Objective: To investigate the longitudinal relationship between physical disability, disease activity, and radiographic damage over 10 years in patients with rheumatoid arthritis (RA).
Methods: A cohort of 238 consecutively enrolled RA patients from the European Research on Incapacitating Disease and Social Support study (age range 20-70 years, mean disease duration 2.3 years, 68% rheumatoid factor [RF] positive) was followed up longitudinally for 10 years. Assessments at baseline and at years 1, 2, 5, and 10 comprised review of demographic variables, measurement of disease activity with the erythrocyte sedimentation rate (ESR), functional evaluations using the Health Assessment Questionnaire (HAQ) and grip strength (average value of the right and left hand), and radiographs of the hands scored by the van der Heijde modification of the Sharp method. Marginal modeling by generalized estimating equations was used to study the longitudinal relationship between the ESR and modified Sharp radiographic damage score with respect to explaining the HAQ score and grip strength. Age, sex, RF status, and disease duration were entered as covariates.
Results: The HAQ score and grip strength were longitudinally associated with the momentary modified Sharp/van der Heijde score as well as with progression in this score, independent of the ESR. Therefore, an increase of 10 units in the modified Sharp/van der Heijde score will result in a 0.03-unit increase in HAQ score and a 0.95-kg decrease in grip strength, after adjustment for the ESR.
Conclusion: This 10-year observational study provides evidence that both radiographic damage and disease activity are independent contributors to impaired physical function in RA, both early and late in the disease process.