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Why Do We Sleep?

By Blondell Peterson
June 2005

Does your battery run down midafternoon? Do you find it hard to focus during the day? Do you find yourself reaching for chocolate or a caffeinated beverage? Chances are, like 72% of adults, you are sleep deprived because of a sleep disorder.

Dr. Bradley V. Vaughn, Associate Professor of Neurology, UNC, conducted a sleep disorders seminar as part of the NIEHS Fitness Week activities. Attendees filled the room to capacity and were jokingly challenged, by Dr. Bradley, to stay awake during the post-lunch presentation. At the same time, he continually illustrated through examples, that many of those attending the seminar had undesirable sleep patterns or lifestyle habits that contribute to sleep deprivation.

"The common question that I get," said Dr. Vaughn, "is why do we sleep?" "We sleep to improve our ability to perform while we are awake," he said. "If you are not sleeping, you are not going to have the best performance during the day. We sleep to be awake."

He gave an example through a video from the inside of a cab driver's cab. The driver, although he survived, was thrown around the inside of the vehicle and landed in the back seat with both feet in the air, as epithets were heard throughout the thrashing. This happened all because he fell asleep while driving. According to Dr. Vaughn, about 15 to 25 percent of automobile accidents occur because the drivers are either inattentive, asleep or drowsy, and sleep related accidents cost us 150 billion dollars a year.

He cited several major accidents that were attributed to lack of sleep. The third mate who was steering the ship that ran aground onto a reef in the Exxon Valdese accident admitted to being awake over 24 hours. The Chernobyl accident occurred at 1:23 a.m. The engineer who made the decision to launch the Space Shuttle Challenger amid concerns that the "o" rings might not tolerate extreme cold, did so at 5:20 a.m. and admitted to sleeping less than three hours per night for the three weeks prior to that decision. In the Three Mile Island disaster, the critical decision that led to the meltdown occurred at 4 a.m. for a crew that was working on their second week of third shift work.

The majority of deep sleep is in first half of the night and the majority of the dream sleep is in the latter half of the night. This evolution is one of the reasons that four 1 hour naps do not equal four hours of continuous sleep. "If you think you are going to catch up on your sleep by taking a series of naps, you're wrong, because you are not allowing this evolutionary process to take place," he said.

About one in three people have a complaint with their sleep to the degree that they will bring it to the attention of their physician. According to the National Sleep Foundation, 72% of individuals will describe a problem with their sleep. One in six people say they have trouble performing during the day because of sleepiness. We are now getting into the range where it's normal to have a problem with your sleep.

There are currently 117 different recognized sleep disorders. Sleep debt is the major reason, for excessive sleepiness during the day. Other reasons are disruption of sleep, trouble with the brain or a problem with the body clock. "We have an inherent body clock because we live in a world that rotates, so we perform best during daytime and sleep best during night time. If that clock gets out of whack with the rest of the world, we can have a problem with how we perceive ourselves during the day."

According to Vaughn, 17 to 18 hours of continuous wakefulness is equivalent to having a blood alcohol level of .08 which in this state is legally intoxicated. Long periods of wakefulness impair the ability to think and perform. Not only does it have an affect on performance, but it also has an incredible affect on the rest of the body. "How many of you gained 10 pounds in the last 15 years?" he asked. Of those of you who have your hands up, how many sleep less than 7 hours a night? Guess what, you accelerated your weight gain---just by shortening your sleep." Even an hour short of sleep per night will increase ghrelin and decrease leptin. Leptin is the hormone put off by fat cells that tells the body it does not need to eat. Ghrelin tells the body to eat. When you eat high caloric food when you are sleep deprived, you will gain weight. One hour per night will result in a five pound weight gain on the average for every six months.

"If you need 8 hours of sleep and only get 7, after the first night, you only lost an hour. After a year, you've lost 365 hours and after 10 years, you have lost 3,650 hours. "How many of you think you're going to pay off 3,650 hours in a weekend?" he asked. "It ain't gonna work." Vaughn said this is very similar to borrowing money from a bank. If you owe a big debt to the bank, you will cut corners to pay the bank back. Falling asleep (at stoplights, reading, driving, during conversation, during sex) at inopportune times are indications that you are sleep deprived and your brain is trying to pay off the debt."

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