The ultimate deep sleep guide

Regeneration, detoxification, learning: While you sleep, a whole series of processes take place that are essential for your physical and mental performance. Despite years of research, not all of the secrets of sleep have yet been revealed. However, research agrees on one thing: sleep is vital, in part because the brain is rid of waste products during sleep. In this article, we explore the role deep sleep plays in this and what you can do to improve it.

1. What is deep sleep?

Deep sleep is the fourth stage of sleep and is particularly deep compared to the others. During this phase, all characteristics of the waking state are particularly weak , meaning your heart rate , breathing rate , muscle tone (muscle tension), and sensory perception operate at an absolute minimum. Your body is maximally relaxed during deep sleep.

Waking yourself up is particularly difficult during the deep sleep phase. If you do wake up directly from the deep sleep phase, it will take a comparatively long time to orient yourself. Phenomena such as sleepwalking or sleep-talking occur exclusively during deep sleep .

2. When are you in deep sleep?

In research, the term "deep sleep" actually refers to two deep sleep stages . They are the third and fourth of a total of five sleep stages.

During sleep, the individual sleep phases alternate in regular cycles . You therefore experience deep sleep not just once, but several times – always alternating with light sleep phases and the dream-rich REM phase . Based on your total sleep, you spend about a quarter of the night in deep sleep .

A sleep cycle for a healthy adult over 30 years of age lasts about 90 minutes . The longer you sleep, the shorter the deep sleep phase becomes, while the REM phase lengthens.

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3. What happens during deep sleep?

During the deep sleep phase, many different regeneration processes take place. You are maximally relaxed, meaning your muscles are not tense, your heart rate and breathing are at their lowest frequency, and nerve activity in the brain also decreases.

Here is an overview of the most important processes that take place during deep sleep:

• Healing wounds and injuries
• the immune system is strengthened
• Growth hormones are released
• Experiences are processed [1]
• Memories and learning are consolidated [2]
• decisions are made subconsciously

4. Our sleep phases at a glance

Deep sleep is one of five sleep phases [3]. While you sleep, these phases alternate repeatedly. This means that you sometimes sleep more deeply, sometimes less deeply. After about six to eight hours, the sleep phases alternate at increasingly shorter intervals until you finally wake up.

These are the five phases of sleep:

1. Falling asleep or light sleep
2. Moderate to light sleep
3. Transition phase to deep sleep
4. deep sleep
5. REM sleep

What happens during the falling asleep phase?

In preparation for a night's sleep, you relax and unwind. Bedtime rituals help you fall asleep quickly. When you close your eyes, your body immediately begins to slow down all processes.

The activity of your nerve cells slows down and your muscles relax. You become less and less aware of your surroundings—you hear and feel less intensely—and slowly drift off to sleep.

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When does the light sleep phase occur?

The light sleep phase is almost indistinguishable from the falling asleep phase. Your awareness and muscle tension throughout your body are still reduced to a minimum. However, it is relatively easy to wake up during this phase. Light sleep phases occur repeatedly and account for about half of your total sleep .

Recovery: This happens during deep sleep

You can benefit most from all the positive effects of sleep during deep sleep. It provides you with rest and regeneration. This means your body processes the previous day's experiences , stores important information in your memory , and consolidates learned content.

Likewise, your body prepares for the new day by building up new strength. Healthy, deep sleep ensures that you're productive every day and optimally prepared for the challenges of work and sport.

The ratio of deep sleep to light sleep

While you sleep, phases of light sleep and deep sleep alternate repeatedly. In these repeating cycles, you drift into deep sleep several times. Before you wake up, you are usually in a light sleep phase.

The dream stage: When do we have REM phases?

You can think of the REM (rapid eye movement) phase as the complete opposite of deep sleep : This phase is characterized by high brain activity , elevated blood pressure , rapid heartbeat , and rapid breathing . Twitching arms and legs , as well as rolling eyes, are also typical .

The REM phase is often referred to as the dreaming phase . While you probably dream during every sleep phase, dreams from the REM phase are the ones you remember best and most vividly.

A healthy adult spends about 1.5 hours in the REM phase of six to eight hours of sleep.

5. What are your sleep phases?

As already mentioned, your sleep phases are organized into so-called sleep cycles [4]. In such a cycle, all five phases occur one after the other and are repeated with each new cycle. This means that you are repeatedly in the light sleep, deep sleep, and REM phases.

While the length of a sleep cycle always remains roughly the same—about 90 minutes—the proportion of each sleep phase changes. You spend less time in deep sleep and longer in the REM phase. Since the REM phase is the longest before waking, you'll likely remember your dreams particularly well. Want to learn more about the different sleep phases? You'll find all the information in our sleep guide .

6. Deep sleep duration in hours: How long does deep sleep last?

The question of how many hours of deep sleep one should have to feel rested is not clearly answered. In a healthy adult, the proportion of deep sleep is approximately 15 to 25 percent . This results in a deep sleep duration of 1.5 to 2 hours. However, this requires a total sleep duration of at least six hours .

• How much deep sleep do you need? About 1.5 to 2 hours
• What percentage of deep sleep is normal? 15 to 25 percent

If you regularly sleep only four to five hours, you'll only get a very short amount of deep sleep and therefore less restful sleep. You'll feel exhausted and worn out.

