Objective: To determine the incidence of giant cell arteritis (GCA) including polymyalgia rheumatica (PMR) and temporal arteritis (TA) in a region of South Norway.
Methods: All physicians in the county were asked to refer all patients suspected of having PMR or TA to the Department of Rheumatology. Patients meeting diagnostic criteria and with disease onset during 1987-94 were included in a prospective study. In addition, all cases admitted to hospital departments other than rheumatology were evaluated retrospectively.
Results: In total, 322 patients with PMR or TA were found. The annual incidence of GCA per 100,000 population aged 50 years or more was 141.7, 177.6 in women and 99.5 in men. Pure PMR was found in 256 cases, while 66 patients had biopsy verified TA. The annual incidence of pure PMR per 100,000 residents aged 50 years or more was 112.6, 137.7 in women and 83.2 in men. The annual incidence of TA in persons 50 years and older was 29.0 per 100,000, 39.9 in women and 16.3 in men.
Conclusion: The high incidence of GCA we found was due to excess of cases with pure PMR. The high number of cases with PMR was most likely due to the design of the study, allowing inclusion of patients usually not detected by retrospective hospital based studies.