October 26, 2016

Slow Wave Sleep – What Is It and Why Is It So Important?

what is slow wave sleep

We’ve all heard the formula for healthy living – eat right, exercise, and get enough sleep. It’s easy to see how your diet and exercise can affect your overall health, but what about sleep? What impact does slow wave sleep have on the body and why is it so important?

As scientists and researchers continue to learn more about the brain, the body and the sleep process, it becomes more apparent that sleep does play an important role in our health, development and longevity. This is especially true for one sleep cycle known as slow wave sleep.

Have you ever been woken by the phone in the middle of the night? Were you confused and disoriented when you answered the phone? You were probably experiencing slow wave sleep. Slow wave sleep is the deep sleep that we experience through about one-third of the night.

The Stages of Sleep

People commonly think of sleep in terms of random eye movement (REM sleep). Research suggests that we experience REM sleep for about 20% of the night. The rest of the night is dedicated to non-random eye movement sleep (NREM).

During the 80% of the night that we experience non-REM sleep, we typically go through four stages of sleep.

Stage 1 Light Sleep: This is the time when your eyes start to get heavy and your muscles start to relax. Picture someone’s head bobbing as they sit through a boring meeting.

Stage 2 Beginning Sleep: Beginning sleep is characterized by decreased awareness and muscle relaxation. Ever jump awake because you feel like your falling? You are experiencing the bridge between light sleep and beginning sleep.

Stage 3 & 4 Deep sleep: Scientists typically combine stages 3 and 4 into the category of deep sleep. Slow wave sleep occurs during the deep sleep cycle.

What is Slow Wave Sleep?

Slow Wave Sleep is characterized as the dreamless state of sleep. It is the deepest of all of the sleep stages and is likely the most important stage of the sleep cycle.

There are marked physical changes during this period of sleep. The heart rate and the respiratory rate are both very low. There is no eye movement at all and very little muscle activity. The body is still, the heart rate is low and breathing is very shallow.

Slow wave sleep is also characterized by low brain waves. This is the time that the body uses to reenergize and rebuild itself. All brain and muscle activity slows down significantly.

It is difficult to wake during the slow wave stage of sleep. This is the time when you experience confusion if awakened.

Why is Slow Wave Sleep So Important?

slow wave sleep

The slow wave sleep stage is the part of the night that the body uses to rest, grow, develop, and reenergize. It’s during slow wave sleep that the body recovers from the day and energizes for the next day.

Researchers have found that during the slow wave sleep stage, human growth hormone is released. Human growth hormone is known to stimulate bone growth, improve immune function and regulate amino acids and proteins in the body.

This hormone is also known to induce fat burning and maintain cardiovascular health. The hormone is released during slow wave sleep and works as the body works to rejuvenate. All of these benefits are realized from a simple, good night’s deep sleep.

According to the National Institute of Neurologic Disorders & Stroke, 40 million Americans suffer from disruptive or inadequate sleep. Inadequate sleep is linked to a variety of diseases such as obesity, heart disease and Type 2 diabetes.

Slow wave sleep is the key to allowing the body to reenergize, regroup and rebuild. If you aren’t achieving enough slow wave sleep during the night, your body doesn’t get the chance to grow and recover. This is how slow wave sleep can affect your health.

How Can You Increase Slow Wave Sleep?

Now that you know the importance of slow wave and deep sleep, how do you make sure you achieve a sufficient amount of this sleep during the night?

Sleep pressure is the key to achieving extended periods of deep sleep. When you’re tired, you are more likely to enter into a deeper sleep. The more time you spent awake prior to going to sleep at night will determine how deep your sleep will be.

Think of it this way, if you take a nap during the day you are less likely to be tired at night. Since the time that you spent awake prior to retiring for the night was relatively short, you will not likely achieve long periods of deep sleep.

On the other hand, if you are sleep deprived or experienced a longer day than usual, you will likely be very tired. Your body will get to the deep sleep stage quicker and stay there longer. This is why people who exercise regularly sleep more soundly at night. Their bodies are tired from the exercise and they achieve deep sleep easier.

Diminishing Slow Wave Sleep

Unfortunately, as we age our slow wave sleep diminishes. We experience a shorter period of slow wave sleep and less opportunity for deep sleep. Research indicates that on average young adults experience slow wave sleep during about 20% of the night. By midlife, slow wave sleep is reduced to about 3%.

With the reduction in slow wave sleep comes the reduction of the production of human growth hormone. This is part of the reason that our bodies cannot repair and rebuild easily as we get older. Research also suggests that men experience less slow wave sleep than women.

Along with the inability to repair and re-energize, lack of slow wave sleep can lead to psychological and sleep disorders including insomnia.


Slow wave sleep is not something we usually think about when we think about healthy living. But sleep is a vital part of maintaining a healthy mind and body. Slow wave sleep allows the body to rebuild and reenergize. Experiencing slow wave and deep sleep will help to keep you healthy, energized and well.

    Caryn Agnes

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