My father has Alzheimer's and talks and shouts non-stop. What stage of the disease is this?

You are at the stage where you are going to lose YOUR mind if you keep listening to him lose his. You need some kind of respite care and he needs medication which won't always work. It is worse when the dementia is combative. Then you will lose teeth when clobbered, like I did.

The gentleman in the hospital room next to my dad's talked non stop, yelled, and roared like a lion.

I asked the nurses what was wrong with him and they told me he'd had a stroke.
Has your neurologist ruled out stroke?

I think it varies. My cousin talks much less now that she has severe dementia than she did when she was in the Moderate stage. She isn't confrontational either.

From what I have seen in the Memory Care unit where my cousin resides, most people with severe dementia don't say much, although, there is one man there who shouts out loud sometimes. He doesn't talk much though.

If you dad is talking nonstop, I would imagine that he is anxious and not at peace. I'd discuss medication with his doctor. Treating mental pain is very important.

If you have a neurogist i would call that doctor. If not call the doctor who diagnosed him and is giving him his present medications. I would see how he reacts to the new MEDS, if you are able, before i went ahead and made arrangements for placement if your intentions were to keep him where he is. Good luck and God bless 🙏

He probably needs sedatives. Poor dear! Alzheimer's is a horrible disease.

Late stage and he probably needs to be in an assisted living facility where people are trained to care for people who are otherwise uncontrollable. He needs a quiet appropriate environment and medications to help him calm down and feel more secure.
It's so sad to think he's so confused that he has to act that way. He needs help from health professionals.
Good luck to you...

Late stage. Get him medicated.