He seems perfectly normal to me. He's always loved to tell stories about the war. But my mother says he has dementia and that what he and I spoke about, isn't reality. I asked them (for the first time ever and I'm 38) for a favor to help me get my credit in order. He said yes. I was elated. Now my mother is saying I shouldn't have done that. My mom does exaggerate but she doesn't lie.
But how can he have this awful disease and be completely aware of who I am, my dogs names and the city I live in? I don't understand. And I'm so sad for him. Can it be reversed??
https://www.agingcare.com/topics/5/alzheimers-dementia/articles
I'd keep in mind what your mother said about it. He likely isn't able to make decisions about money, loans, etc. since judgment is often one of the first things to go. He may have no idea if he's not able to help with your loan. And, when someone is handling money on the behalf of a person with dementia, they can only use that money for their care, not others.
I'm no expert, but, since it involves damage to the brain, I'm not aware of any way to reverse dementia. Some people take medication that may some impact on the progression for some conditions that cause dementia. And it progresses at different rates. Slow for some, fast for others.
I discovered that on some days, my LO seemed fine and you wouldn't even know that she had dementia, but, other days she struggled to do many things and her thinking was greatly impaired. I'd keep in mind that your grandfather may not know of his condition.
The treatment closest to reality for humans is probably video games. Those have been shown to reverse some of the decline by creating new pathways. They are going through clinicals now. But in my opinion, I've seen a few of these specialized games and there's nothing magically about them. What they do for you, you can get out of most video games. So I would suggest people with dementia or other memory problems play video games. Can't hurt. At worse, they can have some fun.