The Effect of Pulmonary Function Testing on the Success of Smoking Cessation

In several studies, low spirometric levels have been shown to increase the success rates of smoking cessation, whereas other studies have indicated that pulmonary function has no effects on quitting smoking. Given the fact that there are contradictory results on this subject, we aimed to investigate the effect of identifying airway obstruction via spirometry and its explanation to subjects on the success rate of smoking cessation in the short term.

Subjects who were admitted to the smoking cessation out-patient clinic, underwent pulmonary function tests (PFTs) and completed at least 3 months of the cessation program following their admittance were included in the study. At the first interview, all subjects were asked about their comorbid diseases and smoking habits. PFTs were performed. Subjects who had an obstruction on PFT were informed that their condition was smoking-related, and that further deterioration could be prevented following smoking cessation. Then the smoking cessation date was determined together with the subject, and one of the smoking cessation medicines was prescribed. All subjects were given control appointments twice for the first month and once per month for the following 2-month follow-up period. Subjects who had CO levels between 0 and 5 parts per million were considered as non-smokers.

The mean age of the 563 subjects was 41.9 ± 12.1 y 340 subjects (60.4%) were male. A total of 162 subjects (28.8%) came to the follow-up visits following the first interview. The success of smoking cessation for 3 months was 11.3% for all subjects and 39.5% for subjects who came to follow-up visits. Of the subjects with obstruction on PFT; 22.8% stopped smoking, whereas 8.4% of the subjects without obstruction did so (P < .001). The percentage of subjects with obstruction on PFT was significantly higher (P < .001) and the FEV1 % (P = .005), FEV1/FVC (P < .001), and forced expiratory flow 25-75% (P = .008) levels were significantly lower in the quitters compared with the non-quitters. Logistic regression analysis showed that age (P = .001) and the presence of obstruction on PFT (P = .029) were independent variables.

Advanced age and the presence of obstruction on PFT increase the success of smoking cessation. Pulmonary function tests should be performed on all patients who apply to smoking cessation out-patient clinics, and patients should be informed about their condition.