Pulmonary Function Changes in Chronic Obstructive Pulmonary Disease Patients According to Smoking Status.

FEV1 decline was accelerated in COPD patients who continued to smoke, whereas this decline was not prevented by inhaler treatments. The Global Initiative for Chronic Obstructive Lung Disease Stage-0 group, which is not included in the current guidelines, needs to be redefined. This group appears to be the most important group for implementing the smoking cessation and prevention strategy.