Good-quality sleep – in sync with the internal clock

Many people experience sleep issues. They may struggle to fall asleep, wake up frequently and not feel refreshed in the morning. A regular sleep-wake cycle, the right sleep environment, dispensing with stimulants, reducing stress and getting exercise are all factors that can combat this.

At a glance

  • People’s internal clock controls when they are tired and when they are awake.  
  • Light is the primary external factor that influences the internal clock.  
  • People sleep best when their circadian rhythm is in harmony with their internal clock. 
  • Stress, but also certain foods and stimulants, can impair sleep.  
  • Tips derived from sleep research and the field of chronobiology can help people sleep better and start the day feeling refreshed. 

Note: The information in this article cannot and should not replace a medical consultation and must not be used for self-diagnosis or treatment.

A woman lies in a bed, stretching.

How does the internal clock affect the sleep-wake cycle?

The internal clock controls the rhythm of many processes in the body. It also determines when people are awake and when they feel tired. The processes roughly correspond to a 24-hour day. The internal clock comprises a network of genes and proteins that mutually influence each other. 

Light synchronizes the internal clock 

The internal clock is predominantly set by light. It can use light to synchronize itself with the environmental conditions.  

Light stops the body from producing melatonin, a hormone that promotes sleep, and starts it releasing serotonin, a hormone that makes people feel energetic and awake. This is why natural morning light helps people wake up. Furthermore, the body releases the stress hormone cortisol in the morning, providing an additional energy boost. When it gets dark, serotonin converts into melatonin to enable people to sleep.

Whether playing, reading or working, several hours of screen time and the associated blue light in the late evening inhibits the body’s natural production of melatonin. This means that the body no longer receives a signal telling it that it is time to go to sleep. If this occurs repeatedly, the internal clock becomes out of sync, potentially resulting in sleep problems.

On the other hand, the internal clock can also be disturbed if people sleep badly or irregularly. The internal clock and sleep mutually influence each other. This is noticeable in the case of jetlag for example: it takes a few days – or sometimes even weeks – for the internal clock to synchronize with the external one and for people to sleep as usual.

The sleep-wake cycle is primarily regulated by light.

Early birds and night owls: sleep based on the internal clock

People sleep best when their circadian rhythm is in harmony with their internal clock. Depending on the person’s chronotype, this can mean getting up and going to bed early – or vice versa. People who tend to start their day early are known as “early birds” whereas those who prefer to lie in and stay up late are known as “night owls”. There are also many levels in between. Most people are classed as “neutral types” and lie somewhere between the two extremes. People’s chronotype is genetically determined. From puberty to middle age, people’s rhythms shift and they start going to sleep and waking up at slightly later times.

How does diet affect sleep?

The way in which diet affects sleep differs from one person to the next. Habits also play a role. If people always eat a lot late on, as in the Mediterranean for example, the body gets used to this. Those who normally only have a light meal in the early evening, however, may notice that a late, heavy meal has repercussions: the unusual stomach and intestinal activity can negatively affect their sleep. On the other hand, a rumbling, empty stomach can make it hard for people to get to sleep and sleep through. A balanced diet is therefore important to restorative sleep.

What are the effects of caffeine, nicotine and alcohol?

Substances that contain stimulants make it harder to fall and stay asleep. For example, coffee, tea or cola contain the stimulant caffeine. The speed at which the body reacts to this and how long it takes for the caffeine’s effect to wane differs from one person to the next. People who experience the stimulating effect for a long time afterwards should avoid caffeinated drinks from late afternoon onwards.

Nicotine also affects sleep. It stimulates the circulation, preventing people from falling and staying asleep. If they experience withdrawal symptoms at night, this also disturbs their sleep.

Anyone who wants to improve their sleep should also avoid alcohol. Although this initially causes tiredness, it makes people wake up more frequently in the second half of the night and makes it harder for them to fall back asleep. Drinking large quantities of alcohol can also increase the risk of snoring and pauses in breathing at night, hallmarks of a condition known as obstructive sleep apnea. This leads to fitful sleep with frequent waking, potentially resulting in increased tiredness during the day, cardiovascular diseases such as high blood pressure and decreasing physical and mental performance.

How does stress affect sleep?

There are many situations in everyday life that can cause stress, such as looming project deadlines, a sick child or an unresolved argument with a partner.

Stress makes the body release cortisol, a hormone that perks people up and keeps them awake. The body is keyed up and ready for action, making it hard to switch off, so that falling asleep is out of the question. 

The body can withstand a certain degree of stress. If the stress persists though, the risk of sleep disorders and mental illnesses increases.

Measures that reduce stress or help to break down stress hormones are therefore beneficial to a restful sleep. These include relaxation exercises but also listening to music or reading in the evening.

Important: It is sometimes not possible for people to eliminate the disruptive factors that prevent them from sleeping of their own accord. If sleep problems persist and greatly impair someone’s quality of life, they are referred to as a sleep disorder or even insomnia. Medical advice should be sought in such cases. 

What else can I do to improve my sleep?

Some simple rules help to promote healthy sleep. For a start, having a comfortable bed and the right sleeping environment can make a big difference. Make sure that the bedroom has a temperature of between 16 and 18 degrees Celsius, is well ventilated and is darkened when sleeping.

Exercise in the afternoon helps people fall asleep. On the other hand, sport just before going to bed can hinder this as it stimulates the metabolism, resulting in an invigorating effect.

Certain rituals also help people fall asleep more easily. This can be a cup of herbal tea before bed, reading a book or relaxation techniques such as meditation.

Things that also support a good night’s sleep: 

  • Only go to bed when you are really tired. 
  • Ideally always go to bed at the same time and get up at the same time. 
  • Try to do regular physical exercise. 
  • Avoid alcohol and all caffeinated drinks about 3 or 4 hours before going to sleep.  
  • Avoid nicotine-containing products and medication such as sleeping tablets. 
  • Only use your bed for sleep and sex.  
  • Don’t put down smartphones, tablets and laptops just before going to bed. You should also switch off the TV well before then. 
  • To get (back) to sleep, it is also recommended that you don’t keep looking at the clock. If you’ve not fallen asleep after 15 minutes, get up and only go to bed when you feel tired. 

Why is healthy sleep important?

Over the long term, a lack of sleep can lead to health problems. Too little or poor sleep affects not only physical ability but also mental performance and the mind. Sleep disorders therefore increase the risk of cardiovascular diseases such as high blood pressure but also type 2 diabetes, dementia, depression and anxiety disorders.

Even though the body may seem to shut down at night, many important processes continue: The immune system is strengthened as we sleep. The brain also continues to work, sorting and storing the many things we have seen, experienced and learned during the day. The same applies to emotions – they are processed at night.

In addition, the hormone system continues to work and releases growth hormones. These enable the recovery and renewal of muscles, bones and internal organs.

How much sleep do people need? 

On average, people in Central Europe sleep for seven hours a night. However, the amount of sleep people actually need differs from one person to the next and also depends on age.

Important: The key to the optimum amount of sleep is how refreshed and rested people feel the next day. There is no set answer as to how much sleep people need as a minimum.

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