新编大学英语第三册unit8 Text B: Surprising Facts About Sleep
UNIT 8 AFTER-CLASS READING 1; New College English (II)
Surprising Facts About Sleep
1 Judging from recent surveys and clinical experiments, most experts in sleep behavior agree that there is virtually an epidemic of sleepiness in the nation. "I can't think of a single study that hasn't found Americans getting less sleep than they ought to," says David F. Dinges, a biological psychologist at the Institute of Pennsylvania Hospital in Philadelphia.
2 Even people who think they are sleeping enough would probably be better off with more rest. This was revealed by studies of several hundred college students conducted at Stanford University, Brown University and Henry Ford Hospital in Detroit.
3 In one experiment, 16 percent of students who averaged between seven and eight hours of sleep a night could doze off during the day in five minutes if allowed to lie down in a darkened room. That's evidence, researchers said, that those students were sleep-deprived.
4 Researchers further discovered that even the students who did not quickly fall asleep under test conditions could benefit from more sleep. If they spent one week getting to bed an hour to 90 minutes earlier than usual, they improved their performance on psychological tests.
5 As added evidence that people don't sleep enough, psychologist Wilse Webb, a sleep-research pioneer at the University of Florida in Gainesville, cites the bedside alarm clock. "If that's how you wake up every day," he says, "you're shortening your natural sleep pattern."
6 The beginning of our sleep deficit crisis can be traced to the invention of the light bulb a century ago. From diary entries and other personal accounts from the 18th and 19th centuries, sleep scientists have deduced that the average person used to sleep about 9 1/2 hours a night. "The best sleep habits once were forced on us, when we had nothing to do in the evening down on the farm, and it was dark," says Dr Howard P. Roffwarg, director of the Sleep Study Unit at the University of Texas Southwestern Medical Center in Dallas.
7 By the 1950s and 1960s, that sleep schedule had been reduced dramatically, to between 7 1/2 and eight hours. Now social and economic trends are slicing ever deeper. "People cheat on their sleep, and they don't even realize they're doing it," says Dr Roffwarg. "They think they're okay because they can get by on 6 1/2 hours, when they really need 7 1/2, eight or even more to feel ideally vigorous."
8 Perhaps the worst robber of sleep, researchers say, is the complexity of the day. Whenever pressures from work, family, friends and community mount, many people consider sleep the most expendable item on the agenda.
9 "In our society, you're considered dynamic if you say you only need 5 1/2 hours' sleep," says Dr Neil B. Kavey, director of the Sleep Disorders Center at Columbia-Presbyterian Medical Center in New York City. "If you say you've got to get 8 1/2 hours, people think you lack drive and ambition."
10 Often, though, our efforts to squeeze ever more tasks into our days and nights backfire. The person who gets a full night's sleep, experts say, will benefit in terms of heightened productivity, creativity and focus.
11 Another thief of sleep is shift work, in which people work regularly in the evening, at night or on rotating schedules. Researchers say the brain has difficulty varying sleep times, which means that these employees one-fifth of the work force, according to Harriet Presser, a sociology professor at the University of Maryland usually suffer a net loss of sleep.
12 Nowadays television is available all night long. So instead of going to sleep, people stay up late to watch late-night programs. Not so long ago most TV stations signed off at midnight or 1 a.m. with "The Star-Spangled Banner," which served as a reminder that it was time to go to bed.
13 To assess the consequences of sleep deficit, researchers have put subjects through a battery of psychological and performance tests requiring them, for instance, to add columns of numbers or recall a passage read to them only minutes earlier. "We've found that if you're sleep-deprived, performance suffers," says Dr Charles Czeisler, director of Circadian and Sleep Disorders Medicine at Brigham and Women's Hospital in Boston. "Short-term memory is impaired, as are abilities to make decisions and to concentrate."
14 Because their reaction time and attention span are affected, sleepy people may be more prone to making mistakes on the job. Surveys by the Department of Transportation suggested that one to ten percent of traffic accidents may be sleep-related, and that perhaps as many as 20 percent of all drivers have fallen asleep at the wheel at least once. Recent studies have also found that sleep-deprived people are impaired by smaller quantities of alcohol than rested people are.
15 Just one bad night's sleep can make a person less efficient on mental tasks. Worse still, the effects of sleep loss are cumulative. A person who chronically sleeps 90 minutes less per night than is necessary will feel far worse on Friday than on Tuesday. "By the fifth night, you've lost 7 1/2 hours, or virtually a whole night's sleep," says psychologist Dinges. "That's the day when you're just praying to get through it."
16 Sleeping in on weekends does help the body recover. "But in chronic cases, you may need weeks of catching up to reverse the effects of sleep loss," says Dr Charles P. Pollak, head of the Sleep Wake Disorders Center at New York Hospital Cornell Medical Center.
17 Are you getting enough sleep? Sleep needs vary, and there is no absolute standard, but most people require about seven to nine hours a night. To determine your optimum sleep schedule, experts suggest tracking your hours of sleep over ten days. If you feel refreshed and vigorous each morning and able to concentrate throughout the day, the average number of hours you've slept per night is close to your ideal.
18 If you need an alarm clock, or if you feel sleepy while doing a repetitive, sedentary or undemanding task, like driving or sitting in a conference, try sleeping an extra 30 to 90 minutes a night. If you can't do that on weekdays and need to make up for lost sleep on the weekend, experts advise going to bed earlier rather than sleeping later. If that is not possible, they suggest taking a midafternoon nap for an hour or less on Saturday or Sunday.
19 But even the specialists have trouble taking their own advice. "I get by on maybe six, 6 1/2 hours," admits Kavey. "I'm just too busy to get a good night's sleep."
