While most people who feel sleepy during the day have nothing wrong with them besides a schedule -- or an attitude -- that doesn't allow enough hours in the sack, others have a different problem: sleeping disorders. These quirks of biology (and occasionally psyche) prevent their victims from sleeping restfully despite long hours in bed -- or in other cases force them to sleep at times when they should be awake.

Many of those with sleep disorders are insomniacs, but others are victims of more exotic disorders such as sleep apnea, narcolepsy and periodic limb movement disorder. These relatively unusual disorders have probably been with us since the dawn of human history, but it's only in the last two decades that it's become possible to understand the physical mechanisms that underlie them and thus to treat them effectively.

This advance in knowledge of sleep disorders is due to the advent and spread of sleep laboratories. The labs' application of technology to the study of sleep has saved many sufferers from the frustration, depression, isolation and despair that can result when their disorders aren't recognized for what they are.

ONE SUCH SUFFERER IS WALter Blucher.

Walter Blucher was always difficult to wake up -- very difficult to wake up. And, even when his parents or his wife finally succeeded in getting him out of the sack, he'd still feel tired, no matter how much sleep he'd had -- even 12 hours a night. Still, working as a maintenance mechanic, he managed to get by -- until he began working the 11 to 7 shift.

"I was unable to adjust," he says. "I began falling asleep all the time."

In addition, he explains, he would have periods when he would appear to be in an unhearing trance, with his jaw slack and his attention elsewhere, or nowhere. Yet if his wife would so much as suggest that anything was wrong, he'd get angry: He was quite unaware of these lapses from ordinary consciousness and he couldn't believe there was anything wrong with him, since he was only 30 and in very good health.

But then he was fired from his job. That initiated a period of personal crisis -- and a willingness to consider that he might have a medical problem. His wife, a nurse, encouraged him to get help, and eventually he found himself at the Maryland Sleep Diagnostic Center in Ruxton.

There he was diagnosed as having narcolepsy, a sleep disorder characterized by excessive daytime sleepiness during which the sufferer may be unable to keep from falling asleep. These attacks can come on not just while resting, but even while walking, talking or driving. Believed to be caused by a defect in the central nervous system, narcolepsy is also sometimes characterized by sudden weakness of the muscles and hallucinations.

The American Narcoleptic Association believes one out of every 100 Americans suffers from this disorder, yet most of them are neither diagnosed nor treated. Mr. Blucher is one of the lucky ones. He was treated with a drug that heightens his awareness and prevents him falling asleep, and thus he was able to get

another job.

"My life is back to normal with the medication," he says. "I'm back to being myself."

NOT SO LONG AGO MR. BLUcher would have been dismissed as just one more guy who couldn't hold a job because he was lazy or stupid or weird. The change comes thanks to the advent of sleep research laboratories.

The first big step toward modern sleep research was taken in 1953, when physiologists Nathaniel Kleitman and Eugene Aserinsky discovered that some sleep was characterized by flickering eye movements -- now known as REM, or rapid eye movements. By that discovery they put an end of the view of sleep as a passive state, and initiated the present understanding of it as both active and inactive.

"It just took off from there," says Dr. Philip L. Smith, the slim, intense director of the Johns Hopkins Sleep Disorders Center at Francis Scott Key Medical Center. He explains that the continuing revolution has been driven by technology: by hooking up sleepers to machines that can measure their biologic functioning. Before researchers came up with the idea of using technology on sleepers, he adds with a laugh, all you could do was watch people lying there with their eyes shut.

The Hopkins sleep lab, as it's called, is a model of how far that technology has come: It can analyze several sleepers simultaneously, with banks of machinery recording many different variables such as brain waves, eye movement, muscle tension, heart action and oral-nasal air flow. Sleep disorders like Mr. Blucher's narcolepsy show up as distinctive arrangements of squiggles on the reams of graph paper covered during each night of sleep.

Not only the machinery has multiplied. So, too, has the number of researchers and centers. The American Sleep Disorders Association, founded in 1975, had 339 individual members at the end of 1984, and has 1,650 now. And the number of centers belonging to the association has expanded from 57 in 1983 to 151 now.

The growing awareness of sleep disorders and the problems they can cause led to the formation of the National Commission on Sleep Disorders Research, a panel of sleep scientists assembled by Congress in 1988. The commission will be issuing its report on the subject later this year or early next year, says Dr. Andrew A. Monjan, deputy associate director of the Neuroscience and Neuropsychology of Aging Program at the National Institute on Aging and executive secretary for the commission. The report will include recommendations identifying "what are the needs and what sort of national plan should be proposed for the national government to support," he says.

