Mortality and Cause of Death in Japanese Patients with Rheumatoid Arthritis Based on a Large Observational Cohort, IORRA

Objectives: To investigate mortality, cause of death, and risk factors related to mortality in Japanese patients with rheumatoid arthritis (RA).

Methods: The IORRA cohort is a large observational cohort established in 2000 at the Institute of Rheumatology, Tokyo Women's Medical University. Essentially, all RA patients were registered and clinical parameters were assessed biannually. For patients who failed to participate in subsequent surveys, simple queries were mailed to confirm survival. Standardized mortality ratios (SMRs) were calculated and mortality risk factors were analysed using a Cox proportional hazard model.

Results: We analysed 7926 patients (81.9% females; mean age 56.3 ± 13.1 years; mean disease duration 8.5 ± 8.3 years) with RA who enrolled in IORRA from October 2000 to April 2007. During the observational period (35 443.0 person-years), 289 deaths were reported. Major causes of death included malignancies (24.2%), respiratory involvement (24.2%) including pneumonia (12.1%) and interstitial lung disease (ILD) (11.1%), cerebrovascular disease (8.0%), and myocardial infarction (7.6%). As death was not confirmed in all patients, the SMR was deduced to be between 1.46 [95% confidence interval (CI) 1.32-1.60] and 1.90 (95% CI 1.75-2.07) for all patients, between 1.45 (95% CI 1.22-1.70) and 1.70 (95% CI 1.45-1.97) for men, and between 1.46 (95% CI, 1.29-1.65) and 2.02 (95% CI 1.82- 2.24) for women. Factors associated with increased mortality included male gender, older age, worse physical disability, positive rheumatoid factor (RF), corticosteroid use, and presence of ILD.

Conclusion: The mortality of Japanese RA patients is comparable to that in previous reports from western countries, even though the causes of death were significantly different.