What Is Core Sleep vs. Deep Sleep? (2023)

What Is Core Sleep vs. Deep Sleep? (1)

A good night’s sleep is often hailed as the cornerstone of a healthy lifestyle, playing a crucial role in our physical and mental well-being. Yet, with so much emphasis on sleep, understanding its complexities can often feel overwhelming. Two terms frequently come to the forefront regarding sleep: core sleep and deep sleep. But what do they mean? How are they connected? And why does it all matter for our physical and mental health?

We’ll explore the fascinating world of sleep, the distinctions between core and deep sleep, their respective roles in the sleep cycle and how they contribute to our overall health and everything related to them. By understanding these vital aspects of sleep and how they fit into the sleep cycle, you will be better equipped to optimize your restorative rest and enhance your overall quality of life.

The Sleep Cycle

Overview of the Sleep Cycle

Embarking on a nightly journey, the sleep cycle is a journey of restoration and rejuvenation. Comprising multiple stages, the sleep cycle offers a rich blend of light, deep and REM sleep. Each cycle lasts approximately 90 minutes, repeating four to six times throughout the night.

What Is Core Sleep vs. Deep Sleep? (2)

Non-REM Sleep

Venturing into the non-REM (NREM) sleep world, we encounter four distinct stages: Drowsiness (N1), Light Sleep (N2), Transitionary Deep Sleep (N3) and Deep Sleep (N4). Each stage serves a unique purpose in our restful repose.

  • N1: The gateway to the dreamworld, N1 is a brief, transitional stage characterized by drowsiness and light sleep. During this phase, our muscles begin to relax and our brain waves gradually shift from wakefulness to sleep.
  • N2: Delving deeper into the world of slumber, N2 represents a more stable, yet still relatively light, sleep stage. Here, our heart rate slows and our body temperature drops as we prepare for the rejuvenating depths of N3.
  • N3: A deeper sleep stage, N3 serves as a transition between lighter sleep and the most restorative stage of non-REM sleep. During this phase, brain waves continue to slow down and our bodies further relax in preparation for the essential stage of N4.
  • N4: Also known as deep sleep or slow-wave sleep, N4 ushers us into the most regenerative phase of non-REM sleep. Our bodies concentrate on healing, growth and energy replenishment during this part. As we surrender to the embrace of deep sleep, our brain waves slow to a gentle rhythm known as delta waves.

REM Sleep

Transitioning from the stages of non-REM sleep, we arrive at the fascinating landscape of REM sleep. Marked by rapid eye movement (thus the name) and vivid dreams, REM sleep serves as a playground for the mind’s creative endeavors. Beyond its dreamlike qualities, REM sleep is crucial for solidifying memories, fostering emotional regulation and promoting cognitive function.

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NREM vs. REM Sleep

As the night progresses, each successive sleep cycle witnesses an increase in the duration of REM sleep, reaching its peak during the morning hours. This peak serves as the final phase of our restful journey, filling our sleep with vivid dreams, memory consolidation and emotional balance. The interplay between REM and non-REM sleep continues throughout the night, creating a recuperative balance that nurtures our well-being. This seamless blend of sleep stages prepares us to greet the new day with renewed energy and a refreshed state of mind.

Core Sleep vs. Deep Sleep

What Is Core Sleep vs. Deep Sleep? (3)

Definition of Core Sleep

Core sleep refers to the essential portion of sleep needed for an individual to maintain optimal cognitive function and physical health. It typically includes deep sleep (N4) and rapid eye movement (REM) sleep, the most restorative stages of the sleep cycle.

Core sleep generally lasts for about four to six hours per night, during which the body and brain undergo critical processes such as tissue repair, memory consolidation and hormone regulation.

Definition of Deep Sleep

Deep sleep, also known as slow-wave sleep or N4 sleep, is a phase of non-REM sleep characterized by slow, delta brainwave activity. It typically occurs during the first half of the night and is the most rejuvenating stage of sleep. During deep sleep, the body undergoes several important processes, including tissue growth and repair, immune system strengthening and energy restoration.

