Objectives: To assess how the diagnosis of airflow limitation (AL) combined with advice to stop smoking in middle-aged smokers influence the smoking cessation rate and to identify predictors of successful outcome.
Design: Prospective, single-center, comparative study of the effects of smoking intervention in smokers with diagnosed AL and in smokers with normal lung function (NLF).
Setting: University hospital, out-patient clinic.
Participants: Of 659 smokers participating in a population spirometric screening for COPD combined with smoking cessation advice, 558 (AL, 297 smokers; NLF, 261 smokers) were invited for a follow-up after 1 year.
Intervention: At follow-up, spirometry was repeated and smoking status was assessed. Nonsmoking status was validated with carbon monoxide measurements in exhaled air. Patients who did not come for the follow-up visit were considered to be smokers.
Results: Of 558 smokers invited, 368 (66%) presented for the follow-up visit. All had tried to reduce their smoking habit. The number of cigarettes smoked per day (cpd) at 1 year was - 5.2 (p < 0.01) in patients with AL and - 2.7 (not significant [NS]) in those with NLF. The 1-year cessation rate in smokers with AL was 10.1% vs 8.4% in smokers with NLF (NS). After stratifying the patients according to AL severity, the highest cessation rate was observed in smokers with moderate and severe AL (16.5%) compared to smokers with mild AL (6.4%; p < 0.001) and smokers with NLF (8.4%; p < 0.05). In a univariate analysis, the cessation of smoking was correlated with older age (p < 0.001), later age when starting smoking (p < 0.005), lower tobacco exposure (in pack-years; p < 0.01), fewer cpd (p < 0.001), and lower lung function (p < 0.05). No interaction effect was observed for any of the studied variables using two-way analysis of variance. In a stepwise logistic regression analysis, age (p < 0.001), tobacco exposure (in pack-years; p < 0.001), and FEV(1) percent predicted (p < 0.01) proved to be significant predictors of success in stopping smoking.
Conclusion: All smokers, irrespective of their lung function, tried to modify their habit as the result of screening for COPD combined with smoking cessation advice. The diagnosis of AL motivated smokers to attempt to quit smoking. Older age, lower tobacco exposure, and lower lung function were the predictors of success in quitting smoking.