When you sleep is also important. Your body typically works on a 24-hour cycle (circadian rhythm) that helps you know when to sleep.
How much sleep we need varies depending on age and varies from person to person. Most adults need about seven to nine hours of restful sleep each night, according to the National Sleep Foundation. The Foundation revised its sleep recommendations in 2015 based on a rigorous review of scientific literature.
Many of us do not get enough sleep. Nearly 30 percent of adults get less than six hours of sleep each night and only about 30 percent of high school students get at least eight hours of sleep on an average school night. An estimated 35 percent of Americans report their sleep quality as “poor” or “only fair.”
More than 50 million Americans have chronic sleep disorders.