What is sleep?
Sleep is the mysterious shift in consciousness that our bodies require every day. It’s vital for our health and wellbeing, and not only do we function less well when we don’t get enough quality sleep, but it can lead to long-term health problems. That’s why we need to do all that we can to ensure that we enjoy quality sleep and deal with any sleep problems.
The Sleep Cycle
During sleep our heart rate drops, our body temperature falls and we experience complex changes in brain activity. An EEG (electroencephalogram) gives us an insight into the brains electrical activity when we sleep:
- When we first fall asleep we enter non-rapid eye movement (NREM) sleep. NREM is divided into three stages: – NREM1 – NREM2 and – NREM3, each stage becoming progressively ‘deeper’.
- Stages 1 and 2 are light stages of sleep from which we can be easily roused.
- Stage 3 is a deeper stage of sleep from which we’re more difficult to rouse, and some may feel disorientated if woken from this stage of sleep.
- Generally, after going through the NREM stages, we enter stage 4 which is known as rapid eye movement (REM) sleep, which the EEG shows as being similar to wakefulness or drowsiness. It is during the REM stage of sleep that we dream.
- Each cycle lasts around 1½ hours and we need to experience all four stages in order to wake up rested.
- A good night’s sleep consists of five or six cycles, whereas disturbed sleep consists of far fewer.
Sleep is largely controlled by sleep pressure, and the circadian rhythm, or our body clock, which is a 24 hour cycle that regulates all our biological and physiological processes. It anticipates environmental changes around us so that our bodies can adapt to them.
In ideal situations, the circadian rhythm will naturally rise in the early morning, promoting wakefulness and alertness, and will reach a peak in the evening. After a waking period of around 15 hours the pressure to sleep becomes greater and greater, in other words, we get tired. With the onset of darkness, the circadian rhythm drops to the lowest level and helps to maintain sleep.
To ensure you experience good sleep it’s essential to follow good lifestyle habits and to eliminate the factors that are causing you disturbed sleep. For example making sure that your bedroom is the right environment, looking at the lighting in your home, and avoiding foods and drinks that can hinder sleep.