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New Considerations in the Work-up of Patients with Chronic Cough
Abstract & Commentary
By Barbara A. Phillips, MD, MSPH, Professor of Medicine, University of Kentucky; Director, Sleep Disorders Center, Samaritan Hospital, Lexington, KY. Dr. Phillips is a consultant to Cephalon and Ventus and serves on the speakers bureaus of Cephalon and Boehringer Ingelheim.
Synopsis:About a third of patients with sleep apnea have chronic cough. Such patients are more likely to be women and to have heartburn and rhinitis.
Source: Chan KK, et al. Chronic cough in patients with sleep-disordered breathing. Eur Respir J 2010;35:368-372.
These authors set out to learn about the factors associated with chronic cough in patients with sleep-disordered breathing (SDB). To do this, they recruited a convenience sample of patients who had overnight sleep studies because of suspected sleep apnea. Patients who agreed to participate completed a questionnaire about demographics, cough symptoms and severity, and conditions commonly associated with cough. Patients were also queried about their general medical history, presence of rhinitis or hay fever, dry mouth, choking, snoring, smoking history, medications, and alcohol consumption. Chronic cough was defined as having had a cough for longer than 2 months. Cough severity was rated on a visual analogue scale. The impact of cough on quality of life was assessed with a standard questionnaire. Sleepiness was assessed with an Epworth Sleepiness Scale.
The investigators considered 108 patients for this study, but excluded nearly half of them because they were smokers, had known respiratory disease, were taking angiotensin converting enzyme (ACE) inhibitors, had a recent upper respiratory tract infection, or had sleep studies that did not show sleep apnea. Thus, the study population consisted of 55 patients. One-third of these patients had chronic cough. Patients with sleep apnea and chronic cough had impaired quality of life in all health domains. There was no relationship between the severity of the sleep apnea and prevalence or severity of cough. Five (9%) of these patients were taking proton pump inhibitors, H2 antagonist medication, or both.
Compared to those who only had sleep apnea, patients who had both sleep apnea and chronic cough were more likely to be women and to report symptoms of nocturnal heartburn (28% vs 5%; P = 0.02), rhinitis (44% vs 14%; P = 0.01), dysphagia (33% vs 11%; P = 0.04), and chest pain (44% vs 19%; P = 0.05). Of the patients with chronic cough and sleep apnea, only 22% did not report symptoms of gastroesophageal reflux or rhinitis. There was a trend for increased thyroid disease in patients with cough compared to those without. There were no significant differences in symptoms of shortness of breath, wheeze, sputum production, snoring, dry mouth, or choking between the patients with chronic cough compared to those without. There were no significant differences in sleepiness, snoring symptoms, or severity of sleep apnea between the two groups. In addition, the prevalence of CVD did not differ significantly between groups with chronic cough and those without.
Chronic cough is a vexing and common problem in primary care. In non-smokers, the commonest causes of chronic cough are asthma, gastroesophageal reflux, and rhinitis.1 Despite comprehensive work-ups, a cause of cough is not found in up to 20% of patients who present with chronic cough.2 Although chronic cough is already known to be commonly associated with sleep apnea and daytime sleepiness,3,4 this is the first study to investigate the prevalence and severity of chronic cough in sleep apnea patients. The primary finding is that about a third of patients with sleep apnea have chronic cough. The possible mechanisms of the relationship between cough and SDB include gastroesophageal reflux, rhinitis, and upper airway inflammation.3
Since the cause of cough is never determined in many patients who report this problem, it is possible that evaluation for sleep apnea might help determine a possible cause and treatment. Although this study did not investigate whether cough would improve in patients with sleep apnea who are treated with CPAP, the authors speculate that it might. When all else fails, consider a sleep study.
1. Irwin RS, et al. Diagnosis and management of cough executive summary: ACCP evidence-based clinical practice guidelines. Chest 2006;129(1 Suppl):1S-23S.
2. Birring SS, et al. Idiopathic chronic cough: Association with organ specific autoimmune disease and broncho-alveolar lymphocytosis. Thorax 2003;58:1066-1070.
3. Birring SS, et al. Obstructive sleep apnoea: A cause of chronic cough. Cough 2007;3:7.
4. Klink ME, et al. The relation of sleep complaints to respiratory symptoms in a general population. Chest 1994; 105:151-154.