Clinical characteristics of the early responders in the treatment of chronic cough

Background: Chronic cough (CC) is defined by cough more than 8 weeks. Common causes of CC are upper airway cough syndrome (UACS), asthma, eosinophilic bronchitis (EB), and gastroesophageal reflux diseases (GERD). However, we do not know the characteristics of responding to treatment early. We conducted this study to evaluate the characteristics of the early responder group of CC. Methods: This study was conducted as multi-center, retrospective observational study. Patients were collected in 15 university hospitals. The severity and quality of life (QOL) of CC were measured by cough numeric rating scale (NRS) and Cough Assessment Test (COAT) scores three times (baseline, 2 weeks, and 4 weeks after treatment). The early responder group was defined by improvement of minimal important difference in both cough NRS and COAT. Results: Early responder group was more diagnosed as UACS compared to non-early responder group (65.7% vs. 49.2%, P=0.006). They also had higher baseline cough NRS (5.5±1.2 vs. 4.9±1.3, P<0.001). After adjusting confounding factors such as sex, age, cough duration, baseline cough severity and QOL, and diagnoses of UACS, asthma/EB, or GERD, higher cough NRS [odds ratio (OR) 1.44; 95% confidence interval (CI): 1.06–1.97; P=0.02] and diagnosis of UACS (OR 1.76; 95% CI: 1.02–3.02; P=0.04) were associated with being early responder group in the multivariate logistic regression analyses. Conclusions: We demonstrated the characteristics of early responders of CC treatment. UACS group and higher baseline cough severity group showed earlier response to treatment than other groups.