April 2006 Health Tip

Sleep: Your body's means of rejuvenation
What's going on in your body while you're dreaming?
Learn what sleep is and why you need it.
Source:  Mayo Clinic's Tools for Healthy Lives

Sleep ranks at the top of the list of human necessities — right along with air, water and food. It's more than a timeout from daily life or a passive retreat. A good night's sleep leaves you feeling refreshed, alert and ready to tackle the day's tasks.

When you don't get enough sleep, you may feel less alert and less vigorous and, perhaps, more confused, irritable and fatigued. Lack of sleep affects not only your energy level but also your mental and social functioning. You may find it more difficult to concentrate. You may find that you lose patience quickly, that you become less interactive in your relationships and that you become less productive at work.

What is sleep?

You likely spend about one-third of your life in the state of unconsciousness known as sleep. But what exactly is going on while you're catching some ZZZs? Probably more than you'd expect.

While sleeping, you move through six phases:

• Awake. It's normal to be awake for short periods during the night. Expect three to 10 brief arousals, though you probably won't remember each one. It's likely part of your body's defense mechanisms to keep you aware of what's going on around you.
  
  
• Stage one. During stage one, you sleep lightly and drift in and out of sleep. During this stage you're easily wakened. Your muscles begin to slow down and your eyes move very slowly.
  
  
• Stage two. In stage two, your muscles relax. Your brain waves slow down, though occasionally you have bursts of brain activity. You spend about half of your sleep in this stage.
  
  
• Stages three and four. Deep sleep sets in. Your brain waves become large and slow. Your breathing becomes rhythmic, and your muscles remain relaxed. At this point your body begins releasing reparative hormones. Stages one through four are referred to as non-rapid eye movement (NREM).
  
  
• Rapid eye movement (REM). During REM sleep your muscles stop moving completely. Your breathing and heart rate become rapid and irregular, your blood pressure is more variable, and your eyes move rapidly in bursts of activity. Your brain waves show a pattern similar to wakefulness. Scientists believe this indicates that your brain is using this time to sort and organize your memories. Dreaming takes place during this stage. If you're awakened during REM sleep, you may recall vivid dreams.

Throughout the night, you continuously move from one stage or type of sleep to another in cycles that can last from 70 to 90 minutes each. Early REM periods are very short, however, usually 5 to 10 minutes long. You may experience several longer REM periods as the night progresses.

Sleep patterns

The natural pattern of waking and sleeping that occurs within a 24-hour day is part of your circadian rhythm. Your circadian rhythm is regulated by a biological clock in your brain that usually makes you sleepy at night and ready to wake up in the morning. Your surroundings, including your exposure to sunlight, help synchronize your biological clock. Your biological clock regulates your body temperature and many of your hormones.

Most people's clocks run on a cycle of about 24 hours, but individual clocks vary. When your natural circadian rhythm is upset — for example, by spending too long in bed, traveling across time zones or experiencing a few nights of insomnia — sleep can become difficult.

For most people a night or two of poor sleep, or even a night of no sleep, isn't that bad. As long as you get back to a normal sleep schedule within a few days, you'll experience no lasting consequences. One good night of sleep after a few poor ones usually is enough to catch up.

What happens when you can't catch up?

Chronically losing sleep results in sleep debt, which can lead to serious consequences. Sleep debt is cumulative, and even small nightly sleep losses can add up to affect your daytime function. Possible consequences include increased accidents and poor performance on the job or in school.

Long-term sleep deprivation can affect your physical and mental health. Sleep helps bolster your immune system so that you can fight off viruses and bacteria. After a few nights of absolutely no sleep, some people begin hallucinating.

Will napping help?

The urge for a midday nap is built into your body's biological clock. Usually between 1 p.m. and 4 p.m. you experience a slight drop in your body temperature, indicating nap time.

If you're not getting enough sleep, napping may or may not help. The best solution is to go to bed earlier. If that's not possible, a daytime nap might give you the boost you need, helping you feel more energized and alert. If you have insomnia, though, a daytime nap may make sleeping at night more difficult.

To discover how naps affect your energy level and the quality of your nighttime sleep, do an experiment. Take a daily nap for a week. The next week, don't nap.

Every morning, rank your sleep quality on a 10-point scale. Every evening, rate your day on a similar scale. After two weeks, judge whether naps work for you.

If you do nap, keep it short — limit it to 20 or 30 minutes late in the morning or in the mid afternoon. And don't rely on naps to keep you going. Try to get enough sleep to avoid building a sleep deficit.

