The cover article of National Geographic (August, 2018) focused on what the 86 billion neurons in our heads do each night to keep us alive, renewed and healthy over the long term. The importance of sleep again comes out as potentially the one best thing you can do to improve the quality of one’s life, mindful of obstacles unintentionally being thrown our way to prevent that (cities lit by LED’s, for example).

Around 350 B.C., Aristotle wrote an essay, “On Sleep and Sleeplessness,” wondering just what we were doing and why. For the next 2,300 years no one had a good answer.

Everything we’ve learned about sleep has emphasized its importance to our mental and physical health. Our sleep-wake pattern is a central feature of human biology—an adaptation to life on a spinning planet, with its endless wheel of day and night. The 2017 Nobel Prize in medicine was awarded to three scientists who, in the 1980s and 1990s, identified the molecular clock inside our cells that aims to keep us in sync with the sun. When this circadian rhythm breaks down, recent research has shown, we are at increased risk for illnesses such as diabetes, heart disease, and dementia.