If cleanliness and nutrition are so important to health, why are there so many old homeless people? (People that have been homeless for years or decades)
How is it they survive? Better genes?
That is a very interesting question.
When I trained briefly in A + E there were almost always a couple of homeless people. Homeless elderly people too. I learned a couple of things.
1. They often aren't as old as they look. The streets take their toll. When I worked in Australia I saw the same in some aboriginal Australians who had had hard lives. Some were in a residential home for the elderly when only in their 50's.
2. Beards make you look old. Dirt gets in your wrinkles and makes them more obvious. Poor nutrition ages you. Sunlight ages your skin.
3. If you can't physically handle living on the streets, you get housed or you die. The ones that are left are by definition the survivors.
4. Dementia and/or the loss of support networks can happen at any age, but often to the elderly. They may lose a partner, lose financial support networks, lose a job, lose a home, lose their ability to understand and manage time and money. They may refuse help. They may end up on the streets, age very quickly and will probably die earlier than they should have.
5. Many homeless elderly people have chronic or recurrent infections. Abscesses, ulcers, sinuses (not what you think), fistulae, carbuncles. These may not be visible. They may be hidden under layers of dirt or clothing. Clothing may be adhered to wounds. Poor healing leads to scarring and poor blood flow which leads to further infections, ulcers etc. Poor nutrition does not aid healing.
So my answer (not that you wanted my answer, you wanted the rogues to address it, but never mind
) is that if they have been homeless for decades, you can bet they know a good spot to sleep and lots of tricks to stay out of trouble and stay fed. They may have chosen that lifestyle, although they may have felt that it was the best option out of a range of shitty options. There may be, IMHO, a genetic factor amongst this small cohort: quick healing, low scarring, rapid recovery, strong cardiovascular system, no major digestive issues.
I think the rest of the homeless elderly people you see are not as old as you think and/or have a range of unseen health issues that will limit their longevity and severely impact their quality of life.