Is the disease course of rheumatoid arthritis becoming milder? Time trends since 1985 in an inception cohort of early rheumatoid arthritis

Abstract

Objective: Based on comparisons of short-term cohort studies or cross-sectional samples of patients from different calendar times, it has been suggested that present patients with rheumatoid arthritis (RA) have a milder disease course compared with that of patients in past decades. This study was undertaken to investigate whether the course of disease activity and functional disability in patients with RA has become milder over the past several years.

Methods: We used the Nijmegen inception cohort of early RA, which included all patients with newly diagnosed RA who had attended the department of rheumatology at Radboud University Nijmegen Medical Centre since 1985. Patients were assessed for disease activity by the Disease Activity Score in 28 joints (DAS28) every 3 months and for functional disability by the Health Assessment Questionnaire (HAQ) disability index (DI) every 6 months. Within the total cohort, 4 subcohorts were defined, based on the date of inclusion of the patients (1985-1990, 1990-1995, 1995-2000, 2000-2005). To investigate whether the course of disease activity and functional disability (over time) was different between the subcohorts, longitudinal regression analysis (linear mixed models) was used, with the DAS28 and HAQ DI over time as outcome variables, respectively, and subcohort as the independent variable, correcting for baseline demographic and clinical characteristics. The treatment strategy was compared between the subcohorts.

Results: The DAS28 at baseline and over the first 5 years of disease was lower in the more recent subcohorts. The HAQ DI did not show improvement but instead a trend toward worsening functional disability. Using longitudinal regression it was shown that disease activity improved early in the disease course and stabilized thereafter, and that this improvement was greater in patients in the more recent subcohorts and in patients with a higher baseline DAS28. Initially, the HAQ DI also improved but stabilized thereafter, and this initial improvement was less pronounced in patients in the more recent subcohorts and was greater for patients with a higher baseline HAQ DI. The treatment strategy was more aggressive in the more recent subcohorts, as shown by a shorter duration from diagnosis to the start of treatment with prednisone or disease-modifying antirheumatic drugs (DMARDs), and a greater prevalence of DMARD therapy.

Conclusion: The course of disease activity in RA patients has become milder in more recent years. The reason for this improving trend remains to be elucidated, although the trend coincides with a more aggressive treatment strategy.