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

The aim of our study was to examine pulmonary functions of patients from all stages of chronic obstructive pulmonary disease (COPD) according to their smoking status.

A retrospective case-control study was carried out. Total of 148 patients were enrolled and divided into two groups in regards to their smoking status (quitters, n=68; non-quitters, n=80). Pulmonary function parameters, COPD assessment test score, Fagerström Nicotine Addiction Questionnaire score, smoking history and status were obtained from the electronic hospital data system. Patients' admission and 12-month data were recorded.

In non-quitters, the mean FEV₁ values decreased from 2.32±1.14 to 2.24±1.12 (p<0.001). Particularly, in Stage-0, in the early high-risk group of COPD, the reduction in FEV₁ was 90 mL, while the reduction was 70, 60, 40, and 40 mL in Stage-I, -II, -III, and -IV, respectively. In quitters, the mean FEV₁ levels increased from 2.10±1.19 to 2.19±1.20 (p<0.001). For COPD patients overall, an average increase in FEV₁ of 80-110 mL was observed. At the end of the 12 months follow-up, 17 (27.5%) of the non-quitters showed deterioration, and five (7.3%) of the quitters showed improvement in COPD stage.

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.