Chronic cough and obstructive sleep apnea in a community-based pulmonary practice

Association between the Risk of Obstructive Sleep Apnea and Lung Function: Korea National Health and Nutrition Examination Survey

BACKGROUND

Obstructive sleep apnea (OSA) is a prevalent sleep disorder associated with various health issues. Although some studies have suggested an association between reduced lung function and OSA, this association remains unclear. Our study aimed to explore this relationship using data from a nationally representative population- based survey.

METHODS

We performed an analysis of data from the 2019 Korea National Health and Nutrition Examination Survey. Our study encompassed 3,675 participants aged 40 years and older. Risk of OSA was assessed using the STOP-Bang (Snoring, Tiredness during daytime, Observed apnea, and high blood Pressure-Body mass index, Age, Neck circumference, Gender) questionnaire and lung function tests were performed using a portable spirometer. Logistic regression analysis was applied to identify the risk factors associated with a high-risk of OSA, defined as a STOP-Bang score of ≥3.

RESULTS

Of 3,675 participants, 600 (16.3%) were classified into high-risk OSA group. Participants in the high-risk OSA group were older, had a higher body mass index, and a higher proportion of males and ever-smokers. They also reported lower lung function and quality of life index in various domains along with increased respiratory symptoms. Univariate logistic regression analysis indicated a significant association between impaired lung function and a high-risk of OSA. However, in the multivariable analysis, only chronic cough (odds ratio [OR], 2.413; 95% confidence interval [CI], 1.383 to 4.213) and sputum production (OR, 1.868; 95% CI, 1.166 to 2.992) remained significantly associated with a high OSA risk.

CONCLUSION

Our study suggested that, rather than baseline lung function, chronic cough, and sputum production are more significantly associated with OSA risk.

Chronic Cough and Obstructive Sleep Apnea

Chronic cough, defined as a cough lasting more than 8 weeks, is a common medical condition occurring in 5% to 10% of the population. Its overlap with another highly prevalent disorder, obstructive sleep apnea (OSA), is therefore not surprising. The relationship between chronic cough and OSA extends beyond this overlap with higher prevalence of OSA in patients with chronic cough than in the general population. The use of continuous positive airway pressure can result in improvement in chronic cough although further studies are needed to understand which patients will experience benefit in their cough from the treatment of comorbid OSA.

International Consensus Statement on Obstructive Sleep Apnea

BACKGROUND

Evaluation and interpretation of the literature on obstructive sleep apnea (OSA) allows for consolidation and determination of the key factors important for clinical management of the adult OSA patient. Toward this goal, an international collaborative of multidisciplinary experts in sleep apnea evaluation and treatment have produced the International Consensus statement on Obstructive Sleep Apnea (ICS:OSA).

METHODS

Using previously defined methodology, focal topics in OSA were assigned as literature review (LR), evidence-based review (EBR), or evidence-based review with recommendations (EBR-R) formats. Each topic incorporated the available and relevant evidence which was summarized and graded on study quality. Each topic and section underwent iterative review and the ICS:OSA was created and reviewed by all authors for consensus.

RESULTS

The ICS:OSA addresses OSA syndrome definitions, pathophysiology, epidemiology, risk factors for disease, screening methods, diagnostic testing types, multiple treatment modalities, and effects of OSA treatment on multiple OSA-associated comorbidities. Specific focus on outcomes with positive airway pressure (PAP) and surgical treatments were evaluated.

CONCLUSION

This review of the literature consolidates the available knowledge and identifies the limitations of the current evidence on OSA. This effort aims to create a resource for OSA evidence-based practice and identify future research needs. Knowledge gaps and research opportunities include improving the metrics of OSA disease, determining the optimal OSA screening paradigms, developing strategies for PAP adherence and longitudinal care, enhancing selection of PAP alternatives and surgery, understanding health risk outcomes, and translating evidence into individualized approaches to therapy.

Burden of chronic cough in the UK: results from the 2018 National Health and Wellness Survey

Background

Chronic cough, defined as daily cough for at least 8 weeks, negatively affects quality of life and work productivity and increases healthcare resource utilisation. We aimed to determine the prevalence and burden of chronic cough in the UK.

Methods

Study participants were general population respondents to the 2018 UK National Health and Wellness Survey (NHWS). Respondents completed survey questions relating to health, quality of life, work productivity and activity impairment, and use of healthcare resources. Prevalence estimates were projected to the UK population using post-stratification sampling weights to adjust for sampling bias. The population with chronic cough was matched 1:3 with a group without chronic cough, using propensity score matchingon age, sex and the modified Charlson Comorbidity Index.

Results

Of 15 000 NHWS respondents, 715 reported chronic cough in the previous 12 months and 918 during their lifetime. Weighted to the UK adult population, the 12-month prevalence of chronic cough was 4.9% and lifetime prevalence was 6.2%. Prevalence of chronic cough was higher among older respondents and those with smoking histories. Chronic cough respondents experienced higher rates of severe anxiety and depression in the past 2 weeks than matched controls. Poor sleep quality and loss of work productivity were also observed. More chronic cough respondents visited a healthcare provider in the past 6 months than respondents without chronic cough with a mean of 5.8 and 3.7 visits per respondent, respectively.

Conclusion

Adults with chronic cough report lower quality of life, reduced work productivity and greater healthcare resource utilisation than matched controls without chronic cough.

Guidelines for the management of chronic cough in adults. Endorsed by the French speaking society of respiratory diseases (Société de Pneumologie de Langue Française, SPLF), the Société Française d'Oto-Rhino-Laryngologie et de Chirurgie de la Face et du Cou (SFORL), the Société Française de Phoniatrie et de Laryngologie (SFPL), the Société Nationale Française de Gastro-entérologie (SNFGE)

Patients with chronic cough experience a high alteration of quality of life. Moreover, chronic cough is a complex entity with numerous etiologies and treatments. In order to help clinicians involved in the management of patients with chronic cough, guidelines on chronic cough have been established by a group of French experts. These guidelines address the definitions of chronic cough and the initial management of patients with chronic cough. We present herein second-line tests that might be considered in patients with cough persistence despite initial management. Experts also propose a definition of unexplained or refractory chronic cough (URCC) in order to better identify patients whose cough persists despite optimal management. Finally, these guidelines address the pharmacological and non-pharmacological interventions useful in URCC. Thus, amitryptilline, pregabalin, gabapentin or morphine combined with speech and/or physical therapy are a mainstay of treatment strategies in URCC. Other treatment options, such as P2 × 3 antagonists, are being developed.

