Some people are able to function with far less than the recommended seven or eight hours of sleep a night. "Short sleepers" make up just a small percentage of the population and are more energized than regular sleepers ? but that's not all.

Source: http://www.npr.org/2011/04/16/135450214/eight-is-too-much-for-short-sleepers?ft=1&f=1007

Holden, Tim Holt, Rush D. Honda, Michael M. Hoyer, Steny H. Hunter, Duncan