Hamsters get very private and nasty tempered if they are ill or in pain quite often. Simply because instinct says that in the wild, the weakest and sick are left to fend for themselves...even though they are solitary theres no doubt some instinct from raising pups as well, that cause a mother to cull her litter rather than have them be a liability....
So they don't show their weakness or pain? They suddenly make you keep a distance so you don't know there's something wrong. You may want to get him to a vet for a thorough checkup if he is really being aggressive with you? I haven't heard of senility in hams, but that doesn't mean it can't happen. Like any living thing, the body wears down, and that would include circulation, the brain, the nervous system etc....so a doctors visit may do a lot to fill you in on what might be happening....keep us posted