[Guidelines for the management of chronic cough in adults]

Patients with chronic cough experience major alteration in their quality of life. Given its numerous etiologies and treatments, this disease is a complex entity. To help clinicians involved in patient management of patients, guidelines have been issued by a group of French experts. They address definitions of chronic cough and initial management of patients with this pathology. We present herein the second-line tests that might be considered in patients whose coughing has persisted, notwithstanding initial management. The experts have also put forward a definition of unexplained or refractory chronic cough (URCC), the objective being to more precisely identify those patients whose cough persists despite optimal management. Lastly, these guidelines indicate the pharmacological and non-pharmacological interventions of use in URCC. Amitriptyline, pregabalin, gabapentin or morphine combined with speech and/or physical therapy are mainstays in treatment strategies. Other treatment options, such as P2X3 antagonists, are being developed and have generated high hopes among physicians and patients alike.

Impact of high-risk of obstructive sleep apnea on chronic cough: data from the Korea National Health and Nutrition Examination Survey

Background

Chronic cough is an extremely common clinical symptom of various diseases. However, the relationship between obstructive sleep apnea (OSA) and chronic cough in the general population has not been sufficiently studied.

Methods

Using the 2019 Korean National Health and Nutrition Examination Survey data, we identified a group at high-risk of OSA via the STOP-Bang questionnaire and determined the association between OSA and chronic cough by a regression model.

Results

Of the eligible 4,217 participants, 97.1% and 2.9% were classified into the non-chronic cough and chronic cough groups, respectively. The chronic cough group had higher STOP-Bang scores than those of the group without chronic cough (2.32 ± 1.38 vs. 2.80 ± 1.39; P < 0.001). In the group at high-risk of OSA, 40.4% and 52.0% of participants scored ≥ 3 in STOP-Bang, depending on the absence or presence of chronic cough (P = 0.012), respectively. Chronic cough independently correlated with impaired lung function (forced expiratory volume in one second ≥ 50–<80% predicted value, P = 0.001; <50, P < 0.001), low household income (P = 0.015), and a group at high-risk of OSA (STOP-Bang score 3–4, P = 0.004; 5–8, P < 0.001). Obesity I had a protective role against the occurrence of chronic cough (P = 0.023).

Conclusion

A high-risk for OSA is a significant risk factor for chronic cough. OSA should be considered when evaluating chronic cough patients.

WAO-ARIA consensus on chronic cough - Part III: Management strategies in primary and cough-specialty care. Updates in COVID-19

Background

Chronic cough management necessitates a clear integrated care pathway approach. Primary care physicians initially encounter the majority of chronic cough patients, yet their role in proper management can prove challenging due to limited access to advanced diagnostic testing. A multidisciplinary approach involving otolaryngologists and chest physicians, allergists, and gastroenterologists, among others, is central to the optimal diagnosis and treatment of conditions which underly or worsen cough. These include infectious and inflammatory, upper and lower airway pathologies, or gastro-esophageal reflux. Despite the wide armamentarium of ancillary testing conducted in cough multidisciplinary care, such management can improve cough but seldom resolves it completely. This can be due partly to the limited data on the role of tests (eg, spirometry, exhaled nitric oxide), as well as classical pharmacotherapy conducted in multidisciplinary specialties for chronic cough. Other important factors include presence of multiple concomitant cough trigger mechanisms and the central neuronal complexity of chronic cough. Subsequent management conducted by cough specialists aims at control of cough refractory to prior interventions and includes cough-specific behavioral counseling and pharmacotherapy with neuromodulators, among others. Preliminary data on the role of neuromodulators in a proof-of-concept manner are encouraging but lack strong evidence on efficacy and safety.

Objectives

The World Allergy Organization (WAO)/Allergic Rhinitis and its Impact on Asthma (ARIA) Joint Committee on Chronic Cough reviewed the recent literature on management of chronic cough in primary, multidisciplinary, and cough-specialty care. Knowledge gaps in diagnostic testing, classical and neuromodulator pharmacotherapy, in addition to behavioral therapy of chronic cough were also analyzed.

Outcomes

This third part of the WAO/ARIA consensus on chronic cough suggests a management algorithm of chronic cough in an integrated care pathway approach. Insights into the inherent limitations of multidisciplinary cough diagnostic testing, efficacy and safety of currently available antitussive pharmacotherapy, or the recently recognized behavioral therapy, can significantly improve the standards of care in patients with chronic cough.

OSA and Chronic Respiratory Disease: Mechanisms and Epidemiology

Obstructive sleep apnea (OSA) is a highly prevalent disorder that has profound implications on the outcomes of patients with chronic lung disease. The hallmark of OSA is a collapse of the oropharynx resulting in a transient reduction in airflow, large intrathoracic pressure swings, and intermittent hypoxia and hypercapnia. The subsequent cytokine-mediated inflammatory cascade, coupled with tractional lung injury, damages the lungs and may worsen several conditions, including chronic obstructive pulmonary disease, asthma, interstitial lung disease, and pulmonary hypertension. Further complicating this is the sleep fragmentation and deterioration of sleep quality that occurs because of OSA, which can compound the fatigue and physical exhaustion often experienced by patients due to their chronic lung disease. For patients with many pulmonary disorders, the available evidence suggests that the prompt recognition and treatment of sleep-disordered breathing improves their quality of life and may also alter the course of their illness. However, more robust studies are needed to truly understand this relationship and the impacts of confounding comorbidities such as obesity and gastroesophageal reflux disease. Clinicians taking care of patients with chronic pulmonary disease should screen and treat patients for OSA, given the complex bidirectional relationship OSA has with chronic lung disease.

