Anecdotal evidence? Let's hear some.
I talked my bro-in-law into buying bees with me a few years ago. As we talked about bees while driving out to where we kept the bees, I mentioned that beekeepers don't get arthritis, or at least not often. He got all excited and wanted to try it on his tennis elbow. So for about 6 weeks I caught 2 bees and stung him right on his elbow every Saturday. His pain went away and hasn't returned. We also tried it on his knees with complete satisfaction.
As for me, I don't go looking for stings, but I when i feel like I need some I just "forget" to be slow and careful when working my bees and get all I need. I was having pain in my hands and a couple of knuckles were beginning to make noise when I moved. That has completely gone away since I took up beekeeping.
So, let's hear it from all you other beekeepers.
"Before I speak, I have something I'd like to say. . . . I will try to keep this short as long as I can." Yogi Berra