Don't be embarrassed about your need for sleep

In today's busy world you may find that others tease you or make light of your need for sleep. But in reality, sleep is just as important as the activities you perform during your waking hours. If you routinely have trouble falling asleep or staying asleep, talk to your doctor about what you can do about it.

Common causes of insomnia include:

• Stress. Concerns about work, school, health or family can keep your mind too active, making you unable to relax. Excessive boredom, such as after retirement or during a long illness, may occur and also can create stress and keep you awake.
  
  
• Anxiety. Everyday anxieties as well as severe anxiety disorders may keep your mind too alert to fall asleep.
  
  
• Depression. You may either sleep too much or have trouble sleeping if you're depressed. This may be due to chemical imbalances in your brain or because worries that accompany depression may keep you from relaxing enough to fall asleep when you want to.
  
  
• Stimulants. Prescription drugs, including some antidepressant, high blood pressure and corticosteroid medications, can interfere with sleep. Many over-the-counter (OTC) medications, including some pain medication combinations, decongestants and weight-loss products, contain caffeine and other stimulants. Antihistamines may initially make you groggy, but they can worsen urinary problems, causing you to get up more during the night.
  
  
• Change in your environment or work schedule. Travel or working a late or early shift can disrupt your body's circadian rhythms, making you unable to get to sleep when you want to. The word "circadian" comes from two Latin words: "circa" for "about" and "dia" for "day." Your circadian rhythms act as internal clocks, guiding such things as your wake-sleep cycle, metabolism and body temperature.
  
  
• Long-term use of sleep medications. Doctors generally recommend using sleeping pills for no more than four weeks, or until you notice benefits from self-help measures. If you need sleep medications for longer, take them no more than two to four times a week, so they don't become habit-forming. Sleeping pills often become less effective over time.
  
  
• Medical conditions that cause pain. These include arthritis, fibromyalgia and neuropathies, among other conditions. Making sure that your medical conditions are well treated may help with your insomnia.
  
  
• Behavioral insomnia. This may occur when you worry excessively about not being able to sleep well and try too hard to fall asleep. Most people with this condition sleep better when they're away from their usual sleep environment or when they don't try to sleep, such as when they're watching TV or reading.
  
  
• Eating too much too late in the evening. Having a light snack before bedtime is OK, but eating too much may cause you to feel physically uncomfortable while lying down, making it difficult to get to sleep. Many people also experience heartburn, a backflow of acid and food from the stomach to the esophagus after eating. This uncomfortable feeling may keep you awake.
  
  
• Inherited condition. Some people have inherited poor sleep tendency. If that's your case, be extremely careful not to overexcite yourself, especially in the evening.

Insomnia becomes more prevalent with age. As you get older, changes can occur that may affect your sleep. You may experience:

• A change in sleep patterns. After age 50, sleep often becomes less restful. You spend more time in stages 1 and 2 of non-rapid eye movement (NREM) sleep and less time in stages 3 and 4. Stage 1 is transitional sleep, stage 2 is light sleep, and stages 3 and 4 are deep (delta) sleep, the most restful kind. Because you're sleeping more lightly, you're also more likely to wake up. With age, your internal clock often speeds up. You get tired earlier in the evening and consequently wake up earlier in the morning.
  
  
• A change in activity. You may be less physically or socially active. Activity helps promote a good night's sleep. You may also have more free time and, because of this, drink more caffeine or alcohol or take a daily nap. These things can also interfere with sleep at night.
  
  
• A change in health. The chronic pain of conditions such as arthritis or back problems as well as depression, anxiety and stress can interfere with sleep. Older men often develop noncancerous enlargement of the prostate gland (benign prostatic hyperplasia), which can cause the need to urinate frequently, interrupting sleep. In women, hot flashes that accompany menopause can be equally disruptive. Other sleep-related disorders, such as sleep apnea and restless legs syndrome, also become more common with age. Sleep apnea causes you to stop breathing periodically throughout the night and then awaken. Restless legs syndrome causes unpleasant aches in your legs and an almost irresistible desire to move them, which may prevent you from falling asleep.

Sleep problems may be a concern for children and teenagers as well. In addition to many of the same causes of insomnia as those of adults, younger people may have trouble sleeping because of conditions such sleepwalking, night terrors or teeth grinding (bruxism). In addition, some children and teenagers simply have trouble getting to sleep or resist a regular bedtime, often because their inherent (circadian) clocks are set later.

When the clock on the wall says it's 10 p.m., their bodies may feel like it's only 8 p.m., because of their delayed clocks.