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Tuesday, November 23, 2004
Why we need to sleep
By Henrylito D. Tacio
Health 101
GRAND RAPIDS, Minnesota -- Does it often take you more than 30 minutes to fall asleep at night? Or do you wake up frequently during the night--or too early in the morning--and have a hard time going back to sleep? When you awaken, do you feel groggy and lethargic? Do you feel drowsy during the day particularly during monotonous situations?
Until the 1950s, most people thought of sleep as a passive, dormant part of our daily lives. We now know that our brains are very active during sleep. Moreover, sleep affects our daily functioning and our physical and mental health in many ways that we are just beginning to understand.
"To sleep--perchance to dream," wrote William Shakespeare in his masterpiece play, "Hamlet.' It's a nice concept. However for many men, women and children, the elusive road to slumberland is anything but a dream.
In the United States, surveys conducted by the National Sleep Foundation (NSF) reveal that 60 percent of adults report having sleep problems a few nights a week or more. In addition, more than 40 percent of adults experience daytime sleepiness severe enough to interfere with their daily activities at least a few days each month--with 20 percent reporting problem sleepiness a few days a week or more.
Why do you sleep and what happens when you sleep? Sleep is not merely a "time out" from our busy routines; it is essential for good health, mental and emotional functioning and safety. For instance, researchers have found that people with chronic insomnia are more likely than others to develop several kinds of psychiatric problems, and are also likely to make greater use of healthcare services.
People suffering from sleep apnea are likely to have higher blood pressure while they sleep and suffer from excessive daytime sleepiness. Recently, scientists have come to recognize that sleep is regulated by two entirely different systems. One system is the sleep homeostat. This functions like a drive that "builds up during wakefulness in pretty much a linear fashion and is discharged when you sleep," explains Dr. Arthur Spielman, associate director of the Center for Sleep Medicine at New York Presbyterian-Cornell Medical College.
The homeostatic pressure to sleep depends not only on how long you are awake but on how active you are while awake. But if you build up a need for sleep in a linear fashion, one would think you'd get sleepier as the day proceeds. It doesn't happen quite that way. Enter circadian rhythms, the regular changes in mental and physical characteristics that occur in the course of a day (circadian is Latin for "around a day"). Most circadian rhythms are controlled by the body's biological "clock."
"The circadian system is tied, albeit imperfectly, to cycles of light and dark," informs Hara Estroff Marano, editor-at-large of 'Psychology Today.'
"We have dedicated sensors on the retina that deliver the daytime/nighttime message directly to the pineal gland tucked deep inside the brain. In response to darkness, this tiny nodule of brain tissue produces the sleep-inducing hormone melatonin, broadcasting the sandman's message to brain areas that govern everything from body temperature to protein synthesis to hormone production to alertness."
Circadian rhythm guides the body through cycles of sleep and alertness. Ironically, it tissues its strongest alerting force in a burst lasting from 6 p.m. to 8 p.m., perfect for dinner-party repartee. After 8 p.m., alertness begins to fade, permitting a person to doze off. This same system makes you sleepiest in the early morning, from 4 a.m. to 6 a.m.
When travelers pass from one time zone to another, they suffer from disrupted circadian rhythms, an uncomfortable feeling known as jet lag. For instance, if you travel from Manila to Ohio, you "lose" 12 hours according to your body's clock. You will feel tired when the alarm rings at 8 a.m. the next morning because, according to your body's clock, it is still 8 p.m. It usually takes several days for your body's cycles to adjust to the new time.
How much sleep do we need? "The amount of sleep each person needs depends on many factors, including age," says the NSF. Infants generally require about 16 hours a day, while teenagers need about 9 hours on average.
For most adults, 7 to 8 hours a night appears to be the best amount of sleep, although some people may need as few as 5 hours or as many as 10 hours of sleep each day. Women in the first 3 months of pregnancy often need several more hours of sleep than usual. The amount of sleep a person needs also increases if he or she has been deprived of sleep in previous days.
(November 23, 2004 issue)
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