Known and less well-known comorbidities in axial spondyloarthritis: what are we overlooking? Results from the SPARTAKUS cohort

Abstract

Objectives: To explore and compare the prevalences of a wide range of comorbidities in axial spondyloarthritis (axSpA) versus the general population, and in non-radiographic versus radiographic axSpA (nr-axSpA/r-axSpA). Method: Well-characterized axSpA patients (n = 246) from the SPARTAKUS cohort (55% men; mean age/disease duration 52/26 years; nr-axSpA/r-axSpA = 82/164) were included, and matched to comparators from the general population (five/patient) randomly drawn from the Swedish Population Register. Fifty-nine comorbidities were determined from ICD-10 diagnosis registrations in primary/specialized care, with data retrieved for the 10 year period preceding SPARTAKUS inclusion (for patients/their respective comparators). Differences in comorbidity prevalences were analyzed using logistic regression and controlled for multiple comparisons. Results: Most investigated comorbidities were numerically overrepresented in axSpA versus comparators with significantly higher prevalences of known extra-musculoskeletal manifestations [anterior uveitis (28% vs 1%), IBD (10%/1%), psoriasis (10%/3%)], and ischaemic heart disease (7%/3%), along with less explored conditions such as fibromyalgia/chronic pain (12%/3%) and nephrolithiasis (8%/3%). Patients displayed significantly higher proportions of well-known side-effects of non-steroidal anti-inflammatory drugs (NSAIDs) [gastritis (21%/10%), hypertension (31%/19%)] and glucocorticoids [cataract (11%/7%), glaucoma (7%/3%), osteoporosis/vertebral compression (4%/1%)]. No significant between-group difference (patients/comparators) was observed for Charlson Comorbidity Index (assessing short-term mortality risk) when excluding rheumatic disease. Moreover, no significant difference in comorbidity was found between nr-axSpA and r-axSpA. Conclusion: axSpA is linked to several comorbidities, whereas no difference was observed between nr-axSpA and r-axSpA. Potential causes of enhanced comorbidity include long-standing inflammation and therapy side-effects (including from NSAIDs/glucocorticoids), both to be considered when aiming to optimize axSpA treatment.