It was the “seeing people” that helped identify The Banjoman’s LBD. Once I picked up on that (I didn’t live with him) and searched on line, it gave me something other than his forgetfulness to mention to his GP. Before that they were looking for physical reasons for his weight loss and other health problems. Once a dementia cause was identified it helped explain some of his problems i.e. he wasn’t eating properly despite being convinced himself that he was (although it was obvious to me that he wasn’t).
By the time SS finally agreed to his need for residential care he was believing The Great British Bake Off team, complete with huge lorry, were there in the lounge of his flat.
He doesn’t seem to have followed a regular down turn but has experienced some features from quite early on that would be expected later in the progression of the disease but avoided others.