We sought to present the epidemiology of idiopathic pulmonary fibrosis (IPF) in adults 18-64 years old in the USA.From adults aged 18-64 years in a large administrative claims data in 2004-2010, patients with IPF were identified using diagnosis codes. We estimated annual incidence and cumulative prevalence of IPF over time, and examined potential risk factors for the IPF diagnosis.The annual cumulative prevalence increased steadily in the first few years (from 13.4 cases per 100 000 persons in 2005 to 18.2 cases in 2010 per 100 000 persons), which is likely due to a methodological reason, while the annual incidence of IPF decreased over time (from 7.9 cases per 100 000 person-years in 2005 to 5.8 cases in 2010 per 100 000 person-years). The overall decrease was mainly driven by a decreasing trend in the younger patients (aged 18-44 years), while the incidence in older patients remained stable. Consistent trends were observed in subgroups defined by previously published more restrictive algorithms for diagnosis. Older age and male sex were associated with a higher incidence of disease (p<0.05).In US adults younger than 65 years, we observed a decreasing incidence of IPF over time which may partially explain the plateau of cumulative prevalence in the last few years of our data.
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