Among patients with spondyloarthritis (SpA), health disparities were associated with socioeconomic status (SES) factors on both individual and country levels regarding disease activity and physical function, according to a report published in the Annals of the Rheumatic Diseases. Biologic disease-modifying antirheumatic drug (bDMARD) uptake did not appear to mediate these relationships.

Many diseases have demonstrated SES inequalities at the individual and at the country level regarding activity and dysfunction, including rheumatoid arthritis, where suspicions have focused on differential access to expensive bDMARDs. However, it remains unknown whether such health outcome differences exist for those with SpA. Investigators sought to answer this question in the first study to examine these potential associations.

A secondary data analysis from the COMOSPA trial — an international (n=22 countries), multicenter, cross-sectional, observational study — was conducted from January 2103 to September 2014, enrolling 3370 participants (mean age, 43 years; 66% male).

As the primary outcomes, Ankylosing Spondylitis Disease Activity Score (ASDAS) and Bath Ankylosing Spondylitis Functional Index (BASFI) results were recorded and compared using regression analysis and were adjusted for confounders in terms of potential associations with SES individual-level (education and gender) and country-level (country, global region, gross domestic product [GDP], and human development index) determinants.

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The possible mediating role of bDMARD uptake was also explored between GDP or education and ASDAS. Odds ratios (OR) were calculated.

The mean ASDAS and BASFI scores for the cohort were 2.02 and 3.10, respectively, with 44% of participants having ASDAS ≥2.1 (the cutoff for dichotomized results). There were 43%, 45%, and 13%, respectively, who completed university, secondary, and lower education, while 38% and 47% were currently taking bDMARDs and were smokers, respectively.

Multivariate adjustment results showed that women and those with lower educational levels had an independent and significant association with poorer disease outcomes. Being female carried an OR of 1.70 (95% CI, 1.43-2.01) for ASDAS ≥2.1, while patients with lower education had an OR of 1.66 (95% CI, 1.29-2.20); both groups also saw higher BASFI scores compared with males and those with higher education.

Both obesity (OR, 1.66; 95% CI, 1.33-2.08) and smoking (OR, 1.21; 95% CI, 1.02-1.42) were also correlated with higher scores on each measure. Although patients taking bDMARDs had lower ASDAS and slightly higher BASFI scores, there was no confounding effect on the relationship between SES factors and disease activity.

Large country-level differences were also observed that were independent of clinical confounders or individual-level SES.

Patients in less-developed countries had significantly worse ASDAS scores, while BASFI differences were found to be insignificant, with similar functional levels among all participants. African citizens displayed considerably higher ASDAS scores and Asian citizens had consistently lower BASFI scores compared with other regions. Patients from nations with lower GDP had an OR of 1.49 (95% CI, 0.91-2.45) for ASDAS ≥2.1, while areas with lower human development index also had increased risk for ASDAS ≥2.1 (OR 1.84; 95% CI, 1.13-3.00).

Study limitations included possible overrepresentation of patients receiving optimal therapy; potential impact of sampling differences on country differences; lack of data on additional SES factors; moderately small number of countries, limiting analysis power; lack of confirmation regarding outcome measures’ sensitivity to SES or cultural factors; and cross-sectional design.

“The identified socioeconomic inequalities in disease activity in patients with SpA are a call for a consolidated action of all stake holders,” concluded the authors. They recommended that future research involve longitudinal studies.

Disclosures: The COMOSPA study was conducted with the financial support from AbbVie, Pfizer, and UCB, which provided an unrestricted grant to ASAS to fund the study.

Reference

Putrik P, Romiro S, Moltó A, et al. Individual-level and country-level socioeconomic determinants of disease outcomes in SpA: multinational, cross-sectional study (ASAS-COMOSPA) [published online January 23, 2019]. Ann Rheum Dis. doi:10.1136/annrheumdis-2018-214259