why do gays age faster? Is it the ass sex? 
No. The reason is we live in visual (read youth obsessed) culture.
Being viable on the meat market often meant having a great (young body). Accordingly, the conventional wisdom was that 20 something was the apex. In the 30s you were still breathing/viable and practically a “daddy.” In the 40s you were a “daddy” or a fossil. In the 50’s you were a troll, out of circulation (a homebody) or otherwise dead.
The AIDS epidemic changed this mentality somewhat. In a very short period of time huge swaths of the 40 and 50 something population were wiped out. So the “daddies” became a thin (in numbers) population. As drug cocktails and steroids became a standard part of treatments lots of guys in the 30s and 40s started bulking up and looking buff. Even healthy (negative) guys starting bulking up as they “borrowed” steroids from men who used them legitimately or found friendly doctors who were willing to prescribe them. The result was a maturing population of 40 somethings and newly 50 somethings that had bulging muscles and still looked good/sexy on the meat market. Hence 50 is the new 40 and 40 is the new 30…
It’s interesting to note that gay social life and bodybuilding have gone hand in hand: it used to be that the bodybuilding peak occurred in the 20s with the 30 something guys pushing the envelope. Back in the day a 40 something bodybuilder was unheard of. Now, 40 something bodybuilders still look great… as do many 50 somethings.
In many ways the history of bodybuilding & physique culture is the history of gay life.