Cough in chronic lung disease: a state of the art review

What causes cough in pulmonary fibrosis, and how should we treat it?

PURPOSE OF REVIEW

To review the current understanding of the impact, mechanisms and treatments for cough in patients with interstitial lung disease (ILD). Evidence suggests that cough is a prevalent symptom in patients with ILD and has a significant impact on patients.

RECENT FINDINGS

There is increasing interest in the role of cough hypersensitivity as seen in chronic refractory cough in patients with ILD, and encouraging recent results suggest that ILD-associated cough responds to opiate therapy.

SUMMARY

Understanding the aetiology of cough in patients with ILD is crucial to continue to develop therapies which might be effective in reducing cough and increasing quality of life.

Patient Perception of Cough in Interstitial Lung Disease; Impact of Cough Hypersensitivity

INTRODUCTION

Cough is common in interstitial lung disease (ILD) and is associated with disease progression, yet its mechanisms are understudied. We investigated cough hypersensitivity features and impact in ILD.

METHODS

Participants with ILD and cough (n = 195) completed a multiple choice and free text questionnaire on cough sensations/triggers and impacts.

RESULTS

The majority of participants were male (54%), aged > 65 (64%), with idiopathic pulmonary fibrosis (IPF, 75%). Common cough triggers were body position (74%), physical activity (72%), and talking (62%). Common laryngeal sensations were globus (43%), and itch/tickle (42%). Cough impacted everyday life in 55%, and all activities in 31%, causing exhaustion (59%), social embarrassment (70%), urinary incontinence (46% females), and syncope/pre-syncope (12%). The total number of cough-provoking sensations/triggers correlated with impacts; ρ = 0.73, p < 0.001.

CONCLUSION

Cough hypersensitivity symptoms are prevalent in ILD and detrimentally affect quality of life. Further studies investigating mechanisms of cough hypersensitivity and targeted pharmacotherapy are warranted.

The Effect of Long-Term Azithromycin on Objective and Subjective Cough in Chronic Respiratory Disease: A Systematic Review and Meta-analysis of Randomised Controlled Trials and Noncomparative Studies

INTRODUCTION

Azithromycin is an effective treatment for various respiratory conditions but its effect on cough is poorly understood. We synthesised data from randomised controlled trials (RCTs) and noncomparative studies (NCT) examining its effect on objective and subjective cough.

METHODS

After prospective registration on PROSPERO, we searched MEDLINE, EMBASE, and CENTRAL for both RCTs and NCT trials examining the effect azithromycin on cough in respiratory disease.

RESULTS

We identified 1240 studies of which 6 (4 RCTs and 2 NCT studies) were included in the meta-analysis, with a total of 275 patients. Azithromycin was associated with significant improvement in Leicester Cough Questionnaire scores at follow-up when compared to baseline scores (SMD = 0.62 [95% CI 0.12 to 1.12], p = 0.01). However, when only RCTs were synthesised, no significant effect was observed (SMD = 0.12 [95% CI - 0.36 to 0.60], p = 0.62). There was no significant reduction in cough severity VAS score (SMD = - 0.39 [95% CI - 0.92 to 0.14], p = 0.15). There was no significant reduction in objective cough count (SMD = - 0.41 [95% CI - 1.04 to 0.32], p = 0.09).

CONCLUSION

Azithromycin therapy improves cough-related quality of life in various chronic respiratory diseases; however, there was no significant effect on cough outcomes when only data from RCTs were synthesised. We believe that to accurately identify which patients whose cough would benefit from azithromycin a large-scale clinical trial of patients with a broad spectrum of respiratory diseases, with sufficiently severe cough, should be undertaken with subgroup analysis of individual disease areas.

Exploring the Common Genetic Underpinnings of Chronic Pulmonary Disease and Esophageal Carcinoma Susceptibility

Background: Pulmonary diseases and esophageal cancer are highly prevalent conditions with rising incidence worldwide. Prior evidence supports shared environmental and behavioral factors, but less is known regarding potential genetic links underlying this comorbidity. This study aimed to elucidate the complex genetic relationship between chronic lung diseases and esophageal cancer risk. Methods: Linkage disequilibrium score regression assessed the genetic correlation between esophageal cancer and asthma, COPD, and idiopathic pulmonary fibrosis leveraging extensive GWAS datasets. Pleiotropic analysis, gene-set enrichment, eQTL mapping, and mendelian randomization causality analyses were then conducted to identify specific shared genetic variants, enriched pathways, causal relationships and gene regulatory mechanisms connecting lung disease and cancer susceptibility. Results: Significant genetic correlations were observed between esophageal cancer and both COPD and asthma, but not idiopathic pulmonary fibrosis. Further analyses identified 13 pleiotropic loci and 6 shared genes including CHRNA4, ERBB3, and SMAD3, as well as pathways related to immune function. eQTL integration highlighted 53 genes like SOCS1, FGF2, and CHRNA5 with tissue-specific regulatory effects on disease risk. Bidirectional relationships were noted, whereby genetic predisposition to asthma and COPD increased esophageal cancer risk, while cancer liability reciprocally raised pulmonary fibrosis risk. Conclusions: These genomic analyses provide initial evidence that shared genetic factors may underpin the comorbidity between lung conditions and esophageal malignancy. The genes and pathways identified offer insights into biological mechanisms linking both diseases, aiding future screening, prevention and therapeutic efforts to mitigate this growing comorbidity burden.

Chronic cough associated with COPD exacerbation, pneumonia and death in the general population

Background

Chronic cough affects up to 10% of the general population and was previously perceived as a comorbidity of underlying conditions, but is nowadays classified as a disease in its own entity that could confer increased risk of morbidity and mortality. We tested the hypothesis that chronic cough is associated with increased risk of COPD exacerbation, pneumonia and all-cause mortality in the general population.

Methods

We identified 2801 individuals with chronic cough, defined as cough lasting >8 weeks, among 44 756 randomly selected individuals from the Copenhagen General Population Study, and recorded COPD exacerbations, pneumonia and all-cause mortality during follow-up.

Results

During up to 5.9 years of follow-up (median 3.4 years), 173 individuals experienced COPD exacerbation, 767 experienced pneumonia and 894 individuals died. Individuals with chronic cough versus those without had cumulative incidences at age 80 years of 12% versus 3% for COPD exacerbation, 30% versus 15% for pneumonia, and 25% versus 13% for death from all causes. After adjustment for age, sex and smoking, individuals with chronic cough versus those without had adjusted hazard ratios of 4.6 (95% CI 2.9-7.2) for COPD exacerbation, 2.2 (1.7-2.7) for pneumonia and 1.7 (1.4-2.0) for all-cause mortality. Among current smokers aged >60 years with airflow limitation, those with versus without chronic cough had an absolute 5-year risk of 10% versus 4% for COPD exacerbation, 16% versus 8% for pneumonia and 19% versus 12% for all-cause mortality.

Conclusion

Chronic cough is associated with higher risks of COPD exacerbation, pneumonia and death, independent of airflow limitation and smoking.