Although you can prevent catastrophic hearing loss by staying away from overly loud sound sources or with the use of hearing protection, there's nothing you can do about gradual hearing loss as you grow older.

I'm 39 and I took this hearing test that I wouldn't necessarily classify is conclusive but it gives a ballpark idea of what happens to us as we age. I'm 39 and I couldn't hear the 'Under 40' 15,000Hz which is likely due to hanging around airplane engines and rock concerts for most of my adult life, but how did you fare?