WHAT IS A GOOD NIGHT'S SLEEP?
Many people would reply by saying a minimum of eight hours of rest. But the answer doesn't depend solely on how many hours you log in bed. Night after night, you need deep uninterrupted sleep in a bed that provides adequate comfort support and space. What matters most of all is how you feel in the morning. If you wake up full of renewed energy, you've had a good night's sleep.
There is no one formula for how much sleep is enough for you. Expecting all people to need the same amount of rest would be as absurd as expecting them to eat the same amount of food every day. Each of us seems to have an innate sleep "appetite" that is as much a part of our genetic programming as hair color, height and skin tone. Normal sleep times range from five to ten hours; the average is 7 1/2. About one or two people in one hundred can get by with just five hours; another small minority needs twice that amount.
How much sleep is enough for you? To figure out your sleep needs, keep your wake-up time the same every morning and vary your bedtimes. Are you groggy after six hours of shut-eye? Does an extra hour give your more stamina? What about an extra two hours? Since too much time in bed can make some people feel sluggish, don't assume that more is always better. Listen to your body's signals and adjust your sleep schedule to suit them.

Keep in mind that sleep needs change with age. And the older you are, the less total sleep time you may need. A newborn may spend 18 hours asleep. From infancy to adulthood, sleep decreases by more than half. Throughout the middle decades of life, seven or eight hours of sleep generally are needed to provide adequate rest. For older individuals, six hours may suffice.

WHAT HAPPENS DURING SLEEP?
Many people think of their sleeping bodies as if they were cars parked for the night--motionless, engines off, headlights dimmed. But sleep is an amazingly complex state of being. As we sleep, muscles tense and relax. Pulse, temperature and blood pressure rise and fall. Chemicals crucial for well-being course through the blood stream. The brain, like a Hollywood director, conjures up fantastic stories, complete with a plot, characters and action.

You don't simply "fall" asleep. You descend slowly through different levels. As you close your eyes and drift off, you enter the first stage of what is called quiet sleep. Your brain produces irregular, rapid waves, and muscle tension decreases. You breathe smoothly, and mundane thoughts float through your mind. If roused, you might jerk awake quickly and deny that you'd slept at all.

In stage 2 of quiet sleep, your brain waves become larger, punctuated by occasional sudden bursts of electrical activity. You've definitely crossed the border between wakefulness and sleep. If someone lifted your eyelids gently, you wouldn't waken; your eyes no longer respond to stimuli.

As you descend into stage 3, your brain waves become slower and bigger. In this state of deep slumber, your bodily functions slow down even more. Finally stepping into stage 4, you reach deepest sleep, the most profound state of unconsciousness. On an EEG (electroencephalogram), your brain waves would appear extremely large and slow. You are so "dead to the world" that a thunderstorm might not wake you.

This step-by-step journey into oblivion usually takes more than an hour. Then you begin to climb upward, moving rapidly through the same sleep stages as before, not all the way to full wakefulness but in active sleep. Because the pupils dart back and forth, this stage is called Rapid Eye Movement or REM sleep. (The four stages of quiet sleep are often referred to as non-REM or NREM sleep.)

During REM, your brain waves resemble those of waking rather than of quiet sleep. The large muscles of your torso, arms and legs are paralyzed, although your fingers and toes may twitch. You breathe quickly and slowly, the flow of blood through your brain accelerates. REM sleep is the time of vivid dreaming, and if wakened, you'd probably recall a fragment of a fantasy.

After about ten minutes in REM sleep, you descend the sleep staircase again. The entire cycle of REM and NREM stages takes roughly 90 minutes. Early in the night, the periods spent in the deepest stages of quiet sleep are longer. In the second half of the night, REM sleep predominates. By morning, you go around the sleep circuit four or five times. This pattern changes gradually throughout life. From infancy to adulthood, REM periods dwindle to less than a quarter of a night's sleep. By their thirties, men spend less time in the very deep stages of NREM sleep. Women begin to sleep less deeply in their fifties. By age 65, both sexes spend half as much time in deep sleep as they did when they were 25. The lighter sleep stages increase later in life, and REM shrinks to about a fifth of total sleep time.

BAD NIGHTS/BAD DAYS
What happens when you don't get the rest you need? The first casualty of too little sleep is a smile. Weariness breeds irritability and depression. Sleepy people mope instead of cope, snap at co-workers, complain about anything and everything. While everyone around them may be laughing, they're yawning.

But bad moods aren't the only consequence of bad nights. Without adequate sleep, people can't perform at their peak. Every half an hour less sleep than usual can impair the way you feel and function the next day. The more sleep you lose, the more you suffer.

