"I was once fond of saying, 'Sleep is the third pillar of good health, alongside diet and exercise.' I have changed my tune. Sleep is more than a pillar; it is the foundation on which the other two health bastions sit. Take away the bedrock of sleep, or weaken it just a little, and careful eating or physical exercise become less than effective, as we shall see."

― from “Why We Sleep: Unlocking the Power of Sleep and Dreams”

Matthew Walker's "Why We Sleep" is one of the two most important books I have read in my life1. Having done a little stock trading along with having survived several tech industry "death marches," things which are quite antithetical to good sleep, I had little idea just how destructive to your health lack of sleep is. A few years back, however, I began to hear that lack of sleep was correlated with diseases such as Alzheimer's, but this did not strike me as convincing since correlation is not causation. Indeed, a little later, I heard about this book at work but was somewhat ambivalent. It's just going to tell me that doctors think sleep is essential but are vague as to why were my thoughts.

Luckily I noticed an episode of Sam Harris's podcast "Making Sense" in which he interviewed Walker. Since Sam Harris is a figure whose judgment I highly respect, and I know he is very discerning about whom he invites on as guests, I decided there was probably more of value to say about sleep than I initially thought.

Correlation and Causation

Walker's book makes a compelling case that sleep is the bedrock of good health. He convincingly demonstrates that lack of good sleep can lead to downward spirals in health with the development of health conditions that make it hard to sleep, leading to more serious health conditions due to lack of sleep, making it even harder to sleep… and so on into a vicious cycle. Walker is careful to lay out in detail when the causal mechanisms are well understood, as in the case of Alzheimer's and cancer, and when lack of sleep is currently a suspect, although the exact causal mechanism has yet to be established. By the end of the book, I realized, however, that sleep is so foundational that even a mere correlation to some bad health condition is enough to make lack of good sleep a prime suspect worth considering as a cause.

Organization and Style

According to Walker, "Why We Sleep" is organized so that later chapters can be read without a strict need to read earlier ones first. Thus, if you use sleeping pills and want to know why you should not, he says it is okay to and, indeed, encourages you to jump to that section right away. That being said, I found the writing style so engaging (with a few minor instances of excessive detail) and the content so important that I read it straight through. Having read it this way, my sense was that the book frontloads its most important content: It explains in detail, with specifics such as the chemicals involved, why you feel more tired at certain parts of the day than others. To give you the motivation to get good sleep, the deleterious effects of lack of sleep also come near the beginning of the book.

The Enormous and Far-Ranging Effects of Poor Sleep

The effects of lack of sleep go beyond just affecting your physical health, however, and Walker shows just how destructive lack of sleep will be on your ability to learn new things. One of the most remarkable findings is that you need to get good sleep after learning new information. You cannot even get a single night of suboptimal sleep the first night, or some information will be lost permanently.

Conversely, if you get that first night of good sleep after learning something new, sleep on subsequent nights will continue to solidify what you have learned: all while you sleep! This is just one case where Walker details how, unfortunately, missed sleep cannot be well compensated for by more sleep later: Permanent losses are involved.

Dreams

Some of the most fascinating information in the book is on the role of dreams. Here we learn of their therapeutic qualities, including some of the underlying biochemistry involved. Discoveries here have led to a better understanding of PTSD, including better treatment methods. Walker also describes how dreams foster creativity by establishing connections between distantly related pieces of information stored in the brain. Here Walker includes a particularly fascinating anecdote of how Edison enhanced his creativity by waking himself from naps and immediately recording his thoughts.

Empathy For Different Circadian Rhythms

Throughout the book, Walker emphasizes how what we have learned about sleep has implications for how we should view people who may not have what seem like "normal" sleep patterns more empathetically. In particular, he emphasizes that teenagers want to get up and go to bed later, not due to laziness but because they run on a different circadian rhythm. It is something that is biologically hardwired into them. A consequence is that forcing school start times incompatible with this has devastating effects on how well they learn compared to well they could. Similar facts are true of people who are naturally "night owls" and run on different circadian rhythms than the rest of us.

Minor Flaws

Walker's book has only a few minor flaws:

1. Although he provides an excellent explanation of why most sleeping pills should be avoided, he does not mention whether this includes melatonin.

2. His discussion of the nationwide dollar impacts of poor sleep could be better presented. The unfortunate truth is that given the numbers we have heard spent on wars and, especially, financial bailouts and stimulus, rattling off numbers that are “merely” in the hundreds of millions or even low billions hits us in a place we are now numb.

