What do we measure with 28-joint DAS in elderly patients? An explorative analysis in the NOR-DMARD study

Insight into the influence of ageing on disease outcomes is limited. The objective of this study was to examine the potential effect of age on disease activity using the 28-joint DAS (DAS28) and its components in patients with RA.

Baseline data of DMARD-naïve patients with RA from the Norwegian Register of DMARDs were used. Linear regression explored the strength of the association between age (<45, 45-65 and >65 years) and each DAS28 component while accounting for education and gender. Adjusted predicted scores for DAS28 components and total DAS28 score were calculated for each age category.

Baseline data from 2037 patients [mean age 55.2 years (s.d. 14.0), 68% females] were available. Regression models had to be stratified for gender (P for interaction <0.001); education was a significant covariate. Males >65 years of age with an intermediate level of education have a 56% higher ESR and 25% higher 28-joint swollen joint count as compared with their younger counterparts (<45 years). For females, corresponding differences were 51% and 27%, respectively. The age effect on the 28-joint tender joint count and patient global assessment was negligible. In patients with an intermediate education level, DAS28 was 5.0 vs 5.5 (10% increase) in the youngest vs oldest age groups, independent of gender.

The age-related increase in ESR and 28-joint swollen joint count scores without a relevant corresponding increase in 28-joint tender joint count and patient global assessment might imply that age-related processes (e.g. soft tissue changes, physiological ESR increase) contribute to a higher DAS28 in elderly patients.