I believe there have been studies into how social life impacts longevity, and probably cognitive decline as well. For some people, like my great-grandmother who kept working well into her 80s by choice, jobs can be a big social outlet. For others a job can be very socially isolating. Those factors probably matter a lot.
Side note: I'm sure we'll see research into these areas used to propose delaying retirement age more in the near future.
Side note: I'm sure we'll see research into these areas used to propose delaying retirement age more in the near future.