I had to take care of my grandpa some ten odd years ago, and he also had dementia. It was genuinely awful, especially cuz he also had several strokes and had to be intubated, and every morning he would pull out all the tubes and catheters he had on and shit, because he had no idea where he was, or who was around him. One day his mind left, and then about a year later, his body followed.
I genuinely forgot what I was gonna say about the story, but it stroke me in a way I didn't like, because these aren't happy memories. I never heard my name come out of his mouth. That being said, it is of course a really damn good piece, because those memories just came flooding in.
I've been taking care of my grandma (Wife of the previously mentioned grandpa) and she's mentally sound (Honestly even more than most of my family lol) and… Yeah, I gotta echo the message: Talk to your grandparents, and just, your family in general. One day you will not be able to, so treasure the time you have with 'em.