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Last Updated: Aug 6th, 2008 - 09:50:39 |
NINDS Hypersomnia Information Page
Hypersomnia is characterized by recurrent episodes of excessive daytime sleepiness or prolonged nighttime sleep. Different from feeling tired due to lack of or interrupted sleep at night, persons with hypersomnia are compelled to nap repeatedly during the day, often at inappropriate times such as at work, during a meal, or in conversation.
NINDS Kleine-Levin Syndrome Information Page
Kleine-Levin syndrome is a rare disorder that causes recurring periods of excessive drowsiness and sleep (up to 20 hours per day). Symptoms, which may last for days to weeks, include excessive food intake, irritability, disorientation, lack of energy, and hypersensitivity to noise.
NINDS Narcolepsy Information Page
Narcolepsy is a chronic neurological disorder caused by the brain's inability to regulate sleep-wake cycles normally. At various times throughout the day, people with narcolepsy experience fleeting urges to sleep.
NINDS Sleep Apnea Information Page
Sleep apnea is a common sleep disorder characterized by brief interruptions of breathing during sleep. These episodes usually last 10 seconds or more and occur repeatedly throughout the night.
Sleep and Circadian Rhythms
Circadian rhythms are 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." This clock, called the suprachiasmatic nucleus or SCN
Narcolepsy Fact Sheet
Narcolepsy is a chronic neurological disorder caused by the brain's inability to regulate sleep-wake cycles normally. At various times throughout the day, people with narcolepsy experience fleeting urges to sleep. If the urge becomes overwhelming, patients fall asleep for periods lasting from a few seconds to several minutes. In rare cases, some people may remain asleep for an hour or longer.
Can't Sleep? Science Is Seeking New Answers
A good night's sleep is more than a luxury. Sleep is as important to survival as food and water. On too little, we humans don't function well--for example, we run a higher risk of accidents, we sometimes perform poorly at work or school, and our moods can turn sour.
What Does Sleep Do For Us?
Although scientists are still trying to learn exactly why people need sleep, animal studies show that sleep is necessary for survival. For example, while rats normally live for two to three years, those deprived of REM sleep survive only about 5 weeks on average, and rats deprived of all sleep stages live only about 3 weeks. Sleep-deprived rats also develop abnormally low body temperatures and sores on their tail and paws. The sores may develop because the rats¡¯ immune systems become impaired. Some studies suggest that sleep deprivation affects the immune system in detrimental ways.
How Biological Clocks Work
Anyone who has traveled has experienced jet lag¡ªthat groggy realization that while your day is beginning in Washington, D.C., the night you just left in San Francisco is hardly over. Jet lag is an inconvenient reminder that the body is set to a 24-hour clock, known by scientists as circadian rhythms, from the Latin circa dies, "about one day." An internal biological clock is fundamental to all living organisms, influencing hormones that play a role in sleep and wakefulness, metabolic rate, and body temperature.
Brain Basics: Understanding Sleep
Do you ever feel sleepy or "zone out" during the day? Do you find it hard to wake up on Monday mornings? If so, you are familiar with the powerful need for sleep. However, you may not realize that sleep is as essential for your well-being as food and water.
What Is Narcolepsy?
Narcolepsy (NAR-ko-lep-see) is a disorder that causes a person to have difficulty staying awake. In extreme cases, narcolepsy can cause a person to suddenly fall asleep during the day. These ¡°sleep attacks¡± occur even after getting enough sleep at night. The unusual sleep pattern that people with narcolepsy have can affect their schooling, work, and social life.
Sleep and Disease
Sleep and sleep-related problems play a role in a large number of human disorders and affect almost every field of medicine. For example, problems like stroke and asthma attacks tend to occur more frequently during the night and early morning, perhaps due to changes in hormones, heart rate, and other characteristics associated with sleep. Sleep also affects some kinds of epilepsy in complex ways. REM sleep seems to help prevent seizures that begin in one part of the brain from spreading to other brain regions, while deep sleep may promote the spread of these seizures. Sleep deprivation also triggers seizures in people with some types of epilepsy.
How Much Sleep Do We Need?
The amount of sleep each person needs depends on many factors, including age. 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. Getting too little sleep creates a "sleep debt," which is much like being overdrawn at a bank. Eventually, your body will demand that the debt be repaid. We don¡¯t seem to adapt to getting less sleep than we need; while we may get used to a sleep-depriving schedule, our judgment, reaction time, and other functions are still impaired.
Sleep: A Dynamic Activity
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.
Dreaming and REM Sleep
We typically spend more than 2 hours each night dreaming. Scientists do not know much about how or why we dream. Sigmund Freud, who greatly influenced the field of psychology, believed dreaming was a "safety valve" for unconscious desires. Only after 1953, when researchers first described REM in sleeping infants, did scientists begin to carefully study sleep and dreaming. They soon realized that the strange, illogical experiences we call dreams almost always occur during REM sleep. While most mammals and birds show signs of REM sleep, reptiles and other cold-blooded animals do not.
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