It doesn't guarantee that people dont get cancer or heart attacks either.
Reagan was years younger than my grandmother (born years after her) but his special condition was noticed ~ 1992 when he was only 81. Something different is going on with those cases.
Hell my Grandmotheers physical conditions didnt really limit her movements till she was in late 80s and mental deterioration slowly followed and got worse and worse as her movements became less and less.
There’s two other related issues to the specific situation I am talking about
1) Isolation (little social interaction)
2) Depression (”My life will just get worse than this’)
There is no easy fix.