The Epidemiology of Cryptogenic Organizing Pneumonia: An Analysis of Data From the Nationwide Inpatient Sample.

Abstract

Cryptogenic organizing pneumonia (COP) is a rare form of interstitial lung disease with limited epidemiologic data. Large epidemiologic studies for COP, to our knowledge, do not exist; this hinders a broader understanding of its incidence, demographic distribution, and hospital outcomes. What is the national incidence, demographic patterns, seasonal and geographic trends, and in-hospital outcomes of COP in the United States? We conducted a retrospective study using the Healthcare Cost and Utilization Project's Nationwide Inpatient Sample (2016-2019) to identify adult hospitalizations (age ≥ 20 years) with a diagnosis of organizing pneumonia (International Classification of Diseases, Tenth Revision, Clinical Modification, code J84.116). COP cases were distinguished from secondary organizing pneumonia (SOP) by excluding patients with known associated conditions. Weighted national estimates were used to calculate incidence rates and demographic distributions. Multivariable logistic regression was used to identify predictors of in-hospital mortality. An estimated 14,210 hospitalizations for organizing pneumonia occurred from 2016 to 2019, including 5,145 COP cases. The annual incidence of COP was 0.51 per 100,000 people, rising significantly with age, and was highest among individuals aged ≥ 70 years (1.65 per 100,000 people; P < .001). Native Americans had the highest age-adjusted incidence (1.38 per 100,000 people; P < .001). Incidence was higher in colder US regions and peaked in spring months. In-hospital mortality was lower with COP compared vs SOP (6.0% vs 8.3%; P = .016). Factors independently associated with mortality included age > 65 years, cancer, cirrhosis, and mechanical ventilation. Median length of stay was 6 days for COP. COP is uncommon but clinically relevant. COP has significant geographic, seasonal, and demographic variation and a hospital mortality rate that is lower than in SOP. However, as with SOP, COP is influenced by age and comorbidities. These findings provide the most comprehensive US inpatient estimates to date.