Age-related increases in erythrocyte sedimentation rate (ESR) and 28-joint swollen joint count (28-SJC) scores without relevant corresponding increases in patient global assessment (PGA) and 28-joint tender joint counts (28-TJCs) may imply that age-related processes such as physiological ESR increase and soft tissue changes contribute to a higher 28-joint Disease Activity Score (DAS28) in older patients, according to results from a concise report published in Rheumatology.

The current study used the DAS28 and its components to investigate the potential effect of aging on patients with rheumatoid arthritis who are naïve to treatment with disease activity in disease-modifying antirheumatic drugs (DMARDs) from the Norwegian Register of DMARDs. Investigators used linear regression to explore associations between age (<45, 45-65, and >65 years) and each component of the DAS28 while accounting for sex and education. They calculated adjusted predicted scores for each component and total scores for each age range. Because significant interactions were found between age and sex for the 28-TJC, PGA, and ESR (P <.001), researchers stratified regression models for sex. Education was a significant covariate, leading investigators to calculate predicted scores across age categories for different levels of education. Disease duration was not included in the model because it proved to not be a significant confounder.

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Baseline data were available for 2037 patients (mean age 55.2 years; 68% women). Compared with the youngest age group, men older than 65 years with an intermediate education level had a 25% higher 28-SJC and 56% higher ESR, and women with an intermediate education level had a 27% higher 28-SJC and 51% higher ESR. The differences between 28-TJC and PGA were negligible (men: 28-TJC 3% and PGA 1%; women: 28-TJC 1% and PGA 2%). The difference in total DAS28-ESR score between the youngest and oldest age category was 10% for both men and women. In absolute values, the DAS28 was 5.5 in the oldest group compared with 5 in the youngest.

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Study limitations included using baseline data from patients who were DMARD-naïve entering the Norwegian Register of DMARDs and the potential for confounding variables; however, the study investigators concluded that “the present study indicates that age has a significant positive relationship with the DAS28-ESR, with the ESR and 28-SJC driving the increase. Validation of disease activity measures in elderly RA patients should be performed in future studies where the influence of comorbidity and physiological ageing is studied. The age effect on DAS28 might be relevant in a treat-to-target strategy, but longitudinal data are needed to further explore this.”

van Onna M, Putrik P, Lie E, Kvien TK, Boonen A, Uhlig T. What do we measure with 28-joint DAS in elderly patients? An explorative analysis in the NOR-DMARD study [published online October 26, 2019]. Rheumatology (Oxford). doi:10.1093/rheumatology/kez490