Smoking cessation and chronic pulmonary disease
Chronic obstructive pulmonary disease (COPD), including chronic bronchitis and emphysema, is the fourth leading cause of death in the United
States (Wise, 1997). More than 25 years ago, the Surgeon General unequivocally stated that the primary risk factor for COPD is cigarette smoking (US Department of Health & Human Services, 1984). Establishing the connection between smoking and COPD, as well as other smoking-related disease, has led to enormous interest in studying the prevention of smoking onset and the cessation of smoking in otherwise healthy smokers. Although the prevalence of smoking among US adults has leveled off at around 25% of the population (Centers for Disease Control, 1999), we have made modest progress in the areas of smoking prevention and smoking cessation. (See Ockene et al.  and Lantz et al. (2000) for reviews of the smoking cessation and prevention literatures, respectively.)
Because of our ability to achieve some level of success at both smoking cessation and prevention, we have been able to quantify the impact of smoking cessation on the onset and progression of respiratory symptoms and lung-function decline. For example, we know that if smokers quit prior to the development of chronic lung disease, their respiratory symptoms and rate of decline in lung function will begin to normalize within 5 years after cessation and, in some cases, will approximate that of someone who has never smoked (e.g., Leeder et al., 1977; Camilli et al., 1987; Brown et al., 1991; Townsend et al., 1991). The landmark Lung Health Study demonstrated a similar effect for individuals with mild-to-moderate COPD (Anthonisen et al., 1994; Kanner et al., 1999; Scanlon et al., 2000), although lost lung function cannot be restored. Speciﬁcally, Scanlon et al., (2000) demonstrated that the lungfunction beneﬁts of cessation were evident in elderly patients with a history of heavy smoking, poor baseline lung function, or hyperresponsive airways. Thus, even those with mild-to-moderate COPD showed clinically and statistically signiﬁcant improvement following smoking cessation.