Epidemiology of idiopathic pulmonary fibrosis

Abstract

Idiopathic pulmonary fibrosis is a chronic fibrotic lung disease of unknown cause that occurs in adults and has a poor prognosis. Its epidemiology has been difficult to study because of its rarity and evolution in diagnostic and coding practices. Though uncommon, it is likely underappreciated both in terms of its occurrence (ie, incidence, prevalence) and public health impact (ie, health care costs and resource utilization). Incidence and mortality appear to be on the rise, and prevalence is expected to increase with the aging population. Potential risk factors include occupational and environmental exposures, tobacco smoking, gastroesophageal reflux, and genetic factors. An accurate understanding of its epidemiology is important, especially as novel therapies are emerging.

Keywords: epidemiology; idiopathic pulmonary fibrosis; incidence; mortality; prevalence; risk factors.

Figure 1

The prevalence of idiopathic pulmonary fibrosis varies widely depending on case definitions in epidemiologic studies. Notes: There is marked variation with the use of ICD-9 code 515 (postinflammatory pulmonary fibrosis) and/or ICD-9 code 516.3 (idiopathic fibrosing alveolitis) to identify cases, with or without added levels of stringency. The Raghu et al broad definition required the presence of ICD-9 code 516.3 or 515 and exclusion of other diagnoses that cause interstitial lung disease. The Raghu et al narrow definition required the broad definition plus additional procedure codes for lung biopsy and radiology studies. The Coultas et al cases were drawn from multiple administrative and clinical sources. Estimates are shown for men in the 65–74 year age group from Raghu et al and Coultas et al.

Figure 2

The incidence of idiopathic pulmonary fibrosis increases with age. Notes: For demonstration purposes, some estimates were averaged where reported by sex separately–, (as opposed to combined15,16).