OP0035 DEPRESSION IN ANKYLOSING SPONDYLITIS AND THE ROLE OF DISEASE-RELATED AND CONTEXTUAL FACTORS: A STRUCTURAL EQUATION MODELLING APPROACH
Authors: Casper Webers, Laura Vanhoof, Carsten Leue, Annelies Boonen, Sebastian Köhler
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Patients with ankylosing spondylitis (AS) are at increased risk of depression compared to the general population. Comorbid depression in AS likely has a multifactorial origin. While several disease-related and contextual factors have been associated with depressive symptoms in AS, a comprehensive model of their interrelations is currently lacking. Such a model could help understand the mechanisms leading to, or maintaining, depression in AS. <h3>Objectives</h3> To determine which factors contribute to depressive symptoms in AS, and to understand the relationships between relevant factors. <h3>Methods</h3> Data from patients with AS participating in the Dutch cross-sectional multicentre survey-based Social Participation in Ankylosing Spondylitis Study (SPASS) were used. Potential determinants included both contextual and disease-related factors. Depressive symptoms were assessed by the depression subscale of the Hospital Anxiety and Depression Scale (HADS-D). A latent 'depression' variable was constructed by regressing the 7 manifest items of the HADS-D questionnaire on the outcome 'depression', to represent it more accurately. Candidate variables for the model were selected using univariable negative binomial regression. Direct and indirect associations between risk factors and the dimensional latent depression outcome were explored using structural equation modelling. Both theory-driven and data-driven approaches were explored. A final model was selected based on model fit criteria, clinical plausibility and explained variance in the outcome. <h3>Results</h3> Among 245 patients, median (interquartile range) HADS-D was 3 (1-6) and 44 patients (18%) had a HADS-D &gt;=8, indicating possible depression. The theory-driven model had poor fit and was rejected. The data-driven approach led to a model with good fit. In this final model (see Figure), contextual factors associated with depressive symptoms were male gender, a history of depression, being employed, lower income, lower mastery and worse satisfaction with social role participation. Regarding disease-related factors, Bath AS Disease Activity Index (BASDAI) was the only determinant in the final explanatory model, acted only indirectly, and had less effect on depressive symptoms than several of the contextual factors. Mastery had a central role in the path diagram and was a mediator for the effects of BASDAI, income and satisfaction with social role participation on depressive symptoms. The final model explained 64% of the variance in the latent depressive symptoms outcome. <h3>Conclusion</h3> Both contextual and disease-related factors contribute to depressive symptoms in AS, but contextual factors have a larger contribution. Mastery, the extent to which one feels in control over life and disease, has a key role in this process. These results support a relevance of self-efficacy in disease management and patient education. In order to improve patients' mental health, research is warranted whether mastery and its relation with depression can be modified. <h3>Disclosure of Interests</h3> None declared