Age restrictions in any job arena are just dumb. I'm 51, and can run circles around all of my co-workers, some of which are still in their 30's. Even the ones that don't smoke have bad diet/exercise habits.
Sure, there's genetics involved (BP 98/68 and HB 64 at last checkup; and I had to jog three blocks to get there on time). But I, thanks to my wife, eat right, and force myself to exercise, one way or the other.
Workplace health guidelines need emphasis on health history, first, then age!