This type of survey or study is referred to as the incidence and prevalence of a disease. Searching for the term "incidence and prevalence of polymyalgia rheumatica" in an Internet search shows several study results. Here is a systematic review that will help answer some of your questions, @wv54.

- Incidence and prevalence of giant cell arteritis and polymyalgia rheumatica: A systematic literature review https://www.sciencedirect.com/science/article/pii/S0049017220302043