Prevalence and incidence of COPD in smokers and non-smokers: the Rotterdam Study

COPD is the third leading cause of death in the world and its global burden is predicted to increase further. Even though the prevalence of COPD is well studied, only few studies examined the incidence of COPD in a prospective and standardized manner. In a prospective population-based cohort study (Rotterdam Study) enrolling subjects aged ≥45, COPD was diagnosed based on a pre-bronchodilator obstructive spirometry (FEV1/FVC < 0.70). In absence of an interpretable spirometry within the Rotterdam Study, cases were defined as having COPD diagnosed by a physician on the basis of clinical presentation and obstructive lung function measured by the general practitioner or respiratory physician. Incidence rates were calculated by dividing the number of incident cases by the total number of person years of subjects at risk. In this cohort of 14,619 participants, 1993 subjects with COPD were identified of whom 689 as prevalent ones and 1304 cases as incident ones. The overall incidence rate (IR) of COPD was 8.9/1000 person-years (PY); 95 % Confidence Interval (CI) 8.4-9.4. The IR was higher in males and in smokers. The proportion of female COPD participants without a history of smoking was 27.2 %, while this proportion was 7.3 % in males. The prevalence of COPD in the Rotterdam Study is 4.7 % and the overall incidence is approximately 9/1000 PY, with a higher incidence in males and in smokers. The proportion of never-smokers among female COPD cases is substantial.