Fascinating. An average 60 year old man sleeps for 20 years (considering a normal 8 hr a day sleep) that is 1/3 of his life. A polar bear and some other hibernating animals sleep for half of their lives. Amazingly polar bear is cognizant enough to feed her baby while she is sleeping.

Sleep also lowers the heart beat. It is generally accepted that all mammals have the same life span in number of hear beats. An elephant lives longer than a mouse because it's heart beats slower. Could that mean that people who live longer generally sleep more.

Whales are known to live for a long time. Wonder how much they sleep.