5 years ago my mother phoned me and said her house was full of poison and she couldn't stay there one more night. So she came over to my house (it was the last time she came here) for 2 nights, and we went and looked at the Anchor place near me but there was a 2-and-a-half year waiting-list and she said she'd be dead by then anyway.
After those 2 nights she decided she'd better go back to her own house and "do the things that need doing" (a phrase we've heard a lot, she has since frequently complained that my brother and I "don't do the things that need doing", as he said I wish we knew what those things were).
I don't know if the poisoning incident (flea powder) actually caused her dementia, it was certainly what she believed. I think there probably really were rats in the shed and fleas in the house but she had over-reacted, poured poison all over everything including the bed she was sleeping in, then suddenly in the middle of the night she decided she had poisoned herself and got up and dressed and walked to A & E (she could still walk further and faster than I could then) with the empty containers. The people at A & E contacted poison experts, said there was no antidote and sent her home. She then slept in her bed full of poison for another week before telling anyone.
So the next few weeks were spent getting her house cleaned up and she threw away a lot of things and then said she knew she'd over-reacted and got a bit paranoid. We tried to get her to move but she wouldn't.
The next 4 years seemed reasonably uneventful, she was slowing down gradually and there were more and more things she wouldn't do, but it was only last October that she made herself ill enough for hospital admission, and only on the 18th November that I first attached the label dementia to her behaviour.
Once people realised it was dementia they started remembering peculiar things she'd done long ago.