Benefits of Deep Sleep and How to Track It

Most adults need seven to nine hours of sleep each night to achieve optimal health.1

Maybe you’re well within that range—but are you getting enough deep sleep?

You see, there are two types of sleep we experience in a typical night: rapid eye movement (REM) sleep and non-REM sleep, which consists of three separate stages. Each stage is linked to different brain waves and neuronal activity.1

And one stage in particular is associated with deep sleep—a key part of feeling well-rested and getting a healthy amount of shuteye.

What are the sleep stages?

Over the course of a standard night, we generally begin by going through the stages of non-REM sleep before moving into a short period of REM sleep. Then the cycle repeats until we’ve gotten a full night’s rest.

During REM sleep, our eyes move rapidly from side to side with the eyelids closed.2 Dreams typically occur during REM sleep, as well. However, we don’t reach this state right when we doze off. It generally takes about 90 minutes.1

First, we cycle through the phases of non-REM sleep—including deep sleep. These phases are as follows:

  • Stage 1 marks the time you fall asleep. This short stage lasts for five to 10 minutes, and it consists of light sleep during which your heart rate, breathing, and eye movements are fairly slow.1

Your muscles are relaxed at this stage, perhaps with the occasional twitch, and your brain waves are relatively slow as well. Since Stage 1 sleep isn’t particularly deep, you’re more prone to waking up during this time.2

  • Stage 2 is the period of light sleep before you enter deep sleep. At this stage, your heart rate and breathing grow slower, your body temperature lowers, and your muscles continue to relax.1-2 Eye movements typically stop as well.

Stage 2 includes only brief spells of electrical activity.1 That said, since it’s meant to prepare you for deep sleep, you spend more time here than in any other non-REM sleep stage. Stage 2 sleep accounts for roughly 50% of the overall sleep cycle.3

  • Stage 3 represents deep sleep. Also known as delta sleep, slow wave sleep, or N3 sleep, it’s the phase that accounts for your feeling well-rested in the morning.4

First, your heart rate and breathing slow to the lowest levels you’ll see all night. Your muscles continue to relax as well, and your brain waves grow even slower.1 It’s also worth noting that it’s difficult to rouse a person from deep sleep, and if someone were to awaken you during this phase, you might feel disoriented for a while.

Deep sleep may last anywhere from 45 to 90 minutes initially.3 It takes place for a longer period of time early in the night and becomes shorter as you progress through the sleep cycle. Overall, this stage accounts for roughly 13% to 24% of our total sleep.3

What are the benefits of deep sleep?

Deep sleep is crucial to our health.2 Our glucose metabolism increases in the brain during stage 3 sleep, which strengthens our memory and capacity for learning.3 In addition, the pituitary gland—which is linked to growth and development among other functions—is very active during this part of the sleep cycle.

Here are some of the benefits of deep sleep:3

  • Tissue regeneration
  • Bone and muscle growth
  • Immune system support
  • Energy restoration
  • New cell growth
  • Increased blood supply

Similarly, not getting enough deep sleep over an extended period can be detrimental to our health—insufficient stage 3 sleep, for instance, is linked to negative affects to the brain and heart.3 Getting enough deep sleep also boosts psychological benefits associated with our mood and energy.4

How can you track your deep sleep?

As we age, we tend to sleep lighter and get less deep sleep.3 However, we can still do our part in tracking the amount of N3 we achieve each night and in working toward the amount of deep sleep we need to feel refreshed in the morning.

When it comes to tracking your deep sleep, you have several options. Consider the following:

  • Phone apps

While there’s something to be said for keeping your phone outside the bedroom at night, if you do sleep with it by your side, there are a number of apps you can use to track the amount of deep sleep you get. These apps use the sonar waves from your phone to detect movement.

Simply place your cell phone on the mattress, and in the morning, you can check how much you moved—and, accordingly, how much deep sleep you got. Just note that sleep-tracking apps like SleepScore (available on Android and iOS) don’t necessarily offer the most accurate approach.5

  • Wearable devices

Do you wear a Fitbit or an AppleWatch? If so, you might want to wear your device—once reserved for fitness and heart rate monitoring—while you sleep.

Similar to phone apps, these devices track your movement throughout the night and offer insights into overall sleep efficiency and quality. That said, since these wearables weren’t designed for sleep tracking, their results aren’t exactly foolproof.5

  • Smart beds and sleep sensors

If you’re looking for a more accurate way to track the deep sleep you get each night, then this is the category for you. You can place sensors over or under your mattress to check not only your movement, but also your heart rate and breathing.

The data will tell you how long you were in REM sleep and how much time you spent in the non-REM sleep stages as well. Smart mattresses like the Sleep Number 360® Smart Bed, and sensors like the iFit Sleep HR or Eight Sleep Tracker, are popular options.

Note that if you’re truly struggling with your sleep quality, you may need to consult a doctor. A specialist can administer a polysomnography (PSG) test to get more information on your sleep habits and overall sleep quality.3


  1. National Institutes of Health Staff. Brain Basics: Understanding Sleep. National Institute of Neurological Disorders and Stroke. Accessed January 29, 2019.
  2. Felson S. What Are REM and Non-REM Sleep? WebMD. Accessed January 29, 2019.
  3. Murrell D. What Is Deep Sleep and Why Is It Important? Healthline. Accessed January 30, 2019.
  4. Cline J. The Mysterious Benefits of Deep Sleep. Psychology Today. Accessed January 29, 2019.
  5. CNET Staff. The 3 best ways to track your sleep. CNET. Accessed January 30, 2019.

Submitted by the Metagenics Marketing Team

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