Does the age of onset of rheumatoid arthritis influence phenotype?: a prospective study of outcome and prognostic factors.

OBJECTIVE: To identify factors affecting prognosis in patients with late-onset rheumatoid arthritis (RA).

METHODS: A total of 400 patients with RA fulfilling the American College of Rheumatology criteria for diagnosis were prospectively recruited from two hospital rheumatology centres. Of these patients, 214 had disease onset above age 65 yr (LORA) and 186 below age 65 yr (YORA). Follow-up clinical, functional, laboratory and radiological assessments were compared. The Ritchie articular index (RAI) and joint erosions were used as markers of disease activity and damage, respectively. Disability was assessed using the Stanford Health Assessment Questionnaire (HAQ).

RESULTS: At median follow-up of 3.6 yr, the frequency of joint erosions was similar (YORA, 51.6%; LORA, 54.2%). The remission rate was greater in the LORA group (YORA, 20.4%; LORA, 45.8%, P < 0.01). Factors associated with the development of erosions were: IgM rheumatoid factor (RF) seropositivity [odds ratio (OR) = 4.24, 95% confidence interval (CI) 2.56, 6.94], HLA DR4 (OR = 2.07, 95% CI 1.28, 3.35) and elevated inflammatory markers (OR = 1.81, 95% CI 1.04, 3.14). Continuous steroid use >3 months for the LORA group was associated with increased erosions (OR = 4.09, 95% CI 1.81, 9.27). LORA patients (OR = 2.99, 95% CI 1.77, 5.02) were more likely to go into remission and IgM RF-seropositive patients less likely to go into clinical remission (OR = 0.47, 95% CI 0.28, 0.77). Female patients with a high HAQ score at presentation experienced a poor functional outcome (female OR = 3.01, 95% CI 1.59, 5.68; high HAQ OR = 3.02, 95% CI 1.98, 4.62).

CONCLUSION: LORA can be as damaging as classical RA and joint erosions are often observed at presentation. Being RF seropositive, DR4 positive, and having elevated inflammatory markers at onset, were associated with poor radiological outcome irrespective of age of onset. Being female and having marked disability at presentation were associated with poor functional outcome in both groups. These findings suggest that treatment approaches used in classical YORA should be instituted with equal vigour in patients with LORA.