Deep Sleep: The Most Restorative Stage of Sleep

How much deep sleep you get each night is directly related to how rested you feel the following morning. This slow-wave sleep stage is central for human health and wellbeing.

By Nicole Gleichmann

Apr 27th, 2022

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Every night when your head hits your pillow and you float off into dreamland, your body cycles through different stages of sleep. While each stage plays a role in your overall sleep quality and waking health, there is one stage that’s considered to be the most beneficial: deep sleep.

Deep sleep has earned its spot as the most beneficial sleep stage because of its influence on how we feel when we awaken. When you get enough quality, deep sleep, you are more likely to wake up feeling refreshed.

Understanding Sleep Stages

When you’re sleeping, your brain cycles through distinct brainwave activity levels as seen on an EEG. These sleep patterns are broken into two primary categories of sleep: REM (rapid eye movement) sleep and non-REM sleep. Non-REM sleep is then further broken down into three stages, the third and final of which is deep sleep.

  • Stage 1 sleep is light, non-REM sleep marked by the gradual slowing of your brainwave activity, easing you into sleep. Your breathing and heart rate slow as your muscles relax, preparing your body for deeper sleep stages. It’s very easy to wake someone up from stage 1 sleep.
  • Stage 2 sleep is also non-REM, light sleep where your brainwaves, breathing, and heart rate continue to slow, with your muscles becoming even more relaxed. Your body temperature begins to dip, preparing for deep sleep. It’s still relatively easy to be awoken during stage 2 sleep.
  • Stage 3 sleep (also known as deep sleep) is the last stage of non-REM sleep. It’s the deepest stage of sleep meaning it’s hardest to wake someone up from this stage. Your brain waves are the slowest that they will be, and your body is very relaxed, with the slowest hear trate and breathing that you experience throughout the night.
  • REM sleep is where most of your dreaming occurs, and it’s important for memory consolidation. It’s called rapid eye movement sleep because your eyes move rapidly from one side to the other during this stage of sleep. During REM periods, your brain waves, blood pressure, and heart rate quicken, becoming closer to those you experience when you’re awake. Breathing is irregular, fast, and shallow.

As you fall asleep, your brain begins to cycle through these sleep stages. On average, it takes around 90 minutes for a full sleep cycle to occur. At this time, unless you wake up, the cycle will continue at stage 1 sleep.

What is Deep Sleep?

The term “deep sleep” stems from the fact that it’s the hardest stage from which to wake someone up. Because deep sleep is marked by the slowest brain wave activity, it’s also known as slow-wave sleep. These waves are low-frequency, high amplitude delta waves, leading to another name for deep sleep: delta sleep.

Every sleep stage plays a role in our health and wellbeing, but it’s the amount of deep sleep that’s believed to play the biggest role in how rejuvenated we feel during the day. Researchers have found that it’s the quantity of deep sleep, not total sleep, that we experience that has the biggest influence on how rested we feel.

What’s more, if you’re woken up during deep sleep, you’re going to feel like you’re still half asleep, an experience termed sleep inertia. This can last for up to four hours when you’re woken up during slow-wave sleep.

The Roles of Deep Sleep

There is more than one reason why slow-wave sleep is so important for our mental and physical rejuvenation and wellbeing. During deep sleep:

Thanks to these effects, deep sleep plays a central role in our cognitive and physical wellbeing. HGH release, for example, is critical for cellular repair in adults and growth and development in children. When you work out or experience an injury or illness, HGH release during sleep is paramount for a speedy recovery.

Additionally, the way that deep sleep supports the brain plays a role not just in storing memories from the previous day, but also in preparing our brains for learning the following day.

What Happens When You Don’t Get Enough Deep Sleep?

Just how important is deep sleep to our wellbeing? According to research, very.

Researchers have found that our bodies prioritize deep sleep. When participants pulled an all-nighter and were allowed to “catch-up” on sleep the following night, the following night of sleep contained a higher percentage of deep sleep than it normally would. This prioritizing of deep sleep demonstrates the importance of this sleep cycle to our health.

Related: What is REM rebound?

When you don’t get enough deep sleep, you’re likely to feel tired throughout the day and experience difficulties with learning and memory. Additionally, if you have lifted weights or injured yourself, you might find that you don’t recover as quickly and that you feel sore throughout the day. It can even increase your chances of coming down with an illness.

How to Get More Deep Sleep

The best way to get enough deep sleep is to simply get enough high-quality sleep each night; your body and mind will do the rest for you. There are many things that you can do to improve your sleep quality, and with it, the time you spend in deep, restorative sleep:

  1. Set a Sleep Schedule: Going to bed and waking up close to the same time each day supports your circadian rhythm, greatly impacting how much rest you get and how well you sleep. Be sure your schedule allows at least 7 hours of time spent in bed each night.
  2. Exercise During the Day: Moderate exercise daily can improve sleep quality. Keep in mind that some people might have difficulties falling asleep if they work out a few hours before bedtime, so try to work our in the morning or early afternoon.
  3. Work on Sleep Hygiene: Sleep hygiene encompasses activities that impact your ability to sleep. Some tips to improve sleep hygiene include limiting alcohol and caffeine consumption late in the day, reducing light exposure at night, and not watching tv in bed.
  4. Save Your Bed for Sleeping: Reading in bed, checking your emails, watching tv, or even having sex in your bed can make it harder for you to fall asleep there at night. If you have troubles falling asleep, save your bed for sleep only.
  5. Take a Bath Before Bed: Taking a warm bath or shower an hour or so before bed can help ease your body into a restful state with a release of melatonin, an important sleep hormone.
  6. Treat Sleep Disorders: If you know that you have a sleep disorder like insomnia or sleep apnea, work with your doctors to treat your condition so you can enjoy good sleep at night.