The impact of chronic cough: a cross-sectional European survey

The effect of gefapixant, a P2X3 antagonist, on cough reflex sensitivity: a randomised placebo-controlled study

We evaluated the effect of gefapixant on cough reflex sensitivity to evoked tussive challenge.

In this phase 2, double-blind, two-period study, patients with chronic cough (CC) and healthy volunteers (HV) were randomised to single-dose gefapixant 100 mg or placebo in a crossover fashion. Sequential inhalational challenges with ATP, citric acid, capsaicin and distilled water were performed 1, 3 and 5 h after dosing. Mean concentrations evoking ≥2 coughs (C2) and ≥5 coughs (C5) post dose versus baseline were co-primary endpoints. Objective cough frequency (coughs·h−1) over 24 h and a cough severity visual analogue scale (VAS) were assessed in CC patients. Adverse events were monitored.

24 CC patients and 12 HV were randomised (mean age 61 and 38 years, respectively). The cough challenge threshold increased for ATP by 4.7-fold (C2, p≤0.001) and 3.7-fold (C5, p=0.007) for gefapixant versus placebo in CC patients; in HV, C2 and C5 increased 2.4-fold (C2, p=0.113; C5, p=0.003). The distilled water C2 and C5 thresholds increased significantly (p<0.001) by a factor of 1.4 and 1.3, respectively, in CC patients. Gefapixant had no effect on capsaicin or citric acid challenge. Median cough frequency was reduced by 42% and the least squares mean cough severity VAS was 18.0 mm lower for gefapixant versus placebo in CC patients. Dysgeusia was the most frequent adverse event (75% of HV and 67% of CC patients).

ATP-evoked cough was significantly inhibited by gefapixant 100 mg, demonstrating peripheral target engagement. Cough count and severity were reduced in CC patients. Distilled water may also evoke cough through a purinergic pathway.

Predictors of prolongation in recent-onset cough

Chronic cough greatly decreases the quality of life and is often refractory to treatment. Interventions at an early stage could prevent cough from becoming chronic. To this end, the patients at high risk of cough prolongation would need to be identified. In this study, we investigated the factors that predicted cough at 12 months among subjects with a recent-onset cough. This was a prospective, observational follow-up study in a community-based population consisting of working-age subjects. The first e-mail survey in 2017 included a comprehensive questionnaire about current cough and its risk factors. The 259 subjects who reported a recent-onset (<8 weeks) cough were sent a follow-up questionnaire 12 months later. The response rate was 72.6% (188 subjects). There were 99 subjects (52.7%) with cough in 2018. The following baseline factors predicted the presence of any cough at 12 months in the multivariable analysis: wheezing (adjusted odds ratio (aOR 2.80, 95% CI 1.3-5.27), dog ownership (aOR 2.56, 95% CI 1.21-5.44), cough duration >3 weeks (aOR 2.29, 95% CI 1.11-4.76), family history of chronic cough (aOR 2.20, 95% CI 1.13-4.30), body mass index >25 kg·m-2 (aOR 2.06, 95% CI 1.02-4.15) and frequent somatic symptoms (aOR 1.36, 95% CI 1.13--1.64). There were 29 subjects (15.4%) with continuous cough and 66 subjects (35.1%) with recurrent cough. The risk factors were completely different between recurrent and continuous cough. It may be possible to identify the risk factors of cough prolongation among subjects with recent-onset cough. Early interventions should be targeted to these kinds of patients.

