My dad repeats things WAY too much; trip plans to stories, he will say the same thing over and over...why?

He is 78 years old. I think their is something wrong with him, I'm not sure, but on a recent trip he was taking he LITERALLY told me about 6 seperate times that he was going on the trip. After the second time I told him "you dont need to tell me anymore, its in my planner when youre going". Still, on and on he went. I used to think he was doing it to be funny, but now Im not so sure....He does it with stories too; over and over and over he will tell the same story; its quite irritating. I have told him countless times "Yeah you told me that already" its not funny anymore.|||might have an alzheimer's disease..try giving him something that will work his mind on, like solving crossword puzzles, reading books, etc..that is one way to cure it|||He has bad memory.|||It's called alzheimer's|||he may need to see doctor, if you or someone eles gose with him reason been link below