(FORTUNE Magazine) – Sleeplessness makes it hard to be the model executive. He comes on crisp and sharp-creased; poor insomniac you, even in a fresh suit, feel like a bag of stale laundry. He's easy with people, interested and quietly humorous. You range from sour to potentially murderous, if you could only work up the energy. He sees the world in a golden light, each leafy lane promising new opportunity. You look at it through gray, crunched-up cellophane. According to the best estimates, in any given year upwards of 50 million Americans have trouble sleeping. While no one keeps statistics on the matter, some evidence suggests that managerial types are just as prone to insomnia as the rest of the population -- or perhaps a little more so. At least one study argues that go-getter Type A personalities suffer sleeplessness in disproportionate numbers. Specialists in sleep disorders report treating their fair share of managers. The experts attribute the problem variously to stress, the evening socializing required of execs, heavy travel across time zones, and general workaholism. If you count yourself among the occasionally afflicted, take hope, slightly. No, you can't exactly manage the sleep process -- 12:30 A.M. to 5:30 A.M.: Fall asleep immediately, get five hours of uninterrupted, deeply satisfying shut-eye. But you can take steps to improve your chances of ending up in the arms of Morpheus. Begin by understanding the lineaments of normal sleep. While the experts still don't know the answers to the truly deep questions -- why do we sleep? why do we dream? -- in the past 40 years they have learned a lot about the basic physiology. They distinguish between two types of sleep, the rapid-eye- movement, or REM, variety -- beneath your shuttered lids, your eyes dart about -- and the non-REM type, also called orthodox, quiet, or slow-wave sleep. Dreams occur during REM sleep. In the course of the prosaic non-REM variety, your body seems to do more of the work of restoring itself. Of a night, the two types alternate, with an adult typically descending into the deepest non-REM slumber within 20 minutes or so of falling asleep, only to be interrupted maybe 90 minutes later by the first burst of REM excitement, a five or ten minute affair. For the rest of the night, your sleeping mind bounces back and forth between the two, with the non-REM sleep growing progressively less profound, and the periods of REM go-go getting longer -- up to an hour in some instances. Which explains why you're more likely to wake up at four in the morning from a nightmare about your boss's latest lunatic move than you are at midnight. From about when you're a teenager, your deepest slumber gets steadily less deep, and from 45 on, the likelihood of sleep disturbances increases. While young adults may complain of trouble getting to sleep, as you get ever more middle-aged you tend to conk out immediately but then awaken more frequently thereafter. In your 40s, you may be visited with the necessity to arise in the middle of the night to visit the bathroom. Individuals vary in their need for sleep. Some genuinely require nine or ten hours a night. A few get by happily on six or less and brag insufferably about it. In general, the experts say, Americans probably don't get enough sleep to feel their absolute best. What with hyperkinetic work schedules, grocery stores open 24 hours a day, and the temptations of late-night television, your unconscious time seems the easiest time to trim. False economy. It isn't just the effect on your affect (ugh, approximately). While almost all research on the effects of sleep deprivation has focused on nonexecutive types -- factory workers, night-duty personnel -- the studies suggest ways that managerial performance may be impaired. Think of how much you do that requires alertness. In the obvious department: chairing meetings; poring over spreadsheets or reports. Among the not-so-obvious: picking up subtle signs in conversations with your co-workers. Now imagine your capacity for alertness diminished 10%, 20%, maybe 30%. Inadequate sleep can do that to you. YOU MAY NOTICE your lack of sharpness. What you may not catch is the damage to that collection of skills commonly labeled ''creativity'' -- your ability to see a problem in a new light, or to devise a solution. Researchers suspect that these skills take the biggest hit from the hours of sleep you lost last night. Says James Walsh, head of the sleep disorders center at Deaconess Hospital in St. Louis: ''It can make the difference between performing adequately and performing optimally.'' Okay, you're convinced of the value of sufficient, high-quality slumber. You just can't manage to achieve it. What's wrong? Dr. Neil Kavey, a sleep specialist at Columbia-Presbyterian Medical Center in New York City, says that serious problems fall into four classes. If you have ever had jet lag, you have experienced what the experts call a circadian rhythm disorder -- a disruption in the timing of your normal