Background. Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) carries a high risk of morbidity and mortality, with outcomes modified by treatment and an incidence that may be increasing. We examined temporal changes in incidence and mortality during 2000-15 using nationwide healthcare registries.

Methods. Patients with incident AAV were identified using International Classification of Diseases Version 10 (ICD10) codes and grouped according to inclusion year (Period 1: 2000-04, Period 2: 2005-09, Period 3: 2010-15). Log link cumulative incidence regression adjusted for age, sex, renal function, cardiovascular disease, diabetes, hypertension and advanced disease severity were used to model survival.

Results. We identified 1631 patients (52% male), corresponding to an incidence of 18.5 persons/million/year (Period 1: 15.1, Period 2: 18.5, Period 3: 21.4). The slope of incident serologic ANCA testing was steeper than that of AAV (P = 0.002). Mean [standard deviation (SD)] age was 60.2 (16.7) years and mean (SD) follow-up was 6.8 (4.7) years. A total of 571 (35%) patients died (5-year mortality of 22.1%), with an absolute risk ratio (ARR) for Periods 2 and 3 compared with Period 1 of 0.80 [confidence interval (CI) 0.65-0.98, P = 0.031] and 0.39 (CI 0.31-0.50, P < 0.001). About 274 patients developed end-stage renal disease (ESRD) [16.8% (Period 1: 23.3%, Period 2: 17.6%, Period 3: 12.5%)], with ARR decreasing over time: Period 2 0.61 (CI 0.42-0.87, P = 0.007) and Period 3 0.57 (CI 0.39-0.83, P = 0.003). The overall risk of death associated with ESRD or chronic kidney disease was 1.74 (CI 1.29-2.37, P < 0.001) and 1.58 (CI 1.21-2.07, P < 0.001).

Conclusions. Incidence of ANCA testing and AAV diagnosis increased over the test period. Falls over time in mortality and ESRD risk may relate to earlier diagnosis and changes in treatment practice.