Sleep – What is this thing we call sleep?
By Pete & Anna
This one is a bit of a personal one for both of us; we’re both terrible sleepers! Always have been. You name it, can’t get to sleep, can’t stay asleep, unrefreshing sleep, waking early, too much sleep…..
Many people we work with also struggle with sleep, so as Psychologists we are all too aware of the impact of poor sleep on health. At the same time as people who have less than ideal sleep patterns, we also have some personal experience and reflections on techniques that have worked for us.
It’s important to distinguish here that we are not aiming this blog to address and define every sleep disorder in great detail (although we will briefly describe some later on). It is more to think about what sleep is, why we do it, what can get in the way, and what can promote it.
We hope that it will be interesting, whether you experience difficulties sleep or not – after all, we all sleep! However, if you do want to seek support for your sleep its worth contacting professional support through your GP, specialist sleep services, or one of us at Avenue Therapies to find out more.
Sleep…. What is it?!
Many of us think every now and then about sleep but have you ever thought about what it is? Why we do it? What might get in the way? And what might help us get a solid 40 winks?
The Oxford English dictionary defines sleep as, “a condition of body and mind which typically recurs for several hours every night, in which the nervous system is inactive, the eyes closed, the postural muscles relaxed, and consciousness practically suspended”.
Sleep has been observed in mammals, birds, reptiles, amphibians, fish and, in some way, insects. During sleep, most of the systems within animals are in an ‘anabolic mode’. This means that they are rejuvenating, growing and strengthen the body (e.g. through the immune system, nerves, bones and muscles).
All mammals sleep in repeating periods, where the body alternates between two different ‘modes’ known as non-REM and REM sleep. By REM we’re not talking classic 80s pop-rock.. REM stands for “rapid eye movement”. This sleep mode is characterised by rapid eye flickering but also can be recognised by other aspects including the almost total paralysis of the body and increasingly vivid dreaming.
Human sleep generally occurs in stages of about 90 minutes. As these cycles repeat – often 4 or 5 times per night – they tend to have a larger proportion of REM sleep. The American Academy of Sleep Medicine divides Non-REM into three stages: N1, N2, and N3, the last of which is also called ‘delta sleep’ or deep sleep stage. The three non-REM sleep stages can last from 5 to 15 minutes each. The whole cycle normally repeats following order: N1 -> N2 -> N3 -> N2 -> REM.
What happens during the different stages?
Non-REM 1: Eyes are closed and the body is still, but it’s very easy to wake. Every time you go through this stage in the night you are very close to waking up.
Non-REM 2: Light sleep. Heart rate slows and body temperature drops as the body gets ready for deep sleep.
Non-REM 3: Deep sleep. It’s hard to wake someone during this stage, and if woken you might feel disoriented for a little while. It is during the deeper stages of Non-REM sleep, the body repairs itself. As we continue through the cycles, the ‘deep’ stages become lighter and lighter as we near waking.
As we age, all stages can become lighter and we can spend less time in deep sleep. This means that people can be woken more easily when they are older and therefore they can get less sleep. However, studies suggest that as a consequence people often get less sleep than they need as they age.
REM sleep: Typically occurs every 90 minutes. The first period of REM typically lasts for about 10 minutes. Normally REM stages will get longer as the night progresses, and the final one may last up to an hour! During this time the heart rate and breathing quickens. You can have intense dreams during this time.
When do we sleep?
Many animals have a naturally inbuilt circadian clock or rhythm that helps maintain their sleep / wake pattern. This is controlled by a part of the brain which is in the ‘visual cortex’ – the part of the brain that deals with vision. The circadian clock measures what time of day it is based on light signals. The circadian clock is able to ‘time keep’ but also affects functions such as body temperature and hormone (melatonin) release – both of which make us feel sleepy.
Individually, human sleep patterns are controlled by both this rhythm but also our ‘willed’ behaviour – essentially when we decide to complete actions like going to sleep! However, there is also evidence that humans are influenced by ‘social time’. For example, the periods in which other people are awake, the periods when work is required, the time on the clock can all influence our sleep patterns. Furthermore, industrialisation and artificial light (increasingly from hand-held devices such as phones and tablets) have substantially altered human sleep habits in the last 100 years – often with negative effects.
What’s in the next blog?
The next blog will focus on why we sleep… What it’s function and why is it important? We have started to describe some ideas above (e.g. rejuvenation and strengthening the body) but this is just the tip of the iceberg in terms of the research out there and there is still so much we don’t know!!
After the next blog, we will move on to think about what might get in the way of sleeping and also what you can do to help get those ZZZZZs
References & further reading
- American Psychological Association – http://www.apa.org/topics/sleep/index.aspx
- NHS Live Well – http://www.nhs.uk/LiveWell/sleep/Pages/sleep-home.aspx
- (American) National Sleep Foundation – https://sleepfoundation.org/
- Pinel, J. P. (2011). Biopsychology. Boston, MA: Pearson.