A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
Termites work 24 hours per day and they do not sleep.
57
People who sleep late have more mental stamina and can outperform early risers.
33
The human brain is more active during sleep than during the day.
28
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
The harder you concentrate on falling asleep, the less likely you are to fall asleep.
34
You burn more calories sleeping than you do watching television.
348