Risk of Interstitial Lung Disease in Patients with Newly Diagnosed Systemic Autoimmune Rheumatic Disease: A Nationwide, Population-Based Cohort Study

Abstract Objective : To assess interstitial lung disease (ILD) risk among patients newly diagnosed with systemic autoimmune rheumatic diseases (SARDs) including rheumatoid arthritis (RA), dermatomyositis (DMtis), polymyositis (PM), systemic sclerosis (SSc), systemic lupus erythematosus (SLE) and primary Sjogren's syndrome (pSS). Method : Using the 1997–2013 Taiwanese National Health Insurance Research Database, we identified 62,930 newly diagnosed SARD patients from 2001 to 2013. We selected 251,720 individuals without SARD diagnoses who were matched (1:4) with SARD patients by age, sex and year of index date. We compared the incidence rates (IRs) of ILD (consistent diagnosis with ICD-9 code 515, 516.3, 516.8, 516.9 or 517 after a ILD-related radiological or pathological procedure) between the specific SARD subgroups and the corresponding non-SARD comparison groups. Using multivariable Cox regression analyses, we estimated hazard ratios (HRs) with 95% confidence intervals (CIs) of ILD in the various SARD groups compared with comparison groups after adjusting for age, sex and Charlson comorbidity index. Results : The IR of ILD was greatest among patients with SSc (1,364 per 105 years), followed by DMtis (1,011 per 105 years), PM (831 per 105 years), pSS (196 per 105 years), RA (109 per 105 years) and SLE (120 per 105 years). Multivariable analyses showed that the risk of ILD was increased among patients with SSc (HR, 172.63), DMtis (HR, 119.61), PM (HR, 84.89), SLE (HR, 32.18), pSS (HR, 17.54), or RA (HR, 8.29). Conclusion : This population-based, cohort study demonstrates that the risk of ILD is significantly increased in patients with newly diagnosed SARDs.