Comparing Core and Deep Sleep

While core and deep sleep are related, they are not identical concepts. Core sleep encompasses both deep sleep (N4) and REM sleep, representing the minimum amount of sleep needed for proper functioning and overall health. Deep sleep, on the other hand, is a specific stage within the sleep cycle characterized by slow-wave, delta brain activity. It is a crucial component of core sleep, playing a significant role in physical and cognitive restoration processes.

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Tips for Improving Sleep

Sleep Hygiene

Sleep hygiene refers to a set of practices and habits that promote healthy and restful sleep. Establishing a consistent sleep routine and environment can significantly impact sleep quality. Sleep hygiene is a set of practices that can help promote better sleep. Here are a few recommendations for improving sleep hygiene:

  • Establish a consistent sleep schedule: Try to go to bed and wake up at the same time every day — even on weekends.
  • Create a relaxing sleep environment: Ensure your bedroom is dark, cool and quiet. Use blackout curtains or an eye mask to block out light, and consider using a white noise machine to mask any outside noise.
  • Avoid stimulating activities before bed: Avoid screen time, exercise and caffeine in the hours leading up to bedtime.

What Is Core Sleep vs. Deep Sleep? (4)

Relaxation Techniques

Relaxation techniques can help calm your mind and body before bed, making falling and staying asleep easier. Here are a few suggestions for relaxation techniques that you can try:

  • Deep breathing: Taking slow, deep breaths can help lower your heart rate and promote relaxation. The 4-7-8 breathing method is a popular technique that involves taking a deep breath for four seconds, holding the breath for seven seconds and then exhaling slowly for eight seconds.
  • Progressive muscle relaxation: This technique involves tensing and relaxing different muscle groups in your body, helping to release tension and promote relaxation. To practice progressive muscle relaxation, lie in a comfortable position and systematically tense and relax each muscle group, starting with your toes and working your way up to your head. As you tense each muscle group, hold the tension for a few seconds before releasing it, focusing on the sensation of relaxation that follows.
  • Meditation: Meditation involves focusing your mind on a specific thought or object, helping to calm your mind and reduce stress. Guided meditation involves following the instructions of a guide to promote relaxation and reduce stress. Novices can benefit from guided meditation by creating a sense of calm and relaxation that can help them drift off to sleep more easily.

Technology and Sleep

The use of screens before bed can interfere with sleep quality. The blue light emitted by screens can suppress the production of melatonin, a hormone that helps regulate sleep. To manage screen time and improve sleep quality, here are a few recommendations:

  • Avoid screens for at least an hour before bed: This allows your body to produce melatonin and prepare for sleep.
  • Use a blue light filter: Many smartphones and tablets have built-in blue light filters that can help reduce the impact of screens on sleep.
  • Consider limiting screen time during the day: Reducing screen time can help improve sleep quality and promote overall health and well-being.

Sleep-Promoting Accessories

What Is Core Sleep vs. Deep Sleep? (5)

Weighted Blankets

Weighted blankets have gained popularity as a potential aid for better sleep because they promote restful slumber. These blankets typically weigh between five and 30 pounds and are designed to provide deep-pressure stimulation, which can promote relaxation and calmness. Using a weighted blanket could potentially offer the following benefits:

  • Reduced anxiety: The deep pressure stimulation provided by a weighted blanket can help reduce feelings of anxiety and promote relaxation.
  • Improved sleep quality: Many people report improved sleep quality and a more restful night’s sleep when using a weighted blanket.
  • Enhanced comfort: The added weight of a weighted blanket can provide a sense of comfort and security, helping to reduce tossing and turning during the night.