It can't be too soon, according to some researchers. "Ther really is a dearth of knowledge about sleep across the board," not only among patients but among health professionals, says Dr. Mary A. Carskadon, director of chronobiology at E. P. Bradley Hospital in Providence, R.I., professor of psychiatry and human behavior at Brown University and a member of the commission.

"We have patients telling us, 'I have this terrible problem with daytime sleepiness and everyone thinks I'm lazy,' whereas in fact it is a sleep disorder," she says. "Even their physicians pooh-pooh sleep complaints. . . .

"All along the line there is a knowledge gap."

"I HAD SLEEP APNEA FOR the last 10 years or before that, and nobody could diagnose what I had," says federal contractor Charles Michael Long.

"Finally I read an article in Parade magazine [that] described everything I had," says Mr. Long, who is 55. He took the article to his doctor, put it on his desk, and said " 'This is what I have.' "

Sleep apnea is a sleep disorder characterized by pauses in breathing during sleep. It affects one out of every 200 Americans, 70 to 90 percent of them men in middle age. Usually they're overweight, says Dr. Susan J. Blumenthal, chief of the behavioral medicine program at National Institute of Mental Health and clinical professor of psychiatry at Georgetown School of Medicine, although people of any age and either sex can be affected. In extreme cases, heart failure can occur.

The chief symptom of sleep apnea is usually extremely loud snoring. "Industrial snoring, we call it, the kind that moves you out of the bedroom or down the hall," says Hopkins' Dr. Smith. "It almost always means apnea in one degree or another."

Another alerting symptom of sleep apnea is that sufferers can actually be seen to stop breathing during their sleep, he says, and yet another is "that the patients are having trouble making it through the day."

No wonder: The breathing stoppages characteristic of apnea usually happen once every minute or two, and they tend to wake the sleeper up for a few seconds each time, although he or she is not aware of being awakened. After a night of this, it's not surprising that the apneic is exhausted in the morning.

"To go for a week is one thing, but to go for two or three weeks without sleep or [with only] half an hour of not quite sleep -- it's hard on you, very hard on you," says Samuel P. Sisler Jr., another sleep apneic.

"By the time they make it to us they may be literally dropping

their fork," Dr. Smith says. "We had one woman who was literally falling into her food."

But now there is an effective treatment for sleep apnea, a gadget researchers call C-PAP. The initials stand for continuous positive airway pressure, which is maintained by a device that forces air through a hose into a mask that sits over a patient's nose and mouth.

It was developed by two Australians and introduced into this country in about 1984, says Greg Mader, membership and media coordinator for the American Sleep Disorders Association, and according to Dr. Smith it works for about 70 percent of apnea sufferers.

Mr. Long is one of the 70 percent. Before he tried C-PAP, he'd been treated by having the back of his throat scraped and part of his tongue removed. This wasn't successful, so an opening was made in his trachea for him to breathe through at night. That was followed by laser therapy, and finally C-PAP.

"I still have the apnea, but it keeps the apnea from occurring," he says. "I do feel much better."

Then he adds that if it weren't for seeing the article in Parade, "I'd be dead right now. I caught it just in time."

SLEEP APNEICS ACCOUNT for the majority of patients at sleep labs, says Dr. Thomas E. Hobbins, director of the Maryland Sleep Diagnostic Center and doctor to both Mr. Long and Mr. Sisler, but they're not the only patients.

Take Diane D., for example, who suffers from periodic limb movement disorder. A one-time alcoholic, she didn't even know she had a sleep disorder till she quit drinking.

"In the past I would go to bed and the alcohol would keep it down," says the 46-year-old Ms. D., who, in the tradition of Alcoholics Anonymous, doesn't want her last name revealed. But when she set out on the long road called recovery, there it was: She'd go to bed, start to drift off, and her legs would start kicking.

By themselves. She wasn't telling them to kick; they were just kicking. And every time they kicked, they woke her up. Every night. All night long.

"I was constantly tired," says Ms. D., who is an alcoholism counselor. And although she got used to her constant fatigue, it made her miserable enough that after eight months of sobriety and sleeplessness she went to a neurologist for help.

He told her that sleep disturbances are common in people recovering from alcoholism and that she should wait till she had made it through two years of sobriety. When she had, she went to the Maryland Sleep Diagnostic Center and was diagnosed as having periodic limb movement disorder, which used to be called nocturnal myoclonus.

Those with this sleep disorder experience a discomfort in their legs or feet just before falling asleep (and sometimes while relaxing) that is relieved by vigorous movement. When they do fall asleep, their legs twitch or kick, awakening them, although they are not always aware of this. Like narcoleptics and apneics, they wake up dead tired, ready to go to back to bed.

(Diane D.'s lab tests, for example, showed that she slept only 3.6 hours out of the eight she was in bed, and that none of the 3.6 hours was spent in the stage of sleep considered the deepest and most restful. Her leg was kicking an average of 31 times an hour, she says.)

