The disease activity in patients with rheumatoid arthritis has improved during the past decade. The availability of new drugs and also a better assessment of the disease have been proposed to be responsible for this improvement. In the present work we estimate the effect of these factors on disease activity and function in patients with rheumatoid arthritis at the beginning of the new century.
The Estudio de la Morbilidad y Expresión Clínica de la Artritis Reumatoide (EMECAR) cohort was assembled in 2000 from the random sampling of rheumatoid arthritis patients registered in 34 centers. The cohort was composed of 789 patients who underwent a baseline assessment plus four annual follow-up visits in which functional ability (Health Assessment Questionnaire score), the disease activity score obtained from 28-joint count with three parameters (DAS28-3) and radiological progression (Larsen score) were recorded. The effect of the calendar year on the DAS28-3, the Health Assessment Questionnaire score, and the Larsen score was obtained from adjusted models in which all treatments were included as dummy variables.
The effect of time as the beta coefficient (95% confidence interval) for 2004, taking 2000 as a reference year, was -0.43 (-0.58 to -0.28) for the DAS28-3, 0.15 (0.07 to 0.22) for the Health Assessment Questionnaire score, and 4.4 (2.68 to 6.12) for the Larsen score. Treatment with new therapies, either leflunomide or TNF antagonists, increased in frequency from 1.1% (n = 8) in 2000 to 30.9% (n = 144) in 2004. Treatment with TNF antagonists (-0.28 (-0.5 to -0.05)) and with gold salts (-0.21 (-0.38 to -0.04)) was independently associated with a decrease in the DAS28-3 over time, whereas cyclosporin A treatment (0.45 (0.13 to 0.76)) was associated with an increase in disease activity.
The mean disease activity of rheumatoid arthritis has improved from 2000 to 2004. An explanation is the introduction of new therapies, but not solely. Other factors related to the calendar year, plausibly a better management of available drugs, show a greater effect on improvement than the drugs used.