My grandad is 96. About month and half he fell in his home during night and injured hipbone, but did not break it. Due to injury, he was forced to lie in bed. We engaged nurse to do exercises with him to avoid muscle atrophy. In the beginning, he was answering good to the treatment, but during the last week he simply denies any cooperation with nurse, sleeps most of the day, and takes very little food or drink. He is also much disoriented, has hallucinations, sometimes I think he can't make difference between reality and dream, and stories that he tells are morbid (about graves, some black and white horses...). Should I expect the worst? Can this behavior be due to the medications?
In any event, you need to report these symptoms to his doctor. They are a serious change in mental status.
What medications is he on right now? Sometimes they can build up in a senior's body over time because their bodies can't process them as quickly as someone younger. Doctor's don't always consider that in prescribing to a very senior person. What you could do would be take a list of his current medications and the dosages to the nearest pharmacist and ask if any of them could cause hallucinations and his other behaviors in someone his age. Your granddad is lucky to have such a caring person looking out for him.