Deep sleep is the third stage of sleep that is responsible for repairing and restoring the muscles and your brain. In order for you to wake up feeling refreshed, you must spend part of your night in deep sleep. Getting enough deep sleep will benefit your memory, muscle growth, and immune system. Without enough deep sleep, you may have learning difficulties, increased risk of infection, and long-term health conditions. Continue reading to learn more about derp sleep and about how much you need.

What is deep sleep? 

Deep sleep is also known as slow-wave sleep. Out of the three non-rapid eye movement (NREM) stages, it is the last one before you enter rapid eye movement (REM) sleep. During this stage, your brain activity is shown on an electroencephalogram as slow, long wave, or delta waves. They must make up at least 6 seconds of a 30-second window to be considered deep sleep. This is not a number that you need to concern yourself with, but it's just something to help you understand how slow these waves are.

Throughout the night, you spend less and less time in deep sleep, but you enter it about an hour after falling asleep. During deep sleep, your breathing and heart rate are very slow, and your body is completely relaxed. It can be very difficult for you to be awakened during this stage, and if you do wake up, you may feel groggy for at least an hour. This is known as sleep inertia. 

Why deep sleep is important 

All stages of sleep are important. But, each one serves a different purpose. Deep sleep offers specific physical and mental benefits that can't be achieved in other stages. Your body releases growth hormone during this stage, which helps to repair muscles, bones, and tissue that may have been damaged during the day. This is especially important for athletes or highly active people. Deep sleep also promotes optimal immune function, glucose regulation, and can replenish energy stores.

There are cognitive benefits, like improvements in memory, language learning, motor skills, and developing the brain. Throughout the day, you receive information that strengthen the synapses, or parts of the nerves that help you to retain information. However, your brain cannot continue to do this without rest. Deep sleep plays a vital role in preserving what your learned from that day, while also preparing your synapses for the following day.  

Amount of time in deep sleep that's necessary

To calculate how much deep sleep you need, it's important to first determine how much sleep you need overall. Most adults need anywhere from 7-9 hours of sleep to properly function. Everybody is different, so this just a recommendation, however there can be severe consequences for those who continuously sleep less than 7 hours.

After determining the amount of sleep that you need (or best function at) then calculate what 20% of that time is. That is typically the amount of time you should spend in deep sleep.

The body self-regulates deep sleep to a certain extent. So, you might spend more time in deep sleep if you're recovering from sleep deprivation, or repaying your "sleep debt". Those who nap frequently, however, may spend less time because their needs have already been met for the day. 

Also, age can play a role. As people age, they tend to spend less time in deep sleep. Older adults usually spend more time in stage 2 sleep, which is less restful.  

Sleep disorders associated with deep sleep

Sleep disorders that are directly tied to deep sleep are called disorders of arousal. This includes any sleep behaviors in which it is difficult to wake the individual up like sleepwalking, sleep terrors, and confusional arousals. Most of these occur in children, but can persist into adulthood.

These episodes are normally short, and the individual does not recall them upon waking. However, these events can still have an affect on daytime hours, as walking around can interrupt your sleep. Excessive daytime sleepiness is a common side effect of those who have arousal disorders. Others could accidentally injure themselves or others during an episode. 

Effects of not getting enough deep sleep

In addition to fatigue, a lack of deep sleep can have other negative impacts on your body. Deep sleep plays a major role in the memory formation process. Therefore, not getting enough deep sleep can cause you to have some issues with learning and memory. Even after just one night of poor sleep, you may have difficulty learning or remembering information from the day. As a student, this can be especially disruptive, as memory and learning are integral to day to day functioning. Therefore all-nighters may not be beneficial for these reasons. 

Not getting enough deep sleep can also increase your susceptibility to infections. The immune system receives a bit of a boost when you are in deep sleep. Also, potentially harmful products are eliminated from your brain. These two combined effects can give you an immune boost and potentially reduce your risk of developing Alzheimer's and Parkinson's. 

Another physical effect of not getting enough deep sleep is the effect on weight. A hormone is released that makes junk foods more appealing. Therefore, we make poor dietary decisions which can lead to increases in weight, and risk for developing metabolic diseases, like diabetes. Getting enough sleep can help to reverse some of these effects. 

Individuals who often do not get enough deep sleep include insomniacs, older individuals, those dealing with stress/anxiety, and those with mental conditions like schizophrenia and Alzheimer's, to name a few. Also, recent research has shown that those with a damaged hippocampus may not be getting enough slow wave sleep either.

If you consistently wake up feeling unrefreshed, drowsy, inattentive, and have trouble learning or struggle with cravings, then that may be a sign you are not getting enough deep sleep. 

How to get enough deep sleep 

Making sure that you get sufficient sleep can help you get the deep sleep that is necessary for optimal functioning. Consistent wake and sleep times can help you manage the amount of sleep that you are getting each day. You can also work on building your sleep hygiene, which is the set of behaviors that you do to get ready for bed. 

Other tips include exercising regularly, reducing caffeine intake in the late afternoon and evenings, making sure that you have a clean, dark, quiet, and cool sleeping environment, and creating a relaxing routine that helps you wind down in the evening.  

If you are struggling with getting enough deep sleep, then please click the orange button to take a free online sleep test and talk with one of our sleep health professionals. 

https://www.sleepfoundation.org/stages-of-sleep/deep-sleep