Review: Why we sleep by Matthew Walker. Available in the UK in Penguin paperback edition (from £7.99), and as an audiobook (from £7.99)
Books on various aspects of sleep take up about five feet of my bookshelves, but if I were to recommend only one for anyone to buy, it would be this (although I do know of another good book that is aimed specifically at occupational therapists). I bought my copy in a supermarket which tells us two things: it must have been selling well for Sainsburys to devote space to it, and that it is aimed clearly at the general reader. Complex material is made accessible by the author who evidently has a comprehensive grasp of the subject and writes clearly and persuasively, unencumbered by referencing. For example, I now begin to understand some of the complexities of electrical activity in the brain through the use of clever analogies (such as comparing brainwaves with AM and FM radio signals, or describing the difference between a microphone picking up thousands of separate voices in a football stadium before a match – as in wakefulness – and picking up the rhythmic chant of a crowd in unison during the game – as in deep sleep: simple. Why has no one else explained it like that?).
In describing the different stages of sleep – or more specifically, light and deep non-REM sleep and REM sleep (rapid eye-movement sleep), Walker shows how each has a different role in memory and learning, and that each is as important as the others. He puts forward a theory that learning to control fire allowed humans to sleep on the ground and thereby begin to have more REM sleep (because in REM sleep the risk of falling out of a tree is high): an increase in REM sleep allows for enhanced social IQ and greater capacity for the integration of learning and memories and, in turn, the development of ideas and skills that have differentiated the human from other primates.
In a section on the importance of sleep in learning and on general health, Walker provides convincing evidence to scare anyone into ensuring that they always have an opportunity for eight hours of sleep: if you get up at 7:00am, remain awake all day and, after an evening out, drive home (sober) at 2:00am, your cognitive impairment is equivalent to that of someone who is above the alcohol limit. He explains how lack of sleep affects the cardiovascular system and explains the complex interactions between sleep, diabetes and weight gain: short sleep increases appetite, yet compromises impulse control and prevents weight-loss when dieting. He also explains the relationships between sleep loss and the immune system and sleep loss and DNA: he suggests that in neglecting sleep “you are deciding to perform a genetic engineering manipulation on yourself each night, tampering with the nucleic alphabet that spells out your daily health story”.
For many years, if a patient or course participant asked about dreaming, I would pass, perhaps observing that we could not rely on Freud and that neuroscience would sometime be able to provide answers. In a section on dreaming, Walker shows that neuroscience does indeed now provide some answers. He suggests, for example, how dreaming could act as an “overnight therapist” helping to manage the emotional content of memories – by working through them in the absence of neurotransmitters associated with stress; he suggests that in post-traumatic stress, that mechanism fails. It is impossible to summarise briefly the richness of the information in this section. Suffice to say that imaging has begun to shine light on the mysteries of dreaming and, along the way, it is shown that, for some, lucid dreaming is really possible.
In the last section, Walker deals with a selection of sleep disorders and how they can be managed, extolling the virtues of cognitive behavioural therapy for insomnia. In considering sleep and society he points out how work practices, especially in medicine, and hours of education (i.e. early starts) are at completely odds with what is known about optimising performance and learning. Only in proposing possible solutions did Walker start to lose me a little, as I began to feel uncomfortable with his suggestions of widespread use of sleep trackers linked with environmental controls. However, it would be foolish to ignore possibilities offered by technology, and he makes many other suggestions for change.
I find it hard to be critical of this book. In one chapter I wondered whether the copyeditor had dozed off, and I failed to find one or two items in the index when I wanted to go back to them. Despite the lack of referencing enhancing the readability, I would have liked a few more pointers to where I could find the original research. Minor details.
Overall, the book made complete sense to me and cleared up a few mysteries too (so that’s why caffeine might help keep you awake and then stop working dramatically) and made me aware of quite a lot that I had not got quite right. I cannot say whether a grounding in sleep studies made the book an easier read for me, but I believe that it should also inform readers who are just starting to explore the subject of sleep and should further stimulate their interest. Either way, this book is a call to arms, and I suggest that there is no more convincing argument than those made in this book for the need for us to stress the importance of sleep for our patients, and ourselves, and then do something about it.