Health: Drowsy America

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Off-duty shift workers trying to get to sleep are still battling their bodies' natural inclinations, this time to get up. When they do manage to doze off, their rest tends to be fitful, since other bodily functions keep to their usual rhythms. "Nightworkers are often up at noon because their brain and bladder wake them up," explains Dr. Charles Czeisler, director of the sleep laboratory at Boston's Brigham and Women's Hospital. "The average nightworker sleeps less than the typical dayworker does."

Even one night of shortened sleep can produce adverse effects. People will briefly rise to an occasion, such as playing tennis or giving a speech, but mental concentration, flexibility and creativity suffer. Two nights of skimpy sleep, and rote functioning is affected. In laboratory tests, sleep-deprived subjects have trouble adding columns of figures or doing simple repetitive tasks like hitting buttons in a prescribed pattern. By the end of a week, people can be seriously impaired. "Driving home on Friday is a greater risk than on Monday, when you haven't been deprived of sleep all week," says Mary Carskadon, director of chronobiology at E.P. Bradley Hospital in Providence. And stopping at a bar with colleagues for a postwork drink can make the situation worse; studies show that it takes less alcohol to make people drunk when they are tired.

One of the most surprising recent discoveries concerns the sleep needs of adolescents. For years they were urged to get eight hours, the same as adults. No longer. Teenagers appear to require more than 9 1/2 hours. Carskadon found that to be the case when she studied a group of children every summer for seven years, from the time they were ages 10 to 12 until they turned 17 to 19. During the experiments, the youngsters got 9 1/2 hours of sleep each night. In the beginning years of the study, they experienced no problems during the day, but after they reached puberty there was an increase in daytime sleepiness.

Teenagers who are struggling to juggle demanding academic schedules, friendships and dating, and sometimes afterschool jobs, are horrified by the idea of nine-plus hours of sleep. "My God, how would I have time to do anything?" protests Kimberly Erlich, 15, of Van Nuys, Calif. "That would mean going to sleep at 8 p.m. I can't imagine that." Kimberly tries to get at least seven hours.

Others appear to be getting even less. And that is interfering with their ability to learn, contend teachers, who say they are confronting more and more draggy pupils, even in elementary school. Sleepy youngsters are arriving late to class, forgetting assignments, moving at a snail's pace from task to task, and sometimes dropping their head on their desk to catch a few winks.

College students are notorious for nodding off in class and hibernating on weekends. Phil Simon, a 20-year-old junior at the University of Oregon in Eugene, is not unusual. During the week, he rises anytime between 7:30 a.m. and 11, depending on his classes, and retires sometime between 1 a.m. and 2:30. He naps whenever he gets a chance, but that does not always work well. "A few weeks ago," he recalls, "I had a break between two morning classes, so I slept. But when I woke up, the morning class I had attended felt like it never happened. It seemed more like a dream." On weekends he heads for bed at 3 a.m. and doesn't get up until 1 p.m.