Would you say that a young man is more prone to side effects from Propecia than an older man? Maybe this is related to the fact that Propecia has more effect when started at a younger age than an older age?
The studies that were done did not classify sexual side effects by age. As young men are far more sexually active than older men and more prone to demand the best sexual performance with their young girlfriends, I would suspect that there are more complaints from the younger men. Many older, married men accept a lesser libido and the incidence of erectile dysfunction is much higher as a man ages, so men may not challenge their penis to do what they may feel it will not do.