A British sleep expert provides an overview of what we know about sleep, which turns out to be quite a lot and also not enough.
Gregory begins by pointing out that animals deprived of sleep will die. Humans who are kept awake become sleepy, confused, and delirious. Everyone agrees that sleep is essential to life, and many explanations exist, which means that no one knows why. “Although we sleep each night,” writes the author, “defining it is tricky. What exactly is it?” The popular (i.e., unproven) belief about why sleep is necessary is that the body must rest to eliminate toxins and regenerate energy. There is better evidence that the brain itself uses sleep to solidify and consolidate the day’s input: learning and memories. Proceeding chronologically, the author describes how we sleep during the various periods of life, with special attention to what happens when things go wrong. She does not neglect neuroscience but emphasizes her specialty, focusing on psychological studies, surveys, educational research, and interviews. Gregory is a researcher, not a physician, but readers will have no doubt that her editors made it clear that the audience for a book on sleep science is minuscule compared with the apparently bottomless market for medical advice. A first-time writer, she takes the hint enthusiastically but mostly pours out generalities—e.g., “big and stressful events in our lives can trigger insomnia.” As a good scientist, she warns that individual responses vary widely, and research backing many treatments and advice is thin or absent entirely.
Readers looking for help on sleep problems should consult one of the books Gregory recommends. Those who are merely curious will learn fascinating details of what scientists know about sleep, including its familiar and bizarre disorders, and how they are learning more.