The human mind needs only 4 hours a sleep per night to maintain itself. Anything else is gravy.
That being said, I work for myself and have odd sleep schedules, but I get around 8-10 hours a night.
It's strange you should said that because I've been researching this topic recently & have you got any sources I could have a look at? I've read inbetween 5-6 at the moment but it states everyone requires different.