Epidemiology of Wegener's granulomatosis in northern Norway

To determine if changes in the incidence, prevalence, and clinical presentation of Wegener's granulomatosis (WG) have occurred in the stable population of northern Norway during a 15-year period.

We performed a retrospective cohort study using hospital discharge records from all 11 hospitals in the region and the databases of the 2 pathology departments in the area. Only patients fulfilling the American College of Rheumatology 1990 criteria for WG were included in the study, and demographic and clinical data at diagnosis were recorded. Incidence, point prevalence, and period prevalence rates were estimated for three 5-year periods.

Fifty-five patients (62% male) with a median age at diagnosis of 50 years (range 10-84 years) fulfilled the inclusion criteria. The annual incidence/ million population increased from 5.2 (95% confidence interval [95% CI] 2.7-9.0) during 1984-1988 to 12.0 (95% CI 8.0-17.3) during 1994-1998. The point prevalence/million increased from 30.4 (95% CI 16.6-51.0) to 95.1 (95% CI 69.1-129.0). The highest incidence rate occurred in men ages 65-74 years. There were no significant period differences in age, first organ involved, delay of diagnosis, or disease activity, but fewer patients had malaise and renal insufficiency during the earliest time period. No seasonal variation in the onset of WG was present, although we noted a pattern of annual fluctuation.

The prevalence of WG has tripled in northern Norway over the last 15 years. While more efficacious therapy may explain part of this increase, we also found a significant trend toward increased incidence over that period. The incidence rate over the last 5 years is the highest reported so far, while the clinical presentation has remained unchanged.