[trimtab]

Because the person with dementia does not have a stable level of cognition. It changes continuously. The article mentions this. At higher levels of cognition they will know whatever the simulation is false and it will upset them.

Spend some time with dementia patients and you'll quickly realize the issue.

Any VR would have to be able to determine current cognitive ability to not cause as much frustration and harm as relief.

[jimduk]

Good point, but it's also the case they forget being upset quickly. My father-in-law had dementia, and as he progressed I found it useful (for me) to interact with him as if he was like an X yr old child (without a medium/long term memory). e.g. If X was 6-8 we would talk about family, have a walk, point things out, express preferences, tell stories. If X was 3-4 we would talk about people and things in the room, discuss food, check he was comfortable, smile and be upbeat.

I had much better time with him like this, than seeing other families who were trying to be 'grown up' and have serious conversations. YMMV. Dementia is awful.

[nabla9]

Declining cognitive state is very random.

Not being able to recognize oneself from a mirror and being spooked by stranger in the mirror. Shadows or even floor lamp in the corner may be scary person. The rest of life can become scary hell where you don't know what is going and where you are. Even very peaceful persons become aggressive when they are confused and scared.

Forget VR. If I get Alzheimer I want euthanasia or drugs. Maybe gradually increasing opiates that take all pain away and I eventually stop breathing at night.