The present meta-analyses indicated the diagnostic potential of Feno measurement as a rule-in test for detecting CVA in adult patients with chronic cough. However, Feno measurement may not be useful to predict EB in nonasthmatic subjects with chronic cough. These findings warrant further studies to validate the roles of Feno measurement in clinical practice of patients with chronic cough.

Cough is frequently self-limiting, but may persist longer in certain individuals. Most of previous studies on the epidemiology of chronic cough have only measured period prevalence, and thus have afforded limited information on the burden and natural course. We aimed to investigate the epidemiology of chronic cough by using a point prevalence measure in a large-scale general population.We analyzed cross-sectional data collected from 18,071 adults who participated in the Korean National Health and Nutrition Examination Survey 2010–2012. Presence and duration of current cough was ascertained by structured questionnaires, and cough was classified into acute (<3 weeks), subacute (3–8 weeks), or chronic cough (≥8 weeks). Demographic and clinical parameters were examined in relation to chronic cough.The point prevalences of acute, subacute, and chronic cough were 2.5 ± 0.2%, 0.8 ± 0.1% and 2.6 ± 0.2%, respectively. The proportion of current cough showed a steep decrease after 1 week of duration. However, 2 peaks in the prevalence of current cough were revealed; cough durations of less than 1 week and longer than 1 year were most common (31.1% and 27.7% of current cough, respectively). Subacute and chronic cough were more prevalent in the elderly (≥65 years); the positive associations with older age were independent of other confounders, including current smoking and comorbidities.This is the first report on the epidemiology of cough using a point prevalence measure in a nationally representative population sample. Our findings indicate a high burden of chronic cough among adults with current cough in the community. The dual-peak of cough duration suggested that the pathophysiology of acute and chronic cough may differ. The preponderance of elderly people in the prevalence of chronic cough warrants further investigation. In addition, more sophistication and validation of tools to define chronic cough will help our understanding of the epidemiology.

Purpose Recent evidence suggests that cough hypersensitivity may be a common feature of chronic cough in adults. However, the clinical relevance remains unclear. This study evaluated the cough-related symptom profile and the clinical relevance and impact of cough hypersensitivity in adults with chronic cough. Methods This cross-sectional multi-center study compared cough-related laryngeal sensations and cough triggers in patients with unexplained chronic cough following investigations and in unselected patients newly referred for chronic cough. A structured questionnaire was used to assess abnormal laryngeal sensations and cough triggers. Patients with unexplained cough were also evaluated using the Leicester Cough Questionnaire (LCQ) and a cough visual analogue scale (VAS), and these scores were assessed for correlations with the number of triggers and laryngeal sensations. Results This study recruited 478 patients, including 62 with unexplained chronic cough and 416 with chronic cough. Most participants reported abnormal laryngeal sensations and cough triggers. Laryngeal sensations (4.4 ± 1.5 vs. 3.9 ± 1.9; P = 0.049) and cough triggers (6.9 ± 2.6 vs. 5.0 ± 2.8; P < 0.001) were more frequent in patients with unexplained chronic cough than in those with chronic cough. The number of triggers and laryngeal sensations score significantly correlated with LCQ ( r = −0.51, P < 0.001) and cough VAS score ( r = 0.53, P < 0.001) in patients with unexplained chronic cough. Conclusions Cough hypersensitivity may be a common feature in adult patients with chronic cough, especially those with unexplained chronic cough. Cough-related health status and cough severity were inversely associated with the number of triggers and laryngeal sensations, suggesting potential relevance of assessing cough hypersensitivity in chronic cough patients.

Purpose Chronic cough is a prevalent condition in the community and may pose considerable impairment to quality of life (QoL). However, its disease burden remains largely undefined in the general population. The present study investigated the relationship between chronic cough and health-related QoL in a Korean nationwide population database, with an emphasis on clinical conditions which may confound the impact of cough. Methods This study analyzed cross-sectional datasets of adults (aged ≥ 40 years) in the Korean National Health and Nutrition Examination Survey 2010–2016. Health-related QoL was assessed using the 3-level EuroQoL 5-dimension component (EQ-5D-3L) index score. The presence of chronic cough and other conditions were defined using structured questionnaires. Results The prevalence of chronic cough was 3.48% ± 0.17% among adults aged ≥ 40 years. The overall EQ-5D-3L index score was significantly lower in subjects with than without chronic cough (0.79 ± 0.01 vs. 0.86 ± 0.00, P < 0.001). In subgroup analyses by age and sex, chronic cough had a notably large impact on QoL in women aged ≥ 65 years (vs. those without chronic cough: 0.55 ± 0.04 vs. 0.70 ± 0.01, P < 0.001), although the mean difference in the scores exceeded the minimally important difference score of 0.05 in all subgroups. In multivariate analyses, chronic cough was significantly associated with QoL, independent of confounders including depression, arthritis, asthma, and chronic obstructive pulmonary disease. In dimension analyses, chronic cough was more associated with anxiety/depression, pain/discomfort, and usual activities than with self-care or mobility in the EQ-5D. Conclusions The present study demonstrated significant associations between chronic cough and health-related QoL in a nationwide large general adult population aged ≥ 40 years, which were independent of clinical confounders. The impact of chronic cough was greater in women aged ≥ 65 years. These findings indicate a considerable burden of chronic cough in the general population and warrant further investigations to assess the disease burden of chronic cough in a global scale.