Cough detection using a non-contact microphone: A nocturnal cough study

An automatic non-contact cough detector designed especially for night audio recordings that can distinguish coughs from snores and other sounds is presented. Two different classifiers were implemented and tested: a Gaussian Mixture Model (GMM) and a Deep Neural Network (DNN). The detected coughs were analyzed and compared in different sleep stages and in terms of severity of Obstructive Sleep Apnea (OSA), along with age, Body Mass Index (BMI), and gender. The database was composed of nocturnal audio signals from 89 subjects recorded during a polysomnography study. The DNN-based system outperformed the GMM-based system, at 99.8% accuracy, with a sensitivity and specificity of 86.1% and 99.9%, respectively (Positive Predictive Value (PPV) of 78.4%). Cough events were significantly more frequent during wakefulness than in the sleep stages (p < 0.0001) and were significantly less frequent during deep sleep than in other sleep stages (p < 0.0001). A positive correlation was found between BMI and the number of nocturnal coughs (R = 0.232, p < 0.05), and between the number of nocturnal coughs and OSA severity in men (R = 0.278, p < 0.05). This non-contact cough detection system may thus be implemented to track the progression of respiratory illnesses and test reactions to different medications even at night when a contact sensor is uncomfortable or infeasible.

WAO-ARIA consensus on chronic cough - Part II: Phenotypes and mechanisms of abnormal cough presentation - Updates in COVID-19

BACKGROUND

Chronic cough can be triggered by respiratory and non-respiratory tract illnesses originating mainly from the upper and lower airways, and the GI tract (ie, reflux). Recent findings suggest it can also be a prominent feature in obstructive sleep apnea (OSA), laryngeal hyperresponsiveness, and COVID-19. The classification of chronic cough is constantly updated but lacks clear definition. Epidemiological data on the prevalence of chronic cough are informative but highly variable. The underlying mechanism of chronic cough is a neurogenic inflammation of the cough reflex which becomes hypersensitive, thus the term hypersensitive cough reflex (HCR). A current challenge is to decipher how various infectious and inflammatory airway diseases and esophageal reflux, among others, modulate HCR.

OBJECTIVES

The World Allergy Organization/Allergic Rhinitis and its Impact on Asthma (WAO/ARIA) Joint Committee on Chronic Cough reviewed the current literature on classification, epidemiology, presenting features, and mechanistic pathways of chronic cough in airway- and reflux-related cough phenotypes, OSA, and COVID-19. The interplay of cough reflex sensitivity with other pathogenic mechanisms inherent to airway and reflux-related inflammatory conditions was also analyzed.

OUTCOMES

Currently, it is difficult to clearly ascertain true prevalence rates in epidemiological studies of chronic cough phenotypes. This is likely due to lack of standardized objective measures needed for cough classification and frequent coexistence of multi-organ cough origins. Notwithstanding, we emphasize the important role of HCR as a mechanistic trigger in airway- and reflux-related cough phenotypes. Other concomitant mechanisms can also modulate HCR, including type2/Th1/Th2 inflammation, presence or absence of deep inspiration-bronchoprotective reflex (lower airways), tissue remodeling, and likely cough plasticity, among others.

Revised Korean Cough Guidelines, 2020: Recommendations and Summary Statements

Cough is the most common respiratory symptom that can have various causes. It is a major clinical problem that can reduce a patient's quality of life. Thus, clinical guidelines for the treatment of cough were established in 2014 by the cough guideline committee under the Korean Academy of Tuberculosis and Respiratory Diseases. From October 2018 to July 2020, cough guidelines were revised by members of the committee based on the first guidelines. The purpose of these guidelines is to help clinicians efficiently diagnose and treat patients with cough. This article highlights the recommendations and summary of the revised Korean cough guidelines. It includes a revised algorithm for the evaluation of acute, subacute, and chronic cough. For a chronic cough, upper airway cough syndrome (UACS), cough variant asthma (CVA), and gastroesophageal reflux disease (GERD) should be considered in differential diagnoses. If UACS is suspected, first-generation antihistamines and nasal decongestants can be used empirically. In cases with CVA, inhaled corticosteroids are recommended to improve cough. In patients with suspected chronic cough due to symptomatic GERD, proton pump inhibitors are recommended. Chronic bronchitis, bronchiectasis, bronchiolitis, lung cancer, aspiration, intake of angiotensin-converting enzyme inhibitor, intake of dipeptidyl peptidase-4 inhibitor, habitual cough, psychogenic cough, interstitial lung disease, environmental and occupational factors, tuberculosis, obstructive sleep apnea, peritoneal dialysis, and unexplained cough can also be considered as causes of a chronic cough. Chronic cough due to laryngeal dysfunction syndrome has been newly added to the guidelines.

Prevalence and Burden of Chronic Cough in the United States

BACKGROUND

Chronic cough is a common complaint but there are little population-based data on its burden in the United States.

OBJECTIVE

To determine the prevalence of chronic cough and its burden on individuals and the health care system.

METHODS

This was a survey of respondents who completed the 2018 National Health and Wellness Survey and questions about sleep and health care resource use. Chronic cough was defined as having a daily cough for 8 or more weeks. Respondents without chronic cough were selected through propensity score matching. Chronic cough prevalence was estimated using poststratification sampling weights calculated using U.S. Census data and post-data Horvitz-Thompson sampling weights to adjust for sampling bias.

RESULTS

Of 74,977 National Health and Wellness Survey respondents, 3,654 had experienced chronic cough in the previous 12 months, for a weighted prevalence of 5.0%. Respondents with chronic cough were older and more predominantly female than respondents without chronic cough (both P < .001). Compared with matched respondents without chronic cough, those with chronic cough had lower mean scores on the Medical Outcomes Study 36-item Short Form Survey v2 physical (P < .001) and mental (P < .001) component summary scores. More respondents with chronic cough than matched controls experienced severe anxiety and severe depression in the past 2 weeks, work productivity impairment, impaired sleep quality and daytime sleepiness, as well as more emergency department visits and hospitalizations in the past 6 months (P < .001 for all comparisons).

CONCLUSIONS

The burden of chronic cough manifests itself as reduced health-related quality of life, increased anxiety and depression, impaired sleep and work productivity, and greater health care utilization.

