Objective: In this study we compared activity limitations, pain intensity, and global health in patients with rheumatoid arthritis (RA) in Sweden and the USA and aimed to determine whether nationality is associated with these outcomes.
Methods: We used longitudinal data from the 'Swedish TIRA project' (n = 149) and the University of California, San Francisco (UCSF) RA panel study (n = 85). Data were collected annually concerning use of medications [disease-modifying anti-rheumatic drugs (DMARDs), biologics, and corticosteroids], morning stiffness, number of swollen joints, and number of painful joints. Three self-reported outcome measures were examined: pain intensity measured on a 0-100 visual analogue scale (VAS), activity limitation according to the Health Assessment Questionnaire (HAQ), and global health. To analyse the data, the Student's t-test, the χ(2)-test, and the generalized estimating equation (GEE) method were used.
Results: Nationality was significantly related to HAQ score and pain intensity, even after adjustment for covariates. The patients in the TIRA cohort reported a lower HAQ score and a higher pain intensity than the patients in the UCSF cohort. Nationality was not related to global health.
Conclusion: Patients with RA should be assessed with awareness of the psychosocial and cultural context because disability seems to be affected by nationality. Further knowledge to clarify how a multinational setting affects disability could improve the translation of interventions for patients with RA across nationalities.