Contribution of Interstitial Lung Disease to Mortality in Patients With Connective Tissue Diseases

<h3>Background</h3> Interstitial lung diseases (ILDs) are common in patients with connective tissue diseases (CTDs), but their role in the mortality of patients with CTDs remains unexplored. <h3>Research Question</h3> What proportion of mortality in patients with CTDs is due to ILD? <h3>Study Design and Methods</h3> In this retrospective, population-based epidemiologic study, we used the Wide-Ranging Online Data for Epidemiologic Research database and extracted mortality data of all deceased US citizens aged ≥ 15 years, from 1999 to 2019. Age-adjusted mortality rate (AAMR) was calculated by sex, racial group, and state of death. The annual trend was examined using the annual percent change and average annual percent change. We identified the rank of ILD as an underlying cause of death compared with the 15 leading causes of death in patients with CTDs. <h3>Results</h3> From 1999 to 2019, CTDs were mentioned in the death certificates of 286,643 US citizens, with 26,406 (7.12%) of them having ILDs simultaneously. The ILD-CTD-related AAMR per 1 million population decreased from 4.26 in 1999 to 3.37 in 2015 and further increased to 4.03 in 2019. The ILD-CTD-related AAMRs during 1999 to 2019 for female individuals and male individuals were 4.53 and 2.80 per 1 million, respectively. In the list of 15 leading causes of mortality, ILD could be ranked as the seventh, 11th, third, fourth, and fourth cause of death in patients with rheumatoid arthritis, systemic lupus erythematosus, polymyositis/dermatomyositis, systemic sclerosis, and Sjögren syndrome, respectively. <h3>Interpretation</h3> Our findings underscore the necessity for developing screening protocols and targeted interventions aimed at reducing ILD-related mortality in patients with CTD. This could significantly improve outcomes and quality of life for these patients.