Why does staying awake inevitably make us sleepy? Researchers at the University of Basel, Switzerland, have identified ...

Eight hours isn’t necessarily the magic number for sleep. Your age, body clock and individual needs all matter.

The middle of the night used to be my special time. I’d use it to cram for a test, read a mystery, or play Candy Crush—with no one around. As I got older, those nighttime hours became time to answer ...

Daniel E. Lieberman is a professor of human evolutionary biology at Harvard University and author of “Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding.” Do you lose sleep over ...