Perhaps but people weren't getting dementia at 40 back then. It's not really relevant what the average life expectancy was
Citation needed. That claim seems clouded by today's standard of living.
Before there was clean drinking water, alcohol was much more widely consumed. Were people demented, drunk, or experiencing alcoholic dementia?
Before OSHA, jobs could cause similar symptoms. "Mad as a hatter" referred to hat-makers commonly getting mercury poisoning, as one example of job-induced dementia.
Before the FDA, we have examples from food and medicine.
Etc.
Exactly. There's no point in putting an upper age limit on a position when no one lives long enough for age to even be a factor.
Socrates made it to 71.