Somewhere along the way, an organization was established to understand the intersection between intellectual disabilities and dementia. The organization is the National Task Group on Intellectual Disabilities and Dementia Practices.
Their primary report is called "My Thinker's Not Working." They also have several committees and if you're interested you can join one. I've just added my name into the "Friends of the NTG" to get updates about their work.
Their website is full of good information. Go check it out!
Dementia in Older Adults with Intellectual Disabilities - March 2009 (PDF)
One of the Directors of the National Task Group has research cited in this survey.