Footwear and Aging

I have been reading through this older study on footwear.  The study looked at the awareness of foot position in both the young and old, in barefoot or in shoes.  For the young and old, shoes led to decreased awareness of foot position.  In the young, this was a large difference.  In the old, however, this was only a very small difference.  The authors conclude that: "sensitivity to foot position declines with age, mainly owing to loss of plantar
tactile sensitivity. Footwear impairs foot position awareness in both young and
old."

I had a few thoughts on this.  In the paper, they talk about how somatosensory ability declines with age, but not evenly across the body.  In the hands, for example, there is only a small loss of abilty.  In the feet, there appears to be a much larger loss.  I think the simplest explanation is that our feet are covered in shoes much of our life, while our hands are not.  I would love to see if foot sensitivity declines in barefoot populations with age.  I would bet not, or perhaps only a small amount.

Therefore, in this study, is the loss of foot sensitivity in the old due to aging, or is it due to a lifetime of wearing shoes?  Enquiring minds want to know.