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
Studies show that the colder the room you sleep in, the more likely you are to have a bad dream.
28
The human brain is more active during sleep than during the day.
28
Cows can sleep standing up, but they can only dream lying down.
745
The record for the longest scientifically documented period without sleep is 264.4 hours (eleven days).
15
You burn more calories sleeping than you do watching television.
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