Comparison of interstitial lung disease diagnoses in urban and rural areas among participants in the pulmonary fibrosis foundation patient registry

Little is known about differences in interstitial lung disease (ILD) diagnosis by geographic location. The aim of this study is to evaluate differences in cross-sectional ILD diagnosis between patients in urban and rural areas. Methods: This is a retrospective analysis of participants (n = 1992) in the Pulmonary Fibrosis Foundation (PFF) Patient Registry. Diagnoses were grouped as follows: idiopathic pulmonary fibrosis (IPF); idiopathic interstitial pneumonia other than IPF (IIP, non-IPF); connective tissue disease-associated ILD (CTD-ILD); fibrotic hypersensitivity pneumonitis (fibrotic HP); exposure-related ILD; and other ILDs. Patient-reported zip codes were mapped to county Federal Information Processing Series (FIPS) codes using data from U.S. Department of Housing and Urban Development (HUD). Frequencies of ILD diagnoses were compared between urban and rural groups using two-sample Z-test with 0.05 significance level. County-level variables including occupation and fuel use were then compared by ILD diagnosis using analysis of variance (ANOVA) with 0.05 significance level. Results: Median age at consent was 69 years, 63 % were male, and 89.5 % were white. By county classification, 12 % resided in a rural area. Rates of IPF, IIP (non-IPF), and CTD-ILD diagnosis were similar between urban and rural residents, however rates of fibrotic HP and exposure-related ILD were higher among rural residents. Residence in a county with coal fuel use or wood fuel use was higher among those with exposure-related ILD (p < 0.0001 and p = 0.0001, respectively). Conclusion: ILD diagnoses differ in urban versus rural ILD patients, with fibrotic HP and exposure-related ILD being significantly more prevalent among residents in rural areas. Type of fuel use also was associated with fibrotic HP and exposure-related ILD.