Penguin Books|4 January 2018|368 p|e-book |Review copy|4*

I have read several books and watched TV programmes on sleeping, but Why We Sleep: the New Science of Sleep and Dreams is one of the most in depth and thorough books on the subject that I’ve come across. It is fascinating and disturbing in equal measures.

It emphasises how important sleep is to our health. Eight hours sleep each night will improve your immune system, help prevent infection, regulate your appetite, lower blood pressure, maintain your heart in fine condition, improve your ability to learn, memorise and make logical decisions.

But be warned if you don’t get eight hours sleep you run the risk of doubling your risk of cancer, of increasing your risk of developing Alzheimer’s disease, diabetes, cardiovascular disease, strokes, and heart attacks, and insufficient sleep contributes to all major psychiatric conditions, including depression, anxiety and suicidal tendencies. It is a terrifying scenario as every major disease in the developed world has very strong causal links to deficient sleep.

Matthew Walker is professor of neuroscience and psychology at the University of California, Berkeley, where he is director of the Center for Human Sleep Science. He goes into great detail examining every aspect of the subject looking at what sleep is, how we sleep, as well as why we should sleep and the external factors that cause poor sleep. There are sections on sleep deprivation, sleeping pills, insomnia and other sleep disorders and on dreams – creativity and dream control. He also considers the sleep requirements of babies, children, teenagers and the elderly.

There are a number of things I highlighted as I read the book, including:

• sleep is the foundation of good health
• every major system, tissue and organ of your body suffers if your sleep is short
• the shorter your sleep, the shorter your life
• the less you sleep you’re more likely to put on weight
• sleeping six hours or less increases your risk of developing cancer by 40%
• routinely sleeping less than six or seven hours a night demolishes your immune system, more than doubling your risk of cancer

He cites the World Health Organization’s and the National Sleep Foundation’s stipulation of an average of eight hours of sleep for adults. So, what can you do to improve your sleep if you don’t get eight hours? I really want to know. Walker refers to behavioural methods for improving sleep, such as cognitive behavioural therapy intended to break bad sleep habits, obvious methods such as reducing caffeine and alcohol intake, removing LED devices from the bedroom and having a cool bedroom. Other things to establish – having a regular bedtime, only going to bed when sleepy, avoid sleeping in the early/mid evenings and daytime napping etc, etc – nothing I haven’t come across before.

Why We Sleep is full of fascinating facts, but at times it is repetitive with lots of detail about sleep experiments that made me worried about the effects on those people who undertook them. Matthew Walker is most certainly on a mission to educate people about the importance of sleep, even if there is nothing new he has to offer about how to improve sleep times.