Epidemiology and Prognostic Significance of Cough in Fibrotic Interstitial Lung Disease

Rationale: Cough is a key symptom in patients with fibrotic interstitial lung disease (ILD). Objective: This study evaluated the prevalence, longitudinal change, associations, and prognostic significance of cough severity in patients with fibrotic ILD. Methods: We included consecutive patients with idiopathic pulmonary fibrosis (IPF) and non-IPF fibrotic ILD who completed the 100mm-Cough Severity Visual Analog Scale (VAS) from the prospective multi-center Canadian Registry for Pulmonary Fibrosis. Baseline cough severity and associations with patient demographics and clinical factors were determined. Relationships between baseline cough severity and health outcomes were evaluated. Measurements and Main Results: Patients with IPF (n=1061) had higher median baseline cough severity than those with non-IPF fibrotic ILD (n=2825) [24 vs 20mm, p<0.001], with worse cough associated with gastroesophageal reflux disease for both cohorts. Worse cough severity was independently associated with worse health-related quality of life at baseline, larger annualized decline in DLCO, development of disease progression, and reduced transplant-free survival in both IPF and non-IPF fibrotic ILD cohorts. The IPF cohort (2.2mm, 95% CI 1.6-2.9mm) had larger annualized increments in cough severity compared to the non-IPF fibrotic ILD cohort (1.1mm, 95% CI 0.8-1.4mm; p=0.004). There was no difference in worsening cough over time comparing those receiving and not receiving ILD-targeted therapy or with and without lung function decline. Conclusion: Cough is common in patients with IPF and non-IPF fibrotic ILD, with increasing cough severity over time irrespective of ILD-targeted therapy. Patient-reported cough severity has prognostic implications on health-related quality of life, disease progression, and survival in fibrotic ILD.