Not being rich per se, but probably stress. The body has no innate knowledge of how wealthy you are, outside of some information stored in the neocortex about financial details (which has little influence on the overall functioning and regulation of the organism as a whole). But it does keep track of a very important signal, and that is neuroception, or safety, absence of threats. And being wealthy, absence of sources of stress, or ability to avoid them, brings about that state of feeling secure, safe, which affects every cell of the body and leads to a good regulation of the whole organism.

Wealth per se has nothing to do with longevity, as a minute's thought will make plain. What wealth does do is enable certain things that help with longevity, such as better medical care. If you're using wealth as a measure, you need to realize that it's only a proxy, and you'll get better data by looking at the actual behaviors that it's a proxy for.