4.1. The etiology of chronic cough
In 2006, the top 3 causes of chronic cough were asthma, asthma-like diseases, UACS and GERC in children of the United States [1]. In 2012, the “Prospective multicenter clinical study on the etiology component ratio of chronic cough in Chinese children” revealed that [6] the sequence of top 3 causes of chronic cough were CVA, UACS and PIC in Chinese children. What’s more, PIC was the most common cause in children under 6 years old. Kantar Ahmad [7] et al suggested chronic cough in preschool children is caused by protracted bacterial bronchitis (PBB), tracheobronchomalacia, foreign body aspiration, PIC or some combination of the above in most cases in Europe. They and ACCP [8] recommend that when evaluating and managing children’s chronic cough, their age and the clinical settings should be taken into consideration. The present study found that PIC (34.8%) was the most common cause of chronic cough in children in Shanghai, and UACS (22.9%) and CVA (21.4%) ranked second and third in the composition ratio of etiology, respectively. In this study average age of children was 5.67±2.59 years (under 6 years old), which matched the result of the research in China in 2012. In analysis of the causes, the differences in the proportion of causes of disease may be related to the ethnic group, society environment, living habits and age structure.