Geography and cough aetiology
Introduction
It has been reported from the Western countries that cough is the most common complaint leading patients to seek medical attention [1], [2]. A multicentre study by general practitioners (GPs) of Japan have also reported that cough was the most frequent reason (11.7% of all) that made patients visit clinics [3]. Such patients are increasing not only in primary care settings but also in respiratory or allergy specialist clinics. These situations have undoubtedly led to recent publications of Cough Guidelines by the American College of Chest Physicians (ACCP) [1], [2], European Respiratory Society [4], the Japanese Respiratory Society [5] and the British Thoracic Society [6]. These guidelines use the common definition of chronic cough, namely cough lasting for 8 weeks or longer, except for the original version of the pioneer guideline published by ACCP in 1998 [1] that used a definition of 3 weeks or longer. When these guidelines and original papers on cough epidemiology are thoroughly reviewed, there are remarkable differences in the aetiology of chronic cough among countries, especially between that of US or UK and that of Japan (Table 1).
In this article, several issues related to chronic cough aetiology will be discussed, including the author's own thoughts derived from his experience in Japan and the UK.
Section snippets
Common causes of chronic cough in the US, UK and Japan
In the US, post-nasal drip syndrome (PNDS), gastro-oesophageal reflux disease (GORD), and cough-variant asthma (CVA) have been the top three causes of chronic persistent cough [7], comprising approximately 90% or more of cases. Especially the prevalence of PNDS has been high (Table 1). Similar aetiology has been reported from the UK, but a diagnosis of rhinitis or rhinosinusitis, instead of PNDS, has often been used [8], [9]. Non-US nations, even those who use English as their native language,
Entities unique to Japan
“Sinobronchial syndrome (SBS)” presenting with productive cough manifests as chronic sinusitis and chronic neutrophilic inflammation of the lower airways such as chronic bronchitis, diffuse bronchiectasis, and diffuse panbronchiolitis (DPB) [5]. DPB is the most severe but most uncommon form of lower airways involvement [19], [20]. It commonly occurs in East Asia, and most reported cases in Western countries are Asian immigrants. Radiologically it presents with diffuse small nodular shadows
Geographic issues that may affect chronic cough aetiology
In addition to the above issues, geographic issues are likely associated with cough aetiology.
Conclusion
There are various issues that likely affect the aetiology of chronic cough, as summarized in Table 3. These issues need to be considered when we compare the aetiologies of chronic cough reported from various countries and institutions.
Acknowledgements
The author would like to thank Professor Kian Fan Chung for his helpful suggestions and support, and Professor Robert Wilson for his useful comments.
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