I just found out my husband has early onset dementia - and he was doing the same thing, among other things.
I'm not sure the context of your conversations. Is he repeating the information to make sure he understands what you are saying? Or maybe what Nighthawk mentioned -- taking time to process the information. If he is doing this to antagonize you that is a different situation. Have you asked him why he does this? Is he even aware he is doing it? If it is innocent in nature, perhaps you can just show some grace even though it annoys you. If he is aware he is doing, what is his payoff? Is he looking for a reaction? Sometimes little things turn into big things if we are not careful. I would let him know, without arguing, that this behavior bothers you. I hope you can communicate with him and work this issue out. Be well.