Greetings, and thank you for the extra information, it is helpful to know your wife's background.
You are quite correct, some of the symptoms of bipolar
overlap with dementia symptoms. Both problems can have quick flares, or insidious flares. Having been alongside her during her bipolar illness all these years, you know the "flavor" of her bipolar. So, if what you see is not consistent with what you have seen before, it may be safe to presume it is not the bipolar but may, in fact, be due to dementia.
The standard dose to start with is 5 mg. As the process progresses, increasing it to 10 mg is called for. Once the dose is increased to 10 mg, many clinicians will add
Namenda. It works on the NMDA receptor to also aid in dementia. A recent study looked at it and said it didn't add too much when combined with Aricept, but other studies have shown it to be helpful. My typical practice is to add it and see if it helps. If it does not, I remove it. But, Aricept should be the mainstay.
I hope this helps!