I'm so sorry, Yaelle. My Dad is 80 and I see some problems with him. It IS like the "vibrant person is gone".
My Mother, also 80, has similar symptoms.
When I am alone with either of them, they tell me how bad the other is doing. I cry when I get home.
Bless you and your Dad and the rest of your family.
It is tough.
It took ten years for this awful disease to kill my mother. The only great President in my lifetime correctly called it “the long goodbye”.
I wish more time and money could be spent to find a cure or a means of prevention. If Alzheimer’s had the funds available that AIDS has received (a completely preventable disease, BTW) there could well be a cure by now.