How much sleep does a person need?

A friend draws my attention to an interesting story at: http://www.nytimes.com/2011/04/17/magazinehttp://www.blogger.com/img/blank.gif/mag-17Sleep-t.html?_r=1&nl=todaysheadlines&emc=tha210


As the story says: "There is a small portion of the population — he estimates it at around 5 percent or even less — who, for what researchers think may be genetic reasons, can maintain their performance with five or fewer hours of sleep. (There is also a small percentage who require 9 or 10 hours.)"

I am in a strange category: I will happily sleep for 24 hours a day, but I actually need about 4 hours to continue performing more or less normally for about a month; my optimal sleep is around 6 hours (though I get up by myself sometimes after 4 hours).

The problem is that unless you try, you don't know if you are in the 5% or whatever that needs 4 hours of sleep or 10 hours.

And the further problem is that, you don't know the answer for some weeks.

Finally, there is a question about the age at which one experiments. It is possible that if one does the experiment at 30, the learned behaviour of needing say 9 hours of sleep overrides the genetic need for only 4 hours. If I hadn't been inspired to try sleeping less than the 10 hours I did at the age of 17, I might still be sleeping 10 hours (or 9) every day. However, as I did experiment, I found that I could learn to perform more or less optimally with something like 4 hours for long stretches of time.

Naturally, as the scientists in the story believe that everyone is a poor judge of the relationship between sleep and performance, they will not place much reliance on my account of my experience.

Equally, why should I live my life on the basis of their results, which relate to 95% of the population, if I am lucky or unlucky enough to be in the 5% at the top or the 5% at the bottom of the scale?