Incidence, mortality, and causes of death in physician-diagnosed primary Sjögren's syndrome in Korea: A nationwide, population-based study

Objectives: The objective of this study was to investigate the epidemiological features of primary Sjögren's syndrome (pSS) in Korea at a national level, including the incidence, mortality, and causes of death.

Methods: We used a national, population-based registry database called the Rare Intractable Disease Registration Program from the Health Insurance Review and Assessment Service to obtain pSS patient data for the period between 2010 and 2014. pSS was diagnosed by a physician based on uniform criteria. We also used data from Statistics Korea to confirm the mortality and causes of death.

Results: Between 2010 and 2014, the total number of patients newly diagnosed with pSS was 5891, resulting in an annual incidence of 2.34 per 100,000 individuals. The female-to-male ratio was 14.5:1. A total of 114 pSS patients died during the study period. The overall survival rate of pSS patients was 99.0%, and the 1-year, 2-year, and 5-year survival rates were 98.7%, 98.1%, and 97.1%, respectively, and the standardized mortality ratio (SMR) was 1.47 (2.14 for males and 1.35 for females). The most common causes of death were respiratory disease (n = 25; 21.9%) followed by circulatory diseases (n = 21; 18.4%), musculoskeletal connective tissue diseases (n = 21; 18.4%), and cancer (n=19; 16.7%).

Conclusions: The national incidence of pSS in Korea presented in this study was lower in comparison with reports from other countries. However, the mortality rate was significantly higher than the corresponding values in the age- and gender-matched general population. The higher mortality in pSS patients is attributable to respiratory diseases and lung cancer.