My mother is 95 and in my care. She has begun to realize that her mental faculties are slipping badly, sometimes to the point of total confusion. When she speaks to her daughter and grandchildren over the phone and tries to tell them of her situation, they always seem to respond by telling her that they forget things too and what she is experiencing is normal. When I have tried to help my sister (who lives in another state and sees my Mother once a year for a few hours) understand her condition, there is more than a fair bit of denial going on and I think this is just a symptom of that denial. One grandchild went off on a tangent telling her about how her mother was getting so forgetful and then on to a story of a person they knew who was totally dependent on his son because of his dimentia, a situation that is very similar to my mother's. It totally diminishes what she is attempting to communicate and can only lead to a greater feeling of isolation. Here at home, we can handle it just fine because we operate together with her as a team and she knows that we all fill in the gaps for each other. I have asked my sister to do something that will help her more fully understand the condition and symptoms, whether it be joining a group, or even reading some books on the subject. It is doubtful that will happen. Short of getting them to understand, I am struggling with any specific advice I can give them on how to handle her comments when she tells them she is struggling with her memory and understanding.
I think others (a) don't really understand the changes unless they see them on a regular basis (b) may be in denial and/or (c) are trying to offer reassurance when reality is more appropriate.
One thing you could do is suggest specific short articles on dementia for them to read. If they don't both (which is probably likely more often than not), you could ask them if that's what they've understood from the literature you suggested. Just a polite way of telling them to learn about the situation and offer helpful, not irrelevant information.
Another thing you could do is think of ways they can help that don't involve addressing the issue. That's a hard one and I don't have any answers offhand.
More of a commitment would be to suggest that they locate a local Alzheimer's assn., or contact it and attempt to purchase the handbook (there may also be a DVD out now) on the Creating Confident Caregivers course.
This is an example of the various locations at which it's held in Michigan:
http://www.aaa1b.org/caregiver-resources/caregiver-trainings/.
If the course has been expanded to other states, there may be multiple locations at which it's being held also. If they don't want to go to a course, ask about the materials and/or DVD.
I took the course; it was free, and it was excellent. A lot does depend on the course leader, though.
After they've read the workbook, they'll have a better idea of how dementia progresses and how to work with someone who has it. If they don't read the material, keep reminding them!