He seems to be going down the same route as myself. Not found any scenic routes yet but the rest is all too familiar. If one is capable in previous years it is nigh impossible to accept one is falling apart at the seams as one ages; so being often annoyed/niggly is an inevitable consequence.
Self respect falls through the floor, reality seems to be permanently against you as things you know you can do seem difficult and things you know you would not possibly do or not do appear to have not happened or happened.
And as an example of words I was talking to someone the other day and afterwards realised I had continually been referring to place A when I should have been referring to place B. No ability to change that, I obviously just looked a fool and I can not stand that.
And the verbal subconscious subroutines start failing and not building the spoken sentences correctly, that the conscious takes for granted they always will do. It's a bad time and difficult to accept.
Apologies but I have no idea if it is dementia or the usual old age failings or something else causing it (I suspect lack of sleep but maybe that's an excuse).
If you are worried maybe you could ask your GP what to do as at least it reports it. Otherwise I'm just coping on a daily basis, trying not to get too angry too often during the day, hoping it's normal deterioration, and hoping it'll find a plateau and stop.