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7. How much deep sleep does a person need?

Compared to the common and healthy sleep duration of six to eight hours, humans need deep sleep of about 1.5 to two hours to be productive.

How much deep sleep per night is normal?

Sleep research has found that healthy adults spend about 15 to 25 percent of their night's sleep in deep sleep. With a total sleep duration of six to eight hours, this translates to a deep sleep duration of 1.5 to two hours. This is the amount of deep sleep necessary for you to feel fit and rested.

How do you know how much deep sleep you have?

While you sleep, you can't distinguish between the individual sleep stages. Even from the outside, it's difficult to determine when someone is in deep sleep. Sleep researchers use EEG (electroencephalography) to identify sleep stages, which measures the electrical waves in the brains of sleepers.

Based on the rhythm and intensity of brain waves, scientists can determine the sleep phase . So-called delta waves characterize deep sleep . These are particularly slow waves with high amplitudes. Of course, you can't see them from the outside.

Rapid eye movements and twitching of arms and legs signal that you are in the REM phase. You were just in the deep sleep phase. Even if you talk in your sleep, you are most likely in deep sleep. But only someone else can tell you that.

Awakened during deep sleep: How our body reacts

It's extremely rare and unlikely that you'll wake up directly from deep sleep. Your body is so relaxed that it perceives its surroundings minimally or not at all. You're probably familiar with the phenomenon of people sleeping through New Year's Eve: Even the loud crash of firecrackers doesn't penetrate your consciousness when you're in deep sleep.

If you are awakened from a deep sleep, you feel extremely sleepy and fatigued . You sometimes find it difficult to orient yourself, and it takes a relatively long time to speak or move.

8. What happens if you don’t get enough deep sleep?

Lack of sleep, especially a lack of deep sleep, can lead to reduced mental and physical performance . Constantly tired people have difficulty concentrating , are fidgety, and irritable . A tired body also performs less well in sports than when it's well-rested and refreshed. Chronic sleep deprivation can even have serious consequences.

What causes insufficient deep sleep?

Very little or no deep sleep occurs when the total duration of your sleep is too short or you are too agitated due to worries or stress to fall into restful deep sleep.

Try to give yourself enough time to sleep, even during stressful periods. At least six hours of sleep is recommended. Relaxation exercises like yoga or autogenic training can help you calm down and get into the right frame of mind for a good night's sleep.

What disturbs deep sleep?

Unwanted stimulants lurk in many places in everyday life: A late-night trip to the gym , a Netflix marathon , or a large dinner party can rob you of sleep and prevent you from experiencing deep sleep. To avoid this, we've compiled 6 tips for better sleep quality in a related article.

9. How can you improve your deep sleep?

There are many tactics to prolong your deep sleep. The first step is to identify and eliminate the disruptive factors that prevent you from healthy deep sleep. Take a close look at your daily routine and try to identify bad habits .

Take a look around your bedroom: What might be keeping you awake at night? It's also worth establishing a calming evening routine . Meditation , reading , or even a short walk can work wonders.

You can solve acute sleeplessness by using supplements containing melatonin. Learn all the benefits of taking melatonin in this article .

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How important is proper sleep hygiene

With proper sleep hygiene, you can improve your sleep and even cure problems falling asleep.

Doctors and scientists refer to sleep hygiene as behaviors that promote healthy, restful sleep and thus prevent sleep deprivation and fatigue. The German Society for Sleep Research and Sleep Medicine (DGSM) has published a handbook outlining the most important rules for sleep-promoting sleep hygiene.

Among other things, they recommend avoiding alcohol and caffeinated drinks shortly before bedtime . Instead, regular exercise and relaxation exercises are said to improve sleep hygiene.

10. Conclusion

Deep sleep is one of five stages of sleep. Your body is at its most relaxed during deep sleep. Important memory and regeneration processes also take place. To get enough deep sleep, you should allow yourself a total of six to eight hours of sleep per night.

11. Sources

[1] Born, J., Rasch, J., Gais, S. (2006) Neuroscientist. Sleep to remember. Vol. 12, Issue 5, p. 410-424 [https://journals.sagepub.com/doi/abs/10.1177/1073858406292647]

[2] Paschek, N. (2015) Spectrum of Science: Learning While We Sleep. [ https://www.spektrum.de/news/lernen-im-schlaf/573062 ]

[3] Sleep stages and sleep architecture. In: Sleep Training – A Therapy Manual for the Treatment of Sleep Disorders. Hogrefe-Verlag, 1999. Excerpts from [ https://www.schlafgestoert.de/site-51.htm l]

[4] Weeß, H.-G. (2009) Psychotherapy in Dialogue: Phenomenology, Function, and Physiology of Sleep. Vol. 10, Issue 2, pp. 101-106 [https://www.researchgate.net/publication/247467289_Phanomenologie_Funktion_und_Physiologie_des_Schlafes]

[5] Crönlein, T. and Weeß, H.-G. (2011) Patient guide of the German Society for Sleep Research and Sleep Medicine (DGSM) [https://www.dgsm.de/patienteninformationen_ratgeber.php]