Impact of Comorbidities and Extra-Musculoskeletal Manifestations on Radiographic Progression in Ankylosing Spondylitis

Objective: To examine whether baseline comorbidity burden and extra musculoskeletal manifestations (EMMs) – psoriasis, uveitis, IBD – are associated with spinal radiographic progression in ankylosing spondylitis (AS).

Methods: We analysed participants fulfilling modified New York criteria with ≥1 lateral cervical or lumbar radiograph. Radiographic progression was quantified using the modified Stoke AS Severity Score (mSASSS), excluding score 1 at each vertebral corner (range 0–48). Comorbidity count (22 self reported conditions: 0,1,2,≥3) and ever presence of each EMM at baseline were exposures. mSASSS change over time with exposure-time interactions was modelled using GEE; coefficients were rescaled to represent mean difference in progression (units/10 years). Models adjusted for baseline mSASSS, sex, symptom duration, CRP, HLA-B27, smoking, TNF inhibitor use, and number of EMMs or comorbidity count. Secondary analyses examined potential sex- and segment-specific effects.

Results: Among 1,150 individuals (mean age 44 years; 75% male; 84% HLA B27 positive), 3,441 patient years were analysed (median follow up 2 years; median 2 radiographs). Compared to those with no comorbidities, progression was greater amongst patients with 2 (2.7 units/10 years; 95%CI 1.9–3.5) and ≥3 (2.3; 1.5–3.1) comorbidities. Uveitis (2.2 units/10 years; 1.3–3.0) and psoriasis (2.4 units/10 years; 1.4–3.5), but not IBD, were associated with greater progression. Sex-specific analyses suggested greater spinal progression in females than males with psoriasis. Cervical-predominant changes were seen with uveitis and psoriasis.

Conclusion: Comorbidity burden, uveitis, and psoriasis are independently associated with greater spinal radiographic progression in AS. These readily identifiable features may inform risk stratification and targeted management strategies.