I read that there are two "waves" of rapid biomolecular aging in the mid-40s and early 60s. Still affects everyone differently and of course a worn-out body will feel that much worse.

In general, though, our bodies start wearing out in our mid-teens, about a decade before we're even fully grown! High-frequency hearing is one of the first things to suffer. Bodily decline is really a constant companion in our lives; it only becomes noticeable when it starts accelerating.