3. Although Walker's discussion of creativity in the dream state and the state when just waking from dreams is a fascinating part of the book, I would have liked to see some discussion of how objectively accurate intuitions are during these moments. Anecdotally, I used to joke that my best ideas came to me during this time or not at all. Sometimes, however, the thoughts just turned out to be overconfident upon more profound reflection. Is that true for just me, or is it true for people, generally speaking?

Conclusion

Overall, Walker's "Why We Sleep" is a must-read for anyone who sleeps: in other words, everyone. This book will not only absolve you of any guilt associated with prioritizing sleep, but it will also arm you with the knowledge to make the best choices for your physical and mental health. Walker guides you through the critical benefits of sleep, from its integral role in memory and creativity to its power to process and put to rest the day's experiences: especially the more troubling ones.

While the damaging effects of lack of sleep seem exponential, Walker argues that some of the most significant benefits come in the final two hours. Thus getting eight full hours of sleep is crucial. After reading this book, you will not want to miss a full night's sleep again.

To help you achieve a full night's sleep regularly, Walker provides 12 concrete steps in an appendix. Some of these suggestions are initially counterintuitive. For example, Walker maintains that a cooler room temperature of around 65F is best for optimal sleep. Already, I've been putting this and his other advice to the test, and the results seem promising.

This book is one of the most eye-opening books I have read about sleep. Why We Sleep explains how deeply sleep affects the brain, body, memory, mood, performance, and overall health.

I appreciated how the book makes the science understandable while still showing how important sleep really is. It helped me think about sleep not as something optional, but as a foundation for energy, clarity, and long-term well-being.

Highly recommend for anyone who wants to better understand why sleep matters and how it impacts daily life.

I bought this book out of general interest. It is an international bestseller by a former professor of psychiatry at Harvard Medical School, and is currently a professor of neuroscience and psychology at the University of California, Berkeley.

Here is why I am reviewing this book in a business newspaper.

I believed, as you may, that “pulling an all-nighter” was a badge of honour, a clear sign of commitment and fortitude. President Trump brags of sleeping only 4 hours a night. Just last week a client told me with an element of pride, that he sleeps less than five hours a night. And he wasn’t the first.

With what we know now, this is about as absurd as bragging that you are a wife-beater, and that you drive drunk!

Consider the facts. Driving without having had sufficient sleep is the cause of hundreds of thousands of traffic accidents and fatalities each year. In the US, one person dies in a traffic accident every hour due to a fatigue-related error, exceeding road deaths caused by alcohol and drugs - combined.

“Every component of wellness, and countless seams of societal fabric, are being eroded by our costly state of sleep neglect: human and financial alike,” author Matthew Walker explains.

Just to get your attention, consider that reams of reliable research indicate that routinely sleeping less than six or seven hours a night demolishes your immune system, and more than doubles your risk of cancer. It is a key lifestyle factor determining whether or not you will develop Alzheimer’s disease. Sleep deprivation increases the likelihood of your coronary arteries becoming blocked and brittle, which boosts cardiovascular disease, stroke, and congestive heart failure.

Less dramatically, you have probably noticed a desire to eat more when you’re tired. This is because too little sleep increases a hormone that makes you feel hungry and suppresses a hormone that signals food satisfaction.

The need to sleep is a foolish biological phenomenon that evolution should have cleaned out of the system. When you sleep you cannot fulfil the basic drives of life: to eat and drink, reproduce and protect yourself. And yet, across the animal kingdom sleeping is a common factor.

The World Health Organization has declared sleep loss an epidemic throughout industrialized nations. Two-thirds of adults do not have the recommended eight hours of nightly sleep. “Society’s apathy toward sleep has, in part, been caused by the historic failure of science to explain why we need it,” Walker explains. The fact that sleeping persists throughout evolution means there must be tremendous benefits that far outweigh all the obvious hazards and detriments.

In the 1950s and 1960s, scientists used recordings from electrodes placed on the scalp to provide a general sense of the type of brainwave activity underpinning ‘REM’ (rapid eye movement) sleep. ‘Deep sleep’ describes the bodily state of inactivity, while ‘REM sleep’ describes high levels of brain activity with the eyes moving rapidly in different directions. The older technology limited our ability to understand what was happening during REM sleep that makes it so important.

In the early 2000s, with the advent of brain-imaging machines, we could reconstruct three-dimensional visualizations of brain activity during REM sleep. This has enriched science’s understanding.

