Why We Sleep

Subtitled 'the new science of sleep and dreams' this book by the Professor of Neuroscience and Psychology and Director of the Sleep and Neuroimaging Laboratory at UC Berkeley is essential reading for anyone who sleeps, summarising as it does 20 years of cutting-edge research on the subject and spelling out the extraordinary implications for our health of not getting a regular eight hours sleep at night. Apparently, two-thirds of adults throughout developed nations fail to sleep the recommended eight hours; routinely sleeping less than six or seven hours undermines your immune system, promotes high blood pressure, doubles your risk of cancer as well as increasing your susceptibility to cardiovascular disease, diabetes and Alzheimer's. Just this list explains why this book is such an important read and makes the reader highly aware of the extensive health implications of sleep. The four parts cover the nature and history of sleep, why we need to sleep, how and why we dream, and sleeping disorders.

In a short review, I can only highlight a few points. The half life of caffeine in the system is 7-8 hours, and it operates by attaching onto adenosine receptors, which regulate sleep pressure. From an evolutionary point of view, we are designed for biphasic sleep, hence the rationale of the siesta, in which context the author cites an extraordinary study of 23,000 Greek adults demonstrating the health hazards of giving it up. Reading from a screen as opposed to a book late at night blocked the rising melatonin release by 50% in a controlled trial. Dolphins sleep with only one half of the brain at time. Sleep deprived mice showed a 200% increase in the speed and size of cancer growth relative to the well-rested group, with obvious implications for humans. Alcohol impairs REM sleep as well as fragmenting sleep more generally – bad news, even for moderate drinkers, especially as the quality of deep sleep diminishes as one ages. Early starts at school to suit hard-working parents is very bad news for children and their performance, so much so there is experimental evidence of significant increases in SAT performance for students starting an hour later (an adolescent getting up at 6 AM is equivalent to an adult rising at 4 AM). Towards the end of the book, the author gives plenty of implementable advice at a number of levels, the most important of which is to stick to a sleep schedule of between eight and nine hours a night – as I said at the beginning, this book really is essential reading for anyone who sleeps and wishes to maintain good health.