My point about dementia was that in the very near future we will be able to identify it years, and almost certainly decades, before it is impacting brain function. Do we then say that a 50 year old whose brain is already accumulating amyloid plaques and tau tangles that they can't be president.

I'm okay with a battery of functional tests as some sort of screening tools, but I think we need to be very cautious about using a diagnostic label to rule out candidates.