Incidence of chronic obstructive pulmonary disease according to the history of chronic cough/phlegm. Incidence of chronic obstructive pulmonary disease according to the history of chronic cough/phlegm. The statistically significant incidence rate ratio (persistence versus absence) was 4.04 (95% CI 2.29–7.11). ECRHS: European Community Respiratory Health Survey. Reproduced from [23] with permission from the publisher. I. Cerveri, and V. Brusasco Eur Respir Rev 2010;19:109-112 ©2010 by European Respiratory Society