Background: Joint space narrowing (JSN) in rheumatoid arthritis (RA) may be a manifestation of (primary) osteoarthritis becoming more prominent with age. We investigated the severity and predictors of JSN progression among different age groups.
Methods: 10-year follow-up data of the BeSt study, a randomised controlled treat-to-target trial in early RA were used. Annual X-rays of hands and feet were scored using the Sharp/van der Heijde score (SHS). Subgroups were defined by age at baseline: ≥55, ≥40<55 and <40 years. JSN progression predictors were assessed by Poisson regression.
Results: Baseline JSN scores (median (IQR)) were higher in patients ≥55 (2.0 (0.0-6.0)) compared with the other age groups: 1.0 (0.0-3.0) ≥40<55 and 0.3 (0.0-3.0) <40, p<0.001. After 10 years, total JSN and SHS were similar in all age groups. In patients ≥55 the mean erythrocyte sedimentation rate (ESR) over time (relative risk 1.02 (95% CI 1.00 to 1.03)) and the combined presence of rheumatoid factor and anticitrullinated protein antibodies (RF+/ACPA+) (3.27 (1.25-8.53)) were significantly correlated with JSN progression. In patients <40 the baseline swollen joint count (SJC; 1.09 (1.01-1.18)) and ESR over time (1.04 (1.02-1.06)) were significantly associated.
Conclusions: At baseline, patients with RA ≥55 years had more JSN than younger patients but after 10 years JSN scores were similar between age groups. Independent risk factors for JSN progression were baseline SJC and ESR over time in patients <40, RF+/ACPA+ and ESR over time in patients ≥55 years. This suggests that mechanisms leading to JSN progression are related to (residual) rheumatoid inflammation and vary between age groups. These mechanisms remain to be elucidated.
Trial registration numbers: NTR262, NTR265.
Keywords: Epidemiology; Osteoarthritis; Rheumatoid Arthritis; Treatment.