It's not always the case, but I believe it is in the majority of situations it is.
I'm deeply sorry for what you went through though. Tough does not even begin to describe the utter destruction that Alzheimer puts a family through. My ex-girlfriend's father went through that. I can't easily put into words the absolute despair I felt watching him fade away from an outsider's perspective. I cannot, and hope I never can, imagine how she felt.