What is Sleep?

Sleep. We all know that we need it. We feel out of sorts when we don’t get enough, and feel refreshed when we do. But what is it about sleep that makes it so important? How much is enough? What can we do to get the most out of our sleep?

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What is sleep?

Wikipedia defines sleep as a naturally recurring state of mind and body, characterised by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and inhibition of nearly all voluntary muscles during rapid eye movement sleep, and reduced interactions with surroundings.

It is distinguished from wakefulness by a decreased ability to react to stimuli, but more reactive than a coma or disorders of consciousness, displaying very different and active brain patterns.

What does this mean?

When resting we go through several phases of sleep: pre-sleep, light sleep, deep sleep (also known as slow wave sleep) and REM (Rapid eye movement sleep). Each of these phases has specific qualities.

During pre-sleep our body slows down, heart rate and breathing rates slow and our muscles start to relax. We are not properly asleep during this phase, alternating between sleeping and being awake.

During light sleep, we are properly asleep, however it is easy for us to wake and when we do we have a good sense of our surroundings. During deep sleep it is hard for us to awaken and when we do we tend to feel confused and disorientated. Deep sleep should encompass the biggest proportion of our sleep.

REM (which takes up about 20% of our sleeping time) we dream.

It is common that we wake for a few seconds every couple of hours

Why do we sleep?

Sleep is a mysterious activity. In evolutionary terms it might be seen to make little sense – when asleep we are open to attack by predators. So, why haven’t we evolved in a way that minimised or eliminated it?

What we do know about sleep is that it somehow allows us to process the day’s activities and thoughts, to repair our bodies and ensure that our hormones and internal biochemistry is working the best it can be.

We also know the effects of too little quality sleep: poor concentration, feeling tired, low mood, grumpy, forgetfulness, stress etc. We also know that inadequate amount of sleeping makes us more prone to health issues such as obesity, diabetes, heart disease etc.

How much sleep do we need?

It is commonly quoted that people need 8 hours sleep. This is an average amount and the real need is dependent on each individual with some people only needing a few hours and others 10 or 12 hours.

See my next blog to see how you can get the most out of your sleep: Ten steps to better sleep.

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