Another one on sleep

Here is another study on the amount of sleep needed:

This is exactly how much sleep you need - MarketWatch

Men need 7.8 hours per night and women need 7.6 hours, according to a study that tracked 3,760 people over seven years and published in the September issue of the journal Sleep.

and, more importantly

“A simple definition for sufficient sleep is a sleep duration that is followed by a spontaneous awakening and leaves the person feeling refreshed and alert for the day”