I live in a Senior Living facility with assisted living and Alzheimer's units as well as those of us who are independent. I have seen some people come here to live who could be marginally on the cusp of Alzheimer's, as long as they remained active and engaged, they did reasonably well. Conversely, there have been those who moved in, ostensibly to enjoy retirement, and watched them fade into full dementia within a little over a year.
They were not encouraged to participate in any activities but were left to their own devices. Granted, some activities are rather juvenile, if not downright childish, but, many are educational and involve much creativity. When I asked one lady why she never came to my Trivia group, she replied that she did not come here to play games, but was retired. End of conversation as far as she was concerned. Sad, but true for far too many, but in defense of the facility, the staff is alarmingly short handed to keep up as well.