ANCA-associated renal vasculitis is associated with rurality but not seasonality or deprivation in a complete national cohort study

Abstract

BackgroundSmall studies suggest an association between ANCA-associated vasculitis (AAV) incidence and rurality, seasonality and socioeconomic deprivation. We examined the incidence of kidney biopsy-proven AAV and its relationship with these factors in the adult Scottish population.MethodsUsing the Scottish Renal Biopsy Registry, all adult native kidney biopsies performed between 2014 and 2018 with a diagnosis of granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA) were identified. The Scottish Government Urban Rural Classification was used for rurality analysis. Seasons were defined as autumn (September–November), winter (December–February), spring (March–May) and summer (June–August). Patients were separated into quintiles of socioeconomic deprivation using the validated Scottish Index of Multiple Deprivation and incidence standardised to age. Estimated glomerular filtration rate and urine protein:creatinine ratio at time of biopsy were used to assess disease severity.Results339 cases of renal AAV were identified, of which 62% had MPA and 38% had GPA diagnosis. AAV incidence was 15.1 per million population per year (pmp/year). Mean age was 66 years and 54% were female. Incidence of GPA (but not MPA) was positively associated with rurality (5.2, 8.4 and 9.1 pmp/year in ‘urban’, ‘accessible remote’ and ‘rural remote’ areas, respectively; p=0.04). The age-standardised incidence ratio was similar across all quintiles of deprivation (p=ns).ConclusionsSeasonality and disease severity did not vary across AAV study groups. In this complete national cohort study, we observed a positive association between kidney biopsy-proven GPA and rurality.

Secular Trends of Incidence, Prevalence, and Healthcare Economic Burden in ANCA-Associated Vasculitis: An Analysis of the 2002–2018 South Korea National Health Insurance Database

“…A previous investigation indicated that ultraviolet radiation has an inverse correlation with the incidence of AAV, suggesting that seasonal variation could be related to disease incidence ( 19 ). Nonetheless, in our study, while the number of AAV cases was highest in March, the influence of season on the incidence of AAV was not significant, which was found similar in a recent national Scottish registry-based study, confirming a non-significant association between seasonality and AAV incidence ( 20 ). On our study, the overall incidence and prevalence of AAV seemed to increase gradually during the observation period.…”

Global epidemiology of vasculitis

“…Seasonality has also been investigated as a clue to infection; however, no clear pattern has been observed. European studies from the 1990s suggested a trend towards an increase in GPA in the winter 123 , 125 , whereas more recent studies have suggested a summer link or no association 126 , 127 , which might reflect differences in case definition by date of symptom onset or date of diagnosis. A study looking at health-care events occurring prior to a diagnosis of GPA in a UK general practice database did not report any health events that predicted subsequent development of vasculitis 128 .…”

“…Other reported risk factors include rural living and farming 131 , 132 . Social factors have also been investigated, but no clear association with socio-economic status has so far been demonstrated, possibly reflecting differences in case definition (such as renal versus non-renal vasculitis) and assessment of socioeconomic status 127 .…”

Environmental factors influencing the risk of ANCA-associated vasculitis

“…Studies in Scotland, Germany, and Canada showed that the incidence of AAV in rural areas is higher than that in cities. This may be related to environmental pollutants and pesticide exposure in remote areas (68,72,78,79). Additionally, a large Swedish case-control study (73) found no association between occupation and GPA (Table 1).…”