Christopher Torrens, University of Southampton, UK

https://doi.org/10.36866/pn.113.21

Sleep is detectable in every animal studied, from insects to worms to humans and even sharks – despite what you may have heard elsewhere. Nevertheless, our understanding of sleep as a biological process has remained relatively mysterious compared with advances in our understanding of disease processes and other key requirements for life such as eating and reproduction. Recently we have been starting to lift the veil of night from sleep, and in his book Why We Sleep, Michael Walker gives a state-of-the-union address on our current understanding.

The scope of the book is huge. It covers topics from circadian biology, dreams, and the impact of a lack of sleep, right up to proposing solutions to cope with such problems on a societal level. Each section is explained clearly and supported by evidence, either experimental or epidemiological data, without ever becoming too in-depth for the non-specialist or too superficial for a physiologist (or at least this one). Despite the easy tone of the writing, this book reads more like a lay textbook than other popular science texts. I say this because it is, quite intentionally, set out to be read either from cover to cover or by cherry-picking chapters in whatever order you choose. Having done bits of both, I can attest that it does little to change the impact or the message conveyed.

What this book does not do is answer the question of why we sleep. When the eminent sleep researcher who initially characterised the five stages of sleep, William Dement, was asked such a question, he replied; “As far as I know, the only reason we need to sleep that is really really solid is because we get sleepy.”
What this book provides is lots of evidence of the consequences of a lack of sleep on our health and well-being. Some such consequences are well known. The number of road-traffic accidents attributed to tiredness is greater than the number attributed to drink and drugs combined. However, there are far more subtle things going on here. Poor sleep is associated with increased rates of coronary artery disease, and adults in their 40s who sleep fewer than 6 hours per night are 200% more likely to suffer a stroke or myocardial infarction in their lifetime compared to those who get the recommended 8 hours of sleep. Similarly, reducing sleep to 5-6 hours per night disrupts leptin and ghrelin signalling, leading to increases in food intake and is equally associated with increased blood glucose levels and rates of diabetes. A reduced immune response, higher rates of infection, cancer, depression, schizophrenia, Alzheimer’s disease, dementia and infertility are all associated with reduced amounts of sleep.

What can be done? Walker does suggest 12 helpful tips for individuals to help improve their own sleep hygiene and also reports on companies trying to change attitudes. Given the questionable decisions made by people who are sleep-deprived, he questions the esteem that we afford people responding to emails at all hours of the day and notes that companies are starting to provide more flexible working and even “sleep pods” and “shhhh zones”. On reading this I could not help but think of Homer Simpson asking Hank Scorpio where he could obtain some business hammocks; that was first aired in 1996 so they were both well ahead of the curve on this one.

Packed, as it is, with a mixture of information and practical advice this is a thoroughly interesting read, whether read cover to cover or picked through over time. My most ringing endorsement of this book is that it has given me food for thought and prompted me to make some change to my own sleep patterns. As a night owl living amongst a family of morning larks, I’ll have an early start in the morning, so it is time for me to go and get some much-needed sleep.