More about sleep

The majority of people associate a good night's sleep with little movement. Research has shown that good sleepers actually move less than poor sleepers. But movement is still very important during sleep!

Movement is necessary. This is because there is still pressure on the body when you are lying down; this can even cause bed sores after a time. To warn us against this, the body has a clever alarm system in the shape of tingling and signals that do not penetrate to the conscious level.

Movement not only relieves the soft tissue but also restores the spine. The intervertebral discs are located between the vertebrae of the back. They have a tough exterior and a jelly-like inside. They work as a type of sponge; due to the pressure on the spine, the interverbral discs suck water and food from their surroundings and eject water and waste products.

The ejection of waste products and water mainly occurs through active movement. When lying down, the discs absorb liquid once more. But lying down in itself is insufficient for a complete recovery. Turning and moving when sleeping also contribute to the recovery of the spine. The pressure differences allow liquid to flow to the discs.

Movement in your sleep therefore relieves the discs. Older people move less than younger ones, in the summer you are more active at night than in the autumn, and your sleep is less restful when you are tense.

More important than the number of movements you make is the ease with which you can move. The easier that it is for you to move, the less this movement will disturb your sleep. You should not concentrate so much on the number of times that you move, as that is difficult to influence; instead focus on the ease of movement. That is what must determine the choice of your bed.

Hormones are substances produced by glands that act to control the physical and mental processes in the human body.

Hormones also play an important role in disorders such as stress and burn-out. Research has shown that there is a reciprocal relationship between the concentrations of melatonin (a hormone that promotes sleep) and stress hormones; an increased level of stress hormones indicates a reduced level of melatonin.

Studies with two groups of test subjects, good sleepers and poor sleepers, showed that the poor sleepers produced significantly higher levels of stress hormones when sleeping. This must be the result of the inability of these sleepers to distance themselves at night from the stresses and strains of everyday life, while good sleepers are able to do so.

Likewise, what applies to sleep also applies to falling asleep; the person who is still concerned about problems at work or in their private life when he or she goes to bed will find it more difficult to fall asleep. People who sleep badly because of daily stress are advised to take time to relax before going to bed. This can be done in many ways, from meditating for half an hour to reading a relaxing book in bed.

People dream on average two hours a night, even though many of them can remember nothing or little of these dreams in the morning.

The brain handles information in a completely different manner when dreaming than it does during the day. It also seems that the mind uses dreams in the same way as a computer rearranges a hard disc; data is reordered, excess material is thrown away. During this process, many very creative ideas can arise; some well-known discoveries and historical events can be traced back to dreams!

Nightmares are extremely frightening dreams from which a person can awake with a start. You can normally relatively quickly orient yourself and often know precisely what you have dreamt after a nightmare. Everyone can experience nightmares, but people suffering from Post Traumatic Stress Disorder (PTSD) in particular can suffer from repeating frightening dreams. There are now a large number of therapies available to help people learn to deal with nightmares.

Sleeping gives the body the opportunity to recover from its daily exertions. The production of growth hormone rises to a high point, the speed of cell division increases and we recharge, in a mental sense.

Many things also happen in a physical sense; with relaxation of the muscles being of particular importance. Some of these muscles have to work for a large proportion of the day. The human skeleton is kept upright by the ‘postural muscles’. If they did not work, we would collapse in a heap. A lot of energy is required to keep the muscles working; walking around slowly demands 60% more energy than lying down.

Lying down (and so sleeping) has another advantage; the intervertebral discs are relieved of strain. Because of gravity, the intervertebral discs are compressed during the day as a result of standing and moving. People are therefore shorter in the evening than in the morning! The pressure is highest in the lower back. The pressure in the lower discs when lying is reduced by 75% when compared to standing.

The brain is extremely active when sleeping; in a different way than to when we are awake. It responds less strongly to sensory stimuli and is less concerned with the body's locomotor system. The brain appears to be doing a type of maintenance when we sleep; all of the information that it has received is processed and a process of archiving and clearing up occurs.

Have you ever woken up after a good night's sleep and found that you suddenly know a name that you could not remember the previous day, or that you suddenly have the solution to a problem? This demonstrates the fact that our brains are actively working when we sleep.

We have known since the 18th century that humans, just like many other organisms, have something like a ‘biological clock’. But how it precisely works is unclear. The biological clock is of great importance for the functioning of our bodies; it controls heart rate, blood pressure, breathing, digestion, muscle tension, hormones, brain functions and body temperature.

The principle of the biological clock is the same for everyone, but everyone also has their own rhythm. Put differently; the biological clock is not set in the same way for each person. The biological clock ensures that more or less all of the physiological processes in our body display a so called circadian (from ‘circa dies’, Latin for ‘about a day’) rhythm. A 24-hour rhythm, such as the change between sleeping and waking.

Our biological clock also controls our need for sleep. This need differs greatly between individuals and between different age groups. There are for instance people who are more active in the morning (early risers) and those who are more active in the evening (night owls). Older people often get a somewhat different sleep rhythm; they wake up more often at night and need a nap during the day. In the respect of their sleeping behaviour, they start to behave more like early risers; they become sleepy earlier in the evening and wake earlier in the morning.

Where you could think that little sleep would be good for your figure, because you are active for a relatively longer proportion of the day, the opposite proves to be the case; a structural lack of sleep promotes corpulence!

Sleep forms part of our twenty-four hour cycle. The quality of our sleep has consequences for our humour, our locomotor system and our behaviour; in short, our entire functioning. Too little sleep can lead to dangerous situations at work, in traffic and in every situation where concentration is required.

The first results of new research also show an unexpected consequence of a structural lack of sleep; an increase in weight. In an American study, thirty test subjects were sub-divided into two categories; one category slept less than six hours a night and were identified as being ‘short sleepers’, the other category slept six to seven hours a night and were identified as being normal sleepers. The results appear to show that the short sleepers are less able to use insulin to break down glucose, which probably encourages corpulence.

It is our body temperature that is responsible for the timing of sleeping and waking, not the change between light and dark. In the evening before falling asleep the temperature of your body is lower than in the morning prior to getting up.

If you have jetlag, your biological clock is confused. As a result, your body can give certain signals at unexpected moments; for instance you suddenly become cold in the middle of the day.

Ambient temperature, in addition to body temperature, has an influence on the feeling of sleep. It is a rather complex influence; in a room that is too hot you can quickly feel sleepy, but often if it is extremely hot at night you can not fall asleep. This means that the climate in your house, especially the temperature and humidity in the bedroom, is extremely important for a good night's sleep.