Studies show that the colder the room you sleep in, the more likely you are to have a bad dream.
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Blue light fends off drowsiness in the middle of the night, which could be useful to people who work at night.
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You forget 90% of your dreams.
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Cows can sleep standing up, but they can only dream lying down.
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Some people have a "natural alarm clock" allowing them to wake up when they want. This is actually caused by a burst of the stress hormone adrenocorticotropin.
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