According to a recent study, one sleepless night sabotages creativity and coping skills. Without sleep, the "walking wounded" are less spontaneous, flexible and original. Unable to break out of intellectual ruts or come up with a fresh perspective, they become rigid, stick to tried-and-true approaches to problems and can't deal with unfamiliar situations. If they concentrate hard enough, they can perform routine tasks or well-known, well defined emergencies--unless they lose a second night of sleep. Then even performance of mundane or familiar chores suffers.

Chronic insomniacs have more problems getting started in the morning than normal sleepers and often feel so exhausted after work that they forego leisure activities and social engagements. The stress of trying to perform well despite their sleeplessness may lead to depression and other psychological problems. Individuals with chronic sleep problems that cause excessive daytime drowsiness, such as the breathing disorder called sleep apnea, may have so much difficulty with attention, concentration or memory that they perform as if their IQs were ten points lower than they actually are.

The best solution may be the most obvious: more and better sleep. In a study at Detroit's Henry Ford Hospital, sleep researchers found that healthy people who slept just one additional hour felt better, became more alert and performed better on the job. Their conclusion: "Ideally, you should sleep until you're slept out. You should awaken spontaneously without an alarm clock and feel fresh and vital in the daytime."

WHEN YOU CAN'T SLEEP
Sometimes all you need to feel better is a good night's sleep, but when you tuck yourself in for the night, nothing happens. Your bed is comfortable. Your room is cool, But you can't fall asleep. What can you do when you find yourself stranded at the edge of night?

Snack on a snooze food. As scientists have learned more about the effects various chemicals have on the brain, they've identified foods that make us alert and others that make us drowsy. Proteins, such as meat, are energizers, while carbohydrates, such as pasta, are sedatives. In one study at MIT the foods that made volunteers drowsiest at bedtime were English muffins and bananas.

Sip a nightcap. Stay away from the alcoholic variety. Warm milk soothes some sleepless souls. Warm herbal teas, particularly those with chamomile or ginseng, can also make you feel drowsy.

Get wet and warm. A bath that's neither too hot nor too cold can induce sleepiness by sending blood away from the brain to the skin surface. Lie back. Close your eyes. Imagine yourself floating in the tub.

Relax your muscles. One of the best techniques is progressive muscle relaxation (PMR), which involves alternate tensing and relaxing. Focus your attention on a specific group of muscles, such as those in your arm. Tense tightly for five to seven seconds, then release for 15 to 20 seconds and repeat with other muscle groups.

Learn a little yoga. These gentle exercises can loosen tense muscles and help you relax. Here's one you can do on your mattress: Inhale to a count of five, raise your arms backward over your head until they touch the mattress. Make two fists. Raise your buttocks. Tense and stretch every muscle in your body including those of your face. Hold for a count of five. Release, keeping arms over head. With eyes closed, let the tension drain from your body. Each night, try to increase the time you spend in this position.

Breathe deeply. Take five deep breaths, counting to yourself with each one. As you count, tell yourself, "I'm getting more relaxed and peaceful. I am slowly falling asleep." Concentrate on this message. If you wake up during the night, immediately take a deep breath and tell yourself, "I'll be asleep again soon."

Get up. If you're not asleep within ten minutes of shutting off the light, leave your bed, go into another room and read or listen to music. When you start feeling drowsy, go back to bed. Once again, if you don't nod off within ten minutes, get up again. The goal: to associate your bed with slumber, not sleeplessness.

Hypnotize yourself. Many people use a form of self-hypnosis to fall asleep. As you lie in bed, breathe deeply, relax your muscles and repeat a simple message, such as, "I am getting sleepy. I am getting sleepy. I am getting sleepy."

Try to stay awake. This approach, called paradoxical intention, may sound contradictory. Rather than worrying about falling asleep fast, you tell yourself you're going to stay awake as long as you can. With the pressure off, you can stop worrying and start sleeping.

Cut back on your sleep time. If you force yourself to spend less time in bed, a technique called sleep restriction, your body becomes more efficient at sleeping. Insomniacs, who often spend hours in bed trying to sleep, fall asleep faster and wake less frequently when their total sacktime is limited.

Play mind games. If your body is weary, but your mind is racing, some mental maneuvers can speed your way to sleep:

Count sheep -- or ducks, or peacocks, or zebras. You can distract both halves of your brain by conjuring up a detailed picture of how they look while counting how many are skipping through your mind.

Play alphabet games. List girls' names, boys' names, states, countries, trees, flowers, food, presidents, animals, and so on, in alphabetical order.

Imagine yourself painting a tall, long wall with a tiny brush. Count your strokes as you dab on the paint.

Imagine you've just won one million dollars in the lottery. Make plans for saving and spending it.

Tell yourself that if you don't fall asleep, you'll have to get up and do an unpleasant chore. (You may have to make good on this threat for a few nights.)

Name every city, then every country, that begins with q, z, or y.