Table 3. Impact: cough and clinical outcomes in respiratory disease.
| Disease | Impact on clinical outcomes |
|---|---|
| Asthma | In individuals with CC compared to those without: |
| Higher symptom prevalence (wheeze, dyspnoea, sputum and chest tightness), frequency of bronchitis or pneumonia (≥6 episodes in 10 years) and healthcare utilisation (≥3 GP consultations in 12 months) (7) | |
| More likely FEV1 ≤60% (7) | |
| More likely to have severe asthma (GINA classification) (29) | |
| Objective CFreq higher in uncontrolled vs. well controlled asthma and associated with ACQ6 (r=0.4) (49) | |
| Objective time spent coughing associated with LCQ (r=−0.54) (50) | |
| Cough not associated with airway eosinophil and neutrophil counts, serum eosinophil and IgE, IL-5, IL-8, TNF-α and FeNO (7,51-54) | |
| COPD | CC is stronger predictor of airflow obstruction in smokers than wheeze and dyspnoea (55) |
| In individuals with CC compared to those without: | |
| Increased dyspnoea, sputum production, episodes acute bronchitis or pneumonia, healthcare utilisation, and lower FEV1 (6) | |
| Risk of exacerbation conflicting: 2 studies found association, 1 did not (33,56,57) | |
| Cough frequency associated with sputum neutrophils, but not eosinophils (1,58) | |
| Bronchiectasis | Objective CFreq higher in stable bronchiectasis compared to health. CFreq correlated with LCQ scores (r=−0.52). CFreq independently associated with sputum VAS and 1-year exacerbation frequency, but not FEV1 or FVC (59) |
| ILD | IPF: self-reported cough significantly associated with disease severity (symptoms, desaturation, lung function), and progression but not prognosis or transplantation (8) |
| Conflicting associations between LCQ scores and outcome: | |
| Saunders et al. In IPF, impaired LCQ at baseline associated with higher MRC dyspnoea score, but not lung function or mortality (60) | |
| Lee et al. In ILD (61% IPF), impaired LCQ associated with increased mortality, hospitalisation, and lung transplantation (61) | |
| IPF, CHP and SSc-ILD: worse lung function (FEV1, FVC, DLCO), and dyspnoea score were predictors of cough (41) | |
| SSc-ILD: self-reported cough associated with impaired LCQ, dyspnoea and disease severity (DLCO and radiological) in 2 studies (43,44) | |
| Sarcoidosis | Patient-reported cough associated with symptoms of dyspnoea, fever, and chest pain, but not arthralgia or erythema nodosum. Also associated with lower FEV1 and FVC, but not radiographic staging, sex, or smoking status (47) |
| Objective CFreq higher in sarcoidosis compared to health and associated with cough severity VAS (r=0.62) and LCQ (r=−0.61) (4) | |
| No association between serum ACE and objective CFreq (4,62) | |
| Objective CFreq not associated with lung function (FEV1, FVC, DLCO), number of organs involved, immunosuppressive treatment or radiological staging (4) | |
| In individuals with reported cough compared to those without: | |
| Associated with presence of endobronchial findings, biopsy-proven tracheitis, and airway neutrophilia, but not lymphocytes, eosinophils, or CD4+/CD8+ ratios (47,63) |
CC, chronic cough; GP, general practice; FEV1, forced expiratory volume in one second; GINA, Global Initiative for Asthma; CFreq, cough frequency; ACQ, Asthma Control Questionnaire; LCQ, Leicester Cough Questionnaire; IgE, immunoglobulin E; IL, interleukin; TNF-α, tumour necrosis factor α; FeNO, fractional exhaled nitric oxide; COPD, chronic obstructive pulmonary disease; VAS, visual analogue scale; FVC, forced vital capacity; ILD, interstitial lung disease; IPF, idiopathic pulmonary fibrosis; MRC, medical research council; CHP, chronic hypersensitivity pneumonitis; SSc, systemic sclerosis; DLCO, diffusing capacity of the lungs for carbon monoxide; ACE, angiotensin converting enzyme.