Objectives: To describe the characteristics of patients between late-onset rheumatoid arthritis (LORA) with young-onset (YORA), and analyze their association with cumulative inflammatory burden. Methods: We performed a nested cohort study in a prospective cohort comprising 110 patients with rheumatoid arthritis (RA) and 110 age- and sex-matched controls. The main variable was cumulative inflammatory activity according to the 28-joint Disease Activity Score with erythrocyte sedimentation rate (DAS28-ESR). High activity was defined as DAS28 ≥ 3.2 and low activity as DAS28 < 3.2. The other variables recorded were inflammatory cytokines, physical function, and comorbid conditions. Two multivariate models were run to identify factors associated with cumulative inflammatory activity. Results: A total of 22/110 patients (20%) met the criteria for LORA (≥ 60 years). Patients with LORA more frequently had comorbid conditions than patients with YORA and controls. Compared with YORA patients, more LORA patients had cumulative high inflammatory activity from onset [13 (59%) vs. 28 (31%); p = 0.018] and high values for CRP (p = 0.039) and IL-6 (p = 0.045). Cumulative high inflammatory activity in patients with RA was associated with LORA [OR (95% CI) 4.69 (1.49-10.71); p = 0.008], smoking [OR (95% CI) 2.07 (1.13-3.78); p = 0.017], anti-citrullinated peptide antibody [OR (95% CI) 3.24 (1.15-9.13); p = 0.025], average Health Assessment Questionnaire (HAQ) score [OR (95% CI) 2.09 (1.03-14.23); p = 0.034], and physical activity [OR (95% CI) 0.99 (0.99-0.99); p = 0.010]. The second model revealed similar associations with inflammatory activity in patients with LORA. Conclusion: Control of inflammation after diagnosis is poorer and comorbidity more frequent in patients with LORA than in YORA patients and healthy controls.