My WW2 Army Air Corp pilot Grandfather died of Alzheimer's disease around ten years ago. I was early twenties at the time and I was glad to have so much time with him. I was surprised at how old he was given the condition he was in. The last time I had a meaningful talk with him I was 19; the conversation was heartfelt though it seemed to repeat every 45 to 60 seconds. A little over two years later was the last time I saw him alive. I went to the "home" he was in with just my Grandmother (which is amazing because i have an enormous family). He was so long gone that he would forget to chew his food with food in his mouth. Somehow the look in his eyes showed me that he was happy to see his sweetheart and he still remembered her.
Alternatively I recognize that my family is likely to carry the same genetics. I guess I'm doing it for all of them plus me.