[the-smug-one]

The amount of sleep required depends on the person and their living situation.

I normally feel best on 7-8 hours of sleep. When training hard I require 9 hours.

There are genetic outliers who require less sleep (google it).

Anecdotally: I have a friend who performs like anyone else, but only requires around 5-6 hours of sleep. I've known him for over a decade now, he seems to be doing fine.

[wincy]

I just watched Iron Lady last night and Margaret Thatcher slept 4 hours a night almost every night for her entire life, and lived well into her 80s.

[BirdieNZ]

She also got dementia. There is some evidence that lack of sleep contributes to the development of Alzheimer's and dementia.