Q. How much sleep do I need?
A. Plenty of research shows that too little sleep can sap health. Kristen Knutson, a biomedical anthropologist at the University of Chicago, says taking into account both laboratory studies and observational studies on how people sleep in their daily lives, “both types of studies have found that short sleep is associated with a variety of health outcomes.” It can alter hormone levels (including hormones associated with appetite), raise blood pressure, impair how people regulate blood sugar, and dampen immune response. Sleep deprivation can interfere with cognitive performance, increase the likelihood of accidents, and exacerbate mood disorders.
“There may be such a thing as sleeping too much,” Knutson says, but the specific effects of excessive sleep are not as well researched (forcing people to sleep in a laboratory is much harder than keeping them awake).
When researchers look at the health of adults who report their nightly sleep habits, “seven to eight hours is the norm and associated with the lowest risk of having or getting diseases,” she says.
The perfect length of sleep, however, seems to be different for different people. But determining a person’s individual sleep needs is difficult, Knutson says, in part because many people are bad at judging when sleep loss is affecting them. Two general signs that you might need more sleep: you always need an alarm clock to wake up, and you tend to sleep more on weekends or holidays when you have the opportunity.