The association between ambient UVB dose and ANCA-associated vasculitis relapse and onset

Abstract

Background The aetiology of ANCA-associated vasculitis (AAV) and triggers of relapse are poorly understood. Vitamin D (vitD) is an important immunomodulator, potentially responsible for the observed latitudinal differences between granulomatous and non-granulomatous AAV phenotypes. A narrow ultraviolet B spectrum induces vitD synthesis (vitD-UVB) via the skin. We hypothesised that prolonged periods of low ambient UVB (and by extension vitD deficiency) are associated with the granulomatous form of the disease and an increased risk of AAV relapse. Methods Patients with AAV recruited to the Irish Rare Kidney Disease (RKD) (n = 439) and UKIVAS (n = 1961) registries were studied. Exposure variables comprised latitude and measures of ambient vitD-UVB, including cumulative weighted UVB dose (CW-D-UVB), a well-validated vitD proxy. An n-of-1 study design was used to examine the relapse risk using only the RKD dataset. Multi-level models and logistic regression were used to examine the effect of predictors on AAV relapse risk, phenotype and serotype. Results Residential latitude was positively correlated (OR 1.41, 95% CI 1.14–1.74, p = 0.002) and average vitD-UVB negatively correlated (0.82, 0.70–0.99, p = 0.04) with relapse risk, with a stronger effect when restricting to winter measurements (0.71, 0.57–0.89, p = 0.002). However, these associations were not restricted to granulomatous phenotypes. We observed no clear relationship between latitude, vitD-UVB or CW-D-UVB and AAV phenotype or serotype. Conclusion Our findings suggest that low winter ambient UVB and prolonged vitD status contribute to AAV relapse risk across all phenotypes. However, the development of a granulomatous phenotype does not appear to be directly vitD-mediated. Further research is needed to determine whether sufficient vitD status would reduce relapse propensity in AAV.

Comprehensive Analysis of Seasonal and Geographical Variation in UVB Radiation Relevant for Vitamin D Production in Europe

“…We found CW-D-UVB more strongly correlated with vitamin D status than diurnal UVB at, or around, the time of vitamin D status assessment [ 7 , 8 ]. Interestingly, CW-D-UVB dose has been associated with health outcomes in previous studies [ 40 , 41 , 42 ].…”

Can active sun exposure decrease the risk of giant cell arteritis and polymyalgia rheumatica in women?

“…In ANCA-associated vasculitis (AAV), the effect of sun exposure has been a long-standing debate. Observations of latitudinal differences in disease phenotype [ 47 ] have led to several studies investigating the effect of latitude and estimated UV exposure in disease onset, relapse, phenotypic and serologic expression [ 12 , 48 , 49 ]. The available evidence suggests an increased risk of granulomatosis with polyangiitis and proteinase 3 antibody positivity with increasing latitude and decreased UV exposure, with an inverse relationship for microscopic polyangiitis and myeloperoxidase antibody positivity.…”