Update on the clinical development of gefapixant, a P2X3 receptor antagonist for the treatment of refractory chronic cough

Chronic cough, or cough lasting >8 weeks, is often associated with underlying medical conditions (ie, asthma, gastroesophageal reflux disease, nonasthmatic eosinophilic bronchitis, and upper-airway cough syndrome). In some patients with chronic cough, treatment of these underlying conditions does not resolve the cough (refractory chronic cough [RCC]), or none of these conditions are present (unexplained chronic cough [UCC]). Despite appropriate medical evaluation, patients with RCC or UCC frequently experience cough persisting for many years, as there are currently no targeted pharmacological approaches approved for the treatment of these conditions. However, the adenosine triphosphate (ATP)-gated P2X3 receptor, a key modulator of the activation of sensory neurons central to the cough reflex, has recently garnered attention as a potential therapeutic target for the treatment of chronic cough. Gefapixant, a first-in-class, non-narcotic, selective antagonist of the P2X3 receptor, recently demonstrated efficacy and was generally well tolerated in phase 2 clinical trials in patients with RCC, validating the utility of targeting this receptor in patients with chronic cough. On the basis of these data, 2 global phase 3 trials, with combined anticipated enrolment exceeding 2000 patients and with treatment durations of up to 1 year, have been initiated. Together, these trials will further evaluate efficacy and safety of gefapixant in the control of cough in patients with RCC or UCC.

Cough in pulmonary tuberculosis: Existing knowledge and general insights

Cough is a prominent symptom of pulmonary tuberculosis (TB), one of the oldest and most prevalent infectious diseases. Coughing probably has a pivotal role in transmission of the causative organism Mycobacterium tuberculosis. Despite this, little research to date has addressed this subject. Current knowledge of the mechanisms of cough in TB and how exactly coughing patterns predict infectiousness is scant, but this is changing. This overview summarises the existing evidence for the infectiousness of cough in TB, clinical correlates, and possible causes of cough in TB. Potential unique characteristics of cough in the disease are discussed, as is treatment and the subjective awareness of coughing in the disease.

Age and Sex Distribution of Chinese Chronic Cough Patients and Their Relationship With Capsaicin Cough Sensitivity

PURPOSE

An older female predominance has been reported among chronic cough patients in Western countries, which is considered to be associated with a higher cough sensitivity in females. However, the characteristics of Chinese chronic cough patients remain unclear. This study aimed to explore the age and sex distribution as well as their relationship with cough reflex sensitivity to capsaicin in Chinese chronic cough patients.

METHODS

We analyzed the demographic features of 1,882 consecutive chronic cough patients who attended our cough clinic in Guangzhou, China. Cough sensitivity to capsaicin, which was defined as the lowest concentration of capsaicin causing 5 coughs or more (C5), was measured in 539 of the 1,882 patients and 68 healthy volunteers.

RESULTS

The mean age of the patients was 43.0 ± 13.7 years and patients aged <50 years accounted for more than two-thirds of the study population. Around 87% of the patients were never-smokers. The proportion of females (51.5%) was almost equal to that of males (48.5%). The pattern of the age and sex distribution was consistently reflected within most common causes of chronic cough, while a female predominance was shown in patients with cough-variant asthma and patients aged ≥50 years. Female patients had higher cough sensitivity to capsaicin than male patients (log C5: 1.58 ± 0.84 vs. 2.04 ± 0.84 μmol/L, P = 0.001), and patients aged ≥50 years had higher cough sensitivity to capsaicin than patients aged <50 years.

CONCLUSIONS

In China, patients with chronic cough have a roughly equal sex distribution and a middle-aged predominance, irrespective of a higher cough sensitivity to capsaicin in females and older patients.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02591550.

Psychometric properties of the German version of the Leicester Cough Questionnaire in sarcoidosis

Background

Cough is one of the most common symptoms in general and pulmonary medicine with profound negative impact on health-related quality of life (HRQL). The Leicester Cough Questionnaire (LCQ) is a validated HRQL questionnaire, yet a validated German version of the LCQ is not available and it has never been tested in a cohort with sarcoidosis.

Objectives

To translate the LCQ into German and determine its psychometric properties.

Methods

The LCQ was translated in a forward-backward approach. Structured interviews in sarcoidosis patients were performed. Subsequently, sarcoidosis patients were asked to answer the German LCQ and comparative questionnaires. Distribution properties, item difficulty, concurrent validity, Rasch model fit and internal consistency of the German LCQ were determined.

Results

200 patients with sarcoidosis were included. We provide evidence for reliability, unidimensionality and internal consistency. However, only a moderate correlation with general and respiratory-specific HRQL questionnaires, no Rasch model fit could be shown. Skewed responses caused by floor effects were detected.

