Quantity required

There's no such thing as a standard sleep requirement, although it's fair to say that most of us need between 7h30 and 8h of sleep a night. Our needs are largely genetically determined, and generally remain constant throughout our lives. Sleep : 

In fact, we can only claim to have had enough sleep if, in the morning, we wake up feeling not only well-rested but also refreshed and fit. For this, some will need more than 9h (or even 12h, like Einstein), others less than 6h.

Very often, work, family, leisure activities, habits, etc., force us to make compromises with our basic need for sleep. Even if they are sometimes unavoidable, these compromises must remain as limited and rare as possible, as they risk degrading our biological rhythms and leading to fatigue, discomfort and even insomnia.