Twenty-Year Changes in Mortality Rates and Underlying Causes of Death in Patients with Rheumatoid Arthritis-Associated Interstitial Lung Disease, 1999–2018

Background: The treatment of rheumatoid arthritis (RA) has advanced considerably in the last 20 years. However, few population-based studies have assessed mortality rates and the underlying cause of death (UCD) in patients with RA and RA-associated interstitial lung disease (RA-ILD). We conducted a study to evaluate trends in mortality rates, demographic characteristics, and UCDs in patients with RA-ILD.Methods: Through data from death certificates (1999-2018) acquired from the U.S. Centers for Disease Control and Prevention Multiple Cause of Death files, we explored trends in mortality rates and UCD for RA and RA-ILD patients. We evaluated trends in crude rates and age-standardised mortality rates (ASMR) for patients with RA and RA-ILD.Results: In both RA and RA-ILD patients, ASMR variation trended downward over a 20-year period. The ASMR ratio of RA-ILD to RA decreased by 5.84%. The ASMR for RA and RA-ILD stratified by sex or age group also trended downward. The change in the ASMR ratio of RA-ILD to RA differed between men and women, trending downward in women and upward in men. Arthropathies and ILD were the two most frequent UCDs for RA-ILD, while the most frequent UCDs for RA were arthropathies and ischaemic heart disease. Conclusions: Although both RA and RA-ILD showed a downward trend in mortality, RA combined with ILD may reduce patient life span. Specifically, the mortality rate for RA-ILD remained relatively stable during the study period when ILD was the UCD, which suggests the necessity of devoting resources to active prevention, early diagnosis, and effective management of RA-ILD.