sleep-wake cycle. People with the second class, hypersomnia, keep nodding off during the day, sometimes because they suffer apnea, a breathing disorder, at night. Those afflicted with parasomnias do wild things in their sleep -- thrashing about, talking, and, yes, walking. The sleep disorder you're most likely to be familiar with is insomnia, or, as some literal-minded experts now label it, DIMS, for disorders of initiating and maintaining sleep. The cause may be physiological: arthritis, say, or myoclonus, a twitching in the sleeper's legs that, you guessed it, becomes more common with age. Or it may be something traditionally thought of as psychological: Depression can bring on nasty insomnia, which may go away only when the underlying problem is treated. Transitory insomnia -- a few bad nights every now and then -- may have its roots in poor sleep hygiene, to use the specialists' shades-of-eighth-grade- gym-class phrase. Improving your habits in this area probably represents the first important step you can take toward better rest. Try to establish a regular time for rising every day. Patricia Lacks, a clinical psychologist at Washington University in St. Louis, notes that this means -- groan -- getting up Saturday and Sunday about the same time you do weekdays. You will thereby avoid so-called Sunday night insomnia -- sleeping in until 11 on the day of rest, then lying awake that night. Realize that you can't work feverishly right up until bedtime and then expect to drift off immediately. Leave yourself an hour or two to putter about and wind down. Some experts caution against using your bed for anything but sleep. Don't work there, they say, or watch television, or argue with your significant other. (Generously, they allow an exception for sex.) The idea: Your mind will learn to associate going to bed with going to sleep. Beginning six hours before you hit the hay, avoid caffeine and foods that may stimulate -- chocolate, for instance. For alcohol, the cut-off is two hours, Lacks suggests, though even stopping then won't do much good if you've knocked back a couple of bottles of high-octane Chardonnay. A nightcap may seem to help you nod off sometimes, but the ensuing sleep will be fragmented and unsatisfying, the experts observe, so don't bother. Regular exercise can promote better rest, but you have to time it right -- jogging in the moonlight will only keep you awake longer. The best time is late afternoon or early evening. Five or six hours after you work out, your body temperature drops, which can help you stay in the land of Nod. STILL CAN'T SLEEP? Or find your eyelids rolling up like window shades at three in the morning? What to do then? Here the experts divide a bit. The associate-bed-with-sleep school maintains that after ten or 15 minutes of wakefulness, you should get up, go elsewhere, turn on a light, and read something boring or watch TV until you feel sleepy. Others aren't so sure: If you're resting comfortably though wakefully, they say, go ahead and remain in the sack while you pursue unstimulating diversions. What you want to watch out for as you lie there: slipping into the state of mind labeled ''racing thoughts'' -- one worry follows another at an accelerating clip -- or becoming so distraught about not being able to fall asleep that you make it harder to do just that. Against such a possibility, try a preemptive strike, advises Peter Hauri, an eminent sleep researcher at Minnesota's Mayo Clinic and co-author of the book No More Sleepless Nights. Set aside a half hour during the day to let your mind wander, free associate, and dredge up worries. List them, along with how you will attack each. Then, when worrisome thoughts come creeping in the wee small hours (''Oh Lord, the Stottlemeyer account'') you can dismiss them with a wave of the plan (''Crawl to Stottlemeyer on hands and knees and beg forgiveness''). Resist the temptation to take sleeping pills. On this front attend to the opinion of the real experts -- the sleep disorder specialists -- rather than to, say, an internist who misguidedly writes you a renewable prescription for the latest Lethean draught: If you're taking sleeping pills more than once a week, you're probably taking them too often. If you're popping them every night, you've got a problem. On those occasions when their use may be warranted -- big presentation tomorrow, and you can't sleep tonight -- you're usually better off with a shorter-acting drug such as Halcion or Restoril than with a longer-lasting soporific like Dalmane, which can leave you a muzzball the next day. According to some experts, the biggest problem in treating sleepless executives is the execs' unwillingness to take time to improve sleep habits. What folly. How much better to view our ability to sleep as a sort of test of how in tune we are with the natural order. However expensive the pin stripes and silks on the outside, underneath there still pulses the body of a human being, an animal who needs to rest when darkness fills the sky.