As a person who gets "dementia" or at least, has witnessed it firsthand in her Grandmother, a woman diagnosed VERY young with a disease that is not well-understood yet, even within medical and scientific circles, you could say the topic interests me as a designer.
In graduate school we had a project aimed at squeezing as many program spaces as possible, and at the time seemed unnecessary, at least in the scope of the exercise, and yet...there was something real about it. I remember thinking...older people are young people in bodies that don't work the way they used to. They still think and feel and do and desire like they always have. I designed a balcony that allowed the elderly and rehabilitation patients to oversee both indoor and outdoor spaces on the site. They could watch the street, the park, the people going about doing their shopping or traipsing around the city visitor's center...but they didn't have to be in the limelight if they didn't want to, and the reality is, a lot of dementia patients can't be in the limelight and they can't be on their own...at least not for long.
It all depends on the stage of dementia, and the scariest and most fascinating thing is how quickly they can go from fully functional and "normal" or "like they used to be" to completely blank: Traveling 50 years into the past in the blink of an eye. If ever there was any science to time-travel...this might be it! What this means, though, with an aging population is a massive increase in the number of people who will likely suffer from dementia...having grown up in a society where health, food, exercise, and well-being have drastically changed because of the way that we produce food, how we work, and how we live, as well as how long we live (I've always wondered if cancer, for example, always would have claimed as many lives centuries ago if people had lived long enough to develop it). No matter the science of the brain, the fact still remains that there are lots of people out there suffering (or enjoying) their dementia, and that means that design has to take some steps to serve them!
There are plenty of studies about gardens and outdoor activities being related to dementia treatments, but I just saw the first real-life equivalent to my graduate school project: Town Square for the Aging (I'd only add, that it's specifically for the aging who have dementia, and there is no city visitor center where they have to stare out of their space, they actually get to live in it). In some ways, it reminds me of the National Museum of Play in Rochester, NY...where you can go to (mini) Wegmans and buy any product they have and go to a checkout to pay with the air-change out of your pockets...except it's bigger. It's more likely to be equated with The Truman Show, where the whole world is a feigned reality as a weird social experiment focused on one person...except in this real-world 2014 example in Holland, it's about a community of people, and most of them wouldn't remember for very long even if they were to notice that they are the stars of a show...at least not long enough to escape the show. And the great thing is...they probably won't want to! If they can have visitors, enjoy the outdoors, eat and do activities that they are capable of, all in a secure environment, I don't see why they would be too bothered by the fact that their surroundings weren't quite the same as their old reality. But, reality isn't exactly the same as their "old reality," either...so I guess it's a pretty good attempt at designing for dementia.