Infrared Sauna Blankets

As the focus on sleep health has grown, infrared sauna blankets have gained recognition as a potential tool for promoting restful and restorative sleep. These blankets use far infrared (FIR) heat to promote relaxation and enhance sleep quality. These are some of the benefits that using an infrared sauna blanket may offer:

  • Increased relaxation: The gentle heat provided by an infrared sauna blanket can help promote relaxation and reduce tension in the body.
  • Improved circulation: The heat from an infrared sauna blanket can improve blood flow and circulation, helping promote overall health and well-being.
  • Detoxification: Infrared sauna blankets are believed to promote detoxification by helping the body release toxins and impurities that can contribute to inflammation, pain, hormonal imbalances and other health issues. By promoting detoxification, these blankets may support overall health and well-being, ultimately leading to better sleep quality.

Sleep Masks

Weighted sleep masks are an innovative and effective tool for improving sleep quality and comfort. These masks are designed to block out light. At the same time, the additional weight provides gentle pressure, creating a dark and calming environment that can promote restful sleep. Here are a few potential benefits of using a weighted sleep mask:

  • Improved sleep quality: By blocking out light and applying gentle pressure, weighted sleep masks can promote deeper, more restful sleep.
  • Enhanced comfort: The added weight of the sleep mask can provide a sense of comfort and security, helping to reduce tossing and turning during the night.
  • Promote relaxation: For those who frequently use screens before bed, a weighted sleep mask can help alleviate eye strain and encourage relaxation, thanks to the combination of darkness and gentle pressure that eases tension and encourages a more peaceful state of mind.

What Is Core Sleep vs. Deep Sleep? (6)

Final Thoughts on Sleep

Understanding the intricacies of core and deep sleep and how they fit into the sleep cycle can greatly enhance our appreciation of the renewing powers of a good night’s sleep. You can achieve better core and deep sleep by recognizing the factors impacting sleep quality and implementing strategies to improve sleep hygiene, relaxation and the sleep environment. And don’t forget about exploring sleep-promoting accessories such as weighted blankets, infrared sauna blankets and sleep masks, which can also enhance your sleep experience.

Ultimately, nurturing your sleep health by understanding and prioritizing core and deep sleep will support your overall well-being, setting the stage for a refreshed and rejuvenated you.

Image Credits:


G-Stock Studio/Shutterstock.com

Dean Drobot/Shutterstock.com



What Is Core Sleep vs. Deep Sleep? ›

It typically includes deep sleep (N4) and rapid eye movement (REM) sleep, the most restorative stages of the sleep cycle. Core sleep generally lasts for about four to six hours per night, during which the body and brain undergo critical processes such as tissue repair, memory consolidation and hormone regulation.

Is deep sleep better than core sleep? ›

Scientists agree that sleep is essential to health, and while stages 1 to 4 and REM sleep are all important, deep sleep is the most essential of all for feeling rested and staying healthy.

How much core sleep is normal? ›

An average sleep cycle lasts about 90 minutes. Ideally, you need four to six cycles of sleep every 24 hours to feel fresh and rested. Each cycle contains four individual stages: three that form non-rapid eye movement (NREM) sleep and one rapid eye movement (REM) sleep.

What does core sleep mean on Apple Watch? ›

A small chart shows how many minutes you were awake, and how much time you spent in the each of the three basic sleep stages: REM (where most dreaming happens), deep (a restorative phase for mind and body), and core (Apple's term for light sleep, which is essentially the time not spent in REM or deep sleep).

How much core and deep sleep should I get? ›

You should aim for about 13 to 23 percent of your sleep to be in these stages. So, if you get 8 hours of sleep, you should be getting anywhere between an hour and just under two hours of deep sleep. However, it's important to note that what time you go to bed can greatly influence how much deep sleep you get.

What is the most beneficial sleep stage? ›

“Many people wake up tired, even with adequate amounts of sleep. This is likely due to insufficient amounts of deep and REM sleep” shares Dr. Ghacibeh. “So while all stages of sleep are essential to overall well-being, deep sleep is considered the most important stage.”

Which sleep cycle is most restorative? ›

Stage 3 and 4 sleep, the most restorative stages, are known as deep sleep. We need about one and a half to two hours of deep sleep a night. In stage 3, very slow brain waves called delta waves are interspersed with smaller, faster waves.

