People who don't get enough sleep show higher levels of inflammation, say scientists who study colds. Smoking, chronic stress and lack of exercise can make you more susceptible to the viruses, too. Frederic Cirou/PhotoAlto/Corbis hide caption

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Michael Arnott, of Cambridge, Mass., says he used to have trouble staying awake on long drives. Sleep specialists discovered he has obstructive sleep apnea, though not for the most common reasons — he isn't overweight, and doesn't smoke or take sedatives. M. Scott Brauer for NPR hide caption

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Sleepy in the day and wide awake at night? Give the screen a rest. Guido Mieth/Getty Images/Flickr RM hide caption

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About 40 percent of high schools start before 8 a.m., which contributes to chronic sleep deprivation among teens, according to the American Academy of Pediatrics. Chris Waits/Flickr hide caption

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Teenagers' sleep patterns may be a clue to their risk of depression. iStockphoto hide caption

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Daniel Horowitz for NPR

Solid friendships can help buffer life's stress. iStockphoto hide caption

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Maggie Starbard / NPR

It may not be the best strategy to stay up late and cram. A new study finds that when teens don't get the sleep they need, all kinds of things can go poorly. hide caption

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Jealous? If you have trouble sleeping, several new apps and devices promise to help you figure out why. In this photo from January, Huan Huan, a female giant panda, sleeps in a zoo in Beauval, France. Franck Prevel/Getty Images hide caption

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Sleepy police were likelier to fall asleep while driving, a new survey of nearly 5,000 officers in the U.S. and Canada finds. About 40 percent of officers surveyed reported sleep disorders, with various health implications. Sean Locke/iStockphoto hide caption

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Sleep researchers say parents of a new child can be a risk for long-term insomnia. Timothy M. Black/ hide caption

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