Sleep guide: Woman stands at the window and stretches
 

How does sleep affect our body?

Sleep is often seen as a mere rest phase, in which our body simply switches off. But in fact, sleep is much more than that. While we sleep, our body performs a whole range of complex tasks. It's the time of the day when it regenerates and gathers new energy for the coming day. We sleep so that we can recover and the mind can process the experiences of the day. But what exactly does our body do while we slumber peacefully?

Sleep and our brain

As a complex control centre, the brain benefits in many ways from good sleep. Our body switches into "standby mode" during sleep, recuperating and regenerating. However, the brain never sleeps. At night it is active and evaluates the experiences of the past day. Important events, information and sensory impressions are sorted into existing categories. 

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Information that you memorise just before falling asleep is processed particularly well. If we want to store information in our long-term memory, it needs to get from the hippocampus to the cerebral cortex. This process takes place during sleep.*1

Unimportant things are deleted. In the awake state, our brain cannot perform this work, otherwise we would not be able to register the information we receive during the day. The processing of these stimuli would get mixed up, which could result in hallucinations.

At the same time, a kind of "cleaning" of our brain takes place during sleep. While the brain is very active during the day, it uses a lot of energy. This creates harmful metabolic products that need to be broken down to prevent brain damage. This process is known as the glymphatic system and frees the brain from toxins and waste products. So while we sleep, a natural detoxification of our brain takes place.

If our brain gets enough good sleep, our cognitive abilities, our attention span, and our problem-solving and reaction abilities improve. We feel mentally balanced and are more resilient. However, if we regularly suffer from sleep deprivation or sleep problems, we may experience memory problems as well as concentration and attention disorders. We become moody and easily irritable. In the long term, there is an increased risk of neurological diseases such as Alzheimer's and Parkinson's.

Sleep and our hormones

Sleep quality is closely related to hormone production. On the one hand, our sleep influences our hormone balance. While we sleep, our body produces and regulates various hormones that perform a multitude of important body functions. At the same time, our hormones influence the quality of our sleep.

Two hormones that have a particular influence on our sleep-wake rhythm are melatonin and serotonin. Melatonin is referred to as the sleep hormone and shapes the quality of our sleep. It makes us tired and promotes falling asleep. Our brain's pineal gland releases the hormone mainly in darkness. The longer it is dark, the more melatonin is produced.

Serotonin is known as the happiness hormone, makes us awake and has a mood-lifting effect. At the same time, it has a calming and relaxing effect. During the particularly restful deep sleep phase, our body produces more serotonin. Since a lack of sleep often comes at the expense of the deep sleep phase, the serotonin level also drops with sleep deprivation.*2

Whilst the two hormones have the opposite effect on our body, melatonin and serotonin are closely dependent on each other. In the pineal gland, melatonin is largely formed from serotonin. If the hormone balance between melatonin and serotonin is disturbed, sleep disorders, daytime fatigue, lack of energy and drive, and even depression can result.

Beurer image - Woman lying on the sofa with her eyes closed and relaxing

In addition, our body produces the growth hormone somatropin during sleep, which initiates physical regeneration processes. At the same time, it also supports wound healing. Damaged tissue recovers faster at night. Somatropin not only promotes growth in children, but also stimulates muscle building in adults. Those who want to lose weight benefit from the positive effect of the growth hormone because somatropin makes fat cells melt. Like serotonin, somatropin is also produced more during deep sleep.

Collagen, which is responsible for the elasticity and youthful appearance of our skin, is mainly formed under the influence of growth hormones. It softens wrinkles and strengthens not only our connective tissue but also bones and tendons. The legendary beauty sleep is therefore not just a myth.

Two other hormones that indirectly affect our sleep are leptin and ghrelin. They control our feelings of hunger and satiety. The satiety hormone leptin allows us to go without food for 8 hours and longer. As soon as we wake up, the hunger hormone ghrelin takes over, signaling hunger to our brain. In the case of chronic sleep disorders, the balance of these two opposing hormones is often disturbed, which can lead to obesity. This is why we feel hungry when we have sleep disorders, even though we are actually satiated. People who watch their weight should therefore also value sufficient restful sleep.