Do you dream during core sleep? ›

There are normally no dreams during this sleep. You feel disoriented when you wake up from this sleep. Deep sleep can last between 1-2 hours which is a quarter of your sleep time. If you want to understand your sleep habits better, you consult one of our sleep specialists in the New York Metro area.

How accurate is Apple Watch sleep? ›

Deep sleep and REM are defined by certain types of brainwaves and physiological states and these devices can estimate these states with about 80% accuracy.

What causes lack of deep sleep? ›

Some people with insomnia experience changes in their sleep cycles and, as a result, may have more stage 1 sleep and less deep sleep. Stress and aging can also reduce levels of deep sleep. Additionally, people with conditions such as schizophrenia and Alzheimer's disease experience less slow wave sleep.

Can Apple Watch detect sleep apnea? ›

Can an Apple Watch Detect Sleep Apnea? Like Fitbit and other wearables, the Apple Watch can detect certain parameters like heart rate and blood oxygen saturation that may indicate sleep apnea, but it cannot comprehensively detect or diagnose sleep apnea.

How does my watch know I'm in deep sleep? ›

Heart Rate and Respiration

Some sleep trackers estimate REM sleep in addition to deep and light sleep stages by measuring heart rate.

How much deep sleep do you need by age? ›

If you're under age 30, you may get two hours of deep sleep each night. If you're over age 65, on the other hand, you may only get a half hour of deep sleep each night, or none at all. There's no specific requirement for deep sleep, but younger people may need more because it promotes growth and development.

How can I increase my deep sleep stage? ›

How to Increase Deep Sleep: 10 Tips + Benefits
  1. Work Out Daily. ...
  2. Eat More Fiber. ...
  3. Find Your Inner Yogi. ...
  4. Avoid Caffeine 7+ Hours Before Bed. ...
  5. Resist that Nightcap. ...
  6. Create a Relaxing Bedtime Routine. ...
  7. Make Your Bedroom a Sleep Sanctuary. ...
  8. Listen to White and Pink Noise.
Apr 29, 2020

Is core sleep better than REM? ›

Deep sleep is as important, if not more important, than REM sleep when it comes to physical rest, so keep an eye on this stage if you're tracking your sleep patterns.

What happens if I get too much deep sleep? ›

The theorized cause behind this link is elevated levels of C-reactive protein (CRP) caused by excessive sleep. Over time, a buildup of this protein places the body and heart in a stressed state, leading to heart disease. This same protein is also known to cause issues with memory.

How many hours of REM sleep do you need? ›

For healthy adults, spending 20-25% of your time asleep in the REM stage is a good goal. If you get 7-8 hours of sleep, around 90 minutes of that should be REM.

Is 3 hours of REM sleep too much? ›

For healthy adults, 20-25% of your total time asleep should be REM sleep. That's where the 90-minute number mentioned above comes from. If you sleep for 7-8 hours, 20% of that equates to roughly an hour-and-a-half, or 90 minutes. However, it's worth noting that the amount of REM sleep we need also declines with age.

When you sleep but don't feel rested? ›

If you aren't feeling rested when you wake up, despite getting to sleep at least 8 hours prior, then it might not be the quantity of your sleep that's the problem. It could be your sleep quality that needs some attention. The amount of sleep you get is important, but equally important is the quality of that sleep.

Why do I never wake up feeling rested? ›

The most common cause of sleepiness is not sleeping long enough. Getting enough restful sleep is crucial for maintaining good health. Research over the past decade has shown that healthy sleep is just as important as exercising regularly and eating a healthy diet.

Why do I never feel rested no matter how much I sleep? ›

The two most likely reasons you're always so tired no matter how much sleep you get are you've got high sleep debt or you're not living in sync with your circadian rhythm. You may also feel sleepy if you're ill, pregnant, or you've got a medical condition like anemia or diabetes.

