Polymyalgia Rheumatica is a relatively "new" disease and wasn't named until 1957, partly because it can be difficult to diagnose. About 7 out of 1,000 people have it, most of them over 50. Twice as many women as men have Polymyalgia Rheumatica. The early symptoms are similar in many ways to those of Rheumatoid Arthritis: the linings of the shoulder joints (synovial tissues) are often inflamed, though muscles are normal. (John Hopkins, Health Discovery)

Since the disease usually strikes people over 50 years of age, the "Baby Boomer" generation is at risk - some 76 million people strong. It would seem reasonable that, due to the difficulty of diagnosis and the huge increase of people in the "at risk" age group, the published statistics could be very conservative and the actual incidence of PMR and GCA could be much larger.