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Sleep health: How does sleep improve overall health?

We humans spend a third of our lives sleeping. While asleep, we reap excellent health benefits, such as improved learning and memory, better physical health, and a stronger immune system.  That’s why learning about sleep health and ensuring that we practice healthy sleep habits and good sleep hygiene is so critically important.

Let’s explore the concept of quality sleep, beyond the sense of feeling rested, and take a look at how a typical healthy sleep cycle works. Learning more about how the sleep cycle works will help you in your quest to obtain better quality sleep.

How much sleep do you need for optimal health?

We typically require seven to nine hours of sleep a night in order to restore our bodies, stay healthy, and keep our minds functioning at peak cognitive performance. If you’re not getting enough sleep, check out our tips to sleep better.

Time is often used as the main indicator for measuring sleep. Let’s explore what quality sleep means beyond when you go to bed and when you wake up. 

In this article, we’ll take a look at how the quality of your sleep helps keep your body and mind healthy. We’ll also give you some tips on how to improve your sleep to keep your health up.

But first things first, let’s define quality sleep.

What is quality sleep and how does it promote overall health?

Beyond the sense of feeling rested, quality sleep can be assessed using these criteria:  

  • Sleeping for at least 85% of the time you spend in bed each night
  • Taking less than 30 minutes to fall asleep
  • Waking up once per night, or not at all
  • Staying awake for less than 20 minutes after one’s initial descent into sleep.[1]

Learn more here.

How does sleep affect your health?

The health benefits of quality sleep concern all aspects of body and mind. Sleep’s health benefits are far-reaching and affect a wide variety of the body’s organ systems.  

Sleep is important for the immune system, which releases cytokines during sleep.[2]  Cytokines are proteins secreted by immune cells that are essential for the body’s response to disease. 

Sleep is also important for muscle recovery.[3] The body releases growth hormones that promote muscle recovery. This means that during sleep, the muscles repair, damaged cells are regenerated, and tissues rebuild.  

Other organ systems which are benefited by sleep include digestion, circulation, and metabolism. Digestion continues during sleep, and the normal movement of food through the digestive system is increased at night compared to during the day.[4]

Sleep is also required for proper cardiovascular and circulatory system function, as lack of sleep can increase the risk of heart disease by raising blood pressure, weakening arteries, and promoting plaque buildup within arteries.[5]  

Finally, sleep is linked to metabolic function, as sleep deprivation can boost levels of hormones that promote hunger, leading to elevated blood sugar and obesity.[6,7]

How does sleep affect your mental health?

The brain also benefits greatly from a good night’s sleep.[8] Sufficient sleep boosts learning and memory, cognition, motor coordination, and mental health. People who do not sleep enough are more likely to experience mood swings, depression, and other mood-related dysfunction.

Tips for better sleep

The key for making sure you get the proper amount and best quality of sleep is to consider both the total time spent sleeping, as well as making sure that you are taking steps to get the best quality sleep. One can feel rested sleeping less than seven to nine hours, and feel tired after sleeping for long periods of time.

An important thing to consider in your sleep hygiene is making sure that you sleep for long enough periods so that your brain and body can go through all the different sleep phases.  

While it’s best to sleep continuously through the night, people suffering from sleep deprivation may be working with a limited amount of sleeping time due to work or other conflicting demands that interfere with one’s ability to get a good night’s sleep. In that case, it’s best to sleep strategically, taking shorter naps when possible.  

Read on to learn more about exactly how to maximize your sleep quality by ensuring you experience all of the sleep phases while catching Zzz’s.

What happens during sleep?

Sleep used to be considered, by both scientists and the general public, as a passive state. For centuries, it was thought that during sleep, both the body and mind were inactive. Today, we know that sleep is an active, important, and restorative process for our bodies and minds to recover from the day’s activities.[9]  

What’s more, we now know that, during sleep, characteristic patterns of brain activity occur during each of the sleep phases, and sometimes these brain patterns are more active when we are asleep than when we are awake.

The brain’s patterns of activity during sleep are highly predictable, so much so that scientists have been able to classify them into different phases.[10]  Each phase of sleep serves a different function to promote your overall health.  In a healthy sleep cycle, your body and mind cycle through all the phases, several times a night.

What does healthy sleep look like?

A night of healthy sleep has several different phases, which we cycle through each night. The order in which we cycle through these phases is predictable, although they change with age.  For example, the amount of time an infant spends in the various sleep stages each night is vastly different from the sleep phase patterns of a middle-aged person.

Severely sleep-deprived people may spend very little time in light sleep and go straight to deep sleep, compared to people who get enough sleep every night, who may spend more time in light sleep and naturally progress to deep sleep.

The different stages, or phases, of healthy sleep 

Clinicians and researchers divide sleep into two main categories: REM and non-REM.[12]

Non-REM sleeps is further divided into three stages:[11] stage N1, stage N2, stage N3 (also called slow-wave sleep). Stages N1 and N2 are non-REM sleep states referred to as “light sleep.” Stage N3 is referred to as delta sleep, deep sleep, and slow-wave sleep.[13]

Originally, scientists called these stages 1, 2, 3/4, and REM, but decided to rename the first three stages N1, N2, and N3, to differentiate them from REM. The N in the first three stages is short for “non-REM.”

When you are asleep, you spend time in all of these states.  Each phase is important for healthy sleep.[14] Let’s take a look at each stage in a little more detail.

