A two-part Series in this week's Lancet explores the extremely common chronic cough. Both papers are authored by Professor Kian Fan Chung, Airway Disease Section, National Heart and Lung Institute, Imperial College London, UK, and Professor Ian Pavord, Institute for Lung Health, Glenfield Hospital, University Hospitals of Leicester NHS Trust, UK. This week's issue is being sent to next month's American Thoracic Society meeting in Toronto, from May 16-21.
The first paper examines the prevalence, pathogenesis, and causes of chronic cough. Chronic cough is defined as cough lasting longer than eight weeks, and the condition occurs in 9-33% of the population in many communities in Europe and the USA. It is often associated with cigarette smoking -- with chronic smokers having a prevalence of chronic cough some three times higher than those who have never smoked, or ex-smokers. Cough is one of the most frequent reasons for consultation with a family doctor, and patients with chronic cough probably account for 10-38% of respiratory outpatient practice in the USA.
Other causes of chronic cough include acute infections, chronic infections, airway diseases, tumours, foreign bodies, cardiovascular diseases, and drugs such as angiotensin-converting enzyme inhibitors. The authors say: "Doctors should always work towards a clear diagnosis, considering common and rare illnesses. In some patients, no cause is identified, leading to the diagnosis of idiopathic cough." As well as the many differing causes of cough, the authors discuss how these causes, plus the cough reflex itself, could actually remodel tissue. Inflammation or remodelling might well cause an enhanced cough reflex, which could in turn maintain cough, via a positive feedback process. They conclude: "Effective control of cough requires not only controlling the disease causing the cough but also desensitisation of cough pathways."
The second paper looks at management of chronic cough, saying that much of the evidence to date suggests that isolated chronic cough is usually due to asthma, gastro-oesophegal reflux disease, or upper airway conditions, and that it can be cured in most people by treatment of these conditions. But the authors say: "There is increasing recognition that satisfactory control of chronic cough is not achieved in a substantial number of patients seen in secondary care. Moreover, there is a concern that perpetuation of the belief that chronic cough is solely due to the effects of comorbid conditions is inhibiting research into the pathophysiology of an abnormally heightened cough reflex, and jeopardising development of improved treatments."
They conclude: "Large-scale recognition is needed of the substantial numbers of patients whose chronic cough cannot be diagnosed or controlled with present investigation and treatment protocols. Hence, we need more research and better treatments. Recognition of this large unmet need and the development of a number of well validated techniques to measure chronic cough can only help in this effort."
Professor Kian Fan Chung, Airway Disease Section, National Heart and Lung Institute, Imperial College London, UK T) +44 (0) 207 351 8995 +44 (0)207 3497736 / +44 (0) 776 218 3223 E) f.chung@imperial.ac.uk
Professor Ian Pavord, Institute for Lung Health, Glenfield Hospital, University Hospitals of Leicester NHS Trust, UK. T) +44 (0) 116 2502388 / +44 (0) 7762 600248 E) ian.pavord@uhl-tr.nhs.uk
PDF OF ARTICLE: http://multimedia.thelancet.com/pdf/press/chroniccough.pdf
Journal
The Lancet