Interrelationships of disease activity, central sensitization, psychosocial and lifestyle factors in axial spondyloarthritis

Objectives In a substantial portion of patients with axial SpA (axSpA), disease activity scores remain high despite anti-inflammatory treatment. This is possibly due to factors beyond active inflammation including different pain mechanisms and psychosocial factors. Therefore, our aim was to build a biopsychosocial model to explore the interrelationships of Axial Spondyloarthritis Disease Activity Score (ASDAS) with central sensitization, psychological and lifestyle factors in patients with axSpA.Methods Consecutive patients from the prospective Groningen Leeuwarden axSpA (GLAS) cohort were included in this cross-sectional study. Assessments included in the model were educational level, BMI, questionnaires on central sensitization, illness perception, pain catastrophizing, coping, anxiety and depression, physical activity (modified Short QUestionnaire to ASsess Health-enhancing physical activity, mSQUASH) and ASDAS. Structural equation modelling (SEM), a multivariate analysis testing hypothesized interrelationships between variables, was applied to investigate the effects of central sensitization, psychosocial and lifestyle factors on ASDAS.Results A total of 332 consecutive axSpA patients were eligible for analyses, of whom 59% were male; median symptom duration was 21 years and mean ASDAS was 2.2 +/- 0.9. The final SEM model had a satisfactory fit [root mean square error of approximation = 0.057 (95% CI 0.45-0.70), comparative fit index = 0.936]. Illness perception, central sensitization and BMI had direct, significant, effects on ASDAS. Psychological well-being and educational level were significantly indirectly associated with ASDAS through illness perception.Conclusion Our analyses exploring the interrelationships of biopsychosocial factors related to ASDAS showed that factors beyond inflammation, especially illness perception and central sensitization, seem to contribute significantly to ASDAS in patients treated for axSpA in our standard-of-care cohort, confirming the need for a biopsychosocial approach.