Clinical Impact of Hospitalization in Patients with Idiopathic Pulmonary Fibrosis: A Retrospective Cohort Study

Background Although hospitalization in idiopathic pulmonary fibrosis (IPF) is associated with poor outcomes, it occurs during the disease course and may lead to overestimation of its prognostic impact when analyzed as a fixed exposure. Objectives We aimed to evaluate the association between hospitalization and transplantation-free survival in patients with IPF by modeling hospitalization as a time-dependent exposure and applying a standardized definition of respiratory-related hospitalization. Design This was a retrospective cohort study conducted at Asan Medical Center, a tertiary referral center in Seoul, South Korea. Methods A total of 223 patients with IPF were included. Hospitalization was treated as a time-dependent exposure in Cox regression models. Changes in pulmonary function and exercise capacity before and after hospitalization were assessed using linear mixed-effects models. Results Seventy patients (31%) experienced hospitalization during follow-up, whereas 153 (69%) did not. Hospitalized patients had significantly worse lung function and exercise capacity at baseline compared with non-hospitalized patients. When modeled as a time-dependent exposure, hospitalization was strongly associated with increased risk of transplantation or death (adjusted hazard ratio: 8.87, 95% confidence interval [CI]: 5.57–14.11; P <0.001). After excluding patients who died within 10 days of hospitalization, long hospital stay (≥10 days) was associated with poorer transplantation-free survival than short stay (<10 days) ( P =0.022). Pulmonary function and exercise capacity declined significantly during hospitalization. Forced vital capacity decreased both before (−7.6%, 95% CI: −11.2 to −4.1; P <0.001) and after hospitalization (−4.8%, 95% CI: −9.4 to −0.2; P =0.04). Minimum oxygen saturation during the six-minute walk test decreased significantly both before (−2.5%, 95% CI: −3.8 to −1.3; P<0.001) and after hospitalization (−2.3%, 95% CI: −4.4 to −0.3; P=0.029). Conclusion Hospitalization in IPF was associated with poorer transplantation-free survival and subsequent physiological decline. It may serve as an important time-dependent marker of clinical deterioration and disease progression.