Obesity Predicts Treatment Response to Proton Pump Inhibitor Therapy in Patients with Chronic Cough

BACKGROUND

Chronic cough management is challenging as this condition is often associated with multiple comorbidities, requiring a multidisciplinary diagnostic approach. Little is known about the characteristics of obese patients with chronic cough. This study aims to describe treatable traits of chronic cough and the response to pump proton inhibitor (PPI) therapy in this sub-group of patients.

METHODS

A retrospective, observational study was performed in patients with chronic cough in a French University Hospital. Characteristics of chronic cough were analyzed for obese (N = 112) and non-obese (N = 355) patients. Refractory cough was estimated at 6 and 12 months.

RESULTS

The 3 main treatable traits associated with chronic cough in obese patients and non-obese patients were gastroesophageal reflux disease (GERD), asthma, and upper airway cough syndrome (UACS). A noticeable difference was the higher frequency of GERD (47.3% vs 34.6%, p = 0.0188) and obstructive sleep apnea (OSA) (9.8% vs 3.1%, p = 0.0080) in obese patients compared to non-obese patients. Pump proton inhibitor (PPI) treatment had a significantly higher success rate in obese patients (32.5% vs 17.0%, p < 0.05) and refractory cough at 12 months was less frequently reported in obese patients (22.3% vs 34.1%, p < 0.05).

CONCLUSION

In a context of chronic cough, a higher prevalence of GERD was noted in obese patients compared to non-obese patients and obese patients were more responsive to PPI treatment. Moreover, OSA was reported more frequently as a treatable trait in obese patients and should be considered early in the diagnostic evaluation. Prospective clinical studies that evaluate the contribution of obesity to chronic cough are further needed.

A Randomized, Controlled, Pilot Study of CPAP for Patients with Chronic Cough and Obstructive Sleep Apnea

BACKGROUND

An association between chronic cough and obstructive sleep apnea (OSA) has been reported in prior studies with resolution or improvement in cough after continuous positive airway pressure (CPAP) therapy. Controlled studies of the benefit of CPAP on cough-quality of life measures have not been conducted.

RESEARCH QUESTION

Does CPAP therapy for OSA improve cough in patients with chronic unexplained cough?

STUDY DESIGN AND METHODS

Patients with unexplained chronic cough (> 2 months duration of cough) and OSA were randomized to receive either CPAP or sham CPAP therapy for 6 weeks. The primary end point was the change in health status assessed with the Leicester Cough Questionnaire (LCQ) in patients treated with CPAP vs. sham CPAP. Secondary end points were changes in exhaled breath condensate markers of airway inflammation (interleukin-6, nitrite/nitrates, hydrogen peroxide and 8-isoprostanes).

RESULTS

A total of 22 patients with chronic unexplained cough and OSA were randomized of whom18 completed 6 weeks of treatments with either CPAP or sham CPAP. The CPAP vs. sham CPAP-treated group were comparable in terms of sex distribution, body mass index, and OSA severity. Following CPAP therapy, there was a significantly greater improvement in total LCQ scores as compared to those treated with sham therapy (ANCOVA p value 0.016). No significant differences were noted in the exhaled breath condensate marker changes between CPAP-treated vs. sham CPAP-treated groups.

CONCLUSION

Treatment of comorbid OSA in patients with chronic cough improved cough quality of life measures following treatment of OSA with CPAP in this pilot study. Larger studies to understand this association and unravel mechanisms of CPAP benefit in chronic cough need to be undertaken. Clinical Trial Registration NCT03172130.

Evidence of Possible Irritable Larynx Syndrome in Obstructive Sleep Apnea: An Epidemiologic Approach

OBJECTIVE

"Irritable larynx syndrome" (ILS) often refers to a constellation of laryngeal-based symptoms including chronic cough (CC), diurnal dyspnea, and dysphonia. In patients with OSA, we examined: (1) the frequency, severity, comorbidity, risks and triggers of each problem, (2) whether these symptoms were compatible with stereotypic ILS and (3) the role of CPAP in their expression.

STUDY DESIGN

Cross-sectional, descriptive epidemiology study.

SETTING

Sleep-Wake Center at University of Utah Health Care, Salt Lake City, UT.

SUBJECTS AND METHODS

Ninety-four individuals with OSA (53 men, 41 women; mean age 54.7 ± 12.8 yrs.) underwent an extensive telephone interview that addressed study objectives.

RESULTS

Long-term CC, daytime breathing and voice problems were common, especially among women despite less severe OSA. Women, more than men, reported all three chronic conditions alone or in combination: CC (44% vs 11.3%), diurnal dyspnea (41.5% vs 13.2%) and voice disorders (41.5% vs 13.2%). Symptoms were not associated with age, BMI or Apnea Hypopnea Index after adjusting for sex. Although evidence supporting stereotypic ILS symptomatology was inconsistent, those participants with a voice disorder were 3.3 (95% CI = 1.8-6.0) times more likely to report CC and 2.4 (95% CI = 1.3-4.4) times more likely to experience diurnal dyspnea. Esophageal reflux, post-nasal drip, and frequent sinus infections were significantly associated with all three conditions. Triggers that provoked or made symptoms worse varied by condition and sex. Nightly, humidified CPAP use was associated with fewer symptoms overall and improved quality of life.

CONCLUSIONS

Symptoms suggestive of possible ILS are common in OSA, especially among women, and lessened by nightly CPAP use.

Chronic cough and obesity

With respective prevalence of 13% and 9.6%, obesity and chronic cough are two common conditions worldwide. The crucial role of obesity has been highlighted in the development and progression of many respiratory diseases. According to the results of epidemiological studies, obesity, particularly abdominal obesity, may also be associated with chronic cough (CC). CC seems to be more severe in obese patients compared to normal-weight subjects. The management of CC may differ slightly in obese patients compared to non-obese patients. Indeed, asthma and reflux diseases, which are considered key factors in the onset of CC, are characterised by more severe symptoms in obese patients. Asthma is associated with a resistance to usual treatments in obese patients but no data are available on the effect of inhaled therapies in obese subjects with cough variant asthma. Other emergent causes of CC have been reported in obese patients. Obstructive sleep apnoea and diabetes may also be involved in the development of CC and should be taken into account in obese patients with CC. The beneficial effect of weight loss on chronic cough has been suggested.

