Sleep is a funny thing. We're taught that we should get seven or eight hours a night, but

a lot of us get by just fine on less, and some of us actually sleep too much. A study out of the University of Buffalo reported that people who routinely sleep more than eight hours a day and are still tired are nearly three times as likely to die of stroke--probably as a result of an underlying disorder that keeps them from sleeping soundly.

Doctors have their own special sleep problems. Residents are famously short of sleep. It is not unusual for them to work 40 hours in a row without rest. They are not in the least worried about it, confident they can still deliver the highest quality of medical care. But an article in the Journal of the American Medical Association points out that in the morning after 24 hours of sleeplessness, a person s motor performance is comparable to that of someone who is drunk. Curiously, surgeons who believe that operating under the influence of alcohol is grounds for sacking often don't think twice about operating without enough sleep.

"I could tell you horror stories," says Jaya Agrawal, president of the American Medical Student Association, Which runs a website for residents. Some are terrifying. "I was operating after being up for over 36 hours," one writes. "I literally fell asleep standing up and nearly planted my face into the wound."

"Practically every surgical resident I know has fallen asleep at the wheel driving home from work." writes another. "I know of three who have hit parked cars. Another hit a ' Jersey gate' on the New Jersey Expressway, going 105km/h."

"Your own patients have become the enemy," writes a third, because they are "the one thing that stands between you and a few hours of sleep."

The U.S. controls the hours of pilots and truck drivers. But until such a system is in place for doctors, patients are on their own. If you're worded about the people treating you or a loved one, you should feel free to ask how many hours of sleep they have had and if more rested staffers are available.

Sleep is a funny thing because ______.

A．the longer one sleeps, the less sound sleep he gets

B．the more sleep one gets, the more likely a stroke occurs

C．many people stick to about eight hours of sleep to stay fine

D．many people who sleep six hours a night still feel energetic in the day