Imagine the distant future. You are retired. You finally have some free time. What are you going to do with it all?
Leisure pursuits would be torture for some. People who have worked hard all of their lives, usually with their hands, cannot go quietly into the night. Instead, an itchy earwig burrows into their brains. It gives them mad ideas, tells them that they're bored, reminds them of their mortality. It gives them obsessive energy and urges them to build, Build, BUILD! They grab hold of whatever is handy -- usually concrete, bottles, and household junk -- and fashion statues and structures until they are spent. Or dead.
This is dementia concretia, the helter-skelter compulsion to cover whatever outdoor space you have with home-made art. It may not always include cement, but it is always built to last. Dementia concretia is commitment and finality. The young punk tags with spray paint, but dementia concretia is an old person's way of saying, "I was here. Look at me!"
Perhaps dementia concretia is associated with seniors because it prolongs the lives of the afflicted. Many of these tireless souls continue their labors well into their eighties. And if you ask them why -- if they have the time to answer you, which is unlikely -- most of them will shrug their shoulders and say, "Well, I had to do something."