New insights in the diagnosis of chronic refractory cough

BACKGROUND

Chronic Refractory Cough (CRC) is a common condition that significantly impairs patients' quality of life. Unfortunately, in many situations patients continue to experience CRC in spite of following published guidelines for diagnosis and treatment.

METHODS

99 patients were referred to National Jewish Health (NJH), a specialty respiratory center for evaluation of CRC (cough ≥ 8 weeks duration). Study duration occurred over 18 months. Intake evaluation for all patients included history, physical examination, spirometry and fiberoptic laryngoscopy. Testing to confirm causes of CRC were performed. Specific therapy for each potential cause was provided. A visual analog cough scale measured cough response.

RESULTS

Ten final diagnostic categories were found in the cohort of 99 patients with CRC: Obstructive sleep apnea (apnea/hypoxia index ≥ 5), rhinosinusitis, Tracheobronchomalacia (≥65% collapse of airway with dynamic expiratory imaging), esophageal dysmotility, gastroesophageal reflux, abnormal swallowing with laryngeal penetration, asthma, COPD, bronchiectasis and paradoxical vocal cord movement. In these patients there were 42 incorrect intake diagnoses and 101 new diagnoses established. Patients with CRC have had multiple diagnoses (3.8 ± 1.6) associated with chronic cough. With directed therapy 71/76 (93%) patients had resolution or improvement in cough symptoms.

CONCLUSIONS

Among patients referred to a specialty respiratory center with CRC multiple concomitant diagnoses for cough were common. Certain diagnoses such as OSA and TBM have not been reported in cough guidelines but in this study are commonly associated diagnoses. Targeted therapy for each recognized diagnosis improves patient response.

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.

Síndrome de apnea-hipopnea obstructiva del sueño y enfermedades respiratorias

El síndrome de apnea-hipopnea obstructiva del sueño (SAHOS) es una enfermedad sistémica con afectación de múltiples órganos. El presente artículo trata la relación que existe entre el SAHOS y algunas enfermedades que comprometen el sistema respiratorio como son la enfermedad pulmonar obstructiva crónica, el asma, la tos crónica, el síndrome de hipoventilación alveolar y la fibrosis pulmonar. Por lo general, cada una de estas afectaciones se diagnostica por separado, pero es importante conocer su relación de coexistencia para definir la necesidad de realizar estudios del sueño diagnósticos a los pacientes con enfermedades respiratorias, en especial cuando hay un grado desproporcionado de hipertensión pulmonar al esperado por solo la presencia de la enfermedad respiratoria.

Etiologies of Chronic Cough in Pediatric Cohorts: CHEST Guideline and Expert Panel Report

BACKGROUND

There is no published systematic review on the etiologies of chronic cough or the relationship between OSA and chronic cough in children aged ≤ 14 years. We thus undertook a systematic review based on key questions (KQs) using the Population, Intervention, Comparison, Outcome format. The KQs follow: Among children with chronic (> 4 weeks) cough (KQ 1) are the common etiologies different from those in adults? (KQ 2) Are the common etiologies age or setting dependent, or both? (KQ 3) Is OSA a cause of chronic cough in children?

METHODS

We used the CHEST Expert Cough Panel's protocol and the American College of Chest Physicians (CHEST) methodological guidelines and Grading of Recommendations Assessment, Development, and Evaluation framework. Data from the systematic reviews in conjunction with patients' values and preferences and the clinical context were used to form recommendations. Delphi methodology was used to obtain consensus.

RESULTS

Combining KQs 1 and 2, we found moderate-level evidence from 10 prospective studies that the etiologies of cough in children are different from those in adults and are setting dependent. Data from three studies found that common etiologies of cough in young children were different from those in older children. However, data relating sleep abnormalities to chronic cough in children were found only in case studies.

CONCLUSIONS

There is moderate-quality evidence that common etiologies of chronic cough in children are different from those in adults and are dependent on age and setting. As there are few data relating OSA and chronic cough in children, the panel suggested that these children should be managed in accordance with pediatric sleep guidelines.

Inflammatory Role of ROS-Sensitive AMP-Activated Protein Kinase in the Hypersensitivity of Lung Vagal C Fibers Induced by Intermittent Hypoxia in Rats

Obstructive sleep apnea (OSA), manifested by airway exposure to intermittent hypoxia (IH), is associated with excess reactive oxygen species (ROS) production in airways, airway inflammation, and hyperreactive airway diseases. The cause-effect relationship for these events remains unclear. We investigated the inflammatory role of ROS-sensitive AMP-activated protein kinase (AMPK) in IH-induced airway hypersensitivity mediated by lung vagal C fibers (LVCFs) in rats. Conscious rats were exposed to room air (RA) or IH with or without treatment with N-acetyl-L-cysteine (NAC, an antioxidant), Compound C (an AMPK inhibitor), ibuprofen (a cyclooxygenase inhibitor), or their vehicles. Immediately after exposure (24 h), we found that intravenous capsaicin, phenylbiguanide, or α,β-methylene-ATP evoked augmented LVCF-mediated apneic responses and LVCF afferent responses in rats subjected to IH exposure in comparison with those in RA rats. The potentiating effect of IH on LVCF responses decreased at 6 h after and vanished at 12 h after the termination of IH exposure. The potentiating effect of IH on LVCF-mediated apneic and LVCF afferent responses was significantly attenuated by treatment with NAC, compound C, or ibuprofen, but not by their vehicles. Further biochemical analysis revealed that rats exposed to IH displayed increased lung levels of lipid peroxidation (an index of oxidative stress), AMPK phosphorylation (an index of AMPK activation), and prostaglandin E₂ (a cyclooxygenase metabolite), compared with those exposed to RA. IH-induced increase in lipid peroxidation was considerably suppressed by treatment with NAC but not by compound C or ibuprofen. IH-induced increase in AMPK phosphorylation was totally abolished by NAC or compound C but not by ibuprofen. IH-induced increase in prostaglandin E₂ was considerably prevented by any of these three inhibitor treatments. The vehicles of these inhibitors exerted no significant effect on the three IH-induced responses. These results suggest that 24-h IH exposure sensitizes LVCFs, leading to an exaggerated reflex and afferent responses to chemical stimulants in rats. Moreover, this IH-induced LVCF sensitization is mediated through a cascade of inflammatory responses in the airways involving increases in ROS, AMPK activation, and cyclooxygenase metabolite release.

