Individual causes of chronic cough may overlap. In this analysis, UACS frequently accompanied asthma, and chest radiographic abnormalities were frequently observed in subjects with both COPD and asthma. In multivariable analysis, the conditions that cause chronic cough were asthma, current smoking, chest radiographic abnormality, UACS, and COPD, in descending order. More frequently associated symptoms were chronic phlegm for current smokers, dyspnea and night sweats for those with UACS, and blood-tinged sputum for those with COPD.