Background: Spirometry is not routinely performed in smoking cessation trials. Smokers with airflow obstruction who are unavailable for follow-up incur the risk of accelerated loss in lung function. We evaluated the prevalence of airflow obstruction among smokers enrolled in smoking cessation trials and the proportion of subjects with obstruction unavailable for follow-up.
Design, setting, and participants: The study was performed in a university research laboratory; 598 smokers participating in two smoking cessation trials were included. All subjects underwent spirometry at entry and after 1 year of follow-up. All received nicotine replacement therapy. At completion, they were classified into quitters, reducers, or continuing smokers.
Measurements and results: At enrollment, spirometry findings were normal in 493 subjects (82.4%). Airway obstruction (FEV1 < 80% predicted) was found in 105 subjects (17.6%): mild obstruction (FEV1 70 to 80% predicted) in 75 subjects, moderate obstruction (FEV1 50 to 69% predicted) in 22 subjects, and severe obstruction (FEV1 < 50% predicted) in 8 subjects. From these subjects, 75 were unavailable for follow-up: airflow obstruction was mild in 52 subjects (69.3%), moderate in 17 subjects (22.7%), and severe in 6 subjects (8%).
Conclusions: Spirometry detected a high prevalence yield of airflow obstruction in participants in smoking cessation trials. Most subjects with airflow obstruction were unavailable for follow-up; they would have remained unaware of their condition if not for spirometry. Smokers with airflow obstruction should be identified and advised to seek further care.