I don't know where it is but there is an age survey here on this site. The one thing I remember when I did see it was that the average age of rebreather users seems to fairly high (plenty of grey hair anyway). I can only assume this has something do with having the cash to spend (which normally increases with age
), alternatively it's a sex substitute.
All said and done the young have the monopoly on good health, so as the Portuguese say about all ailments as the years pass by: "PID" or "Puta da Idade" (Age is a Bitch).
F