Based on the science, you can make somewhat clear statements: The number of people who can survive on six hours of sleep without impairment is zero.
Deep non-REM sleep almost hits the save button on those recently acquired informational pieces so that when you wake up the next morning, you have remembering rather than forgetting.
Sleep is Mother Nature's best effort yet to counter death.
Sleep is the Swiss army knife of health. When sleep is deficient, there is sickness and disease. And when sleep is abundant, there is vitality and health.
I think sleep is probably the neglected stepsister in the health conversation today. I think we've done a good job regarding physical activity and diet, but sleep has remained out there in the cold, and that's surprising to me.