Increasing incidence of Wegener's granulomatosis in Sweden, 1975-2001

OBJECTIVE: Studies of Wegener's granulomatosis (WG) since the late 1980s indicate a probable increase in incidence of unknown cause and significance, possibly related to antineutrophil cytoplasmic antibody (ANCA) testing. To extend these observations and to include calendar periods before ANCA was introduced, we assessed time trends in the incidence of WG in Sweden in the period 1975-2001. METHODS: In the population-based Swedish Inpatient Register, we identified 1938 individuals diagnosed with WG in the period 1975-2001, and calculated the annual age and sex adjusted incidences. RESULTS: The incidence increased from 0.33 (95% CI 0.28-0.39) in the period 1975-85 to 0.77 (95% CI 0.69-0.85) in 1986-90, to 1.19 (95% CI 1.12-1.26) in 1991-2001, resulting in a mean incidence of 0.78 (95% CI 0.74-0.82). CONCLUSION: WG displays a strong temporal trend. While the increase coincides to some extent with the implementation of ANCA testing, suggestive of increased disease recognition, ANCA testing remains an incomplete explanation as increasing incidences were noted before as well as after their introduction.