Book Review: Why we Sleep; Unlocking the Power of Sleep and Dreams

Why we Sleep; Unlocking the Power of Sleep and Dreams, by Matthew Walker

Today’s book review is a topic close to my heart. Many people I work with have heard me say that my KPI for myself is that my team gets enough sleep. That is short hand for quite a few things – not too much stress, not working too hard, and planning well enough in advance of deadlines that the work can be done in good time.

This book is a fascinating review of everything we know about sleep and why it is important. The book starts by introducing you to a few pretty confronting facts:

“Insufficient sleep is a key lifestyle factor determining whether or not you will develop Alzheimer’s diseas. Short sleeping increases the likelihood of your coronary arteries becoming blocked and brittle… Sleep disruption further contributes to all major psychiatric conditions, including depression, anxiety and suicidality.”

With an introduction like this, it is enough to make you put down the book, and go and have a nap. Which is what I did, reading this book on a plane trip. But when you pick it up again, there are scientific studies galore to back up all these (to me) astonishing facts and more.

The first half of the book is a fascinating deep dive into the mechanics of sleep. How do we get to sleep, what exactly happens during sleep, what are the different stages of sleep and what effect do they have on us? Among the nuggets I enjoyed learning were:

• There are two key triggers for sleep – melatonin tells us when it is the right time to sleep, but a chemical called adenosine, creates an increasing desire to sleep – called sleep pressure. That chemical peaks between 12 to 16 hours after being awake.  When you are jetlagged, those two triggers are out of sync.
• Teenagers’ melatonin production does change in timing substantially to being much later than their parents and their younger siblings. Which is why they stay up too late, and can’t get up on time for school
• Every single animal species studied sleeps in some way. Flies, turtles, frogs and sharps as well as (of course) humans. Even very primitive worms! But only birds and mammals dream (that’s REM sleep).
• Afternoon naps are part of the human natural sleep cycle
• Humans have by far the highest proportion of REM sleep of all primates – perhaps that is the reason we have become the dominant species?

There are many more fascinating facts. But the more sobering (and impressive) part of this book was the many studies about how much adequate sleep improves our lives. Walker describes many studies (including his own) which demonstrate the power of sleep to improve the human condition:

• Sleep before learning improves our ability to memorise new facts – a ninety minute nap improved learning in an experiment by an average of 20%.
• Sleep after learning improves retention of facts previous learned by an average of 20 to 40%
• Sleeping improves your performance in something you are trying to learn while awake (for example a pianist who practices just before bed, cannot get the piece right, but can play it perfectly in the morning). Sleep helps your brain to improve motor skill memories.
• Sleep impairment causes the same cognitive impairment as being legally drunk.
• Deep emotional centres in the brain become hyperactive without sleep – the under-slept brain swings excessively to both extremes of emotion – positive and negative.
• Adults who sleep fewer than six hours are night are 200% more likely to have a heart attack or stroke during their lifetime
• The less you sleep the more you eat, which increases your probability of being overweight and/or developing type 2 diabetes – short sleep (four hours a night for a week) reduces your ability to absorb glucose by 40% after a week – ie it makes you pre-diabetic.

I could go on. A list of facts, though, is far less interesting than reading about the experiments that have demonstrated them, and the weight of evidence that shows just how important sleep is for all humans. And fundamentally all those people (eg Margaret Thatcher) who claim not to need that much sleep are likely to be kidding themselves. People who haven’t had enough sleep don’t realise who cognitively and emotionally impaired they are. As well as reducing their current functioning, they are putting their physical and mental health at risk.

When my colleague recommended this book, I was a little sceptical. How can you make a whole book out of sleep. Shouldn’t we just sleep? But I have found myself quoting this book again and again to people. I’ve always been someone who values my sleep, and I’ve previously been slightly embarrassed by needing more than 8 hours on average. But this book made me realise I’m probably just listening to my body a bit more than those around me.

Sleep! Make sure you get enough.