Dementia can come real quick. My mother was afflicted with dementia the last six months of her life. She died at 85. She and my father lived 1000 miles away. Six months before her death I talked with her over the phone and she sounded normal.
A month or two later my older brother, who lived near her and watched over her and my father, called me to say she had dementia. When the wife and I visited her a month before her death, she was able to recognize us and talk somewhat, but she was not the same person. It's a shock to try and talk with a loved who has the disease, but as of now there's nothing we can do.
