I don't see in the paper they adjusted by family size. They mention socioeconomic status but that isn't the same thing. Would it be possible people living in urban areas close to parks have less kids or no children at all? Usually real state closer to parks within the city permiter are much more expensive, the same money buys you less square footage. I have done my own study with 7 siblings in my family half with chi…
The parenting factor is actually quite interesting because while I think most of us would agree that parents look older faster, the overall trend is that they make up for it by living longer than their non-parent peers. It's not a huge difference: 2 additional years in men, 1.5 in women; but it's significant enough[1]. --- [1] https://pubmed.ncbi.nlm.nih.gov/28292784/
I would be careful to conclude causality here. There are a lot of confounding factors in these studies. For instance, most childless people are not childless by choice but due to already existing illnesses which predispose them to shorter lifespans. Socioeconomic factors also play a huge role. For instance, the numerous studies which show that adoptive parents live longer than their childless counterparts need to account for the wealth and lifestyle factors that allow these parents to adopt kids in the first place.
There have also been studies showing an inverse relationship. Nonetheless, a clear fact is this: "People with children live longer than people without". IMHO, they need a robust study on otherwise healthy and socioeconomically stable individuals (perhaps otherwise childless by choice sperm/egg donors) with healthy counterparts. In order to see, if something like, "In order to increase your longevity, its good to have kids." is reasonable or not. Personally, I'd say the judge is still out on that one.