My Father-in-law is 94. He is still mobile and has a strong handshake. However, his understanding of situations than need to be addressed - are becoming more difficult for him mentally, especially changes that have to be made in his daily routine, such as now having a nurse dispense his meds; following Dr's instructions; complying with changes in regulations at his facility. It seems as if along with not understaning changes, he is also becoming more, and more, argumentative - not only with his family, but also with the staff at his facility. He is becoming increasingly more difficult to communicate with. Where is this headed? and what can we do, within reason, to deal with the worsening situation?
He needs to see a doctor to determine what is going on in his brain. There may be medications that can help slow down the decline. Trained staff will also have to learn to cope with these changes he's displaying.
I'm sorry to say that unless the doctor finds that he has a UTI or some other infection that can be cleared (infections can cause dementia-like symptoms), that this situation will deteriorate. That means that you and the others who help him will have to adjust.
A physician can guide you.
Take care,
Carol