Stage N1

In this stage, the first phase of non-REM sleep, you can still hear things and are aware of your surroundings. This phase is a state somewhere between being completely awake and completely asleep.  Although your brain has started the sleep cycle, you don’t feel like you’re asleep.

Stage N2

In this stage, the second phase of non-REM sleep, you’re asleep but can be awakened easily.  This means that you become disengaged from your surroundings. Breathing and heart rate also become regular. Core body temperature also decreases during this phase.

Stage N3

Stage N3 is known as “deep sleep.”  Deep sleep is a restorative process for the body.  Memories are consolidated, and the body repairs its cells and tissues.

Stage N3, the third non-REM stage of sleep, is also known as “slow-wave sleep” or “delta sleep” because of the widespread presence of slow, synchronous brain waves called delta waves. In this phase of sleep, you are much less responsive to outside stimuli.  Breathing slows down, muscles relax, and the heart rate becomes much more regular.

REM Sleep

Rapid eye movement, or REM, sleep is the last phase of sleep. During REM, the mind undergoes restoration.  

Dreaming occurs during this phase and the eyes move rapidly, which is the reason why this phase is called “rapid eye movement” sleep. While the brain is very active during REM sleep, the body is inactive. In fact, the body is paralyzed during REM. 

Each night, our body goes through all the different sleep phases. The first three stages represent three-fourths of our nightly sleep. REM comprises approximately 25% of our nightly sleep.

How much time do we spend in each sleep stage?

To get the best sleep quality, we must go through all of these stages each night, roughly five or six times. However, that may not always happen, for example, in the case of interrupted sleep, or severe sleep deprivation.

As the second component of deep sleep, REM is important for memory consolidation and overall mental and physical health.  Our bodies enter REM first after about 90 minutes of sleep.[11] Then, we experience repeated REM phases every 90 minutes. Over the course of the night, the more you sleep, the longer your REM phases are.  

The lengthening nature of REM cycles are why it’s so important to get uninterrupted sleep for long periods of time.  By sleeping the recommended seven to nine hours a night, your body can enjoy progressively lengthening REM cycles.

What if I can’t get a healthy amount of sleep at night?

It’s best to sleep an average of eight hours a night.  However, if you get insufficient sleep at night, you may want to consider taking naps during the day or other times when you can sleep.

But napping is a tricky issue so you should consider the following before you settle down into an afternoon nap.

Naps have been demonstrated to reduce fatigue, increase alertness, improve your mood, memory and alertness. However, napping during the day can also push back your sleep schedule, leaving you unable to sleep until later in the evening. If you experience insomnia, napping might not be the best choice as it can prolong the cycle of sleeplessness.

Napping in the afternoon isn’t an ideal long term solution for addressing sleep debt as you’ll likely be getting less REM sleep than you would in the same amount of time slept over the period of a night. This is because, as you repeat cycles through the phases of sleep throughout the night, your REM stages become longer and longer.

But, some sleep is better than no sleep so let your body guide you on what works best for you.

Sleep: The ultimate provider of universal healthcare

It’s clear that our quality of life and overall health is tightly linked to how well we are sleeping on a day-to-day basis. The physiological, emotional, and cognitive stress of sleep deprivation not only make everyday life more difficult, but may predispose us to a variety of health conditions

If you’re struggling with regular restless nights, know that the prognosis is generally excellent but it can take lots of time and effort to reverse bad sleep habits. Poor sleep can oftentimes be remedied by the steady adoption of various sleep hygiene practices, but sometimes sleep disorders can be the underlying culprit.

Thankfully, many of these, such as sleep apnea, can be efficiently diagnosed and treated with the help of a sleep medicine professional. At the end of the day, gaining back and maintaining those full five to six sleep cycles every night will go a long way towards next-day peak performance and overall good health.


  1. “What is Good Quality Sleep?” National Sleep Foundation.  Accessible at
  2. “The Science of Sleep: How Sleep Affects Your Immunity.” National Sleep Foundation.  Accessible at
  3. Schletter, M.  “Sleep Your Way to More Muscle.”  Men’s Journal. Accessible at
  4. Dantas, R and Aben-Athar C. “Aspects of sleep effects on the digestive tract.”  Arquivos de Gastroenterologia. Accessible at
  5. Cohut, M.  “How Lack of Sleep Harms Circulation.”  Medical News Today. Accessible at
  6. Graham, S.  “Sleep Deprivation Tied to Shifts in Hunger Hormones.”  Scientific American. Accessible at
  7. “What happens when you sleep?” National Sleep Foundation. Accessible at
  8. “Sleep deprivation and deficiency.”  National Heart, Lung, and Blood Institute.  Accessible at
  9. Murali, N., et al.  “Cardiovascular physiology and sleep.“  Frontiers in Bioscience. Available at
  10. “Brain Basics: Understanding Sleep.”  National Institute of Neurological Disorders and Stroke.
  11. “Understanding Sleep Cycles: What Happens While You Sleep.” Accessible at
  12. “Natural Patterns of Sleep.”  Harvard Medical School. Accessible at
  13. “What are REM and non-REM sleep?” WebMD.  Accessible at
  14. Kosecki, D.  2018. “REM, Light, Deep: How Much of Each Stage of Sleep Are You Getting?” Fitbit.  Accessible at

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