SLEEP NEEDS THROUGHOUT LIFE
The National Sleep Foundation recommends the following amounts of sleep for infants, children, teens, and adults.
need (for more on the many cultural factors that promote sleep deprivation in teens, see Chapter 5). Even when we do drag ourselves away from our computers, TVs, and iPods, we often sabotage ourselves with worries and stress that interrupt and/or shorten our nights. Sleep—as it’s meant to be—is a dynamic process composed of five separate stages, each of which is physiologically different and fulfills different body and brain requirements. We need to cycle through all the stages in an orderly sequence during the night and spend adequate time in each, with as few interruptions as possible, in order to reap their full benefits.
As I discussed in Chapter 1, sleep-wake homeostasis and the circadian rhythm drive the need for and the timing of sleep. When the hormone melatonin is first secreted in the late afternoon, it signals the brain to begin the process that leads to sleep hours later.
Animals, like people, have different sleep requirements. Giraffes sleep only two hours a night, whereas bats sleep 20. Cats are one of the few animals that don’t group most of their sleep time into one long nighttime session, preferring to sleep for fairly even chunks of time throughout the day—cat naps!