The Physics Factbook
Edited by Glenn Elert -- Written by his students
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|Myers, David G. "States of Consciousness." Psychology. 8th ed. Ed. Kevin Feyen, et al. New York: Worth, n.d. 279.||
|Sleep Disorders. Handbook of Disabilities. 2001. Curators of the University of Missouri & RCEP. 19 May 2007.||"Young children sleep 16 to 20 hours a day, adults sleep 7 to 8 hours a day, and the elderly sleep around 6.5 hours per day."
"On average, women between the ages of 30 and 60 sleep 6.5 hours per night according to a 1998 national Sleep Foundation poll."
|Dinges, David F., et al. Time Use for Sleeping in Relation to Waking Activities. 25. University of Pennsylvania School of Medicine. 19 May 2007.||
|Hofferth, Sandra L., and John F. Sandberg. Changes in American Children's Time, 1981-1997. Ed. T. Owens and S. Hofferth. Advances in Life Course Research. 2001. National Institute of Child Health and Human Development. 26 May 2007.||
|American Time Use Survey Summary. Bureau of Labor Statistics. 27 July 2006. United States Department of Labor, Washington. 26 May 2007.||"On an 'average day' in 2005, persons in the U.S. age 15 and over slept about 8.6 hours, spent 5.1 hours doing leisure and sports activities, worked for 3.7 hours, and spent 1.8 hours doing household activities.... By comparison, persons employed full time who worked on an average weekday spent 9.1 hours working, 7.6 hours sleeping, 3.0 hours doing leisure and sports activities, and 0.9 hours doing household activities."||7.6–8.6 hrs|
We spend about a third of our life sleeping. Sleep is irresistible and we inevitably surrender to its temptation. Sleep is a periodic, natural, reversible loss of consciousness that might have served an adaptive role in our ancestors' survival. When darkness made travel treacherous, our ancestors were more likely to leave descendants when asleep and out of harm's way.
Sleep also serves us in other ways. It helps us restore and repair brain tissue by giving resting neurons time to heal. Sleep also enhances memory. During REM sleep, the stage of the sleep cycle during which vivid dreams commonly occur, we sift, sort, and file the day's experiences in our memory. It promotes creative thinking; sleeping on a problem, we may gain insights on the solution more readily than those who stay awake. Last but not least, sleep helps in the growth process. During deep sleep, the pituitary gland is found to release a growth hormone.
Given this much, we now know why we sleep. The average adult sleeps 7 to 8.6 hours a day. Children sleep more than adults; they spent about 10 hours a day sleeping. Newborns, however, may sleep for nearly two-thirds of their day. There is an age-related difference in average time spent sleeping. As a person ages, they require less sleep. The elderly only spent around 6.5 hours a day sleeping.
The amount of time spent sleeping may be genetically influenced. Deprived of sleep, we run the risk of fatigue; depressed immune system; impaired concentration, creativity, and communication; irritability; and deteriorated performance. In the long-run, sleep deprivation may contribute to obesity, hypertension, and memory impairment.
Mimi Lim -- 2007
|Goldman, Bob. Brain fitness: anti-aging strategies for achieving super mind power. 1st Broadway Books trade pbk. ed. New York: Broadway Books, 2001: 96-97.||"According to a survey in American Demographic magazine, about 43 percent of adults who sleep less than six hours a night feel stressed, while just 14 percent of adults who sleep seven to eight hours a night feel stressed."||6â€“8 hours|
|"Sleep." World Book Encyclopedia. 2000 ed., Vol. 17. Chicago: World Book Inc., 2000: 506-507.||"Most adults sleep from 7 to 8.5 hours every night."||7â€“8.5 hours|
|Seppa, Nathan. Eight hours of sleep may not be so great. Science News, 2002.||"Doctors may recommend it for good health, but researchers now find that sleeping 8 to 9 hours a night doesn't necessarily translate into a longer life."||8â€“9 hours|
|Mercola, Joseph. Less Than 8 Hours of Sleep May Not Hurt Health. 27 February 2002.||"The study subjects, friends and family members of the American Cancer Society volunteers, were interviewed in 1982 about diet, exercise, sleep and health problems and then followed up six years later. Participants who reported sleeping 8 or more hours or less than 4 or 5 hours a night experienced a slightly higher chance of dying- at least a 15% increase in risk- within that time compared with those who slept 7 hours a night."||7â€“8+ hours|
|Saunders, Timothy. The Problems With Working More And Sleeping Less. 2002.||"Physicians recommend that the average adult get eight hours of sleep a night; however, in today's workaholic world, the average American sleeps seven hours a night and 30% sleep 6.5 hours or less."||6.5â€“8 hours|
Sleep is the period of rest in which the sleeper loses awareness of his or her surroundings. It is when all of a person's activity decreases and muscles relax. The heartbeat and the breathing rate slow down. During the first two to three hours of the sleep, the brain sends out larger and larger waves. This is when a person goes through a dreaming period. After the dreaming period, the brain sends out small, fast waves causing the person to be awake.
Sleep is very important in the well being of all living things, especially for a healthy human being. Sleep rests the brain so it can replenish itself for the next day's activities. A human being sleeps an average of seven to eight and a half hours a day. At least 6 hours of uninterrupted sleep is recommended. Six hours of refreshing, uninterrupted sleep is preferred over 10 hours of disturbed sleep. If a person sleeping is interrupted, the brain will become active. This prevents the brain from replenishing itself.
The time recommended for sleep varies with age. Seven to eight and a half hours of sleep is the time for an average adult. Children require more sleep than adults do. Babies recommend sleeping 15 hours a day. Kids ranging from ages 4 to 10 are recommended to have 9 to 13 hours of sleep. Children getting enough sleep will help them stay healthy in their growing process. On the other hand, elders at age 60 may only need 7 hours of sleep. There are many variables when it comes to "getting enough sleep". It varies and depends on age, special medical conditions, and how active you are.
Patrick Li -- 2002
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