The Joker as a infant somehow joined in this "gang weed" and smoked a trillion blunts a day and got super high. Despite this he had functional lungs for the majority of his life after this point. After that God told him that he would die or something but that "it would all be fine", however the validity of this statement is questionable since he could have been on weed.
The Joker once he got his architecture degree that went to no use decided to become a lame criminal. Doing nothing much except get caught by Batman. Other than that when he gets home after breaking out of prison the first thing he does is watch Fox News. The knowledge he gets from here makes him a super epic gamer. Eventually he goes on 4chan and also starts hating women and minorities. With this epic gamer fuel he eventually just dies in 1999. Just when it was getting started he died at age 79 after living a uneventful life nobody cared about. Did I mention how boring it was?