In the morning, with increasing daylight, the release of melatonin decreases and is replaced by cortisol. The stress hormone wakes us up and helps us start the day fit. The cortisol level is highest in the early morning hours, between 7 and 8 o'clock.*3 Our body temperature, which drops at night, also rises again in the morning.

At the same time, blood pressure, heartbeat and breathing increase again and get our body going. If we do not get enough sleep, the hormone balance can easily be disturbed, which can lead to depressive moods, increased stress and an increased risk of hormonal diseases, among other things.

Sleep and our immune system

Our immune system is another area that benefits from sufficient good sleep. During sleep, our immune system runs at full speed. Various scientific studies prove the positive effect of a restful night's sleep on our immune defense.

A medical study, was able to prove that the immune function of the body's own T cells is restricted by sleep deprivation.*4 T cells play an important role for our immune system, as they kill pathogens and at the same time regulate the immune defense. After a sleep deprivation of just 3 hours, the adhesion of the T cells, i.e. the ability to dock onto diseased cells and kill them, was demonstrably reduced.

 

 

Beurer HD 75 cosy ocean electric blanket - application image of couple lying on couch under electric blanket

In another clinical study*5, 164 subjects were given common cold viruses via nasal spray. The results of this study also confirm that a shorter sleep duration is associated with an increased likelihood of developing a cold. Particularly in people who slept less than 5h per night, the risk increased. Almost half of the short sleepers fell ill. Those who slept more than 7 hours remained healthy with a probability of more than 80%.

The well-known "sleep yourself healthy" is therefore much more than a well-meant phrase. Those who sleep too little weaken their defenses, which increases the risk of infections, inflammations and chronic diseases. When our immune system needs an extra portion of sleep and rest, our body often signals this to us all by itself. As soon as we feel an infection, we feel more tired than usual and have an increased need for sleep.

Sleep and our metabolism

Our sleep also regulates the metabolism of all products that we have taken in during the day. Those who sleep too little run the risk that the body cannot fully perform the metabolism process. Studies suggest that Type II diabetes and obesity can be the result.*6 One reason for this appears to be an inhibited insulin release, which can promote insulin resistance. The hormonal antagonist, glucagon, which raises the blood sugar level again, is also secreted in smaller amounts.
According to one study, the risk of Type II diabetes increases in the long term with a sleep duration of less than five hours, as well as with more than nine hours of sleep per night.*7

Another study showed that weight gain can occur after just 5 nights with only 4 hours of sleep each.*8 The researchers cited a change in metabolism and an increased appetite due to lack of sleep as possible reasons.

Why does my sleep behavior change with age?

Many people notice changes in their sleep behavior over the course of their lives. This is a completely natural development and depends on both age and the life stages of a person. As a baby, we sleep between 16 and 24 hours a day. Teenagers around the age of 14 sleep on average 8-9 hours, while 70-year-olds only spend 6-7 hours in bed.

In most cases, the proportion of REM sleep, or dream sleep, decreases. This is partly because as we age, we no longer have as many new experiences in life to process, which would be reflected in our dreams.


*1 https://uni-tuebingen.de/newsfullview-landingpage/article/schlaf-macht-den-hippocampus-frei-fuer-neue-gedaechtnisinhalte/

*2 https://www.neurologen-und-psychiater-im-netz.org/aerzte/m%C3%BCnchen-neuhausen/willi/stressmedizin.html#:~:text=Serotonin%20wird%20im%20Tiefschlaf%20gebildet,so%20unter%20Stress%20fortlaufend%20abfallen.
*3 https://neurolab.eu/wissen/hormone/cortisol/
*4 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3256323/
*5 https://academic.oup.com/sleep/article/38/9/1353/2417971?login=false
*6 https://www.aerzteblatt.de/archiv/200872/Epidemiologie-Warum-Schlafmangel-dick-macht
*7 https://www.pharmazeutische-zeitung.de/ausgabe-172011/schlechter-schlaf-stoert-den-stoffwechsel/
*8 https://www.aerzteblatt.de/archiv/200872/Epidemiologie-Warum-Schlafmangel-dick-macht


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