NADPH Oxidase-Derived ROS Induced by Chronic Intermittent Hypoxia Mediates Hypersensitivity of Lung Vagal C Fibers in Rats

Obstructive sleep apnea (OSA), manifested by exposure to chronic intermittent hypoxia (CIH) and excess production of reactive oxygen species (ROS) in the airways, is associated with hyperreactive airway diseases. ROS, particularly when created by NADPH oxidase, are known to sensitize lung vagal C fibers (LVCFs), which may contribute to airway hypersensitivity pathogenesis. We investigated whether CIH augments the reflex and afferent responses of LVCFs to chemical stimulants and the roles of ROS and NADPH oxidase in such airway hypersensitivity. Rats were exposed to room air (RA) or CIH with/without daily treatment with MnTMPyP (a superoxide anion scavenger), apocynin (an NADPH oxidase inhibitor), or vehicle. At 16 h after their last exposure, intravenous capsaicin, adenosine, or α,β-methylene-ATP evoked an augmented apneic response in anesthetized rats with 14-days CIH exposure, compared to anesthetized rats with 14-days RA exposure. The augmented apneic responses to these LVCF stimulants were abolished by bilateral vagotomy or perivagal capsaicin treatment, which block LVCFs neural conduction and were significantly suppressed by treatment with MnTMPyP or apocynin, but not vehicle. Electrophysiological studies revealed that 14-days CIH exposure potentiated the responses of LVCFs to these stimulants. This effect was inhibited by treatment with MnTMPyP or apocynin treatment and was not seen in rats who received 7-days of CIH exposure. Biochemical analysis indicated that 14-days CIH exposure increased both lung lipid peroxidation, which is indicative of oxidative stress, and expression of the p47^phox subunit in the membrane fraction of lung tissue, which is an index of NADPH oxidase activation. The former was prevented by treatment with either MnTMPyP or apocynin, while the later was prevented by treatment with apocynin only. These results suggest that 14-days CIH exposure sensitizes LVCFs in rats, leading to an exaggerated reflex and afferent responses to stimulants and that this sensitization is mediated via ROS generated by NADPH oxidase.

Associations between obstructive lung disease and symptoms of obstructive sleep apnoea in a general population

OBJECTIVES

To examine the prevalence of self-reported symptoms of obstructive sleep apnoea (OSA) in relation to asthma, respiratory symptoms and pulmonary function. A secondary objective was to determine how sex impacted these relationships.

METHODS

A random sample of all adults aged 47-48 and 71-73 years living in Bergen, Norway, were invited. Participants (3506, 69%) underwent spirometry testing and completed a questionnaire on sleep, respiratory symptoms and past medical history. OSA was defined by positive answers to questions on snoring, breathing cessations and daytime sleepiness. Current asthma was defined by ever having received a physician's diagnosis of asthma and current use of anti-asthma medication. Logistic regression analyses, including interaction analyses between sex and the different explanatory variables, were used to examine associations between OSA and current asthma, pre- and post-bronchodilator pulmonary function tests, smoking habits and respiratory symptoms. All models were adjusted for age, sex, waist-hip ratio and smoking.

RESULTS

OSA was more prevalent in the middle-aged compared to the elderly (6.2% vs 3.6%), and in subjects reporting respiratory symptoms. 4.8% had OSA and 6.1% had current asthma. Current asthma and the lowest quartile of post-bronchodilator FVC were significantly associated with OSA with ORs of 2.5 (1.5, 4.2) and 1.7 (1.1, 2.7), respectively. In interaction analyses, women with post-bronchodilator FEV₁ /FVC < 0.7 had an increased risk of OSA [OR of 4.1 (1.7, 9.7)] compared to women with a FEV₁ /FVC ≥ 0.7.

CONCLUSIONS

Current asthma was associated with increased risk of OSA. Women with chronic airflow limitation, but not men, had increased risk of OSA.

The Korean Cough Guideline: Recommendation and Summary Statement

Cough is one of the most common symptom of many respiratory diseases. The Korean Academy of Tuberculosis and Respiratory Diseases organized cough guideline committee and cough guideline was developed by this committee. The purpose of this guideline is to help clinicians to diagnose correctly and treat efficiently patients with cough. In this article, we have stated recommendation and summary of Korean cough guideline. We also provided algorithm for acute, subacute, and chronic cough. For chronic cough, upper airway cough syndrome (UACS), cough variant asthma (CVA), and gastroesophageal reflux disease (GERD) should be considered. If UACS is suspicious, first generation anti-histamine and nasal decongestant can be used empirically. In CVA, inhaled corticosteroid is recommended in order to improve cough. In GERD, proton pump inhibitor is recommended in order to improve cough. Chronic bronchitis, bronchiectasis, bronchiolitis, lung cancer, aspiration, angiotensin converting enzyme inhibitor, habit, psychogenic cough, interstitial lung disease, environmental and occupational factor, tuberculosis, obstructive sleep apnea, peritoneal dialysis, and idiopathic cough can be also considered as cause of chronic cough. Level of evidence for treatment is mostly low. Thus, in this guideline, many recommendations are based on expert opinion. Further study regarding treatment for cough is mandatory.

Cough in obstructive sleep apnoea

Obstructive Sleep Apnoea (OSA) has recently been reported to be a cause of chronic cough. It should be considered when cough remains unexplained following investigations and treatments for common causes. The presence of nocturnal cough, snoring and gastro-oesophageal reflux may be helpful in identifying patients who require further investigation. Daytime somnolence is often absent. Continuous positive airway pressure (CPAP) therapy has been reported to be effective in alleviating cough. Therapy for gastro-oesophageal reflux disease, if present, should be optimised. The mechanism of the association between OSA and cough is not clear, but airway inflammation, gastro-oesophageal reflux disease, increased cough reflex sensitivity and tracheobronchomalacia are possible explanations. Further studies should identify clinical predictors of OSA-cough, establish mechanisms and the optimal therapy.

