Rationale: The few prospective studies aimed at assessing the incidence of chronic obstructive pulmonary disease (COPD) in relation to the presence of chronic cough/phlegm have produced contrasting results.
Objectives: To assess the incidence of COPD in a cohort of young adults and to test whether chronic cough/phlegm and dyspnea are independent predictors of COPD.
Methods: An international cohort of 5,002 subjects without asthma (ages 20-44 yr) with normal lung function (FEV(1)/FVC ratio >/= 70%) from 12 countries was followed from 1991-2002 in the frame of the European Community Respiratory Health Survey II. Incident cases of COPD were those who had an FEV(1)/FVC ratio less than 70% at the end of the follow-up, but did not report having had a doctor diagnose asthma during the follow-up.
Main results: The incidence rate of COPD was 2.8 cases/1,000/yr (95% confidence interval [CI], 2.3-3.3). Chronic cough/phlegm was an independent and statistically significant predictor of COPD (incidence rate ratio [IRR], 1.85; 95% CI, 1.17-2.93) after adjusting for smoking habits and other potential confounders, whereas dyspnea was not associated with the disease (IRR = 0.98; 95% CI, 0.64-1.50). Subjects who reported chronic cough/phlegm both at baseline and at the follow-up had a nearly threefold-increased risk of developing COPD with respect to asymptomatic subjects (IRR = 2.88; 95% CI, 1.44-5.79).
Conclusions: The incidence of COPD is substantial even in young adults. The presence of chronic cough/phlegm identifies a subgroup of subjects with a high risk of developing COPD, independently of smoking habits.