Brief Review: “Why We Sleep”

6 min readApr 25, 2020

“Why We Sleep: Unlocking the Power of Sleep and Dreams” by Matthew Walker, PhD is a research-backed, insightful book about the importance of sleep.

This book is an interesting read and provides some great research backed information to rethink and reconsider our many notions about sleep.

Like many people with an engineering background I spent many days and nights of my youth avoiding sleep while working on some project. At the time I was convinced that sleep was a waste of time and very much subscribed to the theory that you’ll have plenty of time to sleep…when you’re dead! As such I tried a number of techniques to sleep less. The most extreme experiment I tried was shifting to a 28 hour day — where I would work for 24 hours and then sleep for 4 — shifting my wake-up time by 4 hours each day. Not only was the 4 hours of sleep not enough, but waking up at odd hours of the night and 4 hours later each day really messed with my circadian rhythms. After approximately 3 weeks of that crazy schedule — hundreds of hours of work — I did finish my Masters Thesis project. I do seem to recall that towards the end of the project thoughI ran into a particularly challenging problem that I could not solve. I spent a few days using brute force to try to solve the problem and then, finally, I believe I allowed myself to get a good night sleep — and like many stories I’m sure you have heard before, the answer came to me in my sleep. After reading this book, it is not surprising that the extra bit of sleep helped my sub-conscience — research has shown that sleep and deep sleep in particular are critical for creative thought and problem solving.

While the book makes a strong case for the importance of sleep — in the grand scheme of life it is still hard for me to believe that there are not times when hard work and perhaps a little bit of sleep deprivation aren’t necessary. A perfect balanced life of exactly the right amount of sleep, eat, etc. does seems great in theory, but the richness of life seems to be in those ebbs and flows and some of those exceptional moments of imbalance.

So on to the book! There were a few key points and answers that this book provides:

Why do we sleep?

While the exact answer is still not exactly clear — the bottomline — sleep is evolutionarily necessary for all living animals. The book goes through numerous analysis of all sorts of animals and human studies that demonstrate the benefit and attempt to start explain the reason we sleep. One basic summary is that sleep is a “neurochemical bath” that to restore and improve our brain in many ways including improving memory, “mollifying painful memories”, developing complex relationships between information that leads to creativity, and much, much more.

What are the stages of sleep and what are they for?

There are 4 stages of sleep that we cycle through in 90 minutes cycles. While I knew some of the stages of sleep — I never thought about the fact that evolutionarily being unconscious for 1/3 of the day was a big risk to survival or predators — and hence the number of phases and cycles that humans circulate through that give both the cognitive benefits and leave a certain amount of alertness to wake up in case of threat.

Light sleep, N1 — the first phase, and as indicated by the name is “light”and takes place immediately and is quite short (~10 minutes). There is some awareness of what’s going on around and you can be awakened easily.

Light sleep, N2 — this phase is 30–60 minutes, where muscles are more relaxes and the brain is heading towards deeper sleep. This stage often comprises a large share of our nightly sleep.

Deep NREM, Slow Wave Sleep, N3 — this is the very important phase for restoring the body, growth and repair of muscle, and strengthening the immune system.

REM, N4 — the well known “rapid eye movement” where the eyes move rapidly and vivid dreaming takes place. In many ways our brain is “awake” during REM sleep and, interestingly, to prevent our bodies from acting out those dream, most of our muscles are paralyzed during this stage.

REM sleep is also know to provide “emotional first-aid” — helping individuals to recover from emotional trauma and “recharge” to be able to deal with social/emotional challenges. You’ll notice that you feel short with people and have less “reserve” when you are not well rested. Lack of sleep, amplifies negative emotions.

How much sleep do we need?

It was quite interesting that we ALL need 7–8 hours of sleep a night. Even if you think you dont, you do. And what is meant by that is that ALL of us demonstrate degraded cognitive functions with less sleep.

What happens if you don’t get enough sleep?

There were an incredible number of findings about short-term and longterm health issues from lack of sleep. Sleep depravation can lead to serious trauma — but even just sleeping 1–2 hours less a night — can lead to poor health outcomes — immunity, infections, cardiovascular health, and possibly even leading to Alzheimer’s (not conclusive).

One of the interesting findings from the research is that sleep debt is real, that it can persist over many days, and you cannot “recover” from sleep debt. Even jet-lag, daylights savings all take several days to recover from.

The recovery we are talking about here is cognitive function — alertness, reaction time, creativity, brain function, cognitive skills, memory, etc. Much research and many tests demonstrate that will less sleep we perform with substantially degraded functions. For example, post daylight savings time — the number of traffic accidents spike as a function of individuals having lack of sleep and poorer reaction time. Most concerning, is that all of this cognitive degradation takes place even though you likely do not FEEL impaired — which is the real danger.

There were a number of interesting studies that showed strong broad health benefits including strong benefits for mental health — and correspondingly negative repercussions for mental and physical health with lack of sleep.

How to get better sleep?

One of the key take-aways was to go to bed and wake-up at the same time every day (including weekends). Some known items like slightly reduced temperature at night, comfortable clothing and bedding, and reducing computer time/screentime before bed.

There were also some good clarifications that alcohol, melotonin, and sleep drugs do NOT provide real help for sleep. While they may help you become drowsy and may lead to some “sleep” — they do not aid, and sometimes in fact, inhibit the deep restorative sleep we need to get each night.

As a personal aside, for me a sleep tracker has really helped. There are many good ones and several emerging all the time but I use this sleep tracker, which does not require me to wear anything and requires the simple installation of a small sensor under my mattress. The tracker tracks total sleep, quality of sleep, phases of sleep, time to fall asleep, etc. Most importantly for me is that I attempt to track my deep and REM sleep and see what adjustments I can make to get more of both. But critically for me, is just like a fitbit, it has made me cognizant of my lack of sleep and has definitely encouraged me to try to sleep more and boost my score.

References and Nice Summaries: