Chronic cough

In clinical guidelines chronic cough is defined as a cough lasting more than 8 weeks in adults ^{[1][2][3][4][5][6]} and more than 4 weeks in children^[2] (some studies suggest that a chronic cough must persist upwards of three months).^[7] The prevalence of chronic cough is about 10% although the prevalence may differ depending on definition and geographic area.^[1][8] Chronic cough is a common symptom in several different respiratory diseases like COPD or pulmonary fibrosis^[9] but in non-smokers with a normal chest x-ray chronic cough are often associated with asthma, rhinosinusitis, and gastroesophageal reflux disease or could be idiopathic^[1][10] Generally, a cough, for example after an upper respiratory tract infection, lasts around one to two weeks; however, chronic cough can persist for an extended period of time, often several years.^[2] People with chronic cough often experience more than one cause present. The current theory about the cause of chronic cough, independent of associated condition, is that it is caused by a hypersensitivity in the cough sensory nerves, called cough hypersensitivity syndrome.^[10] There are a number of treatments available, depending on the associated disease but the clinical management of the patients remains a challenge.^[11] Risk factors include exposure to cigarette smoke, and exposure to pollution, especially particulates.