Effect of Roflumilast on Exacerbation Rate in Patients With Chronic Obstructive Pulmonary Disease. Ratio-Study. (BY217/M2-112)

Main Inclusion Criteria: * FEV1/FVC ratio (post-bronchodilator) ≤70% * FEV1 (post-bronchodilator) ≤50% of predicted * Current smoker or ex-smoker * Clinically stable COPD indicated by no exacerbation and no change in COPD treatment of within 4 weeks prior to baseline * Availability of a chest x-ray dated a maximum of 6 months prior to study baseline visit B0 or a willingness to have a chest x-ray performed before baseline Main Exclusion Criteria: * COPD exacerbation indicated by a treatment with systemic glucocorticoids not stopped 4 weeks prior to baseline * Lower respiratory tract infection not resolved 4 weeks prior to baseline * Diagnosis of asthma and/or other relevant lung disease * Known alpha-1-antitrypsin deficiency * Need for long-term oxygen therapy defined as ≥16 hours/day