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OBJECTIVES: This study aims to study the framework describing the longitudinal association between disease activity and function (independent variables) and health-related quality of life (HRQoL, outcome) in axial spondyloarthritis (axSpA). METHODS: Patients with AxSpA (symptoms <3 years) from the Devenir des Spondylarthropathies Indifferénciées Récentes cohort were followed up for 10 years. The association of disease activity (ASDAS) and function (BASFI) with HRQoL (physical component summary PCS and mental component summary MCS of 36-item short-form health survey, ankylosing spondylitis quality of life ASQoL) was assessed. Multivariable generalised estimating equations models were built with PCS, MCS, or ASQoL as outcomes (higher PCS/MCS = better HRQoL, higher ASQoL = worse), and ASDAS and BASFI as main predictors. Standard and autoregressive (i.e., corrected for prior HRQoL) models were used. The impact of ASDAS vs BASFI on HRQoL was compared through standardised coefficients. Mediation analysis assessed whether the effect of ASDAS on HRQoL was mediated by BASFI. Confounders/effect modifiers (eg, contextual factors) were considered in all models. RESULTS: A total of 663 patients with axSpA (46% males, mean age 33.5 8.6 years) were included. In standard and autoregressive multivariable models, significant associations for ASDAS and BASFI with HRQoL were found (beta coefficient 95% CI for autoregressive models: PCS -2.93 -3.28, -2.58; -2.13 -2.31, -1.96), MCS (-2.38 -2.91, -1.86; -1.10 -1.36, -0.84), ASQoL (1.18 1.02, 1.36; 1.08 0.99, 1.17). A larger influence of BASFI, compared to ASDAS, on HRQoL was noted. Mediation analysis showed the ASDAS effect on HRQoL was mostly (∼75%) mediated by BASFI, but a direct effect (∼25%) also existed. CONCLUSIONS: A validated longitudinal framework has been established for interpreting HRQoL: even correcting for contextual factors, disease activity consistently impacts HRQoL-primarily through functional impairment, but also directly. While HRQoL is an overarching outcome in axSpA, targeting low disease activity is crucial to optimise HRQoL.
Ortolan et al. (2025) studied this question.