Why We Sleep by Matthew Walker, Review

Sleep is probably our most underestimated and overlooked physical need. As students, we often indulge in sleepless nights to revise for an exam. As workers, our nights are shortened by early starts. As parents, we mistake our adolescent children’s lie-ins for laziness and chastise them for it. In Why We Sleep, neuroscientist Matthew Walker debunks the myths and shows us how badly we understand sleep. But, most importantly, he reveals how closely our bad sleeping habits are related to many critical diseases and accidents.

His introduction might seem almost apocalyptical as he lists all the consequences of chronic sleep-deprivation – that is, getting seven hours of sleep or less on a regular basis. It ‘demolishes your immune system’, can be a contributing factor to developing Alzheimer’s disease, increase risks in cardiovascular problems and worsen mental health disorders such as anxiety and depression. This terrifying overview is somewhat ironic, as it keeps the already sleep-deprived reader awake and flipping the pages to see why and how all these horrific consequences of bad sleep can happen. But Walker’s book is not just a general warning against undervaluing sleep. As a neuroscientist genuinely interested in the workings of sleep, its origins and our need for it, his book explains why we sleep, so that we can understand why we need to sleep enough.

Neuroscientist Matthew Walker | © Frederick M. Brown/Getty Images
Neuroscientist Matthew Walker | © Frederick M. Brown/Getty Images

With its emphasis on public health, Why We Sleep is aimed at a large audience. But while Walker often uses metaphors to clarify his arguments, the book is never victim of oversimplification. For instance, he uses our scepticism towards genetically modified food to highlight our own contradictions, since a lack of sleep alters our genetic activity and, as a consequence, affects the very composition of our chromosomes. By depriving ourselves of sleep, we too become, to a certain extent, genetically modified beings. These kinds of analogies make the book accessible and help us understand the complexities of our sleeping brains.

Walker follows a pedagogical logic when explaining how sleep works. He begins by describing what the circadian rhythm is, how it evolves with age, and which molecules are involved in the process. It is surprising to discover that, contrary to the commonly-held belief, older people do not need less sleep, and adolescents do not need more than an adult. Rather, it is their circadian rhythm that affects when they feel the urge to sleep. For elderly people, the rhythm evolves backwards, starting early in the evening, and ending early in the morning. For adolescents, it is the reverse: they feel the urge to sleep much later than adults, and therefore need to sleep longer in the mornings. However, the circadian rhythm is not taken into account by parents, or even the educational system and its early start times. As a consequence, chronic sleep-deprivation in adolescents can dramatically impair focus and memory, as well as increase mental health risks, already a major issue for adolescents and young adults.

Walker also examines the two stages of sleep known as NREM (non-rapid eye movement) and REM (rapid eye movement) sleep. NREM sleep is the stage of deep sleep that occurs mainly at the beginning of the night, while REM sleep is the dreaming stage, becoming more dominant as the night evolves. These two stages both act on our brain’s evolution from a very early age but in different ways. NREM sleep will mostly help with blood-pressure regulation or memory. Here Walker uses an enlightening analogy: NREM brainwaves are akin to AM radio transmissions. Compared to FM radio stations, they use lower frequency radio waves, meaning that they travel more slowly, but can reach far more distant locations. This ‘long-range communication’ connects distant areas of the brain, allowing memory storage. Most importantly, sleep does not help with memory solely after learning a new fact, but before as well: getting a good night’s sleep will help neurons make the right connections quickly during the day, so that the information can be processed adequately the following night. As a dire consequence, deprive someone of NREM sleep and their memory will be altered – sometimes permanently in the form of Alzheimer’s disease.

By contrast, REM sleep is where dreaming happens. Walker gives a refreshing explanation of dreams thanks to his colleague Robert Stickgold’s discovery: departing from the Freudian conception of dreams as a retelling of someone’s life experiences, wishes and desires, Stickgold shows that dreams are rather a mash-up of the day’s emotions, as if helping to process them. And indeed they do. Strong emotions felt during the day – especially negative ones – will lose their power after a good night’s sleep. This is partly why disrupted sleep is so closely related to mental health issues such as anxiety, depression and PTSD (post-traumatic stress disorder), where unprocessed emotions are felt in a crippling way. Sleep then becomes a therapeutic means to help overcome such disorders.

Walker proposes sleep to be a major contributor to healing. Before treating someone for a specific illness or disorder through pills, if sleep deprivation is involved, it should be addressed first, and not by sleeping pills, but through therapy. The most effective one is Cognitive Behavioural Therapy, which, when applied to sleep disorders, is called CBT-1. Walker therefore proposes a radical change in our treatment of numerous diseases, especially since acquiring more sleep should only be a matter of a slight change in habits for most people.

Why We Sleep by Matthew Walker | © Simon & Schuster
Why We Sleep by Matthew Walker | © Simon & Schuster

But there is a catch: most people are not aware of how permanently sleep can affect our lives. Children are not taught at school about the importance of sleep and yet ‘vehicle accidents caused by drowsy driving exceed those caused by alcohol and drugs combined’. This is due to the fact that when you fall asleep behind the wheel, ‘you stop reacting altogether’, while when drunk, you are ‘late’ in reacting. Information on the dire necessity of sufficient sleep is thus crucial, not only to prevent us from developing a frightening number of diseases, but to avoid mortal accidents.

A further issue arises in our underestimation of sleep as a society: modern society is not made for adequate sleep. We are consistently solicited by artificial light, of which the blue emissions suppress the release of melatonin. Students see their sleep, and especially their REM sleep, hampered by early school start times. This is even worse for children who live far from school and whose working parents means they have no choice but to take the school bus at even earlier pick-up times. Finally, employees are often required to work long hours, depriving themselves of the mere eight-hour window for sleep.

What is needed, and what Walker hopes for, are changes in society that would benefit everyone physically, mentally and financially. As if the physiological gains of good sleep were not enough, Walker presents us with data proving that sleep loss results in financial loss for companies. An underslept worker will not be as focused and will need more time to complete tasks; he or she will lack creativity and quick problem solving skills. Some companies are already on the right track, providing employees with flexible working hours and ‘nap pods’. But wider changes are still needed.

What is encouraging is that we as individuals can change our habits. Walker proposes a list of twelve tips taken from the governmental website of the National Library of Medicine. I strongly encourage everyone to have a look. Sleep is not only about feeling rested. It is about living a healthy life, about prevention over cure. It is a basic human necessity and should be regarded as such by everyone.