Conclusion

We demonstrate that the German LCQ is valid and reliable and its psychometric properties fulfil the standards required for its use in clinical settings as well as in interventional trials.

The impacts of cough: a cross-sectional study in a Finnish adult employee population

Given the very high prevalence of cough, little is known about its impacts. A questionnaire was sent via e-mail to all public service employees in two towns in Finland. There were 373 subjects with acute cough, 174 with subacute cough and 421 with chronic cough. Cough-related quality of life was assessed with the Leicester Cough Questionnaire (LCQ) and depressive symptoms with Patient Health Questionnaire-2. In addition, data on doctor's visits and sick leave days were collected. Mean LCQ (95% CI) total scores were 16.2 (15.9-16.5), 14.5 (14.1-15.0) and 14.6 (14.3-14.9) among subjects with acute, subacute and chronic cough, respectively (p<0.001). The prevalence of depressive symptoms was 5.4%, 7.5% and 4.8%, respectively, and 5.0% among subjects without current cough (p=0.50). The respective proportions of subjects with at least one doctor's visit due to cough during the previous year were 27.6%, 44.8%, 49.6% and 16.1% (p<0.001). The respective proportions of subjects with at least one sick leave day due to cough during the previous year were 28.9%, 39.1%, 36.3% and 15.3% (p<0.001). Any current cough was associated with an increased the risk of several (three or more) yearly doctor's visit due to any reason (adjusted odds ratio (aOR) 1.49, 95% CI 1.27-1.76) and several (seven or more) yearly sick leave days due to any reason (aOR 1.43, 95% CI 1.22-1.68). Cough decreases quality of life, and has a large socioeconomic impact by increasing doctor's visits and sick leave days. However, it is not associated with depressive symptoms. The impacts of subacute and chronic cough are comparable, and larger than those of acute cough.

Managing patients with chronic cough: challenges and solutions

Chronic cough is a common complaint and a frequent cause of medical consultation. Its management can be difficult. We present here an overview of the current guidelines for the management of chronic cough. Different steps are detailed, including the initial research of an obvious etiology and alert signs that should lead to further investigation of underlying condition. The diagnosis of the most frequent causes: asthma, non-asthmatic eosinophilic bronchitis, gastroesophageal reflux disease and upper airway cough syndrome should be considered, assessed and treated accordingly. Recent advances have been made in the comprehension of refractory chronic cough pathophysiology as well as its pharmacologic and non-pharmacologic treatment, especially speech pathology therapy.

The Use of Online Health Forums by Patients With Chronic Cough: Qualitative Study

Background

Online health discussion forums are used by different patient groups for sharing advice and information. Chronic cough is a common problem, and people with chronic cough use online health forums alongside formal medical therapies.

Objective

The objective of this study was to assess how chronic cough sufferers use online health forums, including the treatment advice they share with one another and the possible clinical uses of online forums in chronic cough.

Methods

Three open-access health forums were searched for threads related to chronic cough. Identified threads were screened against inclusion and exclusion criteria adapted from the British Thoracic Society (BTS) Guidelines related to chronic cough diagnosis. Included data were subjected to qualitative thematic analysis. All study data were cross-validated by a second author and discrepancies were resolved.

Results

In total, 96 threads were included in the analysis, consisting of posts by 223 forum users. Three main themes were identified: the effect of chronic cough on the lives of patients, the treatment advice shared between users, and the provision of support within forums.

Conclusions

Chronic cough symptoms had impacts on multiple aspects of patients’ health and well-being. To try and combat these issues, forum users suggested a variety of treatments to one another, ranging from mainstream traditional therapies to odd alternative remedies. The provision of support and empathy were also prominent themes in discussion threads. Online forums themselves may provide increasing benefit to users through the addition of a moderator.

Long-term prognosis of chronic cough: a prospective, observational cohort study

Background

The long-term prognosis of chronic cough and its determinants need to be clarified.

