What is Deep Sleep?

Prior to about 100 years ago, most scientists and doctors gravely misunderstood what was happening when we went to sleep. It was generally accepted that humans just sort of went into a blank mode and not much was going on. In recent years, as studies on the brain and body during sleep have made their way into science, it’s become very clear that the brain and the body are going through very important processes during sleep.

Sleep is separated into two categories: light and deep sleep. Within the category of light sleep are stages 1 and 2 of sleep.

Within deep sleep are stage 3 and REM (Rapid Eye Movement) sleep. The body and brain move in and out of these sleep stages in cycles throughout the night. While all of the stages of sleep are important, the deep sleep that you get during stage 3 and REM sleep are the most critical.

Deep sleep stages are also sometimes referred to as delta wave sleep or “slow wave sleep” (SWS). Typically it takes about 20 minutes after falling asleep to enter into stage 3, the first deep stage of sleep.

Why You Need Deep Sleep

Getting enough deep sleep every night is critical for your ability to function properly during the day. A number of things are happening to your brain and your body during deep sleep that cause you to be healthy and happy.

Here are some of the ways you benefit from deep sleep:

Building Up Energy

During Stage 3 deep sleep, your body is building up the physical energy that you will need in order to sustain yourself the following day. In children and young adults, the deep sleep process helps with maturing.

Repair of Cell Damage

While you are sleeping deeply, your body reduces the breakdown of proteins. Proteins are building blocks with contribute to the repair of cell damage done by ultraviolet rays, stress, and more. During the deeper stages of sleep, your body is releasing human growth hormone which is particularly effective in promoting repair to stressed muscles due to weight training or working out.

Increased Cell Production

In addition to repairing damaged cells, the deep stages of sleep also assist with the growth of new, healthy cells.


During deep sleep a person is going through the process of removing toxins from the brain and body to improve function and reduce disease.

Increased Cognitive Function

People who are unable to sleep deeply often suffer from limited cognitive function such as memory loss and struggles with learning new things. Scientists believe that as the metabolism of glucose in the brain increases during sleep, this supports both the long-term and short-term memory, as well as overall learning capacity.

Emotional Balance

More recently it has been discovered that getting deep sleep at night aids a person in their ability to balance their emotions, as well as reading the emotions of other people, the next day. One study showed that people who got enough deep sleep were able to better cope with trauma and were less susceptible to PTSD (Post-traumatic Stress Disorder).

How Much Deep Sleep is Optimal?

While there are a few things you can do to make sure you get enough deep sleep, the most important thing is to make sure that you get enough sleep in total. Normally it works to aim for enough total hours of sleep, your body and brain can typically keep you balanced between the amounts of light and deep sleep. As long you aren’t hijacking your deep sleep with substances such as alcohol and nicotine, or spending too much evening time in front of bright lights, then your brain and body will take you in an out of deep sleep naturally.

Usually this means that just under half of the sleep you are getting at night is deep sleep, and the rest is mostly comprised of light sleep in stage 2.

Although there is no prescribed amount of deep sleep needed by everyone, most experts agree that younger people are in need of more deep sleep than older people. This is related to the fact that growth happens during sleep. Younger people may need about 9 hours of total sleep, while older adults may be able to function just fine on only 6 hours.

Sleep tracking is becoming a popular trend in order to minimize the problems related to insomnia and lack of sleep. Hundreds of apps are available for various devices and these are fine to use, but they can also cause even more stress because their data can be unreliable. Normally, about 1.5-1.8 hours of stage three deep sleep per night is fine, but some people can get up to 4 hours of deep sleep. It really just depends on you.

Ideally, if you can try to go to bed at the same time every night and wake up on your own (without an alarm clock) in the morning, then your body will tell you how much sleep it needs each night.

How to Get More Deep Sleep

Although most people’s bodies will naturally get enough deep sleep naturally, you may be doing things that are keeping your body and brain from getting the much needed deep sleep that it needs. The types of activities that could be keeping you from entering into deep sleep stages include:

Avoid Drinking Alcohol

Although it can make you sleepy initially, alcohol can keep your brain from entering into the deeper stages of sleep. Avoid drinking alcohol within a couple of hours of going to sleep. The same goes for the nicotine that comes from smoking cigarettes.

Avoid Caffeine

This stimulant can also keep you from entering into the best stages of sleep. Even if you think you are sleeping well, if you’re having a cup of coffee in the late afternoon or evening, you may be sabotaging yourself.

Avoid Blue Lights

Our brains are highly stimulated by the blue lights that come from televisions, computers, smartphones, and tablets. Help your brain calm down and enter deep sleep by avoiding the use of screens and blue lights within a couple of hours of your bed time.


Getting enough deep sleep is something that your body will do naturally as long as you are in the right environment. Sleep in a cool dark room, limit exposure to substances such as alcohol or nicotine, and go to bed at the same time every night. You’ll be sleeping like a baby in no time!

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