My Mother-in-Law had it. She lived with us for two years, and it was not pretty. It is a cruel disease because the person that was once bright, loving and personable becomes a walking mental vegetable. What makes it really bad is that it goes on for decades, gradually.
I know, my grandmother had it for 30 years.
It is a cruel disease, harder on the family than on the patient. My grandpa has it and it makes me sad when I think how he used to be versus his present circumstances.