Late-onset versus young-onset rheumatoid arthritis: comorbidities, disease activity, and treatment patterns in a nationwide real-world registry from Kuwait

ObjectivesLate-onset rheumatoid arthritis (LORA) may differ clinically from young-onset rheumatoid arthritis (YORA), but real-world data from the Middle East and North Africa are limited. We compared characteristics, comorbidities, disease activity, and treatment patterns between LORA and YORA in the Kuwait Registry for Rheumatic Diseases (KRRD) and assessed whether age at onset was independently associated with disease activity.MethodsThis retrospective analysis of prospectively collected KRRD data included patients with RA enrolled between January 2012 and April 2026. Patients were classified as YORA (symptom onset 18–59 years) or LORA (≥60 years). Baseline characteristics, disease activity, treatments, and one-year outcomes were compared. Multivariable logistic regression examined factors associated with moderate-to-high disease activity (DAS28-ESR ≥3.2). Sensitivity analyses additionally adjusted for current age, assessed collinearity, and repeated comorbidity and ESR comparisons after age adjustment and within patients aged 60–79 years.ResultsAmong 2,629 patients, 303 (11.5%) had LORA and 2,326 (88.5%) had YORA. LORA patients had shorter disease duration (2.9 ± 4.0 vs. 5.0 ± 7.1 years; p < 0.001) and higher comorbidity burden (2.0 ± 1.5 vs. 0.9 ± 1.2; p < 0.001). Most disease activity measures and treatment patterns were similar. Among 1,402 patients with follow-up of at least one year, disease activity at the last visit was similar (DAS28-ESR mean difference 0.10, 95% CI −0.12 to 0.30), including after inverse-probability weighting and multiple imputation. ESR was higher in LORA (40.9 vs. 33.3 mm/hr; p < 0.001), whereas CDAI was not (mean difference 0.7, 95% CI −0.9 to 2.3). Age at onset was not independently associated with moderate-to-high disease activity (adjusted OR 1.08, 95% CI 0.83–1.41; p = 0.559). After adjustment for current age and sex, the comorbidity excess in LORA was no longer evident (adjusted rate ratio 0.79, 95% CI 0.70–0.89), while ESR remained modestly higher (adjusted ratio 1.17, 95% CI 1.02–1.33). Adding current age did not materially change the onset-group estimate (adjusted OR 1.05, 95% CI 0.76–1.44).ConclusionLORA and YORA showed similar disease activity, treatment patterns, and follow-up outcomes. The higher comorbidity burden in LORA was explained by chronological age, while ESR remained modestly elevated after age adjustment. Findings support treat-to-target principles regardless of age at onset, alongside management of comorbidities in older patients.