Epidemiology of Idiopathic Pulmonary Fibrosis among U.S. Veterans, 2010-2019

Rationale: The development of novel therapies for idiopathic pulmonary fibrosis (IPF) has brought increased attention to the population burden of disease. However, little is known about the epidemiology of IPF among U.S. Veterans. Objectives: This study examines temporal trends in incidence and prevalence, patient characteristics, and risk factors associated with IPF among a national cohort of U.S. Veterans. Methods: We used data from the Veterans Health Administration (VHA) electronic health record system to describe the incidence, prevalence, and geographic distribution of IPF between January 1, 2010, and December 31, 2019. We evaluated patient characteristics associated with IPF using multivariate logistic regression. Results: Among 10.7 million Veterans who received care from the VHA between 2010 and 2019, 139,116 (1.26%) were diagnosed with IPF. Using a narrow case definition of IPF, the prevalence increased from 276 cases per 100,000 in 2010 to 725 cases per 100,000 in 2019. The annual incidence increased from 73 cases per 100,000 person-years in 2010 to 210 cases per 100,000 person-years in 2019. Higher absolute incidence and prevalence rates were noted when a broader case definition of IPF was used. Risk factors associated with IPF among Veterans included older age, White race, tobacco use, and rural residence. After accounting for interactions, the average marginal difference in IPF prevalence between males and females was small. There was significant geographic heterogeneity of disease across the United States. Conclusions: This study is the first comprehensive epidemiologic analysis of IPF among the U.S. Veteran population. The incidence and prevalence of IPF among Veterans has increased over the past decade. The effect of sex on risk of IPF was attenuated once accounting for other risk factors. The geographic distribution of disease is heterogeneous across the United States with rural residence associated with higher odds of IPF. The reasons for these trends deserve further study.