Okay you guys are confusing me now lol, because if the cure is supposed to make older vampires age fast, then in that case it really doesn't make a lot of sense that Damon plans to take it?

Katherine's age did start catching up with her and it was explained to her that that was what was happening, but that was always only after she lost the cure to Silas from what I remember? I guess you could argue that, in a roundabout way, having and then losing the cure did kill Katherine, because that was what caused the ageing process to be accelerated, but she would have continued living as a human and being physically healthy if not for Silas draining her