PALO ALTO, Ca. — If you’re sleeping habits are thrown out of whack by the changing of the clock, a Stanford University sleep researcher has some advice for staying alert.

“If you’re young, sleep an hour extra,” says William C. Dement, director of Stanford’s Sleep Disorders Center and a professor of psychiatry and behavioral sciences.

“If you’re older, go to bed an hour earlier,” he suggests.

Dement says about 60 million Americans suffer from “sleep debt,” or simply lack-of-sleep, triggered when daylight-savings time begins. He explains that the debt, “builds up if you sleep less than your personal need — from six-to-10 hours a day, depending on the person.

There is good news, he says. “You can repay the debt without interest. Someone who needs 10 hours of sleep could pay back a 10-hour debt over 10 days by sleeping one extra hour each night.”

You can catch up faster, of course. But Dement notes the money in this case is actual sleep–not lying in bed wide awake like a bad check ready to bounce at the bank.

Long-distance truck drivers are prone to bad sleep debt, according to Dement’s research conducted in the mid-1990s. Using simulations, the study revealed that a seriously sleep-deprived driver was prone to doze off while driving, even if he’d had three nights of eight-hours sleep each night.

“There overall debt was too large to overcome,” Dement explained.

How will you know when a sleep debt is paid in full? “You’ll feel it,” says the scientist.