Hey Mark, how are you?

I saw this the other day and thought it looked suspiciously like you were writing to yourself!!

Anyway as your Muhammad Ali reference looks a bit outdated so I thought you might be interested in this article ...

Steve Thompson: 'I can't remember winning the World Cup' | England rugby union team | The Guardian

Steve Thompson is a Rugby Union world cup winner from 2003 and like many former players have suffered from as you describe "hundreds or more sub-concussive impacts." that has left him in cognitive decline. As rugby union players become larger and the collisions more brutal surely the incidence will only increase.
Even repeatedly heading a football (soccer) is associated with dementia.

Anyway best wishes you guy

Atty