A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
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Studies show that the colder the room you sleep in, the more likely you are to have a bad dream.
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The record for the longest scientifically documented period without sleep is 264.4 hours (eleven days).
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"Dysania" is the state of finding it hard getting up out of bed in the morning.
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Those who get out of bed by 7am are more likely to be thinner and happier.
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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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People who sleep late have more mental stamina and can outperform early risers.
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Sleeping on your stomach can induce weirder, scarier, and sexier dreams.
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