It's impossible to tell if someone is really awake without close medical supervision. People can take cat naps with their eyes open without even being aware of it.
Humans sleep on average around three hours less than other primates like chimps, rhesus monkeys, squirrel monkeys and baboons, all of whom sleep for 10 hours.
Teenagers should sleep 9 hours and young children require 10 hours of sleep.
If you lose two hours of sleep, you can impair your performance equal to a .05 blood-alcohol level.
The record for the longest period without sleep is 18 days, 21 hours, 40 minutes during a rocking chair marathon.
An average human will spend 1/3 or their life sleeping.
No-one knows for sure if other species dream but some do have sleep cycles similar to humans.
Ducks at risk of attack by predators are able to balance the need for sleep and survival, keeping one half of the brain awake while the other slips into sleep mode.
Snoring occurs only in non-REM sleep.
Some studies suggest women need up to an hour's extra sleep a night compared to men.
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