My wife just flew to Denver to help put her mom in a nursing home. Her mom is only 65, so it's way too early for this and has been really hard on her whole family.
She started showing signs a couple years ago, but the last few months she has developed Capgras Syndrome, which is basically Imposter Syndrome. A couple times a day, she thinks my father in law is an intruder and she screams and curses at him and runs away. He can't get her back into the house because she thinks he is trying to hurt her. She then calls whoever is easily accessible on her phone frantic about it and they have to try to talk her back into the house. Hard on my wife when she is in the middle of a 12 hour work day and has to talk her mom back into her own home. My mother in law actually called the cops once and they came out to the house, which was an interesting experience for my extremely straight laced father in law.
She also constantly wants to go to a party, and when they get people together to make her happy she asks "where is everybody?" The "party" is never good enough. She wasn't a super social person to begin with, so definitely a weird way her dementia has changed her. My sister in law lives in Denver with her family and she is exhausted because she has to host her mentally deteriorating mom constantly to give her a "party" and she has two little kids and a job.
My father in law is definitely not one to give in or complain, so if he thinks he can't take care of her and she needs to go into a home, I can't imagine how hard it is on him.