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Lower education and living in countries with lower wealth are associated with higher disease activity in rheumatoid arthritis: results from the multinational COMORA study
  1. Polina Putrik1,2,
  2. Sofia Ramiro3,4,
  3. Andras P Keszei5,
  4. Ihsane Hmamouchi6,
  5. Maxime Dougados7,
  6. Till Uhlig8,
  7. Tore K Kvien9,
  8. Annelies Boonen1
  1. 1Department of Internal Medicine, Division of Rheumatology, Maastricht University Medical Center and CAPHRI, Maastricht University, Maastricht, the Netherlands
  2. 2Health Promotion, CAPHRI, Maastricht University, Maastricht, the Netherlands
  3. 3Department of Clinical Immunology & Rheumatology, Amsterdam Rheumatology Center, University of Amsterdam, Amsterdam, the Netherlands
  4. 4Department of Rheumatology, Hospital Garcia de Orta, Almada, Portugal
  5. 5Department of Medical Informatics, Uniklinik RWTH Aachen University, Aachen, Germany
  6. 6Mohammed V University, Faculty of Medicine, Laboratory of Clinical Research and Epidemiology, Rheumatology Department, El Ayachi Hospital, Rabat, Morocco
  7. 7Paris Descartes University, Rheumatology Department, Cochin Hospital, Assistance Publique-Hôpitaux de Paris, INSERM (U1153): Clinical Epidemiology and Biostatistics, PRES Sorbonne Paris-Cité, France
  8. 8National Advisory Unit on Rehabilitation in Rheumatology, Department of Rheumatology, Diakonhjemmet Hospital, Oslo, Norway
  9. 9Department of Rheumatology, Diakonhjemmet Hospital, Oslo, Norway
  1. Correspondence to Polina Putrik, Department of Internal Medicine, Division of Rheumatology, Maastricht University Medical Center and CAPHRI, Maastricht University, PO Box 616, 6200 MD, Maastricht, the Netherlands; polina.putrik{at}gmail.com

Abstract

Objectives To investigate the relationship of socioeconomic status (SES) on an individual and country level with disease activity in rheumatoid arthritis (RA) and explore the mediating role of uptake of costly biological disease-modifying antirheumatic drugs (bDMARDs) in this relationship.

Methods Data from a cross-sectional multinational study (COMOrbidities in RA) were used. Contribution of individual socioeconomic factors and country of residence to disease activity score with 28-joint assessment (DAS28) was explored in regression models, adjusting for relevant clinical confounders. Next, country of residence was replaced by gross domestic product (GDP) (low vs high) to investigate the contribution of SES by comparing R2 (model fit). The mediating role of uptake of bDMARDs in the relationship between education or GDP and DAS28 was explored by testing indirect effects.

Results In total, 3920 patients with RA were included (mean age 56 (SD 13) years, 82% women, mean DAS28 3.7 (1.6)). After adjustment, women (vs men) and low-educated (vs university) patients had 0.35 higher DAS28. Adjusted country differences in DAS28, compared with the Netherlands (lowest DAS28), varied from +0.2 (France) to +2.4 (Egypt). Patients from low GDP countries had 0.98 higher DAS28. No interactions between individual-level and country-level variables were observed. A small mediation effect of uptake of bDMARDs in the relationship between education and DAS28 (7.7%) and between GDP and DAS28 (6.7%) was observed.

Conclusions Female gender and lower individual or country SES were independently associated with DAS28, but did not reinforce each other. The association between lower individual SES (education) or lower country welfare (GDP) with higher DAS28 was partially mediated by uptake of bDMARDs.

  • DAS28
  • Epidemiology
  • Rheumatoid Arthritis

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