Do you tell someone with dementia that their niece has passed away?

It really depends how far into his Dementia he is. And how close he was. If not close, then I wouldn't say anything. And if I do tell him, once is enough. I read something one time that even when they ask and you constantly you shouldn't tell them because they grieve all over again.

Is this is a person that they have a close relationship with who would be missed? If not I wouldn't mention it unless you think someone else will.