I hope the image of me pretending to sleep didn’t put you off clicking through to read this blog; the reason for it is that I have been reading the rather wonderful book “Why we sleep: The New Science of Sleep and Dreams” by Matthew Walker (Penguin, 2017), which is (as you might guess) all about sleep.

I genuinely think everyone, and I mean everyone, should read this amazing book;  I think it would change most people’s perceptions about something that many people consider to be a waste of precious time (and the less of it we can get away with the better).  The book makes it clear that this is far from true: sleep is vital for our well-being both physical and mental.  It is worth nothing that due to the severity of health problems that sleep deprivation causes, The Guinness Book of World Records has banned any attempts that prevent people sleeping and is deleting the records for staying awake.


Scientists have discovered a revolutionary new treatment that makes you live longer. It enhances your memory and makes you more creative.  It makes you look more attractive.  It keep you slim and lowers food cravings.  It protects you from cancer and dementia.  It wards off colds and the flu.  It lowers your risk of heart attacks and strokes, not to mention diabetes.  You’ll even feel happier, less depressed, and less anxious.  Are you interested?

A tongue in cheek fake ad for sleep, from p.109 of Why we sleep.


What does sleep do?

OK. This is a massive subject (most of the 340 page book) and I’m going to try to condense into a few of paragraphs, so any errors that creep in are totally my fault and not Matthew Walkers.

Sleep is when our body heals, recharges, clears things down and gets to deal with the rubbish we generate internally during the day.  It is also when we assimilate the information and experiences we accumulate each waking moment.  This process is not just for our physical well-being, but also our mental health.  Sleep is a necessity that every living creature does to a greater or lesser level, and which evolution has not found a way for us to do without. It remains a part of us and our bodies require it and fail if we do not get it.  The book includes a description of a terminal condition where people stop being able to sleep, and it sounds horrific.  

A night’s sleep has two very different stages, both of which are vital to our health.  REM (Rapid Eye Movement) sleep, which is when we dream and our eyes dart backwards and forwards behind our eyelids.  During this phase the body naturally stops any movement other than the eyes, presumably so we don’t act out our dreams.  The other stage is Non-REM sleep, when nothing much seems to happen, and we don’t dream. We cycle through these two stages every 90 minutes or so throughout the night, with more Non-REM sleep at the start, and more REM sleep towards the end of the night.

Non-REM sleep was considered the boring and non-useful stage, but actually our brain waves go through a slow and steady wave of activity that sweeps from the front of the head backwards.  This period clears unnecessary or no longer needed neural connections; it also allows the removal of waste products within the brain and allows various systems to re-calibrate. All animals undergo this stage of sleep and if we stay up all night we prioritise more Non-REM sleep the first night we are able to sleep.  That suggests it’s the more important stage of sleep as far as our survival is concerned

REM sleep helps us to process things we have learned during the day from short term memory to longer term memory.  It does this, but also simultaneously cross-references and indexes the whole thing so that we can make amazingly creative solutions to problems and situations we find ourselves in.  REM sleep also allows us to be more social animals and to therefore live well together (I immediately thought of how less tolerant and grumpy I can be after a bad night’s sleep).  Humans are very different from other animals in that we have a greater level of REM sleep, and the book suggests that that might explain why our social networks are more complex.  Other animals may sleep more, but they may not dream as much.

We each have our own natural circadian rhythm so some of us are naturally larks, others night owls and there is nothing wrong with either.  Matthew Walker gives a plausible reason why evolution would allow 30% of us to prefer staying up later, whilst 40% wake earlier: when we were more at the mercy of predators and attacks the lark/night owl differences minimised the amount of time when all were asleep.  So you larks can keep your 5am wake ups, I’m towards the other end of the spectrum.

This book is absolutely full of amazing information and facts, including changes within our sleep patterns from before we are born until old age: for instance there is a reason teenagers need as much sleep as they seem to crave as their brains are undergoing a massive change and they need sleep in which to achieve this.  However, as I don’t really want blog to go on forever, there are a few elements that really stood out for me:


I only need 5 hours a night

No, you don’t*, you need a lot more.  We all need the opportunity to sleep for eight to nine hours a day. We are sleep deprived if we consistently get less than this, according to the science.  We do become habituated to the way that we feel whilst sleep deprived and will say that we are sufficiently rested, even though we are exhausted as far as our body is concerned.

If we get less than this we miss out on important parts of the sleep cycle, as it processes different things during the night (not just REM vs Non-REM) and we are putting our health at risk.  Matthew Walker discusses how lack of sleep makes us more likely to have a huge range of health conditions, which I’ll cover below.


I can catch up on my sleep at the weekends.

Um, no.  This was a big surprise, and disappointment, for me: sleep does not work like a bank balance.  We cannot get less during the week and top up at weekends. The processes that we use sleep for are lost for that night of bad (or no) sleep. Processing like dealing with memories and filing new bits of information is reduced by about 50% just by not allowing ourselves to sleep the night after we learn them. That opportunity to process this information has been lost and we can’t just wait for the next night to finish the job.



Caffeine, the active ingredient in coffee (and also tea, dark chocolate, and present in some fast acting painkillers) blocks receptors within our brain that respond to the chemical that promotes sleepiness, which is why it makes us feel less tired.  According to the book, even decaffeinated drinks can still contain some caffeine, just not as much as the full strength drinks.

