Risk of interstitial lung disease following COVID-19 infection in patients with autoimmune diseases: a retrospective cohort study

OBJECTIVE: This study aimed to determine the risk of developing interstitial lung disease (ILD) as a major post-COVID outcome in individuals with autoimmune diseases. METHODS: This retrospective cohort study utilized data from the TriNetX U.S. Collaborative Network. The case group comprised individuals with autoimmune rheumatic diseases who contracted COVID-19, whereas the control group included those who remained uninfected during the follow-up period. Patient baseline characteristics were balanced using propensity score matching (PSM). The primary outcome was newly diagnosed ILD. A Cox proportional hazards regression model was employed to calculate PSM-adjusted hazard ratios (HRs). Kaplan-Meier curves and log-rank tests were used to evaluate survival differences. RESULTS: The study included 174 256 individuals (26 768 COVID-19 cases and 147 488 controls) from January 1, 2020, to December 31, 2022. After propensity score matching, two cohorts of 26 763 individuals were identified, both with balanced baseline characteristics. During the follow-up period, the COVID-19 group exhibited a significantly higher risk of ILD (HR: 1.23; 95% CI: 1.10-1.36). Subgroup analyses by age, sex, and autoimmune disease consistently revealed higher risks in the COVID-19 group than in the control group. CONCLUSIONS: COVID-19 infection was identified as a risk factor for the development of ILD in patients with autoimmune diseases, highlighting the importance of vigilant pulmonary surveillance in this population. Nevertheless, these findings should be interpreted with caution due to potential residual confounding, diagnostic misclassification, and the heterogeneity of autoimmune diseases, which may mask disease-specific risk variations and lead to potential misattribution of ILD risk across different autoimmune conditions.