As far as I know it is generally progressive and in the end deadly.
You may die of something else first, but....
I met and became friends with a GRAND fellow back around 2016, he was in stage 4 COPD, he would get out of breath just walking around his house.
He couldn't DO anything without his oxygen tube (like drive to the store or church etc.)
He finally gave up and died about 2019. Such a loss, he was a great musician, a lawyer and just a good friend to have.
I still miss him