Sleep phases and chronotypes: What your internal clock has to do with sleep and performance

Do you actually know the phases of sleep that people go through every night and know at which stage of your sleep you are actually dreaming? Or have you ever heard of chronotypes? In this article you will learn what happens in your sleep phases and what role your chronotype has on your performance.

While you sleep and recover, your body goes through several sleep phases in which your brain is at full speed and processes things that you have experienced and learned during the day. You may even dream of your new experiences and insights. Healthier Sleep, by allowing your body to regenerate and recharge optimally, includes an undisturbed sequence of sleep phases. If you also know your internal clock well and thus your chronotype, you can do a lot to do something good for your restful sleep at night on the one hand and for your performance the next day on the other.

 

What are the phases of sleep?

Two phases can be distinguished from each other during sleep: normal sleep phases (non-REM) and REM sleep.¹ But what does REM mean? REM stands for rapid eye movement and means that the eyes move quickly back and forth during sleep. Non-REM phases are phases without any movement of the eyes and can be divided into 3 stages.

These different stages can be differentiated with electroencephalography (EEG). With this method, which is used in neurology and sleep research, electrical currents (so-called potential changes) of the brain are recorded, amplified and recorded with the help of electrodes on the scalp. The recording (called an electroencephalogram) then shows current curves that are generated by the electrical activity of the nerve cells in the brain. Different states of consciousness also generate different waves and frequencies in the EEG.

 

The graphic shows the different waves that play a role in the sleep phases. The state of wakefulness in the EEG largely depicts beta waves. Here you are in a normal state of alertness and can consciously carry out all tasks and activities. If you are in a relaxed or meditative wakefulness state with your eyes closed, you are still conscious in that state. In the EEG, however, more and more alpha and theta waves appear and your body produces more serotonin. In addition, various health benefits have been shown when people remain in this state of alertness with the help of meditation and other relaxation methods.^{2, 3, 4}

 

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What happens in the individual sleep phases?

As already mentioned, there are four phases of sleep that we will now introduce to you. Of these, three phases are in the non-REM stage and one phase is in REM sleep.

 

Sleep phase N1: The first non-REM stage

This phase forms the Transition from wakefulness to light sleep. It lasts about 10 minutes and often shows theta waves with irregular oscillations in the EEG. Theta waves are slower than alpha waves, but they are higher in the EEG. You can in this deep meditative phase still change your position in bed and lets you wake up easily. If you woke up for any reason, you wouldn't feel like you were asleep.

 

Sleep phase N2: The second non-NREM stage

N2 is another light sleep phase of 20 to 30 minutes, in which you only move slightly and your Breathing slowly and calmly is. In this state, the EEG shows so-called sleep spindles. Sleep spindles are short phases in which the frequency of the waves increases. The frequency varies between 11 and 16 Hz. The Brain activity is higher than in the previous stage and dreams are possible in this stage. Getting enough sleep at this stage of sleep improves motor skills.⁵ Even at this stage you can still be woken up easily.

 

Sleep phase N3: The third non-NREM stage

At this stage the Breathing stable and the Sleep deeply. The EEG shows slow delta waves between 0 and 8 Hz and the muscles are totally relaxed. Heart rate, body temperature and blood pressure all decrease. The Release of growth hormones begins and start regenerative processes in our body. You are just here difficult to wake up, These Phase lasts 30 to 40 minutes and can be shortened by up to 6 minutes in the elderly.

 

Sleep phase: REM sleep

During REM sleep your eyes move rapidly back and forth. The The brain is awake while the body is sleeping. Muscles are paralyzedwhat to prevent sleepwalking. Dreams most often take place during these sleep phases. On average, everyone has 4 or 5 REM phases at night. These phases are important for that Regeneration of our brain cells.⁶ Research into the effects of lack of sleep has shown that REM sleep is absolutely necessary. Too little of this can lead to irritability, memory loss, poor concentration, and fatigue. In newborns, up to 50% of their 16-hour sleep phases are REM sleep.⁷

 

Sleep cycle: sequence of sleep phases

Normally, sleep works in such a way that when you fall asleep, you are only in the N1 stage and then sink through N2 to the third non-REM stage (N3). This is where the delta waves occur until you return to N2 and either wake up or your REM sleep phase occurs. A whole cycle can be described in this way.

In our graphic you will find a 4th phase, which can be combined with the 3rd non-REM phase and both are the deep sleep phases.

 

How many sleep cycles are there per night?

Every night you go through about 4 to 5 sleep cycles. After the 3rd cycle you will not return to the N3 stage. From then on you only switch back and forth between N2 and REM phases. The REM phases gradually become longer and the time in the N2 stage decreases.

A full sleep cycle lasts 90-110 minutes. To ensure a good recovery, you should go through the deep sleep phases in any case. These phases take place in the first three sleep cycles.

 

Sleep phases in connection with power naps

Sometimes the day is so stressful that you could use a little nap during the day. A short sleep break, such as a power nap, can help cope with this stress. The secret for efficient nap is that you fall no lower than sleep phases N1 and N2. Therefore, Power Naps no longer than 20 minutes last. You have probably already seen that long naps often lead to drowsiness and fatigue, which is exactly the effect that you actually wanted to combat. But if you want to catch up on lost sleep or speed up the ability to learn⁸, it can sometimes be beneficial to sleep a little longer. In such cases, it would make sense to plan your sleep to last a full cycle, around 90 minutes. The best time to sleep is around 6-8 hours after waking up.

