It can be very difficult to get a person to agree to visiting GP or memory clinic for a diagnosis of dementia, since people often refuse to believe there’s anything wrong with them. And it may not be ‘denial’ as such, since at any given moment they can’t remember that they can’t remember anything, if that makes sense.
I know of a case where lack of a diagnosis enabled someone to virtually steal a substantial estate. A live-in carer, apparently with impeccable credentials, moved in with a parent with fairly early dementia. She soon turned him against his formerly very close family and refused to allow them to see him.
Subsequently she took him abroad and married him, without informing any of his family, and evidently got him to make a new will, leaving everything - a lot - to her.
And he died not too long afterwards.
The family took the case to court but the woman was so clever and plausible, that they lost.
The person who told me this suspected that the woman, a former medical professional, had contrived to hasten his end, but he had quickly been cremated - the wife’s choice as legal next of kin - so there could never be any proof.
An awful warning, if ever there was one.