yep - and how that translates to what they think, remember andcan do, though there are no clear stages as it is a gradual decline and, as they slide, there are good days and bad days....the good perhaps plus two and the bad minus one. One other thing, the rate of decline can vary with the dementia - look at Terry Pratchett with his fast demise and then there is my mother, now at least six years.....
One of the things to bring out perhaps are the 'life/behaviour changing' triggers - these could include hygiene, toilet, cooking, family recognition, or even violence.....