My Mum died of dementia, but I knew something was wrong for years before that.
She went through menopause at 53, and was never the same. She would send me Christmas cards that were for a little girl, and she didn't remember people she had known for years.
I always felt that it was a hormonal issue that threw her into dementia, I tried to tell my Dad that she needed medical treatment, but he wouldn't listen.
Oops sorry, this is the time slip thread - so let me just say that I do believe someone else is living my life in a parallel universe!