You can’t sleep? People suffering from insomnia or have other trouble with their sleep, get here information about the nature of sleep.
Wrong convictions can cause unnecessary fear and aggravate existing problems. On the following pages you can find the most important information about what happens during a night of sleep and the steps you can take to try and improve your sleep. Scientists know surprisingly little about sleep, even if it must be considered a relatively recent branch of science.
The state of sleep has still a lot of unknown details. But the existing knowledge is at least sufficient to be able to analyze and improve any trouble you might have in your sleep.
Changes during our history in sleep and culture of sleep
Sleep has always troubled and simultaneously fascinated mankind. It was often regarded as a completely inactive state, in which most functions of body and mind would be „reset“.
In ancient Greek mythology, sleep is even compared to death: „Hypnos“, the god of sleep is the brother of „Thanatos“, god of death. Ancient Germanic traditions also define sleep and death as siblings – both are known as „Sandmen“.
Regarding sleep and its „how“, „when“, „where“ and „how long“, it has undergone lots of changes during history. Most people today have a separate bedroom. This achievement is quite recent; it started at the courtyards of royalty, and then was adopted by aristocracy and wealthy citizen. In this way, the bedroom was transformed from a multi-purpose room that was shared by many people, into the well-protected private territory of an individual person.
A long time ago, not only the place but also the times for sleep had a less rigid organization. It can be perceived by consulting paintings and calendars from the middle ages, that people frequently took a rest during the day on the field, besides houses or besides their workplace. In the western world after industrial revolution, sleeping during the day has been declared as the ultimate demonstration of laziness. Electrical lights and labor hours only started to define our rhythm of sleeping and being awake about 100 years ago. The human has to adapt to a certain frame.
Modern research on sleep: facts about sleep
In the past 60 years we were able to find out more about sleep than in the preceding 6000 years. Main contribution to that achievement was the ability obtained in the 1930s to measure and record electrical currents in the brain, the electroencephalogram (EEG). With the aid of the analysis with EEG it became possible to measure present brain activity. It was only possible with the EEG to prove for the first time that sleeping was a dynamic process, a special activity of the brain.
Sleep is therefore everything but a death-resembling state. In the last 10 years took place a fast proliferation of medical centers specialized on sleep, where everything that took place at night was precisely recorded and analyzed.
A night at the sleep lab: sleeping states and sleeping architecture.
To be able to analyze sleep it is necessary to record several biological signals of our body:
- Electrical currents in the brain: EEG (Electroencephalogram),
- Eye movements: EOG (Electrooculogram),
- Muscle tension in the chin: EMG (Electromyogram).
Following these three graphs of electrical currents it is possible to conclude that sleep can be divided into different phases: these phases reflect different physiological body states, but also varying experiences.
Today we defend the existence of five sleeping phases that good sleeping people as well as people with trouble in their sleep, experience in varying form and intensity night after night. What are the processes taking place during a night of sleep?
State of being awake.
At the beginning of the night, when sleep hasn’t arrived yet and the person is resting in bed, with lights turned out, an alpha rhythm, for this state typical, can be observed on the EEG. The EOG shows movement, eyes still move a lot, the EMG show high muscle tension.
Phase 1: Falling asleep.
After some time (in the case of a normal sleeper usually minutes) begins the phase of falling asleep. The alpha rhythm of the brain is progressively exchanged for slower, smaller theta waves. The EOG shows rolling eye movements, sending a clear signal to the observing scientist: the phase of falling asleep is being initiated. This first phase is a transition between being awake and asleep, during which can occur bizarre visions and thoughts. From a subjective point of view this phase can be called dozing. One frequently awakes from this state, startled, without knowing if one had been asleep or awake. Our conscious is still very active. The human spends about 1/10th of an average night in that phase or being awake.
Phase 2: The light sleep.
After some minutes in phase 1, the graph of electrical currents suffers another change: waves with more intensity appear, from time to time short waves are layered on top of them – the so called sleep spirals. During this phase, eyes are already quiet and the eyelids are firmly closed. Muscle tension has been mostly reduced compared to the state of being awake. The organism starts to create a protection against the surroundings. Most scientists today agree that this phase should actually be considered as the real start of sleep. But even in this phase, our conscious is still not completely turned off. This is shown very clearly by the fact that the average person in this state – even having normal sleep – can be very easily wakened up. Individuals suffering from sleep problems frequently believe, if they wake up from this phase 2, that they didn’t actually feel sleep at all yet. Their often very concentrated thoughts appear to continue during this phase. People spend approximately half of their sleep in this phase of light sleep.