I was surprised to learn exactly how long it takes for our body to deal with caffeine:  it apparently has a half life of 5-7 hours. This means that the double espresso we have in the morning will still have the potency of a single espresso until after lunchtime.  I am fairly aware of this as I can’t drink coffee after about 4pm if I want to sleep the following night. The most recent example of this for me was I had an espresso martini (really nice) at 5pm and I couldn’t sleep until 2am the following morning.  Very, very annoying to say the least.

Alcohol and Sleeping pills

These are both, essentially, sedatives.  We may be dead to the world, but sedatives interfere with the processes that we need from a night’s sleep.  We are asleep and we get more non-REM sleep, but it is of a poorer quality than it naturally would be. We miss out on the deep Non-REM sleep when the processes are working optimally .  We also get less of the REM sleep, so we retain less information, are less productive (see below) and have worse social interactions.

We also, apparently, wake up more from alcohol-influenced sleep and so are less rested overall.

According to the author, and I’ve not independently verified this, sleeping pills are not as effective as we might believe. Many of them are also very addictive.  He would argue that getting help with sleeping issues using CBT (Cognitive Behavioural Therapy) is significantly more beneficial, longer lasting and with no adverse side-effects, compared to sleeping pills.

Impact on your health

I will admit that some of the statements that the author makes sound astonishing, and I haven’t had the opportunity to completely check out all the research that he references, but if even only half correct we really need to prioritise sleep for our general health both of body and mind.

According to Matthew Walker, reduced sleep can massively increase our chances of heart conditions, infections, obesity, diabetes and Alzheimer’s Disease.  This is because the stages of sleep help to reset the system and allow the body to deal with any issues. Lack of sleep, which apparently 60% of people are affected by, can be an underlying cause of many chronic diseases.

One of the big things that I had never heard about was that Greece, in the early 2000s, was encouraged to give up its midday siesta when everything closed “because it was not good for the economy”.  This massive change to a population’s sleep pattern had never been done before and many sleep scientists ran huge scale studies. What they found is really quite scary and very, very worrying. Heart disease levels have increased massively, with people in manual jobs 63% more likely to die from a heart condition.  Just because they no longer stop, have a lunch and a nap.

When sleep deprived, we can try to catch up when bored and have micro-naps (you have probably had a few dropping-off moments reading this blog) and Matthew Walker says that during these micro-naps we actually lose complete control of our body (head nodding).  So imagine what can happen if we’re in control of a two or more tonne machine… You know, like the car that we get into to drive to work… He gives some horrific details about the number of car accidents that appear to be caused because the person fell asleep at the wheel, and it’s not just your own safety that is at risk.

Some of these claims seem so incredible that I wonder why this information is not being investigated and shared much more widely.  However, the cynic in me wonders if the fact that sleep is free and therefore can’t be monetised by pharmaceutical companies might be the reason we don’t get as much research into its effectiveness, nor any public relations advertising it.

Impact on your productivity

In the modern world there is a culture that we should be at work for increasing lengths of time as it shows that we are working really hard (sometimes referred to as presentee-ism) and therefore we are productive..  However, it seems that the opposite might be the case.  Our minds and bodies become less productive. We will struggle to cope with complex tasks and it will take us longer to perform them.  The lack of sleep means we won’t be as creative in our problem solving issues as we would be if we were properly refreshed and fully utilising the power of REM sleep.  Matthew Walker gives figures that countries lose about 2% of GDP (a measure of the productivity of the country) to lack of sleep.

The dreaming of REM sleep is when our brains connect and join up the information we learn during the day, and then integrate it into our experiences.  This can be one of the reasons we can go to bed with a problem that we can’t solve, but through our dreams we can wake knowing the solution.  

Impact on social interaction

In the animal kingdom we are one of the few animals that has a high level of REM sleep, other animals sleep for longer than we do, others shorter, but generally they are experiencing more of the non-REM sleep cycles.  Social creatures, like us, have significantly more REM sleep.

Matthew Walker suggests that one of the functions of REM sleep is the associative problem solving and mixing together of memories to help us function in society.  We use the dreams to tease out how to interact with our fellow humans and to function as part of a team.

I know that my tolerance for people is diminished when I have less sleep and I can be in a far grumpier mood.  I do wonder if some of our  current societal issues might be better if we all got a better level of sleep.

What to do?

So, that’s the bad news, is there anything that we can do?  We can prioritise sleep, acknowledge that it is vital for us, and give it the attention we need.  Then there is sleep hygiene, which is a series of steps that we can take to get a better quality of sleep.  These include:

  • Going to bed and waking at the same time each night, even at weekends.  This helps the body to retain a rhythm and cycle so it knows when to settle down and to sleep.  
  • Giving yourself the opportunity to sleep for 8-9 hours each night.  Sorry, but if you need to be up at six each day, then you need to be settling down to sleep by 10pm the night before.
  • Avoid blue light (LEDs especially) as the light triggers the side of the body that says we should be awake.  Mobile devices and TVs emit this very frequency, and so should be avoided during the night.  Oh, and keep them out of the bedroom.
  • Keep the bedroom cooler over night, if your body temperature cools then you will feel sleepier and sleep better.  OK, not cold enough to make you shiver, but not as hot as some people like to have.  This regulation of your body temperature is one of the reasons you will stick feet out of the bed at time during the night.


But do try to get more sleep.

Thanks for reading this my lovely Interonauts.


*Ok, there is a very slight chance that you have a gene that allows you to survive on less. But the chances of this are less than being hit by lightning.