Update: July 28
An obvious question is whether musicians would be less likely to develop dementia or Alzheimer's. Hopefully that's true, but composer Aaron Copland had some dementia symptoms in his 70s, even though he could conduct "Appalachian Spring' his whole lofe. PBS covered this in it's American Experience film "The Forgetting", link. I'll have to check whether I've actually seen this program -- it rings a bell.