Yes this is typical. My dad is slowly losing his ability to communicate. I think in my dad's case, he has a hard time following a conversation or remembering what's being said. I think this is the reason he goes into the silent mode. He does still respond fairly appropriately to short, to the point sentences. His answers are also short and to the point.
In the beginning, dad started getting a bit sloppy about housework and upkeep on the house but still was able to get by well. Around the same time, dad began repeating the same stories. At this point, the progression was so slow that we never even paid attention to it. We chocked it up to his age and the loss of my mother a few years before. Dad was also becoming more reclusive.
Then the bills were going unpaid. Home and car insurance lapsed. Property taxes went unpaid. He was losing things. Bills went unopened while junk mail was carefully opened and preserved. Then dad just piled all the mail up. My family and I moved in with dad. We thought it would be easier for him to stay in familiar surroundings. It was around this time that I began to notice that dad's personality was changing. He was becoming more argumentative and depressed. This was the most difficult time for me because I was taking the brunt of his verbal abuse. The verbal abuse almost went into physical when he drew his fist up at me. It was a short time later that I realized I could no longer take care of dad and remain healthy myself. It's just too much for one person.
My sister offered to come get dad and take him home with her. He's been there for a couple of years. My sister has a lot of in-law's there who help her. I had no one here where I live to help me.
Dad is getting worse. He cries more than he ever did. He's semi incontinent now. But even in the midst of that, my sister says it's getting easier. Gone are the threats of suicide and disappearing with the car followed by calls to the police. And gone is the rude police officer who told me to get dad a cell phone! My answer to that? How on earth will I teach him to use a cell phone when he can no longer use the type of phone he's used for 77 years because he forgot how to?
I can only imagine how he'd try to dial the phone here now. We now have to dial 11 digits to phone our next door neighbor! We have that overlapping area code thing.
Long story short (too late for that!

), it took dad about 12 years to get where he is now. Judging from other's reports, dad seems to be progressing probably a bit slower than most.
Love, Barb