Another good tip is to combine caffeine and a nap. This can be very efficient because it takes about 20-45 minutes for the caffeine to set in your body. A cup of coffee before a nap only starts to work after an afternoon napwhich means the caffeine does not adversely affect sleep.⁹

Now that you have got to know the phases of sleep that you go through every night, let's take a look at chronobiology.

 

Chronobiology: the circadian rhythm

Circadian rhythms are biological processes that are related to the circadian rhythm. These rhythms include:

• Body temperature
• Pulse and blood pressure
• reaction time
• Sleep-wake rhythm
• Production of melatonin, serotonin and cortisol
• Bowel activity

Anyone who regularly takes long-haul flights knows the importance of these rhythms. We know the problem of adjusting to the time zone as jet lag. Not being able to get used to such rhythms can limit cognitive functions.

Humans have an internal clock, it lasts around 25 hours and is reset in daylight. The light intensity should reach at least 1000 lux for this effect. For a comparison you can go for a typical office with 320-500 lux and active in direct sunlight with 32.000 to 130.000 lux expected.¹⁰ Light has a direct influence on the production of melatonin, which is mainly released by the pineal gland in the dark. Melatonin plays a crucial role in regulating the sleep-wake cycle. If you want to know more about the sleep hormone and Buy melatonin you can find out more about the topic under the link.

A newborn baby does not produce melatonin until it is three months old. From then on, production increases more and more until it reaches its peak in adulthood. In middle age, melatonin production begins to decline again. Researchers suspect this is a factor in the fact that older people normally do not need as much sleep as younger people.

The intensity of the light is not the only factor in the production of melatonin. The wavelength also has an influence. At We have a lot of blue light in daylightwhich one has a very short wavelength of approx. 420-485 nm. This light inhibits the production of melatonin. Research shows that short-wave LED lighting blocks the production of melatonin five times more efficiently than incandescent lamps.¹¹

You can see the circadian rhythm of an average person in the graphic.¹²

In order to optimize sleep, it is therefore important to understand how other neurotransmitters and hormones affect the circadian rhythm. For example, high levels of dopamine and serotonin have been associated with feelings of alertness and low levels of sleepiness. Cortisol, which is also known as the stress hormone, contributes to sudden wakefulness in the middle of the night. The production of cortisol is particularly active in the first 30 minutes after waking up.

But the most individual and independent factor in sleep is you! Because there are also genetic factors that play an important role in sleep. A distinction is often made between so-called chronotypes.¹³

 

What are chronotypes?

Chronotypes come from chronobiology and differentiates people into categories who, because of their internal clock, perform differently at different times of the day.

The nucleus suprachiasmaticus (SCN for short) plays a large part in the internal clock. This is a collection of nerve cells in the ventral hypothalamus and ensures that our pineal gland releases melatonin. The stimulus of the light goes from the retina of the eye to the SCN and is there converted into a stimulus that stimulates the pineal gland.¹⁴

But does every SCN work the same way? The stimulus of light is processed by all people differently early or late after sunrise and sunset and passed on to the pineal gland. That means that the Melatonin release takes different amounts of time from person to person. So the answer is no.¹⁵ The role and differences of the SCN are so diverse and varied that it can only be described very briefly and superficially how much each person can differ from one another.

 

What is the meaning of chronotypes?

There are different chronotypes. That means there are different types of sleep that are active at other times of the day. Some wake up especially early and are full of energy in the morning and others wake up very late and can barely roll out of bed in the morning. That means to a certain extent the health of your sleep behavior also depends on when you go to bed and when you get up. It is also possible that you perform better than other people at different times of the day. One study tested the performance of different swimmers and was even able to determine a gene that had an influence on it.¹⁶

So if you notice that all attempts to make your sleep healthy have failed and that doctors can also rule out clinical causes, then you should consider whether your current daily rhythm is really suitable for you. Sleep problems often affect people who have to work in shifts.

 

Determining Chronotypes: Am I a Lark or an Owl?

A common division is that of morning and evening types. These are used for illustration Larks and owls called. As an early riser, larks get up early in the morning, are active and ready for the day. The owls, on the other hand, are late risers and are more alert in the evening and at night. But this is not just about being awake. Larks and owls also differ in their individual performance during the day. At other times of the day, larks are more productive and more concentrated than owls. In the morning hours, when the owl is still totally unmotivated, the lark, for example, has probably already checked off a large part of its tasks.

The determination of the chronotype can be measured in many different ways. An example of a valid test is the MCTQ, i.e. the Munich ChronoType Questionaire, which you can find online if you are interested. But you can also observe yourself for a while at what time of day you perform and how and write it down if you are not sure how to assess your type.

The chronotypes are even associated with different probabilities of mood disorders, depression, bipolar illness and anxiety disorders.^{17, 18, 19, 20}

 

Can the chronotype change?

The data situation is not yet clear, but suggests that the daily biological rhythm changes in the course of life. For example, the exact reasons why many people fall asleep earlier in old age, wake up earlier and generally sleep less has not yet been conclusively clarified. However, especially in adolescence, we tend towards the evening chronotype. That is why some researchers advocate that school should start later in the day.