Although some sleep problems can be caused by alcoholism, Ms. D.'s probably was not, since her mother suffers from the same disorder, though less severely. Ms. D.'s sleep disorder remains for the most part untreated: Although there are two medications she could take, she says, she does not want the side effects of the one, and the other is addictive. Given her history of alcoholism, Ms. D. says, she is afraid to take it except when she's "desperate."

"DESPERATE" IS A WORD LOretta Augustin understands all too well.

But her sleep difficulties didn't start out desperately: At first she hardly noticed them, she says, but then they became a habit. But while your habit may be smoking, or nail-biting, or hair-twisting, Ms. Augustin's was not sleeping.

She used to go to bed about 11 or 11:30 and then lie awake till about 3 -- "or it would feel like all night long I'd be awake." She'd get up with her two small sons at 7:30, and then she'd go back to sleep.

Not that that helped much: She still felt tired all the time. "I couldn't concentrate, I couldn't work out a simple math problem, my attention span was just not there." She snapped at the kids, she felt nauseated, she didn't feel like doing anything.

But Ms. Augustin, who is 36, accepted the way she felt and the way she slept: She told herself that it was the way everyone slept, and continued that way for several years.

Then one morning she almost had an accident while driving, and her attitude changed. She heard from a friend of a friend of her husband about sleep centers, and she ended up spending a night at the Johns Hopkins Sleep Disorders Center.

(Only about 4 percent of the patients evaluated in the Hopkins sleep lab are insomniacs, though, says program coordinator Norman Schubert. Dr. Smith notes that the lab is more suited to the evaluation of the other sleep disorders, while insomnia is usually better defined through in-depth interviews. Still, some long-term insomniacs do go through the sleep lab, and Ms. Augustin was one of them.)

The tests done at the lab indicated that her problem was not caused by leg movements or sleep apnea but by a biological clock that was out of sync. Richard P. Allen, co-director of the Hopkins sleep lab, treated her by consolidating her sleep and by reinforcing her natural sleep rhythms:

He had her go to bed at 1 a.m., so that she fell asleep immediately and slept soundly, though not for long, and she also had to forgo her morning naps. Then her time asleep was extended gradually by making her bedtime earlier and earlier by 15-minute increments, until it reached its present 11:15 or 11:30 p.m. In addition she goes out in the sunlight for two hours every morning, since recent research has shown that bright light can help reset the human biologic clock.

The first few days of this regimen were grim, Ms. Augustin says, but at least when she slept she slept well, better than she had in years. And as her sleep time was extended, she felt better and better. Her morning headaches disappeared. Since she began her treatment last April 13, she says proudly, she has had only two nights of disturbed sleep.

IT'S A RECORD MANY INSOM- niacs could envy.

Estimates of how many people suffer from insomnia -- the inability to fall asleep or to stay asleep -- run as high as 30 percent of the population, which makes it the most common of the sleep disorders. But it's also the least well understood and the least studied.

Brown's Dr. Carskadon says she regards it not as a true disorder, but as a complaint, because it can be caused by many things that have nothing to do with a specific medical condition. This makes it hard to understand and to deal with.

"Clinicians shy away from it because it is difficult and problematic, not like sleep apnea where you give people a prescription and they feel better," she says.

"And it's a subjective problem. Subjective problems are always hard to study," says board certified sleep-medicine specialist David Buchholz, director of the Neurological Consultation Clinic at the Johns Hopkins Hospital and neurological consultant to the Hopkins sleep lab.

In addition, he says, "The system of medical research encourages superspecialization. You succeed in academics by finding a tiny niche that no one else occupies and staking out your claim. That's how you're most likely to gain new information and grant funding.

"So we do much better in making medical progress in these limited and rather uncommon disorders than in the more prevalent disorders that plague so many of us -- like insomnia."

Progress has been made in treating some forms of insomnia -- like Ms. Augustin's -- by using new knowledge of how human circadian rhythms work, says Dr. Allen, but other forms of the problem "are much harder to get a handle on."

Many researchers hold to the idea that insomnia is often associated with mental disturbance; others see it as frequently related to lifestyle issues and the average person's ignorance about sleep itself. (See box on sleep hygiene.) Dr. Carskadon calls insomnia a "large frontier" that remains for sleep researchers to stake out and settle.

So for now it seems that although some bedtime stories have happy endings, for others the conclusion has yet to be written.

Readers who think they may be suffering from a sleep disorder may write to the National Sleep Foundation, 122 S. Robertson Blvd., Suite 201, Los Angeles, Calif. 90048. They will be sent a brochure about the type of disorder they believe they have and a roster of accredited centers. Brochures on the special sleep problems of children and the elderly are also available.