Incidence and predictors of demyelinating disease in spondyloarthritis: data from a longitudinal cohort study

Objectives: The objectives of this study were to investigate the incidence of demyelinating disease (DD) among SpA patients and to identify risk factors that predict DD in this patient population. Methods: Axial SpA (axSpA) and PsA patients were identified from a longitudinal cohort database. Each group was analysed according to the presence or absence of DD. Incidence rates (IRs) of DD were obtained, with competing risk analysis. Cox regression analysis (with Fine and Gray's method) was used to evaluate predictors of DD development. Results: Among 2260 patients with follow-up data, we identified 18 DD events, corresponding to an average IR of 31 per 100 000 persons per year for SpA. The IR of DD at 20 years was higher in axSpA than in PsA (1.30% vs 0.13%, P 1/4 0.01). The risk factors retained in the best predictive model for DD development included ever- (vs never-) smoking [hazard ratio (HR) 2.918, 95% CI 1.037-8.214, P 1/4 0.0426], axSpA (vs PsA) (HR 8.790, 95% CI 1.242-62.182, P 1/4 0.0294) and presence (vs absence) of IBD (HR 5.698, 95% CI 2.083-15.589, P 1/4 0.0007). History of TNF-a inhibitor therapy was not a predictor of DD. Conclusion: The overall incidence of DD in this SpA cohort was low. Incident DD was higher in axSpA than in PsA. A diagnosis of axSpA, the presence of IBD, and ever-smoking predicted the development of DD. History of TNF-a inhibitor use was not found to be a predictor of DD in this cohort.