Impact of Smoking Cessation Therapy on Pulmonary Function: Identification of Factors Predicting Improvement of Forced Expiratory Volume in 1s - Abstract
Background: Stopping smoking has beneficial effects on pulmonary function, but few studies have investigated which factors predict a favorable outcome. Methods: We analyzed the results of a prospective 3-month smoking cessation program. Smokers who had quit were defined as those abstaining from smoking between visits at 8 and 12 weeks (verified by exhaled carbon monoxide ?10 ppm). Baseline pulmonary function was compared with that at the end of the program.Results: From August 2007 to December 2020, 952 smokers participated in the program, of whom 509 completed it and had pulmonary function tests available before and after the program. We recorded the following differences in pulmonary function: ?forced vital capacity (FVC) = 0.054±0.364 L (p=0.0008), ?forced expiratory volume in 1s (FEV1)= 0.055±0.273 L (p<0.0001). An increase of FEV1 >100 mL was observed in 182 (35.8%) of the participants. We then compared these 182 with participants having no increase of FEV1 (n=327), finding significant differences between them in the presence of underlying conditions like COPD (31.3-vs-21.4%, P=0.014), bronchial asthma (20.9 -vs-11.6%, P=0.006) and baseline FEV1 (1.84±0.77 L-vs-2.20±0.74 L, <0.0001). Bronchial asthma (odds ratio [OR] 1.761, 95% confidence interval [CI]: 1.059, 2.926) and baseline FEV1 (OR 0.566, 95% CI: 0.431, 0.743) were independently significantly associated with an increase of FEV1 >100 mL by multivariate analysis. Conclusions: Participation in our smoking cessation program resulted in significantly increased FVC and FEV1 overall, regardless of the actual success or failure of quitting smoking. Factors predicting FEV1 improvement were identified as bronchial asthma and baseline FEV1.