Sleeping aids the body by restoring our immune system to fight malignancy, prevent infection, and ward off all manner of sickness. Adequate sleep maintains a flourishing microbiome in your gut which ensures nutritional health. The physical and mental impairments caused by one night of bad sleep dwarfs those caused by an equivalent absence of food or exercise.

Dreaming provides humans with many gifts, among these are nightly neurochemical baths that mollify painful memories, and allow the brain to combine past and present knowledge, and inspire creativity.

It is believed that “time heals all wounds.” However, Walker suggests that it might be that time spent in dream sleep offers a form of overnight therapy. REM sleep dreaming takes the painful sting out of difficult, even traumatic, emotional episodes you may have experienced during the day, offering emotional resolution when you awake the next morning. This happens because REM sleep is the only time during the twenty-four-hour period when your brain is completely devoid of the anxiety-triggering molecule. Sleep is clearly needed for us to heal emotional wounds.

Sleep is also a creative incubator. In the dreaming sleep state, your brain will cogitate on vast amounts of knowledge you have acquired, and then extract overarching rules and commonalities. When we wake we are often able to find solutions to previously impenetrable problems. This is the difference between knowledge (retention of individual facts), and wisdom (knowing what they all mean when you fit them together).

Mendeleev formulated the periodic table in a dream, something his waking brain was incapable of. When he awoke he wrote it down, and in only one place was a correction necessary.

The neuroscientist, Otto Loewi, formulated how nerve cells communicate with each other in a dream. For this he received a Nobel Prize.

Paul McCartney’s origination of the songs “Yesterday” and “Let It Be” were derived from dreams and then written down. “I couldn’t believe I’d written it. I thought, no, I’ve never written anything like this before. But I had, which was the most magic thing!”

Keith Richards of the Rolling Stones had a similar experience with his music. Mary Shelley’s dreams provided the vision and narrative for the spectacular gothic novel, Frankenstein.

Laboratory tests have shown how problem-solving abilities increase by 15 to 35 % when participants are emerging from REM sleep compared with daytime performance! The REM-sleep dreaming brain was utterly uninterested in bland, common sense, linear type links. In REM-sleep the brain drops the logic guard and ignores the obvious in` favour of very distantly related concepts.

So, how do you know whether you’re routinely getting enough sleep? The rule of thumb is whether you could go back to sleep at ten or eleven that morning, or whether can you function optimally without caffeine before noon. And of course, whether you would sleep past your waking time if you didn’t set an alarm clock.

Like a loan in arrears, your sleep debt will continue to accumulate. It will roll over into the next payment cycle, and the next, and the next, producing a condition of prolonged, chronic sleep deprivation from one day to another.

The implications for your professional performance or management style should be clear. Coming to work sleep-deprived is no better than coming in hungover. And when next you hear someone brag about how little sleep they get, give them Walker’s book to read, or even just this column.

We need to revise our cultural appreciation of sleep and reverse our neglect of it.

Readability Light --+-- Serious

Insights High +---- Low

Practical High -+--- Low

*Ian Mann of Gateways consults internationally on leadership and strategy and is the author of the recently released ‘Executive Update.

I actually bought this copy as a gift because I think this book is one every human should read as a user's manual for our bodies and minds. Walker is one of the world's leading experts on sleep and provides a well researched, fascinating, and helpful book in understanding one of the most important things that we can do for our health. I cite it all the time, use it with clients (as a therapist), and have gotten many folks to read it. Get a copy!

I became interested in this book because I wanted to learn how to sleep better. Did it answer my questions? Most of them, I would say.

The book is divided into four parts. Readers can choose to read each part independently and not in a specific order. That’s exactly how I read it—out of order and focusing on topics that interested me most—such as jetlag, sleeping pills, dreams, and healthy sleep.

Part 1: This Thing Called Sleep

What I liked most about this book is how it dispels myths about sleep. Let's start with sleeping pills. Most of the sleep aids on the market are based on Melatonin. Essentially, melatonin helps regulate when sleep occurs, but it doesn’t put you to sleep. Using melatonin for jet lag may not guarantee sleep, but it significantly improves the chances by providing the right timing signal. Another common misconception is that drinking alcohol before bed helps us sleep better. It actually has the opposite effect.

Part 2: Why Should You Sleep

I used to hear stories about great people who only slept a few hours a night and got more done than most folks. However, even people like Bill Gates now say that getting eight hours of sleep is important. Sleep deprivation can lead to serious problems. People who don’t get enough sleep tend to lose productivity, and their health can suffer as their immune system weakens. A more dangerous situation is when sleep deprivation affects our ability to drive safely.

