I'm half his age and usually considered pretty sharp, but I still call one of my small children by the others name once or twice a week, usually when they're up to shenanigans and my mind is focused on that. They're not even the same gender.

He's been known for small gaffes and misspeaking his whole career, and I'm sure having to focus on not stuttering doesn't make it easier. None of what I've seen looks like dementia at all. Trump on the other hand I have more doubts about.