A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
Lack of water is the #1 trigger of daytime fatigue.
148
The average cat sleeps about 2/3 of the day.
203
One reason that kittens sleep so much is because a growth hormone is released only during sleep.
212
The harder you concentrate on falling asleep, the less likely you are to fall asleep.
34
The average person falls asleep in seven minutes.
115
The human brain is more active during sleep than during the day.
28