Despite a stable incidence of ANCA-associated vasculitis in southern Sweden, the prevalence of the condition has increased, according to a population-based study spanning a 23-year period.
From 1997 to 2019, the incidence remained constant at approximately 30 cases per 1 million population, with a prevalence of 428 cases per 1 million population on January 1, 2020.
“The prevalence is the highest ever reported in [ANCA-associated vasculitis], indicating improved management and, therefore, survival,” Jens Rathmann, MD, of Lund University in Lund, Sweden, and colleagues wrote in RMD Open.
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The study population included 623,872 adults in 2019. During the 23-year study period, 374 patients with a median age of 67.5 years were diagnosed with new-onset ANCA-associated vasculitis. The incidence was 30.3, 30.4, and 29.5 cases per 1 million population in 1997-2003, 2004-2011, and 2012-2019, respectively, the investigators reported. The incidence increased with age and was highest among individuals aged 70-84 years (96 cases per 1 million). The study also revealed a higher prevalence in men than women (479.7 vs 377.8 cases per 1 million).
Further, the study revealed a seasonal variation in ANCA-associated vasculitis diagnosis. The highest number of cases were diagnosed in March and May (37 cases in each month), followed by April (36 cases). ANCA-associated vasculitis was 38% more likely to be diagnosed in spring compared with winter. “A plausible pathophysiologic mechanism is that respiratory infection during winter may trigger the onset of [ANCA-associated vasculitis] a few months later,” the authors wrote.
Reference
Rathmann J, Segelmark M, Englund M, Mohammad AJ. Stable incidence but increase in prevalence of ANCA-associated vasculitis in southern Sweden: a 23-year study. RMD Open. Published online March 9, 2023. doi:10.1136/rmdopen-2022-002949
