Why We Sleep

By Matthew Walker

In this book, neuroscientist Matthew Walker leads us to a better understanding of sleep. This book approaches sleep in a plethora of conceivable ways: the process of sleep, how sleep can affect you, whether nine hours sleep is too much, the effects of sleep deprivation and risks from sleep deprivation.

A structured review of sleep

It’s an international bestseller, and is structured as follows: How Sleep works covers aspects such as the urge to wake and sleep is driven by Adenosine and sleep pressure (Process-S) and Circadian rhythm (wake drive). REM (rapid eye movement) and non-rapid eye movement (NREM). The book establishes the key sleep-related processes and how they work.

Caffeine and its effect on sleep was included early on, within the chapter establishing the basics of sleep processes. Perhaps it was included here because it is useful for an understanding of how adenosine works: caffeine replaces adenosine latching onto neural receptors, making one feel alert and delaying tiredness (but, that adenosine will latch on when caffeine leaves your system, hence causing a slump): adenosine contributes to the sleep pressure that makes one feel tired.

After that chapter, sleep cycles are discussed, as are the differences in how animals and humans sleep, then across different age groups of humans only (mainly the difference between child and adolescent sleep, and adult).

The third part of the book discusses dreams, what they are and what we know scientifically, before the final part of the book dealing with what afflicts our sleep in the modern day and what we can do about it, as well as a summary in the appendix for tips on how to sleep.

The approach

The approach works well, establishing the basics, expanding upon it and then ending with probably the most relevant and practical advice. I probably would have weighted the book more towards practical advice, but I have to concede from my limited knowledge compared to Matthew Walker’s that plenty of groundwork has to be laid to understand something as complicated as sleep.

Some of the insights are truly riveting. Sleep can help iron out complex patterns in thinking, for example test subjects typing sequences on keyboards could type particular transitions more effectively. Naps, Narcolepsy, Lucidity and many more aspects are discussed in ways which separate fact from fiction.

Succinct but detailed

Sleep deprivation has effects we might not be aware: we all know we become more irritable, our emotion is more erratic, such as jumping perhaps between angry, sad, happy, ecstatic. But sleep deprivation, less than eight hours and, as Walker writes, less than six hours, time to physical exhaustion in exercise drops by 10 to 30 percent. Aerobic output, muscle strength or aspects such as vertical jump height are impaired. Walker also ensures to provide you with the specifics, in the case of sleep deprivation the sympathetic nervous system is the culprit, causing myriad challenges in respiration, immune function and blood pressure and heart rate. Deficient sleep drives an overactive nervous system, like that which sufferers of trauma might experience.

I rarely found myself feeling like Walker was over-elaborating. Examples were usually fairly to the point, included the important scientific information and explained terminology clearly, whilst including relevant anecdotes and/or experience. But this book heavily favours the scientific viewpoint.

Review of other effects is comprehensive. Sleep deprivation also has unusual effects such as causing muscle mass to be reduced and fat retained, hence contributing to potential weight retention versus somebody who gets adequate sleep. Insomnia, bright light, caffeine, alcohol, exercise – I could continue ad nauseum.

Similarly, the beneficial effects, such as on PTSD sufferers, and whether sleep can be used as therapy or to help psychiatrically, is discussed. Dreams, which are perhaps the most mysterious phenomena when it comes to sleep are reviewed, and I was glad that Walker included relevant information to Freud or Aristotle where suitable. This is not a book confined to neuroscience, although it is its focus. Unsurprising given the authors credentials.

Although interspersed through the book, I do wonder if there could have been a longer summary of the tips. Sleep is quite complicated, so the appendix and conclusion could have been longer. One could argue that most of the final part of the book – which reviews the common habits and trends of sleeping in the modern day – serves as an extended conclusion.

Final Score

Certainly detailed, comprehensive, and probably contains everything you would want to know about sleep. I did find myself losing interest, which is more a reflection of my preferences than the book itself. Perhaps it could have been more upbeat in places, but it’s harsh to dock points for that. Rigorous and full of great information, complex but explained succinctly and effectively, you will get a great understanding of sleep from this book.

8/10