Sleep

Day is followed by night, and waking is followed by sleep. As natural and logical as this sequence may seem, our nightly rest is just as unfamiliar and mysterious to us.
What do all those hours in this supposed twilight state actually do for us? Findings from several research centres offer some answers. Life is short. Too short to sleep through. And yet we spend a third of our existence in this drowsy state. Couldn't we simply cut back on sleep in favour of a longer life?

The opposite seems to be true: we need sleep to survive. In somnology, the study of sleep, sleep researchers examine behaviour and all the physical processes and states of consciousness that occur during sleep. So far, researchers have gathered findings on sleep phases and sleep disorders, but not on why we sleep. For that, there are only so-called well-founded hypotheses.

Why do we sleep?
Although we can spot a sleeping person very easily, sleep itself is very hard to define. Everyone senses when they need sleep and that this tiredness must serve some purpose, yet only vaguely what that purpose is: sleep is necessary to keep the brain functioning and for the survival of the whole organism. During this nightly twilight state, our reserves can be replenished, experiences processed and what we've learned stored away. But anyone who thinks this happens calmly and peacefully is in for a surprise.

From one sleep phase to the next
As recently as a hundred years ago, people assumed that the brain simply switched off during sleep. But it's not only the body that moves restlessly at times — brain activity does too. Sleep is an active, highly organised sequence of events and physiological states. It consists of two clearly distinct states. On one hand, there's REM sleep (rapid eye movement sleep), the phase marked by rapid eye movements; on the other, non-REM sleep, which is itself divided into four stages. Sorted by the speed of the brain waves the sleeper produces, two stages each can be classed as light and deep sleep. The latter is marked by slower brain waves and is commonly regarded as healthy sleep, since the sleeper is in a highly relaxed state.

Dream sleep
During REM sleep – the phase in which dreaming is most likely – you can observe the sleeper's eyes moving beneath their closed eyelids. Some researchers see a link between the pattern of eye movement and the images seen in the dream. During this phase, which grows longer as the night goes on, the body is in a state of muscular slackness. Only the heart, the eye muscles and a few others stay active. Many myths and stories exist about what's dreamed during this phase. Theories range from wish fulfilment to the preservation of memories. But we needn't be afraid of nightmares. Often, they're simply the mind working through its fears.

Sleep disorders
Even so, poor sleep can have a negative impact on our health system. Occasional trouble falling asleep, restless and shallow sleep, or waking up several times during the night needn't worry us just yet. The causes can be strong emotions, thoughts and problems, minor illnesses, or an unfamiliar environment. However, if these nightly conditions persist, they should be checked by a doctor, so that daytime tiredness, restlessness and depression can be prevented.

Learning to sleep better
First of all, it should be said that reaching for sleeping pills is no lasting solution — it's more likely to end in dependency than to improve your sleep quality. The slow route, taken in small steps, is far more suitable, because restful sleep can be learned. So-called sleep hygiene is a technique that enables healthy sleep through simple advice. Here, it should first be made clear that sleeping through the night is not the same as healthy sleep. Even the best sleeper wakes up several times during the night. Nor can a fixed sleep duration be set that guarantees freshness and recovery the next morning. Depending on the individual, this can vary between six and twelve hours. Anything less, however, is decidedly too little.

Sources: Luzia Kunz