Do dreams mean good sleep? ›

Experts aren't sure, but there's evidence that suggests dreaming plays a role in supporting brain functions that occur while we're awake, such as processing thoughts, memories, and emotions. So, is dreaming a sign of good sleep? Researchers believe it either reflects or contributes to healthy sleep.

Does remembering dreams mean good sleep? ›

Remembering your dreams doesn't necessarily have anything to do with how restful your sleep is, Dr. Harris says. Instead, recalling those dreams is a lot more likely to depend on a number of factors, from your current level of stress to the medication you're taking.

What does it mean if you remember your dream when you wake up? ›

Alarm clocks, and irregular sleep schedules can result in abrupt waking during dream or REM sleep, and thus result in recall of dreams. Sleep apnea, alcohol, or anything that disturbs sleep can also cause dream recall,” Dimitriu says.

Does Apple Watch underestimate deep sleep? ›

The Apple Watch shows more light or core sleep and less deep sleep than the Fitbit. Tracking your sleep stages and cycles is most accurately done by polysomnography; it's not as simple as monitoring your heart rate all night.

What is better Fitbit or Apple Watch? ›

While both brands offer outstanding, high-quality wearables, Fitbit has more budget-friendly options, superior battery life, and better health and fitness tracking than the Apple Watch. The Apple Watch edges out the Fitbit in terms of accuracy, convenience, and extra features, but it may be too pricey for some users.

Can Apple Watch detect snoring? ›

Do you know how often you snore? Or how loud it is when you do? With SleepWatch Snore Tracking, all SleepWatch users are able to record, listen to, and track their snoring from their Apple Watch or iPhone. You can now listen to your top snores and track where your snoring ranks on a scale from minimal to heavy.

Why am I so tired but can't sleep? ›

If you're tired but can't sleep, it may be a sign that your circadian rhythm is off. However, being tired all day and awake at night can also be caused by poor napping habits, anxiety, depression, caffeine consumption, blue light from devices, sleep disorders, and even diet.

Does melatonin increase deep sleep? ›

Taking a melatonin supplement can help increase deep sleep in a few ways. First, it can help to regulate your sleep cycle. This makes it easier for your body to fall into a deep sleep state. Second, melatonin can help to reduce stress and anxiety.

Why do I wake up at 2am and can't go back to sleep? ›

Reasons this might happen include drinking caffeine or alcohol late in the day, a poor sleep environment, a sleep disorder, or another health condition. When you can't get back to sleep quickly, you won't get enough quality sleep to keep you refreshed and healthy.

Does blood oxygen show on Apple Watch during sleep? ›

Blood oxygen measurements only occur during sleep if the Track Sleep with Apple Watch setting is turned on.

Does snoring mean sleep apnea? ›

Snoring is often associated with a sleep disorder called obstructive sleep apnea (OSA). Not all snorers have OSA, but if snoring is accompanied by any of the following symptoms, it may be an indication to see a doctor for further evaluation for OSA: Witnessed breathing pauses during sleep. Excessive daytime sleepiness.

Can an Apple Watch detect AFib? ›

The irregular rhythm notification feature on your Apple Watch will occasionally look at your heartbeat to check for an irregular rhythm that may be AFib. This usually happens when you're still to ensure a more accurate reading.

How accurate are watches for deep sleep? ›

Most new wearables also track the sleep stages you cycle through throughout the night. But “in terms of tracking light, deep, and REM sleep, basically all of the devices performed at only a medium level of accuracy,” says Chinoy. Translation: There's only about a 50-percent chance your data is accurate.

What is a normal heart rate for a woman while sleeping? ›

During sleep, it is normal for a person's heart rate to slow down below the range for a typical resting heart rate. Between 40 to 50 beats per minute (bpm) is considered an average sleeping heart rate for adults, though this can vary depending on multiple factors.