Deep sleep (before: phase 3 and 4).
As the night further progresses, the graph of electrical currents in the brain suffers modifications. The EEG waves become higher and slower. The eyes are completely quiet and absent muscle tension signalizes deep relaxation, blood pressure is lowered, breathing and heartbeat become slower. In this phase, it is normally quite difficult to wake up and body functions are mostly set to „standby“ or regeneration. During this phase, the body especially produces human growth hormones. This suggests that deep sleep is the principal way for our body to regenerate. Some time ago, this phase was divided into phase 3 and 4.
The third phase was called early deep sleep. Our conscious mind is still not completely shut down during deep sleep. Any important or life threatening signal from the surroundings will still be perceived and cause the person to wake up. Studies indicate that when young individuals, who sleep normally, is woken up during deep sleep, frequently believe they had not slept at all yet. This suggests that perception of sleep is not always clear, even in the case of people who don’t have trouble with sleeping, as the brain never shuts down completely. The adult average person spends about 20% of the night in this phase. Older people clearly spend less time. The frequently desired and understandable wish of people suffering from sleeping problems, to finally be able to sleep deeply and without waking up, is actually not possible within normal physiology of sleep.
REM phase: The sleep where we dream.
Between 80 and 100 minutes after falling asleep the deep sleep usually stops suddenly, normally followed by a change of body position. After this short episode of body movement, the person will continue to sleep deeply for a few minutes. But then, in a matter of seconds, the graph suddenly changes completely. Muscle tension disappears almost totally, the electrical currents in the brain are now similar to the phase where the person is falling asleep, small and fast. In the EOG can be observed single or several eye movements (therefore the denomination of REM = Rapid Eye Movement). The preceding almost vegetative rest is over: heart beat, blood pressure and breathing become faster and irregular, a man will get an erection in every REM phase, a woman will have increased blood circulation in her clitoris. The adult human spends about 20% of his time of sleep in this phase. Small children and babies spend even more.
It is also during the REM phase that we dream: people who wake up from this phase usually (80%) report to have been dreaming. But that’s not the only reason that this phase has always fascinated scientists. They also discovered that the brain actively controls the strange and extreme relaxation of all muscles of the skeleton. Without it, the person sleeping would really try to execute all movements he/she is doing in the dream. This would logically have severe consequences.
Therefore, our brain makes us almost paralyzed during the REM phase of sleep (that’s why we often experience in a bad dream that we want to run away but actually can’t move). Sleepwalking actually doesn’t occur during REM phase of sleep but during the phase of deep sleep. Regarding the strange eye movements during deep sleep, scientists are still looking for a convincing explanation: The logical assumption this could be caused by following images we see in our dreams, revealed as being far too simple. Some results confirmed a connection between the REM phase, solidification of memories and emotions. But even then the discussion between scientists still continues.
Architecture of sleep
Not only the right occurrence of the different phases of sleep is important for a sleep that recovers. Even the time sequence in which the phases occur night after night is relevant. It is possible to recognize in the profile of sleep the raise and fall of a line in form of a stairway: each step represents a phase of sleep.
After falling asleep (phase 1), the person reaches deep sleep passing through the phase 2. After about 90 (+-10) minutes occurs the first REM phase (bold horizontal line on the graph): the first cycle of sleep is completed.
The night continues and these cycles occur over and over, each taking between 90 and 120 minutes. The amount of time taken by each phase is adjusted during the night from cycle to cycle: in the beginning of the night, phases of deep sleep take more time than the REM phases. Towards the end of the night, there are almost no phases of deep sleep anymore, but REM phases are getting longer and longer. Also during the second half of a night of sleep, body movements increase and it becomes easier to wake up, also body temperature raises a little and more hormones of stress are produced. The organism is preparing to wake up…
It is normal to pass through short periods of being awake, often for only a minute (they become far more frequent as the person ages), but isn’t even remembered the next morning, as long as they don’t exceed a certain amount of time (ca. 4 minutes). People who suffer from sleeping problems especially experience the frequent but short periods of being awake during the second half of sleep as like they were a single continuous period of not sleeping.
The worry and anger about waking up again often lead to a real period of not being able to sleep.