Oh no, it's impossible! Because there's no way to prove that everything you experience is not in your head. Cause it could be. You could be some sort of demented genius in a cell with padded walls.

Maybe it's like a matrix concept (our memories, that is). Maybe we're really not in the form we think we are. Maybe all of this exists only virtually in our minds. The concept of that movie is really genius.

As for Alzheimer's yeah you're right, but I guess I mean just memory loss in general. If you were to have your memory erased somehow, you would be in that state at this very moment from your perspective. None of this wouldbe happening.