This is true. But we as a society are at a point where you cannot terminate someone's employment because their demographic might be *statistically* less productive or more costly due to health factors... employers would love nothing more than to leverage modern technology (exams, genetic testing) to cherry pick the healthiest and potentially most productive workers. Very slippery slope, and there's a reason we don't allow it.

The old airline astronaut physicals were 100% about that, and not safety.

There is of course a legit safety factor with advancing age, but that comes down to how stringent and how frequent do the exams need to be? At some point it becomes impractical... a 99 year old who passed an astronaut medical this morning could still keel over later this afternoon. I suspect that point of practicality is around age 70-ish.