Background In RA, previous studies observed inequalities in health across countries as well as across individual level socio-economic factors, and unequal uptake of biologic DMARDs (bDMARDs) played an important role in these inequalities. It is not known whether the same pattern is present for patients with spondyloarthritis (SpA).
Objectives To assess: (1) independent associations of individual and country level socio-economic determinants with health outcomes in patients with SpA and (2) if confirmed, whether this relation is mediated by uptake of bDMARDs.
Methods Data from the cross-sectional multinational COMOrbidities study in SpA (COMOSPA) were used. Contribution of individual socioeconomic factors (age, gender, education) and country of residence to ASDAS and BASFI was explored in regression models, adjusting for clinical confounders. Next, country of residence was replaced by gross domestic product adjusted for purchasing power parity (GDP PPP) (low, medium, and high, based on tertile distribution). Finally, the role of bDMARDs uptake in the relationship between education or GDP and ASDAS was explored by testing indirect effects.
Results In total 3,984 patients with SpA from 22 countries were included: 65% males, mean age 44 (SD14), ASDAS 2.0 (±1.1) and BASFI 3.0 (±2.7). Five to 68% of patients were currently treated with bDMARDs. Females (vs. males) had higher ASDAS (β=0.21 [95%CI 0.13;0.28]) and BASFI (β=0.45 [95%CI 0.31;0.59]). The effect of age was negligible for both outcomes. Low vs high educated individuals had higher ASDAS and BASFI (β=0.29 [0.21;0.36] and β=0.46 [0.24;0.69], respectively) (Table). Independent of the individual confounders, large country differences were observed. Low GDP (vs. high GDP) was associated with higher ASDAS (β=0.27 [0.17;0.36]) and higher BASFI (β=0.20 [0.03;0.38] (Table). Current uptake of bDMARDs did not mediate relationship between education or GDP with ASDAS.
Conclusions Health inequalities across individual and country level socio-economic factors exist also among SpA patients. Females, lower educated patients and patients from low income countries had higher disease activity and physical function.
Disclosure of Interest None declared