Once more, only personal family experiences to draw on; in simple terms, the early stages tend to go unnoticed, as were are all apt to be clumsy, repetetive or forgetful from time to time. A little later mood swings, if they occur, are by nature unpredictable and can be in turn, frightening, amusing, and sometimes very deflating; in my experience this goes for both the sufferer and those around him / her.
"The contented demented" referred to earlier in the thread can be hard to take for the observer - it took quite a while for us to stop correcting my Nan all the time, and to accept that if in her mind it was 1936 and "Michael will be home from work soon and expecting his tea," then it was and he would be.
We found that constant corrections only led to added confusion and sometimes unwinnable arguments; a tough subject.
At the risk of being shot down, I did once ask if the "contented demented" situation was maybe a part of nature's defence mechanism, shutting a part of cognitive conciousness down ahead of approaching death. Understandably, it wasn't well received by some, but it was a thought that crossed my mind when faced with some close family members suffering from it.
My last comments are not intended to offend or upset, so I sincerely hope they have not.