Hello
I remember my mum went through a period of repeating the same questions. Yes it is frustrating but it helped when I reminded myself to mum it was always the first time. A few things helped at times.
1) I think sometimes the repeated questions is born out of anxiety. Mum still asks if I heard her turn a light off several times. Ignore the underlying feeling and the anxiety guarantees that she will ask again. Hold her hand and say yes I heard you do it and much more chance the underlying emotional driver has stopped.
2) Try distraction. No I am alright I do not need a drink but what shall we do this afternoon, Do you fancy doing so and so, etc. Open up a new vesta and the old one may be allowed to slip away.
My mum fails to appreciate she is hungry or thirsty so I have to ensure she eats regularly and takes enough fluids. Perhaps the opposite for you and the person forgets they have just eaten.
Try taking a different approach yourself. These things can be annoying, frustrating, etc. However ultimately if all else fails you have two choices. Accept this is the Dementia talking and acting, roll with it and accept the situation. Or get anxious, frustrated, annoyed, bounce of the wall for ten minutes, etc, but still find yourself in the same situation. Not easy but the former will be better for both of you. A PWD picks up on a carers frustration, anxiety, etc, reflecting it back in their own way. If you feel yourself tending up, etc, walk away for a few moments, go and make a drink, pop to the loo, just buy yourself a few moments to reset the dial.
if the above sounds idealistic please be assured I was in your situation at onetime and posted here. I got advice like the above from several people. Yea right I thought but tried it and slowly but surely it helped. No one is a perfect human being and carer, but small things can make a difference.
please try and stay positive and keep ranting here if it will help. There are no perfect answers just possibilities. Trial and error on distraction, remembering what worked today may not tomorrow.