There are studies: https://www.thelancet.com/journals/lanhiv/article/PIIS2352-3018(23)00028-0/fulltext
It is hard to follow but my takeaway from the study was for someone aged 40 at diagnosis, life expectancy was reduced a few years (4-5 years). I suspect if diagnosed at a younger age, the decline would be greater. I have read that the bias corrected decline caused by smoking is 4.3 years and suspect zero for the impact of climate change. They never want to make harmful effects of actions understandable.