Productive cough is an independent risk factor for the development of COPD in former smokers

Background and objective: It has yet to be determined whether the presence of productive cough is a risk factor for the development of COPD. The aim of the present study was to obtain more information on this potential association in Japanese men. Methods: Seven hundred and eighty-three men with normal spirometry who did not have respiratory disease were recruited. The subjects were divided into three groups: group A, non-smokers; group B, those with a positive smoking history without productive cough; and group C, those with a positive smoking history and productive cough. The incidence rates of COPD were compared among the three groups and the relative risks for the development of COPD were assessed. Results: During the mean follow-up period of 33.6 +/- 20.4 months, 19 (2.4%) subjects developed COPD. The incidence rate of COPD was significantly higher in group C than in group B (10.1 vs 2.2%, P = 0.003). A multivariate analysis of data for all subjects, current smokers and former smokers revealed that productive cough was an independent risk factor for the development of COPD in all subjects and former smokers but not in current smokers. Conclusions: Productive cough was an independent risk factor for the development of COPD in Japanese men. In particular, former smokers who complain of this symptom should be regarded as being at high risk for the development of COPD. The data suggested that stage 0 disease, as defined in the Global Initiative for Chronic Obstructive Lung Disease 2001 guidelines, is relevant for the identification of subjects at risk of developing COPD.