Book Review: Why We Sleep by Matthew Walker

Sleep is the original biohack

Rating: ★★★★★★

If you look at sleep objectively, it’s an odd practice. Humans and other creatures literally shut down for a number of hours each day and are vulnerable to predation and other nasty things while they sleep.

But if almost every creature on Earth sleeps, there must be a very good reason why. Matthew Walker’s book Why We Sleep gives you a comprehensive list of reasons why we sleep and talks about how this miraculous event we take part in every night repairs our brains, tweaks our body functions and strengthens for our memory and learning.

This book is not your average self-help or biohacking manifesto centered on a new alternative sleep style. Rather it’s a primer grounded in science about how one of the most critical functions of the body works, and a sobering warning bell about how technology and modern society is corrupting our natural sleep cycle.

Walker starts with a scary assertion: lack of sleep is literally killing us. From increased cancer risks to increased cardiovascular disease, risk of Alzheimer’s and an increased appetite, a lack of sleep can have a disastrous impact on us.

After reading this book I was motivated to severely reduce my caffeine intake and get into bed much earlier. It’s had a huge impact on my post-exercise recovery and has reduced my mental fragmentation. I feel like my memory has improved dramatically without even trying, and my mood is better.

The basics of sleep

Walker divides the book into a number of sections, first explaining the basics of sleep, then talking about the different phases of sleep – Rapid Eye Movement (REM) and Non-Rapid Eye Movement (NREM) – and its impacts on the body and brain.

After reading this book it seems like there’s not a thing that sleep doesn’t have a hand in. Sleep has a big impact on your learning, both when starting a new skill and remembering it after. REM sleep dampens your emotional responses to stimuli, making you less likely to have mood swings. Dreaming in particular boosts your creativity, in fact being responsible for many great inventions and songs. The list goes on and on.

There are also other interesting tidbits, such as when Walker busts the myth that old people require less sleep.

Next up in this tome is dreaming: when in the sleep cycle does it happen, what does it do to the mind, and why we do it at all? Walker briefly delves into lucid dreaming, but if you’re buying this book solely for this information you’ll be left wanting as he glosses over it a little bit.

The book then goes into the problems associated with low sleep and briefly covers sleep disorders and modern treatments. It’s a sobering explanation of how modern sleep pills “work” and why they’re not an effective treatment of insomnia.

This part in particular touches on the problems with modern technology, especially lighting, modern work and early school start times. All of these changes to our sleep cycle have many impacts on drivers, school-age children and more.

The book ends with a possible view of the future if we realise the importance of sleep. It then lists some useful advice about how to improve your sleep with Walker’s 12 tips for healthy sleep, many of which he has mentioned on public podcasts such as Joe Rogan’s.

These include going to bed and waking up at the same time every night, avoiding caffeine and nicotine, avoiding alcohol, keeping your room cool, avoiding napping after 3pm and more. I’ve implemented many of these tips and it has been one of the most positive changes I’ve made recently.

It’s a useful summary on how to apply these learnings to your own life, although by the time you’ve reached the end of the book many of these tips will already be hammered into your mind.


I would strongly recommend this book to anyone looking to improve their productivity and health. The book wasn’t short at around 340 pages, but it doesn’t overstay its welcome, even during parts which didn’t apply to me, such as the information about sleep disorders. I felt like I was learning enough useful information about sleep even in these sections to warrant me reading through them.

After reading this book you’ll realise how important sleep is, yet how little you probably knew about it. Among the thousands of performance ‘hacks’ out there, it feels like sleep was the one that I and many others thought was least important. The truth as it turns out is quite the opposite.


  • Interesting facts from cover to cover
  • Presents a great wake-up call about the importance of sleep
  • Packed with information you’ve probably never seen before


  • Not much. As always, it would’ve been interesting to read about Walkers take on how daily exercise factors into how much sleep you need.

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