Part 3: How and Why We Dream

I always try to interpret my dreams, especially scary ones, to understand what they mean. The author examined dreams from a scientific perspective. It's almost like fortune telling when we try to decode a dream. However, with scientific data, they showed that people become more creative and better at solving difficult problems during dreams. He shared examples from well-known individuals like Thomas Edison and Paul McCartney—very interesting findings. I think I need to dream more so I can boost my creativity!

Part 4: From Sleeping Pills to Society-Transformed

This part was my favorite because it answered many of my questions. With modern society, we face increasing distractions every day. Aside from computers at work and home, we have numerous electronic devices like iPads, cell phones, and smartwatches. Spending too much time on these devices before bed isn’t healthy. It was eye-opening to learn that factors such as the blue light from LED screens, room temperature, and lighting can all impact our sleep.

The author clearly states at the beginning that his book isn’t meant to be a self-help guide, nor is it targeted at treating sleep disorders. However, he includes an appendix titled "Twelve Tips for Healthy Sleep."

This book is grounded in data and facts. I learned a lot from reading it and thoroughly enjoyed the experience. For those who aren’t interested in all the experimental details, you can still gain valuable insights from it.

Our understanding of sleep has made large steps. It is only in the past two decades that we have a much better understanding of its function and, importantly, on the serious health repercussions of sleep deprivation, the overarching theme of the book. At its extreme it’s fatal (fatal familial insomnia, a very rare genetic mutation) but even a mild degree of deprivation e.g. 6h vs. 8h have a long series of detrimental effects: higher blood pressure and higher heart rate, higher level of stress hormone cortisol, lower degree of growth hormone, increased probability of weight gain (sleep is intensely metabolically active), drop in testosterone (less focus, less strength, and lower bone density) and, icing on the cake, more damages to telomeres (protective caps of genes). In certain experiments 10 consecutive nights with 6h of sleep are equivalent to 24h without sleep, which, as far as concentration is concerned is equivalent to being legally drunk.

For healthy sleep, humans, as well as most other species, need a correct balance between non-REM (NREM) sleep, very important for transferring short term memories into long term and ‘cleaning up’ for irrelevant memories (e.g. where we parked the car the previous day) and REM sleep, very important for emotional processing as well as problem solving and creativity (deep and unconventional connections are formed). While these phases cycle through the night approximately every 90 minutes, their relative periods are not constant. In particular, the REM portion of the cycle is far more prominent towards the end of the 8 hours. Cutting the night short might deprive us of an important dose of REM sleep.

The author corroborates findings with plenty of scientific experiments and their findings and touches on many aspects of the science of sleep and related illnesses like clinical insomnia, somnambulism, sleeping in older age, and narcolepsy. Especially the former is important to guide the reader between ‘bad sleep’, quite common, and clinical insomnia. Coffee, for example, blocks adenosine receptors making us less aware of our need to sleep. Alcohol suppresses REM. Lastly, sleeping pills provide more ‘sleep’ but at the expense of REM sleep.

He concludes the book with 12 advises for obtaining sound sleep. If one can only achieve one then it is suggested to go to sleep and wake up at the same time every day, weekends included.

The book is very readable, rich in details and very informative. Understanding why we sleep and having a better sense of the dynamics of sleep is fascinating, personally, but can also help improving sleep, thus health, in general.

Slightly repetitive at times but overwhelmingly a great read. Given the importance of the topic and all the light shed on the obscure nature of sleep, I give it full marks, without hesitation!

This is a fascinating book. Sleep is one of the least-understood aspects of life, even though it constitutes one-third of our human experience. Or it should. The ingrained attitude for many of us is that sleep is a necessary evil, something that interferes with our ability to work and produce. On the contrary, the absence of sleep makes us less productive, less happy and healthy and more prone to disease.

I have always been fascinated by the subject but disappointed by the absence of research on that subject. Professor Walker’s book digests the available research and presents it in a lucid manner that will be accessible to all curious readers. If I have a single criticism it is the relative paucity of material on dreams and dreaming, but that is a vastly complex subject that is not as susceptible to analysis as, e.g., the effects of light on the release of Melatonin and the ways in which we could physically and temporally structure our environment to correspond with our bodies’ needs.

One of the most important themes of the book is the fact that our lives are structured in such a way as to encourage ill-health, medical mistakes, automobile accidents and poor learning. Early school start times, e.g., deny children and teenagers the important, early-morning REM sleep that their brains require. The sleep-deprived schedule for medical residents was fashioned by a cocaine addict who was himself sleep-deprived. The absence of sleep and interruption of sleep have statistically-demonstrable, negative effects on our lives. As they say on ‘Shark Tank’ when ridiculing infomercials: “Stop the Madness.”

