Background/Purpose:

Joint space narrowing (JSN)
and erosions are the major radiologic markers of radiographic progression in
rheumatoid arthritis (RA), as scored by the Sharp/van der Heijde score (SHS).
JSN may also be a manifestation of (primary) osteoarthritis becoming more
prominent with age. We hypothesize that the severity of JSN progression and predictors
of JSN progression may differ between older and younger RA patients.

Methods:

Ten year follow-up data of
the BeSt study, a randomized controlled treat-to-target (Disease activity score
(DAS)≤2.4) trial in early RA were used. Annual X-rays of hands and feet
from baseline to year 10 were scored with the SHS by two independent readers,
blinded for patient identity and time order. Subgroups were defined by age at
baseline: ≥55 (median age), ≥40<55 and <40 years. Poisson
regression with multiple imputation for missing data (7% and 45% of the
radiographs at baseline and year 10) was used to identify univariate
predictors. Factors with p<0.2 were entered in a multivariate regression
analysis. Post-hoc Bonferroni corrections were used to correct for multiple
testing.

Results:

Baseline median
(interquartile) SHS scores were higher in patients ≥55 compared to the
other groups (≥55: 2.5 (1.0-7.4); ≥40<55: 1.0 (0.0-4.5); <40:
1.0 (0.0-3.0); p≤0.001). Also, higher baseline JSN was observed in
patients ≥55 compared to the other groups: 2.0 (0.0-6.0), 1.0 (0.0-3.0)
and 0.3 (0.0-3.0), p≤0.001, respectively. After ten years, total JSN and
SHS scores were similar in all age-groups. Although fewer patients <40 years
appear to have JSN progression, if they do show JSN progression it is more
severe (figure 1).

Table 1 shows significant
univariate risk factors. In the multivariate regression, in patients ≥55
mean erythrocyte sedimentation rate (ESR) over ten years follow-up (RR 1.02,
95% CI (1.00-1.03)) and the combined presence of rheumatoid factor and
anti-citrullinated protein antibodies (RF+/ACPA+) (3.27 (1.25-8.53)) were
significantly associated with JSN progression. In patients ≥40<55 no significant
risk factors were revealed. In patients <40 baseline swollen joint count
(SJC) (1.09 (1.01-1.18)) and mean ESR (1.04 (1.02-1.06)) were significantly associated.

Conclusion:

At baseline, RA patients
≥55 years had more JSN but after 10 years of DAS≤2.4 targeted
treatment they do not show more often or more severe JSN progression. Independent
risk factors for JSN progression were mean ESR in patients <40 and those ≥55
years, RF+/ACPA+ in patients ≥55 years and SJC in patients <40 years.
This suggests that mechanisms leading to JSN progression vary between age
groups.