My father is 84 & has dementia. Lately, I've noticed some behavior change. I pray I am not over reacting.

My father is 84 & has dementia. Here lately, he has become sort of withdrawn. He sits now & just stares downward. I ask what are doing. He says... thinking about my wife. My mom has been deceased now for 10 years. He also just want to sleep more. Is this normal for a pt with dementia? What are some of the signs of end of life?