Utility of continuous positive airway pressure therapy for treating chronic coughs in patients with obstructive sleep apnea

We experienced two patients with chronic coughs whose symptoms persisted after initial treatment under a diagnosis of suspected upper airway cough syndrome or cough variant asthma. Neither patient exhibited daytime somnolence, although both were subsequently found to have severe obstructive sleep apnea. Following the administration of nocturnal continuous positive airway pressure therapy, the cough symptoms rapidly improved in both cases. These cases represent the first reports of obstructive sleep apnea-induced chronic cough in Japan.

Chronic cough and obstructive sleep apnoea in a sleep laboratory-based pulmonary practice

BACKGROUND

Obstructive sleep apnoea (OSA) has recently been identified as a possible aetiology for chronic cough. The aim of this study was to compare the incidence of chronic cough between patients with and without OSA and the impact of continuous positive airway pressure (CPAP) treatment in resolving chronic cough.

METHODS

Patients referred to the sleep laboratory from January 2012 to June 2012 were retrospectively enrolled. Clinical data, treatment course and resolution of chronic cough were analysed. Specifically, gastro-oesophageal reflux (GERD), upper airway cough syndrome, asthma, apnoea-hypopnoea index and the impact of CPAP treatment on chronic cough were assessed.

RESULTS

A total of 131 patients were reviewed. The incidence of chronic cough in the OSA group was significantly higher than the non-OSA group (39/99 (39.4%) vs. 4/32 (12.5%), p = 0.005). Both GERD and apnoea-hypopnoea index were significantly associated with chronic cough in univariate analysis. After multivariate logistic regression, GERD was the only independent factor for chronic cough. Moreover, the resolution of chronic cough was more significant in the OSA patients with CPAP treatment compared with those not receiving CPAP treatment (12/18 (66.7%) vs. 2/21 (9.5%), p = 0.010).

CONCLUSION

The incidence of chronic cough was significantly higher in the OSA patients. In addition, CPAP treatment significantly improved chronic cough. Therefore, OSA may be a contributory factor to chronic cough.

A longitudinal study of CPAP therapy for patients with chronic cough and obstructive sleep apnoea

Background

Chronic cough patients are rendered therapies for gastro-esophageal reflux (GERD), upper airway cough syndrome (UACS) and cough-variant asthma (CVA) with varying benefit. Idiopathic or unexplained cough has emerged as an important clinical entity in both primary care and subspecialty clinics. Recent evidence points to a link between chronic cough and untreated obstructive sleep apnea (OSA).

Methods

A prospective observational study was done to evaluate the effect of OSA therapy in patients with chronic cough. Patients enrolled into the study underwent questionnaires to evaluate for GERD, UACS and CVA along with screening questionnaires for OSA and daytime sleepiness. The Leicester cough questionnaire (LCQ) was done at baseline and during serial visits to evaluate cough intensity and was used as the primary outcome measure of the effect of CPAP therapy on chronic cough.

Results

Out of 37 patients enrolled into the study, only 28 patients had follow up LCQ scores available and therefore underwent analysis. 22/28 patients were suspected to have OSA based on abnormal STOP-BANG screening questionnaire scores and overnight oximetry abnormalities. Of these 19/28 patients had overnight attended polysomnography with definitive diagnosis of OSA yielding a 68% prevalence of OSA in our chronic cough population. Chronic cough patients treated for OSA tended to be older with a significantly higher BMI than chronic cough patients without OSA. Significant improvement of LCQ scores occurred with CPAP therapy for OSA in chronic cough patients.

Conclusion

OSA is significantly prevalent in chronic cough patients. Subjects with chronic cough and OSA tend to be older and obese. Treatment of OSA in chronic cough patients yields significant improvement in their health status.

The difficult-to-treat, therapy-resistant cough: why are current cough treatments not working and what can we do?

Cough can persist despite exhaustive diagnostic and therapeutic effort and has been termed 'idiopathic' or 'unexplained' but perhaps 'difficult to treat' cough is a more appropriate description. In this article the reasons for poor treatment response are discussed. These include a lack of physician fidelity to management guidelines, patient non-adherence and the lack of effective medicines. A number of randomized controlled trials have been undertaken including low dose opiate therapy, the use of a speech pathology intervention, oral antibiotics and antidepressants. The success or otherwise of such interventions will be discussed. A number of approaches to deal with the problem of 'difficult to treat cough' will be considered.

Cough, sarcoidosis and idiopathic pulmonary fibrosis: raw nerves and bad vibrations

Cough is a common symptom in people who develop interstitial lung diseases (ILD). The pathological features of the ILDs are many and varied suggesting that the cause of cough may also vary with each disease. This article reviews what is currently known about cough in sarcoidosis and idiopathic pulmonary fibrosis; two of the commonest ILDs. It also outlines some of the theories which have been proposed to explain why cough develops in these conditions and describes what little is known about how to treat it.

Novel antitussive strategies

Acute and chronic cough represent one of the most common symptoms of medical importance but effective pharmacotherapy is, to all intents and purposes, absent. Numerous initiatives targeting the recently discovered tussive pathways are in progress. Here, we review the current antitussive armamentarium and provide an update on the novel strategies and compounds in development.

Analysis of systemic and airway inflammation in obstructive sleep apnea

PURPOSE

The presence of both systemic and airway inflammation has been suggested in obstructive sleep apnea (OSA) by increased levels of inflammatory biomarkers in the circulation and respiratory specimens. We aimed to investigate the relationship between systemic and airway inflammation in OSA.

METHODS

This study was conducted by simultaneously measuring various biomarkers both in serum and induced sputum of 43 patients. We compared the relationships of these biomarker levels with polysomnographic data and obesity measurements and also investigated their interrelationships between systemic and local compartments. We also assessed the relation of inflammatory markers with proximal airway resistance measured by impulse oscillometry.

