Agback
I'm 37, and I first played (A)D&D in May 1980.
but here's the clincher:
I'm 28 and I first played D&D in June 1980. That made me 6 years old when I first played. I was DMing soon after at 8!
Personally I think starting this early was very healthy for my intellectual development. Because of this I've been very biased since then about the positive mental benefits of roleplaying games (i.e. when my peers where making mud pies, I was graphing dungeons and thinking of sinister ways to do my players in - READ--> creative problem solving).
I've always considered RPGing at a young age to be as good as early musical or language training (if not better ;-)
-Eysia