Anti-social behavior DOES come with dementia, which is normally but not exclusively in old age.
I am not a doctor, but it is obvious that she is in poor health and it has been that way since her “bad fall” when she was Sec of State. The office of President is a very intense job and all of us have seen how it aged the occupants of the office.
If you lack the energy and stamina to make campaign appearances it is reasonable to ask if you are up for the job. Trump looks like the energizer bunny and Hillary looks like the lady who is afraid to leave the house.
In a sane world the media would be all over the lack of appearances, the failure to have a press conference, and the highly scripted events. In our world they don’t express a bit of curiosity about it - they are too busy dissecting every sentence from Trump who is constantly making statements and taking questions.