For many people, sleep seems to be the #1 productivity booster. Certainly, the research seems to suggest focus suffers significantly thanks to lack of sleep - not to mention IQ.

Needless to say there seem to be exceptions - Margaret Thatcher famously coped with 4 hours a night. It's been suggested that some people's ADRB1 expression continues while they're awake, which means they need less sleep. However, less sleep is also associated with dementia late in life.