I wish I had an answer to that. I was 45 when ALS was first mentioned as a diagnosis. I rejected the idea because I felt okay barring a few issues. I continue t believe it was all a result of some cervical issue despite being advised otherwise. I am 47 now and awaiting a third opinion.
I still like to believe that I am a slow progressor, particularly when I read other PALS stories here. But I'm really not so sure. I can see continual decline but at least I am still functioning relatively normally. I just make adjustments.
However, when I look back at the last couple of years, I can see where there was much faster and noticeable decline and it always seemed to coincide with me pushing my body too hard and too far. Denial was a huge contributor. Now I'm really careful in that respect. I don't know if it the two are related to the rate of progression or not, though in my case I feel they are tied. At least, that's how I feel at the moment.
I suspect my breathing is changing but I have never had it tested. I lived in a country that didn't really understand what to do with a patient like me. The fact that I have had pneumonia twice this year makes me suspect there is now a breathing component. Again, when I read others PALS and CALS stories breathing appears to be a large predictor or rate of decline. But I could be completely wrong. I'm so new here and have lots to learn. This is just my interpretation.