Apparently a non trivial percent of the population gets by with 5-6 hours due to having a certain gene. I had assumed it was quite rare, but found out that I know several of them.
It is weird to say hi to my co-workers in the morning and they are all yawning and sucking down coffee, saying how tired they are. I just grin and realize I got around 1/2 the amount of sleep and drove 1.5 hours to work and not a drop of coffee has touched my lips.
They are more awake during the day than I am.