CRP and rheumatoid arthritis: Patients aged ≥ 75 years exhibited a higher incidence of advanced-stage RA, higher ABA and GC usage, higher pre-existing lung disease prevalence, lower MTX usage, stronger inflammatory responses (e.g., CRP and ESR), higher RF levels, higher CDAI scores, and higher HAQ-DI scores than patients aged < 65 and 65–74 years.