The bottom line is that we need regular, appropriate sleep to maintain a healthy immune system and to heal our spirits. While this is solid and informative, the result of serious and significant research, it is not counter-intuitive. Popular sayings across the world and insights from such acute observers of the human condition as Shakespeare anticipate many of the book’s conclusions, but as I stated earlier, while these principles may be reinforced by common sense they often run directly counter to our current behaviors. Alcohol, for example, does not contribute to effective sleep and caffeine can have longer-term effects than we believe. LED lighting is superb for some purposes, disruptive for others. The book includes a succinct two-page list of tips for healthy sleep as well as a commonsensical set of public policy recommendations.

This is an important book as well as a fascinating one. Highly recommended.

As humans, why must we sleep roughly a third of our lives? What is the function of our dreams? If these questions intrigue you, consider reading Matthew Walker's excellent book Why We Sleep. The book delves into all aspects of sleep from a person who is passionate about the subject. It starts by discussing the different portions of our sleep, including REM sleep, when our eyelids flicker while the rest of our body is paralyzed, and the very deep NREM sleep with its associated rhythmic brain waves. The book talks about what controls the circadian rhythms in our sleep, from the suprachiasmatic nucleus, which samples the light near our eyes, to the different chemicals, melatonin and adenosine, that are part of these daily sleep rhythms.

Interestingly, much of what we know about sleep was discovered by explorers, who subjected themselves to the tremendous darkness deep in Mammoth Cave and performed sleep experiments. The book goes into great detail about exactly what happens when we go into deep NREM and REM sleep. In particular, memories are initially formed in the hippocampus, which acts as a short-term repository; in REM sleep, many connections are made, and the memories are spread throughout the cortex, which can be seen in fMRI imaging. The book presents a nice analogy of how our mental picture is like a sculpture, and NREM sleep takes off bits of it, whereas REM sleep refines and solidifies the features. The balance between these two types of sleep changes throughout our life as we have different needs for creating connections and removing extraneous memories. Even the nightly balance between the two changes, with more REM sleep later on.

The book also discusses the bad things that can happen to us if we don't sleep enough, from obvious consequences of getting into car accidents or forgetting things, to diseases, such as cancer, heart disease, and obesity. The book finishes with a lengthy discussion of what we can do if we can't sleep and how medicines for insomnia work. It presents some simple rules for getting a good night's sleep, such as avoiding alcohol and caffeine and keeping a regular bedtime. One suggestion I found interesting was staying away from blue LED light at night. Although its discovery in the '90s resulted in a Nobel Prize, blue LED light has been bathing people in sunlight-like light more and more in the evenings from our many screens, impacting sleep.

Overall, I felt this was a great read from a person very committed to the subject.

I can't say anything about the book yet, I'm sure it's good...

But I was upset by the condition it arrived in. It's sticky and scratched. It looks as if it's already been read, and it's unpleasant to hold. The price was ok, otherwise I would return it straight away

Lettura estremamente interessante ed educativa: esaustiva, dettagliata, con decine di studi scientifici a supporto degli argomenti trattati.

Descritto così sembra quasi si tratti di un libro universitario, ma non lo è affatto! L'autore, professore di Neuroscienza e Psicologia e direttore di un laboratorio di ricerca su sonno e neuroimaging, è riuscito a mettere a terra l'argomento in maniera da rendere la lettura interessante, piacevole, e soprattutto di facile comprensione.

Sicuramente consigliato a chi, come me, è sempre stato incuriosito dal sonno e voglia saperne di più. Tra gli argomenti più interessanti in mia opinione: cos'è il sonno e dove ha origine, a che cosa serve, come cambia nel corso della vita, quali possono essere gli innumerevoli effetti del dormire poco (ad esempio su apprendimento ed emotività), a cosa servono i sogni, e come sia possibile migliorare il proprio sonno senza ricorrere a farmaci.

What a brilliant book. This has changed the way I look at nutrition, sleep and health.

Que gran libro, si tienes problemas de insomnio o quieres informarte con lo mejor en los estudios del sueño es un libro ideal

This book compiles a lot of scientific findings about sleep. Sleep is essential for our mental and physical health. A lack of sleep can cause many serious problems. I have changed my recognition of sleep entirely. I want to recommend everyone who engages in health care.