How does Netflix know when I fall asleep? ›

In its prototype of the feature, Netflix said, it collects data from a FitBit fitness tracking device to determine whether a user is still watching or has fallen asleep. If the user is snoozing, Netflix will turn down the audio and pause whatever the user is watching.

Why do I always wake up at 3am? ›

If you wake up at 3 a.m. or another time and can't fall right back asleep, it may be for several reasons. These include lighter sleep cycles, stress, or underlying health conditions. Your 3 a.m. awakenings may occur infrequently and be nothing serious, but regular nights like this could be a sign of insomnia.

Do you get less deep sleep as you get older? ›

Total sleep time, sleep efficiency, and deep sleep (slow wave sleep) decrease with aging; and number of nocturnal awakenings and time spent awake during the night increase with aging.

Are people snoring in a deep sleep? ›

So does snoring mean deep sleep? No it doesn't. REM sleep becomes very fragmented and interrupted by snoring so snorers aren't able to reach deep sleep. Only frequent, prolonged and severe snores mean possibly obstructive sleep apnea.

What interferes with deep sleep? ›

Caffeine, benzodiazepines , and opioid pain medications can all affect deep sleep. Caffeine is a stimulant that can reduce deep sleep even hours after you consume it (for example, in a cup of coffee or tea). Benzodiazepines like Valium and opioid pain medications can also reduce deep sleep.

Is 2 hours of deep sleep a lot? ›

The average healthy adult gets roughly 1 to 2 hours of deep sleep per 8 hours of nightly sleep. There are various ways to gauge whether you are, from personal trackers to a sleep study. If you're waking up tired on a regular basis, it's a good idea to talk to a healthcare provider.

Is 5 hours of deep sleep too much? ›

Deep sleep describes a particular stage of sleep that is important for waking up feeling refreshed and alert. Although there are no definitive guidelines for how much deep sleep you need, experts say that most adults need between seven and nine hours of sleep each night.

Is core sleep deep sleep? ›

Definition of Core Sleep

It typically includes deep sleep (N4) and rapid eye movement (REM) sleep, the most restorative stages of the sleep cycle.

How many hours of deep sleep do you need? ›

In adults, 20% of total sleep time is spent in deep sleep (stage 3). Going with the recommended 7-9 hours of sleep each night, that means the average adult needs 84-108 minutes or 1.4-1.8 hours of deep sleep each night.

Is core sleep the most important? ›

Core sleep is the essential part of the sleep and is mainly slow wave sleep. This type of sleep is composed of stages 3 and 4 on non-REM sleep (NREM 3-4). Core sleep is obtained during the first three sleep cycles and the remainder of the night sleep is considered optional sleep.

Is deep sleep more restorative? ›

The most important sleep stage is Stage 3, Non-REM or, Delta (Slow Wave) Sleep, it takes up 25% of our total sleep cycle, and it's known as the 'deepest' period of sleep. It's in Stage 3 that sleep is at its most restorative, helping our bodies heal themselves and our minds rest.

Is 4 minutes of deep sleep enough? ›

Adults generally average 1-2 hours of deep sleep per night, somewhere between 15 and 25% of your nightly sleep. Most of our deep sleep comes in the first sleep cycle of the night, usually 45-90 minutes. Age has a major effect on how much deep sleep we get each night and how much we need.

Does Fitbit underestimate deep sleep? ›

Researchers concluded the Fitbit was equivalent to the actigraph in almost every way. Yet, when compared with polysomnography, the Fitbit was largely underestimating deep and REM sleep, missing roughly half of the former and a third of the latter. It also overestimated light sleep.

Is 6 hours of core sleep enough? ›

While some people regularly function on short periods of sleep, research mostly agrees that six hours of sleep is not enough for most adults. Experts recommend that most adults need at least seven hours of sleep every night.

Do you dream in REM or core sleep? ›

Dreaming. A majority of your dreams take place during REM sleep. However, REM is not the only stage in which dreams occur — that's actually a common myth about sleep. That said, the dreams you experience in REM sleep are usually more vivid than non-REM sleep dreams.

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