Smoking reduction and the rate of decline in FEV₁: results from the Lung Health Study

Abstract

Previous findings from the Lung Health Study have shown that smoking cessation and sustained abstinence substantially reduce the rate of decline in forced expiratory volume (FEV1) among smokers with early chronic obstructive pulmonary disease (COPD) when compared with continuing smoking. Intermittent quitters demonstrated rates of FEV1 decline intermediate between those of sustained quitters and continuing smokers.In this study, data from 1,980 participants were analysed from 10 centres of the Lung Health Study in the USA and Canada. All participants were smokers with mild-to-moderate COPD who were unable to quit smoking at any time during the 1st yr of the study.No linear relationship was found between reduction in cigarettes per day and changes in FEV1 during the 1st yr of the study. However, examination of the data revealed that this relationship was nonlinear. Further analysis found that smokers who reduced their cigarettes per day to very low amounts had smaller declines in FEV1 than those who did not. Reduction in cigarettes per day was associated with only minimal changes in the presence of chronic respiratory symptoms.In conclusion, compensatory changes in smoking behaviour may account for the limited and unpredictable impact of smoking reduction on lung function decline and symptom prevalence when compared with smoking cessation.KEYWORDS: Forced expiratory volume in one second, smoking cessation, smoking reduction S ustained smoking cessation substantially reduces the smoking-related accelerated rate of decline in forced expiratory volume in one second (FEV1) and decreases the frequency of chronic respiratory symptoms among smokers with early chronic obstructive pulmonary disease (COPD) when compared with continuing smokers [1][2][3]. Intermittent quitting is associated with rates of FEV1 decline intermediate between those observed in sustained quitters and continuing smokers [4]. Conversely, it is not known whether partial reduction in the number of cigarettes smoked per day among continuing smokers is associated with improvement in the subsequent course of lung function decline when compared with that observed when daily consumption remains unchanged. For smokers with COPD who find it difficult to quit smoking entirely this is an important issue, since they may assume that smoking reduction is an effective alternative strategy for slowing disease progression. In the only previous long-term prospective study of smoking reduction (from o15 to ,15 cigarettes?day -1 ) on the rate of FEV1 decline, smokers ,55 yrs showed a significant reduction in FEV1 decline, although older smokers did not [5]. In that study, only two measurements of lung function were performed at an interval of 5 yrs and details of changes in the smoking rate, including the timing of changes in smoking amount relative to the measurement of lung function, were not reported.The present analysis examines the relationship between smoking reduction and change in FEV1 in a subset of the participants in the Lung Health Study, a large...

Interrelated role of cigarette smoking, oxidative stress, and immune response in COPD and corresponding treatments

“…Additionally, other researchers studied LHS data to examine lung function decline in intermittent smokers and smokers that simply reduced the number of cigarettes smoked per day. The loss of lung function in these two subgroups was noted as similar to that of the continued smokers (56,112). The findings of these studies underscore the importance and benefits of complete and sustained tobacco cessation in reducing COPD morbidity and mortality.…”

A COPD Health Management Program in a Community-Based Primary Care Setting: A Randomized Controlled Trial

“…26,28 It can delay the impairment of pulmonary function and significantly alleviate the symptoms of coughing, excess phlegm, and asthma, thereby improving patient health status. [29][30][31] Long-term smoking cessation has been found to improve the natural course of COPD and to mitigate the deterioration of lung function in patients with COPD. 32 Thus, we included smoking cessation as a key component of our program.…”

COPD disease progression and airway inflammation: uncoupled by smoking cessation

“…The controlled evidence is obtained from prospective studies, such as the Lung Health Study [6], where FEV1 improved in the first year and the subsequent rate of decline was reduced by ,50% in sustained ''quitters''. Intermittent complete abstinence from smoking led to rates of FEV1 decline that were intermediate between sustained quitters and continuing smokers, and only a very substantial reduction in smoking to less than five cigarettes daily was associated with reduced FEV1 decline [7]. In addition, exacerbations appear to be related to decline in FEV1 in smokers, but not in ''quitters'' [8].…”