It’s every man for himself (and every woman for herself) when it comes to answering this question. Only you know how much sleep you need to feel rested and ready for the day.
But advice-givers for hundreds of years have offered prescriptions about how much sleep people need as if it were a matter of standard hygiene. Rinse your face when you get up in the morning. Brush your teeth twice a day. Wash your hands after using the toilet. Get 7 to 8 hours of sleep a night.
In reality, scientists have never found a way to determine how much sleep each person needs, so judgments about sleep need remain subjective. But there is quite a range in sleep ability, or how much sleep people report that they get.
What the Numbers Say
Sleep scientist Daniel Kripke analyzed a survey of over a million people and found that while a majority reported sleeping 7 or 8 hours a night, about 8 percent reported sleeping 9 hours or more, 16 percent reported sleeping about 6 hours, and 4 percent said they slept 5 hours or less. The best survival rate occurred for people who reported sleeping 6.5 to 7.4 hours a night.*
An average night’s sleep for me falls well below this, but I don’t worry too much about my mortality. I don’t care about the numbers as long as I wake up feeling pretty good.
Pronouncements About Sleep Need from the Past
- “Much sleep ingendereth diseases and payne,” says The Schoole of Vertue in 1557, “It dulles the wyt and hurteth the brayne.”
- “Nature requires five (hours), custom takes seven, laziness nine, and wickedness eleven.”
- “Ten to 11 hours for children, 9 to 10 hours for women and feeble persons, and 6 to 7 hours for men,” says an eighteenth century book of devotions.
- “For the healthy normal human being of sedentary occupation to … spend much more than a quarter of his time in sleep, is lazy neglect of his duty to himself and the race, and a reversion toward the stage of the amoeba,” says Dr. Fred W. Eastman in The Atlantic Monthly in 1911.
How much attention did people pay to pronouncements like these when they were delivered? Who knows. What I do know is that when claims about sleep need sound prescriptive, you’re better off taking them with a grain of salt.