And irrelevant to the conversation unless managers are better protected for cognitive loss (I doubt it) or managers requires less cognitive load (I doubt that too, but you can make a joke about that :)
It's none obvious that various cognitive skills (and the amount of energy/motivations) decline at the same rates and that managing and programming requires the same skills.
My father (not a programmer, but an administrative clerk) would say that he's slower but he can instead rely on experience more.
I'd love to program until I am in my 70's (if programming still exists) this is why I ask.