Methods

This is a prospective, observational cohort study. Eighty-nine unselected subjects with chronic (> 8 weeks’ duration) cough were carefully investigated: Clinical examination, symptom questionnaire, Leicester Cough Questionnaire (LCQ), skin prick tests, ambulatory peak expiratory flow monitoring, spirometry before and after 0.4 mgs of salbutamol, exhaled nitric oxide concentration measurement, hypertonic saline cough provocation test, and histamine bronchial provocation test. After five years, a letter was sent to the subjects containing questions about continuation of cough, smoking, indoor exposures, presence of co-morbidities, and current medication. It also contained LCQ and Cough Clinic diagnostic questionnaire. Sixty-eight subjects (76%) responded.

Results

At five years, continuing regular cough was present in 31 (46%) of the subjects and continuing impairment in cough-related quality of life (less than 1.3 points’ improvement in LCQ) in 32 (47%). Continuing regular cough was associated with presence of chronic rhinitis or esophageal reflux disease, baseline mild airway responsiveness to histamine, and baseline strong cough responsiveness to hypertonic saline. Continuing impairment in cough-related quality of life was associated with high body mass index, absence of atopy, absence of pets, and high number of background disorders (esophageal reflux disease, asthma, or chronic rhinitis).

Conclusions

Almost half of subjects with chronic cough suffered of the disorder at five years from initial assessment. Several possible determinants of poor prognosis could be identified.

The Emerging Role of The Eosinophil and Its Measurement in Chronic Cough

Although the aetiology of chronic cough in guidelines is clearly stated as asthma and related syndromes, gastro-oesophageal reflux disease (GORD), and upper airways disease, the inflammatory mechanisms underlying these conditions differ. Recent studies on asthma have increasingly focused on its molecular phenotypes instead of clinical characteristics. Here, we proposed the hypothesis that divides cough into two groups; the eosinophilic and neutrophilic. This division will enhance our ability to recognise the type of airway inflammation which, as a consequence will lead us to more targeted and personalized treatment approaches.

Physiotherapy and Speech and Language therapy intervention for chronic cough

There are few effective pharmacological therapies available to treat refractory chronic cough. Functional MRI studies of the brain have recently shown that patients with chronic cough have dysfunctional inhibitory control of cough. Self-management therapies delivered by physiotherapists or speech therapists are effective at suppressing cough. They enable patients to consciously suppress the urge to cough. The intervention consists of education, laryngeal hygiene, cough suppression and distraction measures and behaviour modification. The efficacy of Physiotherapy and Speech And Language Intervention (PSALTI) has been confirmed in two randomised control trials. In one trial, there was a 41% reduction in cough frequency with PSALTI, assessed objectively with the Leicester Cough Monitor, and a clinically significant improvement in quality of life. Importantly, the improvement in cough was sustained when therapy was discontinued. The addition of the Speech Pathology Treatment to neuromodulator drug therapy, Pregabalin has also been evaluated in a clinical trial. There was a clinically significant improvement in quality of life, and this was sustained when therapy was discontinued. The mechanism of action of PSALTI is not known and this should be investigated in future. Further studies are needed to identify the components of PSALTI that deliver the most benefit, and determine whether PSALTI is effective in cough associated with other chronic lung disorders.

The nervous system of airways and its remodeling in inflammatory lung diseases

Inflammatory lung diseases are associated with bronchospasm, cough, dyspnea and airway hyperreactivity. The majority of these symptoms cannot be primarily explained by immune cell infiltration. Evidence has been provided that vagal efferent and afferent neurons play a pivotal role in this regard. Their functions can be altered by inflammatory mediators that induce long-lasting changes in vagal nerve activity and gene expression in both peripheral and central neurons, providing new targets for treatment of pulmonary inflammatory diseases.

