How much sleep do we need?

Sleep has been on my mind a lot lately, as you likely know from my Sleep Cycle reviews, so the timing of this article seems more than a little coincidental:

National Sleep Foundation Updates Recommendations For How Much Sleep You Really Need

The changes themselves aren't terribly significant for adults, unless you have kids.  For the most part they just widened the recommended ranges to acknowledge that some kids need slightly less sleep than was previously recommended.  (I'd err toward the middle or end of the range, though -- a chronically over-tired kid is no fun for anyone.)  But there are some interesting changes that pertain to adults, too.

For instance, they split adults into three categories.  Instead of lumping everyone 18 and over into the same category, they are now recognizing that different age groups have different sleep requirements.  For instance, they have a senior age group now, 65 and older, that is recommended to get 7-8 hours of sleep a night, slightly less than the rest of adults.

They also created an 18-25 age group, and while that age group currently is at the same recommendation as the 26-64 age group (7-9 hours of sleep a night), the fact that they created the group in the first place indicates that they think there's something different about people's sleep habits and needs during those years.  I won't be surprised if they increase the recommendations for people that age to be similar to the suggestions for teenagers (8-10 hours).

I've been trying for seven hours a night myself lately -- with my early mornings I'd be hard pressed to get more than that -- but I've found that I function best (with no tiredness during the day) with about nine hours of sleep.  Eight is a middling number that doesn't seem to work for me very well -- if I can't have nine, in other words, I'm better off with seven that settling for eight.  Strange, isn't that?

What about you?  How much sleep do you need in order to be at your best?