47% of people have a nightmare at least once a month.
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A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
Sleeping on your stomach can induce weirder, scarier, and sexier dreams.
22
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.
15
Sea otters hold hands while sleeping so they don’t drift away from each other.
104
One reason that kittens sleep so much is because a growth hormone is released only during sleep.
212
"Dysania" is the state of finding it hard getting up out of bed in the morning.
33