RESULTS

In multiple regression analyses, each measured serum biomarker [leptin, interleukin-6 (IL-6), IL-8, tumor necrosis factor-α (TNF-α), and vascular endothelial growth factor (VEGF)] significantly correlated with waist circumference or fat area determined by computed tomography. In contrast, regarding airway inflammation, sputum IL-6, IL-8, TNF-α, and VEGF significantly correlated with OSA severity as indicated by the respiratory disturbance index or oxygen desaturation indices. Sputum IL-6, IL-8, TNF-α, and VEGF were significantly related to sputum neutrophil number, and sputum IL-8 and TNF-α were related to proximal airway resistance independently of body mass index. There were no significant interrelationships between the same biomarkers in serum and induced sputum.

CONCLUSIONS

Systemic and airway inflammation in OSA might be differently regulated by OSA itself and comorbid obesity, depending on the type of cytokine. Although we did not find apparent interrelationships between systemic and local compartments, further studies are needed to clarify this concept.

Chronic cough and OSA: a new association?

Chronic cough is defined as cough lasting more than 2 months. Common causes for chronic cough in nonsmokers with normal chest radiographs and pulmonary functions include gastroesophageal reflux disease (GERD), cough-variant asthma (CVA), and upper airway cough syndrome (UACS). Current guidelines recommend diagnosing the etiology of chronic cough based upon the results of therapy for suspected GERD, CVA, and UACS. Despite following current recommendations for diagnosis and treatment, the cause for a significant proportion of chronic cough remains unexplained.Recent reports indicate the resolution of chronic cough following treatment of concomitantly diagnosed obstructive sleep apnea (OSA). Whether this represents a co-occurrence of two commonly prevalent disorders or a pathophysiologic relationship between OSA and cough remains unknown. This review offers insights into a pathophysiologic link between OSA and the commonly purported etiologies for cough, namely, GERD, UACS, and CVA. In addition, evidence for a relationship between airway inflammation that can trigger or perpetuate cough and OSA is discussed. This review explores mechanisms by which nocturnal continuous positive airway therapy resolves cough by improving underlying airway inflammation secondary to OSA and impacts upon GERD, CVA, and UACS.

Therapy for cough: where does it fall short?

Studies on cough have come a long way but many shortfalls still exist. These shortfalls can be attributed to: the lack of randomized controlled studies with a focus on cough; studies not using robust cough outcome measures, poor definition of target groups in studies and guidelines, the lack of safe and efficacious treatments; difficulty in defining etiological factors, and the lack of data on the predictors of response to therapies for cough dominant etiologies. Addressing shortfalls in cough therapy that focuses on improving the lives of people with cough requires a systematic approach that includes better medications, high quality studies, improved multidisciplinary guidelines and education (of both health professionals and patients). To achieve new cough therapeutics requires an improved understanding of cough in humans (i.e., not just in animals). Development of new medications without substantial adverse events is long awaited for cough.

Brief communication (Original). Sleep-disordered breathing and risk factors in Thailand

Background: Sleep-disordered breathing or obstructive sleep apnea (OSA) has an important effect on the quality of life. Very few data of OSA are available for Thai persons.

Objective: Investigate the prevalence of high risk to OSA and the relationship between OSA and risk factors in Thai medical students.

Materials and methods: Three hundred seven subjects were recruited from all of the medical students (fourth year to sixth year) the Faculty of Medicine, Srinakharinwirot University, Thailand for this cross-sectional study. Data was collected between June and September 2010. The Berlin questionnaire was used to determine risk for OSA. Logistic regression analysis was performed with p-value less than 0.05 for statistical significance.

Results: The prevalence of high risk to OSA was 6.8%. Total mean of sleep duration, bedtime, and wake-time was 6.59 hours. Bedtime of male students was significantly later than female students. The medical students with body mass index (BMI) >23 kilogram/meter2 and with underlying diseases were at high-risk for OSA.

Conclusion: Prevalence of high-risk to OSA of Thai medical students was 6.8%. The medical students with BMI >23 kilogram/meter2 and with underlying diseases were at high risk for OSA but gender, age, academic year, and academic achievement did not relate to OSA.

Relationship between gastro-oesophageal reflux and airway diseases: the airway reflux paradigm

Our understanding of the relationship between gastro-oesophageal reflux and respiratory disease has recently undergone important changes. The previous paradigm of airway reflux as synonymous with the classic gastro-oesophageal reflux disease (GORD) causing heartburn has been overturned. Numerous epidemiological studies have shown a highly significant association of the acid, liquid, and gaseous reflux of GORD with conditions such as laryngeal diseases, chronic rhinosinusitis, treatment resistant asthma, COPD and even idiopathic pulmonary fibrosis. However, it has become clear from studies on cough hypersensitivity syndrome that much reflux of importance in the airways has been missed, since it is either non- or weakly acid and gaseous in composition. The evidence for such a relationship relies on the clinical history pointing to symptom associations with known precipitants of reflux. The tools for the diagnosis of extra-oesophageal reflux, in contrast to the oesophageal reflux of GORD, lack sensitivity and reproducibility. Unfortunately, methodology for detecting such reflux is only just becoming available and much additional work is required to properly delineate its role.

New concepts in the management of chronic cough

There has been significant progress in the field of cough in the past 10 years. Obstructive sleep apnoea, tonsillar enlargement and environmental fungi have recently been described as causes of chronic cough. The advances in the assessment of gastro-oesophageal reflux (GOR) have led to a greater understanding of the relationship between cough and GOR and are likely to change the approach to managing patients with GOR-cough. The investigation of the phenotype of patients with idiopathic chronic cough has provided novel insights. Patients with an idiopathic chronic are predominantly female, have an onset of cough around the menopause and have a high prevalence of organ specific autoimmune disease, particularly hypothyroidism. The presence of bronchoalveolar lymphocytosis suggests there is homing of inflammatory cells from primary sites of autoimmune inflammation to the lungs. A heightened cough reflex is a key feature of most patients with chronic cough and has led some investigators to suggest that chronic cough be recognised as a unique entity called Cough Hypersensitivity Syndrome (CHS). A number of subjective and objective tools have been developed recently to assess cough severity. Antitussive drug development is an emerging and exciting area of cough research.