How Little Sleep Can You Get By On?

The jig is up. Publications have been filled with stories of high achieving people like Martha Stewart, P. Diddy and Jerry Weintraub who supposedly need only three or fours of sleep a night. But the boasters--and their work--might be eyed with more suspicion now that the evidence is out that the less sleep you get, the worse you perform.

Maggie Jones described one study in an eye-opening article in the New York Times magazine in which subjects were allowed to sleep four, six or eight hours a night for two weeks and were then tested with the psychomotor vigilance task, or P.V.T., which measures sustained attention, a gold standard of sleepiness measures:

Not surprisingly, those who had eight hours of sleep hardly had any attention lapses and no cognitive declines over the 14 days of the study. What was interesting was that those in the four- and six-hour groups had P.V.T. results that declined steadily with almost each passing day. Though the four-hour subjects performed far worse, the six-hour group also consistently fell off-task. By the sixth day, 25 percent of the six-hour group was falling asleep at the computer. And at the end of the study, they were lapsing fives times as much as they did the first day.

Why 7 Hours Isn't Enough

She reported that in another study of seven-hour sleepers, "their response time on the P.V.T. slowed and continued to do so for three days, before stabilizing at lower levels than when they started." So sleeping seven, which most of us think is ok, is not either.
But people are different and some of us can get away with one or two nights of less sleep. If you're lucky, you might not feel the effects of a five hour sleep the first day--some people can go a few days before their performance starts to go down hill.

Chronically Getting Less Hurts Performance
The problem is, for many of us, sleeping less is chronic, not just an once a week occurrence. And you can be sure of one thing. You probably won't realize when you're flagging. The subjects in the studies reported they were slightly sleepy, but, wrote Jones,

they insisted they had adjusted to their new state. Even 14 days into the study, they said sleepiness was not affecting them. In fact, their performance had tanked. In other words, the sleep-deprived among us are lousy judges of our own sleep needs. We are not nearly as sharp as we think we are.

How much sleep do you think you need?

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