Int J Clin Exp Med 2017;10(8):12733-12741 www.ijcem.com /ISSN:1940-5901/IJCEM0021730 Case Report Obstructive sleep apnea-induced chronic cough: three case reports and a review of the literature Jiaxing Xie, Xu Shi, Qingling Zhang, Kefang Lai, Jing Li Guangzhou Institute of Respiratory Disease, The First Affliated Hospital of Guangzhou Medical University, State Key Laboratory of Respiratory Diseases (Guangzhou Medical University), Guangzhou 510120, Guangdong, China Received December 12, 2015; Accepted February 15, 2016; Epub August 15, 2017; Published August 30, 2017 Abstract: Objective: The aim of this study was to analyze the clinical features of obstructive sleep apnea (OSA)- induced chronic cough and improve the current understanding of the association between chronic cough and OSA. Methods: We used chronic cough and obstructive sleep apnea as the key words with which to retrieve relevant lit- erature from the PubMed database from January 2002 through November 2014. Eight articles were included: four were case reports of nine patients (three male and six female patients aged 46-73 years); the other four articles were epidemiological studies of patients with concurrent OSA and chronic cough. A literature review was performed by combining the characteristics of the cases reported in the literature and the three cases in the present report. Results: Case 1 involved a 60-year-old woman with a 3-month history of cough. Case 2 involved a 52-year-old man with a 3-year history of cough. Case 3 involved a 63-year-old man with a 5-year history of cough and chest tight- ness. Common causes of chronic cough were excluded in these three cases. Polysomnography indicated a diag- nosis of severe OSA, and the patients’ symptoms were resolved after continuous positive airway pressure therapy. Conclusions: OSA is a possible etiology of chronic cough. Chronic cough can be the sole presenting symptom in patients with OSA. The incidence of chronic cough is signifcantly high in patients with OSA. Continuous positive airway pressure treatment can signifcantly improve chronic cough. Keywords: Chronic cough, obstructive sleep apnea, continuous positive airway pressure Introduction Chronic cough is defned as a cough that lasts for ≥8 weeks in patients with no obvious anom- alies on chest X-ray and who present with cough as the main or sole symptom; it is the most common symptom in medical patients [1]. Epidemiological studies have shown that the main causes of chronic cough include cough variant asthma (CVA), upper airway cough syn- drome (UACS), eosinophilic bronchitis, gastro- esophageal refux cough (GERC), and allergic cough, all of which account for 70% to 95% of the etiologies of chronic cough. Other causes account for a small proportion of the etiologies and vary widely [2, 3]. Obstructive sleep apnea (OSA) is a sleep disor- der with frequent apnea as the prominent man- ifestation. OSA is caused by complete or partial repetitive obstruction of the upper airway dur- ing sleep. Its prevalence is approximately 4% in adults and can reach 20% to 40% in the older population aged >60 years [4]. Recent studies have found that patients with OSA also fre- quently have chronic cough in addition to other symptoms such as snoring, nighttime awaken- ings, and daytime sleepiness; a few case reports on OSA-induced chronic cough have been published [6-8]. We recently treated three patients with OSA with chronic cough as the main etiological factor. We herein report the diagnosis and treatment of these three patients and present a review of the relevant literature. Clinical data The clinical data were summarized in Table 1. Case 1 A 60-year-old woman was admitted to our hos- pital because of a >3-month history of recur- rent cough. The patient reported that the cough