Influence of interstitial lung disease on systemic sclerosis hospitalizations, a national study (2002-2020)

Systemic sclerosis (SSc) is an autoimmune connective tissue disorder that can cause generalized inflammation and is characterized by fibrosis of the skin, organs, and vasculopathy. Limited SSc is more common and typically associated with a milder disease course, whereas diffuse SSc, although less common, is linked to a higher mortality rate due to more frequent visceral organ involvement. One of the most common complications of SSc is interstitial lung disease (ILD). ILD is characterized by fibrosis, scarring, and inflammation of the lungs. ILD has a 30% prevalence and a 40% 10-year mortality in patients with SSc worldwide. Hospitalizations for SSc from 2002 to 2020 were obtained using the National Inpatient Sample (NIS), an all-payer administrative database that captures 97% of hospital discharges in the United States. The primary aim was to evaluate whether inpatient mortality, length of stay (LOS), and hospital cost differed if SSc patients had underlying ILD. We estimated multivariable logistic regression and log-normal models controlling for age, biological sex, race/ethnicity, income, and hospital setting. ILD was associated with 88% greater adjusted odds of inpatient mortality (aOR 95% CI: 1.53 to 2.31, p < 0.001), 15% longer stays (aOR 95% CI: 1.04 to 1.28, p = 0.001), and 33% higher adjusted hospital costs (aOR 95% CI: 1.26 to 1.40, p < 0.001). These findings suggest that SSc-ILD has a significant impact on hospitalization outcomes.