How many of us lose our abilities to be productive, whether mental or physical, and when did it start?

Loss of the ability to be "productive" will happen to everybody. It's a question of what gets to you first, the mental or physical game. For me when I turned 60, it got to be a tie. Physically I can't referee soccer like I used to and that translates to stomping up hills, whatever. I had the great fortune to recognize the best path to a pay raise was to quit everything. The mental game didn't diminish. It's more of a matter of other things becoming more important. Getting away from the crowd, having some land, not working for The Man, and the list goes on. I feel sadness for all the senior citizens who struggle to work because they need to eat and pay for medicine. That percentage is increasing greatly given the lack of retirement benefit capacity because the millennials are not investing in themselves. You see article after article about the increasing percentage of the population that has no retirement planning.

my date of shutdown was March 15, 2015, I was 50 att

I was diagnosed with GWI in 2006 even though I was in earlier, because the DoD tested unknown substances on us without our knowledge. I studied the matters in depth and noted that I first began experiencing issues in my early 30's that led to a major loss of ability to be productive in my 40's and 50's. These issues are clearly described in the scientific research I came across. Anyone?