Cough Hypersensitivity Syndrome: A Few More Steps Forward

Cough reflex is a vital protective mechanism against aspiration, but when dysregulated, it can become hypersensitive. In fact, chronic cough is a significant medical problem with a high degree of morbidity. Recently, a unifying paradigm of cough hypersensitivity syndrome has been proposed. It represents a clinical entity in which chronic cough is a major presenting problem, regardless of the underlying condition. Although it remains a theoretical construct, emerging evidence suggests that aberrant neurophysiology is the common etiology of this syndrome. Recent success in randomized clinical trials using a P2X3 receptor antagonist is the first major advance in the therapeutics of cough in the past 30 years; it at last provides a strategy for treating intractable cough as well as an invaluable tool for dissecting the mechanism underpinning cough hypersensitivity. Additionally, several cough measurement tools have been validated for use and will help assess the clinical relevance of cough in various underlying conditions. Along with this paradigm shift, our understanding of cough mechanisms has improved during the past decades, allowing us to continue to take more steps forward in the future.

Evidence-based Evaluation and Management of Chronic Cough

Chronic cough is common and has a significant impact on the wellbeing of patients and the use and cost of health care services. Traditionally the approach to chronic cough in patients who are nonsmokers and are not taking an angiotensin-converting enzyme inhibitor has focused on the diagnosis and management of the upper airway cough syndrome, asthma, and reflux disease. The evaluation of patients with chronic cough frequently involves trials of empiric therapy for these 3 conditions. Chronic cough may be perpetuated by abnormalities of the cough reflex and sensitization of its afferent and central components.

Associations of Cough Prevalence with Ambient Polycyclic Aromatic Hydrocarbons, Nitrogen and Sulphur Dioxide: A Longitudinal Study

Information on potential cough triggers including environmental irritants is vital for successful management of chronic cough in patients. We investigated the relationship between ambient levels of particulate polycyclic aromatic hydrocarbons (PAH), nitrogen dioxide (NO₂) and sulphur dioxide (SO₂) exposures with cough prevalence. Eighty-three adult patients, who had been physician diagnosed with at least asthma, cough variant asthma and/or atopic cough, were divided into asthma and non-asthma groups. They recorded daily cough symptoms during 4 January-30 June 2011 study period while daily samples of total suspended particles were simultaneously collected by use of glass fiber filters and the particulate PAH content determined by high performance liquid chromatography coupled with a fluorescence detector. Ambient concentrations of NO₂ and SO₂ were obtained from a local monitoring site. Logistic regression models using generalized estimating equations were used to determine population-averaged estimates of association between cough prevalence and ambient pollutant exposures for the two groups. Fully adjusted odds ratios from single pollutant models were 1.083 (95% confidence interval (CI): 1.029, 1.140) and 1.097 (95% CI: 1.016, 1.185) per 0.57 ng/m³ for lag2 PAH exposure, while only for asthma group had significant associations with NO₂ and SO₂ exposures for both lag2 and lag02. Similar associations were observed in multipollutant models. This finding suggests that ambient PAH, NO₂, and SO₂ exposure even at low levels is related to cough prevalence in adult chronic cough patients and may be considered as aggravating factor during clinical management of the condition.

Diagnosis and investigation in the severe asthma clinic

Severe asthma is recognised as an important and emerging area of unmet need in asthma. The assessment of severe asthma should include three steps; (1) determining the diagnosis of asthma, including verification that the disease is severe asthma, (2) assessing comorbidities and contributing factors that will impact on clinical severity, as well as (3) assessing asthma phenotypes. These steps recognize the importance of heterogeneity in asthma as a key factor that determines the disease course and increasingly the choice of successful therapy. This assessment should be undertaken systematically and is best done by an expert multidisciplinary team. Here, we will outline the important aspects that should be included in the clinical assessment of the patient in the severe asthma clinic, including diagnosis, clinical history, the assessment of important comorbidities and the key investigations needed to support them.

A traditional herbal medication, Maekmoondong-tang, for cough: A systematic review and meta-analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Maekmoondong-tang (MMDT) is a traditional herbal medication widely used to improve cough in Korea, Japan, and China. It is composed of six herbs (Ophiopogonis Tuber, Pinelliae Tuber, Glycyrrhizae Radix, Zizyphi Fructus, Ginseng Radix, and Oryzae Semen).

