Can I simply say that the Canadian longitudinal study on aging is going to pose this exact question. We're not choosing people who are working. In fact we're not choosing; it's population based. Maybe some of you have already received a phone call to be part of that study. It's random in the population.
Given that 50,000 will be involved, we will end up with a number of individuals who will have decided exactly what you describe. Because of all the measures that are taken in that study following people for three years, inviting them to the data collection centres, taking a little bit of blood, looking at their grip, at their physical health, their bones, and so on, this is how we will know if there's something different here.
You're totally right that this is a very important question to be answered.