Rationale: Idiopathic pulmonary fibrosis is a chronic interstitial lung disease of unknown etiology; its epidemiology in the United States has not been well characterized.
Objective: To estimate the annual incidence and prevalence of idiopathic pulmonary fibrosis in the United States.
Methods: Retrospective cohort design utilizing a large health care claims database spanning the period January 1996 through December 2000.
Measurements and main results: Persons with idiopathic pulmonary fibrosis were identified based on diagnosis and procedure codes. Using broad case-finding criteria, prevalence was estimated to range from 4.0 per 100,000 persons aged 18 to 34 yr to 227.2 per 100,000 among those 75 yr or older; annual incidence was estimated to range from 1.2 to 76.4 per 100,000. Using narrow case-finding criteria, prevalence ranged from 0.8 to 64.7 per 100,000 persons; comparable figures for incidence were 0.4 to 27.1 per 100,000 persons. Extrapolating these rates to the overall United States' population, prevalence was estimated to be 42.7 per 100,000 (incidence, 16.3 per 100,000) using broad criteria; with narrow criteria, prevalence was estimated to be 14.0 per 100,000 (incidence, 6.8 per 100,000).
Conclusions: Our results suggest that idiopathic pulmonary fibrosis is probably more common in the United States than previously reported.