AIM OF THE STUDY

This study is aimed to systematically review the relevant randomised controlled trials (RCTs) to determine the effectiveness and safety of MMDT for cough.

MATERIALS AND METHODS

Electronic and hand-searching of 7 databases (Cochrane Library, MEDLINE, EMBASE, OASIS, RISS, CNKI and CiNii) was systematically conducted up to February 2015 for RCTs testing MMDT in patients with cough. The primary outcome was cough symptom improvement using cough diary, visual analog scale, or response rate. Risk of bias of the included trials was evaluated with the Cochrane risk of bias assessment tool. The dichotomous data were pooled to obtain a risk ratio (RR) of cough persisting after treatment, with 95% confidence intervals (CI).

RESULTS

Nine RCTs involving 2453 participants were included. The methodological quality was largely poor for a majority of the studies. MMDT reduced the severity of cough by 74% compared with the conventional antitussive medications in various conditions (n=1145; RR of cough persisting after treatment=0.26; 95% CI, 0.19-0.34, I(2)=0%). The addition of MMDT to conventional medication in patients with postinfectious cough significantly alleviated symptoms up to day 5 but the effect was not maintained one week afterwards. For other diseases/conditions including chronic obstructive pulmonary disease, lung cancer surgery, and asthma, the evidence is inconsistent for MMDT/mMMDT for cough. Adverse events appear to be rare but the reporting was poor.

CONCLUSIONS

The current evidence from our systematic review and meta-analysis on MMDT for cough is inconclusive and we propose that rigorously designed, placebo-controlled trials of MMDT should be conducted to establish its place in management of cough.

Comparative analysis of clinical profile: Chronic cough vs paradoxical vocal fold motion

BACKGROUND

Ongoing contention surrounding typical demographic and clinical attributes of chronic cough (CC) and paradoxical vocal fold motion (PVFM) impedes timely diagnosis and optimum patient care. Designed to reduce preventable patient morbidity through improved recognition and differentiation, the current study aimed to determine representative clinical profiles for CC and PVFM, with identification of distinctive attributes from the general population and risk factors associated with each diagnosis.

METHODS

Self-reported medical questionnaires, demographic and lifestyle attributes of CC and PVFM cases from a disease-specific outcomes database were compared to US population data and published normative values. Univariate comparison and multivariate regression modelling of age, sex, alcohol intake, smoking, Reflux Symptom Index (RSI), Voice Handicap Index (VHI), and Generalized Anxiety Disorder 7-item Scale (GAD-7) determined distinguishing features between the clinical groups, including odds ratios for presenting with CC versus PVFM.

RESULTS

Clinical profiles developed from 283 (128 CC, 155 PVFM) adults (18-91 years) were significantly different from the general population across each demographic, lifestyle and clinical variable (all p < .01), with the exception of obesity. Age (55.39 ± 13.54 vs 45.07 ± 16.51 years, p < .01) and mean RSI score (21.5 ± 9.02 vs 18.1 ± 9.08, p < .01) most reliably distinguished CC from PVFM, with those aged 60-69 years (OR = 9.45) most likely to be diagnosed with CC.

CONCLUSIONS

Standard clinical profiles of CC and PVFM are distinct from the general population, aiding determination of relative probabilities and risk factors in the differential diagnostic process. Variations between CC and PVFM were subtle, reliably distinguished by age and relative severity of laryngopharyngeal reflux symptomatology.

Cough hypersensitivity as a neuro-immune interaction

Cough is an intrinsic protective reflex. However, chronic cough affects a considerable proportion of general population and has a major impact on quality of life. A recent paradigm shift to ‘cough hypersensitivity syndrome’ suggests that chronic cough arises from hypersensitivity of the airway sensory nerves. As cough reflex is determined by interaction of the nervous system with immune system, persistent dysregulation of one or both of these systems may lead to chronic cough hypersensitivity. Here we review the current evidence for the neuro-immune interactions that underlie cough hypersensitivity and discuss future therapeutic strategies.