It sounds like you take some concern into your dads health and that you care. I would encourage you to be open and ask questions and find the information you need to help how you can. Maybe that is talking to your mom or if he is alone perhaps start a conversation with his doctor. If this is just something you have noticed but hasn't gone through the doctor I highly encourage you to do so. There are several causes to dementia. One being Alzheimer's as most know example but there are other types of dementia like vascular dementia where medications absolutely can help to some extent. Anyways don't be afraid to ask the questions. Wish you and your family best regards with all this.