Deb, are you keeping a journal ? I have found it very interesting and helpful to note when something changed and what followed a change.
My journal was nothing big.. just a spiral notebook.. jot a few lines a couple times a week.
I almost felt like I could predict a change coming. SOMETHING would happen.. then the change.
Does he still call you by name ? I still remember vividly when it occurred to me Ron hadn't said my name for a few days. That was a biggie.

I was keeping a journal but then I stopped, probably should start up again. He hasn't called me by my name for months. When he can't see me he says, "Helllooooo?" until I show myself to him. By show myself I mean I have to look at him face to face, I can't just say, I'm right here, he can't follow my voice. If he asks other people where I am he says, "Where's that lady?" However, on a good day I can ask him, "What's my name?" and he will be able to answer 'Deborah' about 50% of the time. Now if I ask him who I am am he says, 'my friend' and very occasionally will say, "my wife".

I believe he still considers me a friendly, safe person and he still understands that he needs me around because he will panic if I leave.

Deb; I think your last sentence says it all. I think that is the case often for all of our loved ones hit with this....even when they aren't sure "who we are" they know we are the safety net and welcome our presence.

I think Judy's idea of the journal is such a good one. My husband is slipping faster now and by keeping a journal we will have at least some idea as to how fast they are slipping.
I think we should all start today.

I have been keeping one for some time now and do believe it helps me spot some triggers. Anything to help is good.

I am trying to laugh about this one, he is standing beside and is asking, 'Where are you?" and then he looked at the dog and said, "Is that you?'

I'm so sorry but damn, that was funny!

ditto to Pam's post...