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How much sleep do we really need?

Are people who claim to feel good on hardly any sleep just lying? NBC's Robert Bazell investigates.

Benjamin Franklin said “early to bed early to rise,” but he claimed he needed only a few hours of sleep. So do Martha Stewart, Jay Leno and others not so famous.

Are people who claim to feel good on hardly any sleep just stronger than the rest of us?

Actually, studies in sleep labs reveal that a small percentage are actually deceiving themselves.

“They thought they had three to four hours,” says Dr. Sigrid Veasy of the University of Pennsylvania. “They're really getting five, six, maybe even seven hours.”

But the studies also prove some feel just fine after only a few hours of shut-eye. How did they get that way?

“It really is just luck of the draw,” says Veasy. It "doesn't have to be the most intelligent person who really only needs three hours of sleep. It's luck of the draw.”

And then there is the other side of the bell-shaped curve — those who say they require at least 8 to 10 hours of sleep to function properly.

It turns out that the need for sleep is like hair color, body type and so many other things. It is one of the characteristics that varies enormously from person to person.

But no matter how much sleep they need, many people never get it. How do you determine how much sleep you really need?

According to Vesey, “Take a week where you really don't have so much on your plate — not a lot of pressure. And just try to get as much sleep as you can.” Then see how much you function best with.

If only that were possible.

So millions are destined to be groggy — unless they are among the lucky few who need little sleep.