The Burden of Persistent Cough in Idiopathic Pulmonary Fibrosis (IPF) and Other Interstitial Lung Diseases (ILD): A Systematic Evidence Synthesis

OBJECTIVES: As cough remains a challenging symptom of IPF and other ILDs, we aimed to synthesise evidence on its associated burden.

METHODS: Following pre-registration (PROSPERO CRD42022369379), a search was performed for articles published between 2010 and 2022 using databases including Embase, MEDLINE and Cochrane. Observational and interventional studies reporting cough-related measures in IPF and other ILDs were included. Here, we provide a narrative synthesis of a subset of studies in patients with persistent cough.

RESULTS: Ten studies; 6 in IPF (n=271 patients), 2 in ILDs including IPF (n=294 patients), 1 in CTD-ILD (n=1 study, 11 patients) and 1 in sarcoidosis (n=21 patients) were included. Definitions for persistent cough included self-reported chronic cough, stable cough frequency for >4 weeks and cough for >8 weeks, with some studies requiring additional criteria such as refractory cough, 24-hour cough count of >10/15 coughs per/hour and/or cough severity VAS >40mm. Cough severity VAS (n=8 studies, mean range=38.8–73.4/100mm) and cough counts (n=4 studies) were the most frequently used cough measures, and the LCQ (n=7 studies, mean range=11.0–15.3/21), SGRQ (n=4 studies, mean range=57.2–57.4/100) and CQLQ (n=2 studies, mean range=56.5–60.5/112) were the most frequently used impact/HRQoL measures. Four studies assessed concurrent/baseline associations between cough and impact/HRQoL measures, including three trials in IPF where cough severity VAS was negatively correlated with SGRQ, LCQ and/or CQLQ scores, in one of which cough counts were negatively correlated with LCQ scores, and an observational cohort study in ILD where cough severity VAS had an independent negative impact on SGRQ scores. None of the studies examined the HCRU/economic burden of cough.

CONCLUSIONS: Our study highlights the heterogeneity in assessing cough burden. The findings confirm the negative impact of cough on HRQoL in IPF, with indications of a similar impact in other ILDs. Our synthesis underscores the need for standardised assessment and dedicated studies, particularly in non-IPF ILDs.