A couple things come to mind. From the tone of your question, it sounds as though you are concerend that dementia
is beginning to set in - and you may be (unfortunately) right. Late 60's is a little early, but not unheard of for dementia, and short-term memory loss and paranoia can be two symptoms. Particularly if there is a history within yours/her family tree, this is more likely. A trip to the neurologist will be your first step to begin the evaluation process.
But before you do any of that, there are a couple other avenues which are less invasive, and which have a better prognosis. First, the cocktail of medicatins she is currently taking may have side effects that affect thinking and perception. If it is not the same physician writing all of the scripts, then please consult with the one you like the best, XXXXX XXXXX a list of the meds she is on so that their interactions can be assessed. If this is a medication issue, adjustments may be able to be made which will bring her back.
Second, and this is more of a long short because her bouts with paranoia are not acute (i.e., they are not short duration and bizaare), but when older women develop urinary tract infections, they can sometimes demonstrate psychotic symptoms. I don't think anyone knows exactly the connection, but this is something I have seen somewhat often when I have worked with geriatric population, and ends up with the women in the ER. A round or two of antibiotics later, they are good to go.
Best of luck. If it is dementia, please accept my sympathy. But know this: despite dementia (and its later stage, Alheimer's) being incurable and progressive, there are medications available which will slow the deterioration. Agian, the neurologist will help guide this process.
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