The Hohokam tribe lived there for at least 2000 years and westerners have been established there for over 150 years. Since only 10% of the people are over 60, does this mean the constitution of adult's have become very much poorer?
For example, I lived in Tucson, AZ and there was a road nearby called "Silverlake" that at one time led to a silver lake with enough power to support a flour mill (see https://tucson.com/news/blogs/streetsmarts/street-smarts-sil...). Now it leads to apartments and houses and an Air Force base.
More people + less water = hotter environment, even before climate change is factored in. A huge amount of the water in the area goes to agriculture as well.
Source: https://patch.com/arizona/phoenix/how-obesity-rate-arizona-c...
https://en.wikipedia.org/wiki/Cold_and_heat_adaptations_in_h...
If you're living in a hot area but used to AC, you're far less able to cope with loss of AC than someone who's been living without it the whole time.
Further, modern dwellings are build with AC in mind. Older ones—by which I mean 50+ years ago, let alone dwellings the native people of the area lived in—were built with airflow & cooling in mind. They might be situated to take advantage of local conditions like shade or prevailing wind. Building for AC means some of that's less important, so gets ignored, and other aspects are deliberately broken to improve AC efficiency (window sizes shrink and there are fewer of them, maybe with none at all on some entire exterior walls, open paths to attic areas that allow up-and-out airflow are avoided, et c). Modern houses become traps in extreme heat if the AC is off, not shelters.
A number of years ago we had an HVAC issue at work on a sunny week. It was shocking how much harder it was to focus and work in the afternoon as the air got stuffy and hot. Our office had some options for airflow, but not many. I've been meaning to look into what ti would take to put some tints on the windows to reduce the heat in the summer.