Bodywork: How much sleep is enough?

How much sleep do I need? Or, more accurately, how little sleep can I get away with?

Dr. Prescott prescribes

Eight hours seems to be the magic number.

In studies that divided groups up into four-, six- and eight-hour sleepers for two weeks at a time, the four-hour group displayed a steady decline in its ability to pay attention with each passing day. The six-hour group also displayed a consistent drop, though not as sharp as the four-hour folks.

Still, by the end of the study, the six-hour sleepers showed focus deficits equal to subjects who, in another study, had stayed awake for 24 hours straight. Put another way, the six-hour sleepers showed the same cognitive impairment as people who are legally drunk.

In contrast, people who slept eight hours every night showed no drop-off during the two-week period. When tested, they performed equally well at tasks both tedious (pressing the space bar as soon as they saw a flash of numbers in random intervals) and more challenging (solving mathematical problems).

When researchers looked at splitting the difference between six and eight hours, they found that seven was no lucky number. Subjects who slept seven hours also showed declining ability to focus and respond optimally in testing situation. Unlike with the four- and six-hour groups, their decline seemed to stabilize, but it still left the subjects at lower functioning levels than when they'd begun the study in well-rested states.