How much do you know about sleep?

Couple in bedroom. (iStockphoto)
Couple in bedroom. (iStockphoto)

This is a summary of an article written by Dr. Till Roenneberg, a professor of chronobiology and medical psychology at the Ludwig-Maximilians University in Munich, and published in the Washington Post on November 21 2012 titled, “Five myths about sleep.” Roenneberg is the author of “Internal Time: Chronotypes, Social Jet Lag, and Why You’re So Tired.”

Roenneberg says, “We spend between a quarter and a third of our lives asleep, but that doesn’t make us experts on how much is too much, how little is too little, or how many hours of rest the kids need to be sharp in school.”

First myth Roenneberg would like to debunk is – you need eight hours of sleep per night. He quotes Napoleon, who said, “Six hours for a man, seven for a woman and eight for a fool.” But this is not correct either. The truth is the ideal amount of sleep is different for everyone and depends on many factors, including age and genetic makeup.

Roenneberg’s research team has surveyed sleep behavior in more than 150,000 people. About 11 percent slept six hours or less, while only 27 percent clocked eight hours or more. The majority fell in between. Women tended to sleep longer than men, but only by 14 minutes.

When comparing various age groups – ten-year-olds needed about nine hours of sleep, while adults older than 30, including senior citizens, averaged about seven hours. Roenneberg’s team identified the first gene associated with sleep duration – if you have one variant of this gene, you need more sleep than if you have another.
Roenneberg says that we generally cannot oversleep. When we wake up unprompted, feeling refreshed, we have slept enough. In our industrial society we sleep about two hours less per night than 50 years ago and this significantly decreases our work performance and compromises our health and memory.

Second myth – early to bed and early to rise makes a man healthy, wealthy and wise. There was some truth in this when most of the work was done outdoors in natural light. The timing of sleep – earlier or later – is controlled by our internal clocks, which determine our optimal “sleep window.” With the widespread use of electric light, our body clocks have shifted later while the workday has essentially remained the same, says Roenneberg. This leaves us chronically sleep deprived.
Studies show that teenagers who sleep later and start school later exhibit improved academic performance, higher motivation, decreased absenteeism and better eating habits.

Third myth – exercise helps you sleep. Exercising may contribute to falling asleep earlier, and it certainly helps us sleep soundly through the night, says Roenneberg. But it’s exposure to light, not physical activity, that synchronizes our body clocks with daylight. Sleep is not only regulated by the body clock, but also by how long we were awake (also known as the buildup of “sleep pressure”).

Fourth myth – sleep is just a matter of discipline. Parents who think that putting their children early to bed will make it easier for them to wake up early in the morning will be disappointed. Roenneberg says early-to-bed teenagers will still have a hard time getting up at the crack of dawn. They go to school at their biological equivalent of midnight with profound consequences for learning and memory. Teenagers should sleep with daylight coming into their bedrooms and should refrain from using light-emitting devices after 10 p.m.

Fifth myth – most couples have very different sleep habits. Roenneberg says this is a matter of biology and genetics, not habits and personal preference. Women generally fall asleep earlier than men. Women, however, tend to control the sleep times in a partnership. Given how much time we spend in our beds, men and women don’t seem to give any consideration to sleep patterns when choosing a mate, concludes Roenneberg.

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