mode" so no EMFs on your body). It is amazing for tracking so much more find a discount code and it is $250. Well worth the money

  8. My Fitbit (Charge 2) is amazing. I just discovered how much information it can generate each night and am using that to plot my total sleep time, sleep efficiency (time in bed/time asleep), REM, Light and Deep sleep as well as awake amount. I have sleep Apnea and use a CPAP. By moving my bed time to an earlier hour from midnight, using f.lux app to eliminate blue light from my computer screen and removing night lights from my bedroom, my Deep sleep periods have gone up 45%. I'm 78 years old and feeling much better now.

    Now if I can juust talk the CPAP makers into building sleep monitoring into the machine and letting me get at it, that would be great.

  9. My thoughts on deep sleep are based on a book I recently read, “The End Of Alzheimer’s,” by Dale Bredesen, M.D. I don’t think it’s a coincidence that seniors like me typically begin having problems with sleep in general and with getting sufficient deep sleep in particular. Dr. Bredesen notes that during deep sleep, our brains engage in chemical cleansing of substances (including amyloids) that block communication between synapses in the brain.
    One way to increase deep sleep is to avoid eating just before going to bed; ideally, several hours before. (The theory is that if you put food in your gut just before going to sleep, your body sends too much of its blood supply to the gut for digestion to have a sufficient supply for deep sleep cleansing of the brain. Makes sense to me.)
    I try to consume zero calories after 8 pm.
    More to the point: I’ve started fasting through one dinnertime per week; that is, one day a week, no solid food after lunch.
    I’m six weeks in. My FitBit watch just told me I had 70 minutes of deep sleep last night. Previously, I wasn’t getting more than 30 minutes (out of the same period, approximately seven hours, of sleep per night).
    I’ll keep on checking (and I know a watch is not scientifically calibrated, but still...).
    Would be interested if others have a similar experience.

  10. And one thing that was not addressed in this article is hypersonia. Those of us that suffer with hypersomnia feel tired and groggy all day, every day no matter how much sleep we get. It feels like you're sleeping you're life away and it's miserable. Do you have any suggestions on how to deal with it

  11. I have a Garmin watch to record the sleep time, last night the numbers was as following:

    Deep 1h 30m
    Light 4h 20m
    Rem 1h 10m

    Are deep sleep enough? It is not, how can I increase?

    Thanks in advance


  12. Cheryl you may want to check to see if you have sleep apnea. And Gregg thanks for the advice I will try it, no carbs past 1. No food 2 hrs before sleep.

  13. I was not able to properly sleep during 40 years then decided to go with the a couple of neurologist and the don't found anything worn in my brain. I started to reduce my weigh but was not able to reduce a lot reducing fat, after seeing them documentary of fed up I discovery that sugar is worst than anything else so I stop eating sugar as much as possible, after three months by the first time in my life I star sleeping better my wife steel eat a lot of sugar and she is able to sleep good and right a away. I am coming here due I was looking s way to increase my deep sleep but probably I am not to bad now. leaving as much as I can sugar and exercise regularly was the best decision in my life.

  14. I've got a sleep tracker and I am low in deep sleep, am on a diet so its not that as its low sugar, low fat.. I don't eat after 7 pm.. I exercise loads Inc cycling and walk an avg 12500 steps a day.. I will either crochet or watch TV before bed so I'm never on the net.. I have tried listening to music.. Not crocheting, laying in bed with lights off hours before bed.. Going late, going early, and I cannot get it right.. I am starting to feel exhausted constantly.. I don't get it at all.. Any suggestions? Am trying a bath and essential oils tonight.. To see if that helps and a bedtime app for my little one.

    1. Hi Cheryl, The article mentioned deep sleep being associated with the brain’s metabolism of fat. Do you think you may need more healthy fat vs low fat?

    1. You cant get more deep sleep than what you need. It's not like a drug or something where you can overdose. You get what your body needs

      1. You dont know what your talking about. Deep sleep varies for many reasons and a lot of people suffer a lack of that stage of sleep which affects them in many ways.
        New studies suggest stress, diet and other factors contribute to the amount if time spent in each stage if sleep. Research and experience suggests you have a big mouth and little brain.

    2. How do you know the sleep tracker is accurate? I've heard they aren't which is why I would hesitate to buy one.

      1. It shows the minute you sleep and wake up, or if you wake up in the night. Which is easy to check if its accurate especially after a week.

  15. I went from 0 to 15 mins of deep sleep for about 1 year to over 1 hour for the last three weeks by not eating before bed (2 hrs.) and no carbs past 1 o'clock pm. I feel more awake sharper with less sleep. I'm a little pissed I've read this in only one book and found nothing about laying off carbs at night on any site. I also started eating in a 12 -8 pm window and fall asleep at 10 of all these changes think it was mostly laying off the carbs after my noon meal that increased my deep sleep. (used a sleep tracker )

    1. Hey, greg. When you say "lay off carbs" what are you talking about? Almost everything has carbs. Are you only eating meat? I'm trying to increase my deep sleep time and just received a fitbit tracker and the only night that I reached the "benchmarker" for deep sleep was after a meal with steak. No potato just salad with that. Just trying to figure out how to increase my deep sleep.

    2. I'm beginning to wonder about the effects of carbs on my sleep or lack thereof and think it is certainly worth a try. Can you tell me the book that you read this in? Perhaps they have some more useful tips to try.

  16. “ In addition, the ingestion of antidepressants and certain SSRI’s can increase the duration of slow-wave sleep periods; however, the effects of THC on slow-wave sleep remains controversial”
    I had to look up THC —amazing is there a medical study anywhere that shows this increases slow-wave sleep. Is it controversial because it is a Federally illegal drug or because there are no reliable studies to back up the inference?
    Poorly written —SSRI’s are a antidepressant. The statement above would lead some to think that antidepressants and SSRIs are 2 different medications. Excluding SSRIs not all antidepressant increase deep wave sleep in fact Please SHOW ME A LIST OF ANTIDEPRSSANT THAT INCREASE DEEP WAVE SLEEP!

  17. “Why Is Slow-Wave Sleep So Important?”
    Ok so how do I find a sleep medicine doctor that will pay attention to this?
    All they want to do is tell me my CPAP readings are fine while my sleep studies always comment on how little slow-wave sleep I have.
    Where is the research and the emphasis to find a reliable way to monitor sleep stages at home?

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