Prevalence and incidence in patients with autoimmune rheumatic diseases: A nationwide population‐based study in Taiwan

Objective The purpose of this study was to determine the prevalence, incidence, and mortality rates of autoimmune rheumatic diseases (ARDs) by using a population‐based database. Methods We used the longitudinal health insurance database (comprising 1,000,000 beneficiaries) of the Taiwan National Health Insurance from 2000 to 2008 and the National Death Registry of Taiwan from 2000 to 2008. Results The overall prevalence of major ARDs was 101.3 (95% confidence interval [95% CI] 27.5–107.9) per 100,000 populations; the prevalence was 165.1 (95% CI 44.8–177.1) in women and 40.1 (95% CI 10.9–46.1) in men. The prevalences of rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Sjögren's syndrome, progressive systemic sclerosis, polymyositis/dermatomyositis, vasculitis, and Behçet's disease were 52.4 (95% CI 14.2–57.2), 37.0 (95% CI 10.0–41.0), 16.0 (95% CI 4.3–18.7), 3.8 (95% CI 1.0–5.3), 2.9 (95% CI 0.8–4.2), 5.7 (95% CI 1.6–7.4), and 1.4 (95% CI 0.4–2.3) per 100,000 persons, respectively. Between 2001 and 2008, the incidence rates (per 100,000 person‐years) for these diseases were 17.3, 8.4, 10.6, 1.5, 1.5, 1.2, and 0.8, respectively. The incident cases with ARDs had a higher risk of mortality, with the standardized mortality ratio (SMR) ranging from 1.3 to 3.7. Conclusion In 2000, the prevalence of major ARDs was 1.4–52.4 per 100,000 persons in Taiwan. Between 2000 and 2008, the incidence rates of various ARDs were 0.8–17.3 per 100,000 person‐years. The prevalence and incidence of RA were the highest, followed by SLE and Sjögren's syndrome, and those of Behçet's disease were the lowest. Patients with different types of ARDs had higher mortality and SMR than those of the general population.