Jeph has had problems with poor sleep patterns, worry, and sometimes depression, for as long as the comic has been going. He has also had ear problems leading to surgery in the past, and recently worried about them returning. He has not taken a holiday over the time the comic has run (he is planning one in the New Year).
It is obviously reasonable to be concerned for his health, as we would be for anyone; but I think that he should be the one to choose the nature of any debate about it, so I'm going to cut it off here.
These days Jeph rarely views this forum. If you wish to contact him directly (bearing in mind how many people might want to do the same), his email address is on the QC website (I don't think he often responds to strangers that way, though); and he reads, and responds selectively to, questions addressed to him through his Tumblr.