2 years ago dad said he thought Mum was starting to lose the plot. Looking back I think this was a big step for him to make. I just thought it’s part of the aging process. But mum’s behaviour has become very erratic. She’ll forget things and I think at times gets stuck on a thought or in a loop. She has always left very depressing voice messages but is now making outrageous claims and demands and is really angry towards my sister and I. My sister and I joke about how “it’s always about her”- dad’s 80th Birthday it becomes about how dad didn’t mention her in his speech for their 50th wedding anniversary 2 years earlier etc. So where do we start? It sounds like dementia or Alzheimer’s. How do we broach the subject, who do we see? Thanks for your time
Part of the preliminary stuff is of course to talk to your father. What has he noticed, when, how quickly are things progressing? You are fortunate that he already thinks that she is ‘losing the plot’, which should make the talk more helpful and less stressful for both of you. Then find out what he thinks is the best way forward, for your mother and also for himself. Options are aides for in-home care, independent living, assisted living, nursing home and nursing home/ memory care – quite possibly not the first three, unless you want a place where they can both to together with separate levels of care.
Then go ahead with doctors to get the diagnosis. Other people may disagree with the priority of these steps, but that’s the way I would go. If you want feedback and suggestions about the options you are looking at, write again.
As your mother is not on good terms with you and your sister, your father may also have the best chance of getting mother along to a doctor's appointment. He could make up a reason (flu injection? a nasty spot on your back that you can't see, dear, but it's worrying me?), or just ask her to come with him to his own appointment for support because he is so worried that he might have bubonic plague. (I'll leave the detail up to you!)
I can guess that the diagnosis seems the most important thing at present, but please at least consider getting the paperwork in place first. Once a 'not competent' diagnosis is made you can't go back. Even if she is not really competent now, you should be able to wing it before the formal medical decision is made. There must be a place on this site explaining all the paperwork, but it's not relevant for me so I have never chased it up. The detailed rules (even the labels for things) are inconsistent from state to state in the USA, so you need local information.
Best wishes, and keep asking.
I am so sorry your family is facing this challenge.