Effects of randomized assignment to a smoking cessation intervention and changes in smoking habits on respiratory symptoms in smokers with early chronic obstructive pulmonary disease: the Lung Health Study

Abstract

Purpose: To evaluate the effects of randomly assigning smokers who have early chronic obstructive pulmonary disease (COPD) to a smoking-cessation intervention on the symptoms of chronic cough, chronic phlegm production, wheezing and shortness of breath, and to determine the effects of quitting smoking on these symptoms.

Subjects and methods: A total of 5,887 male and female smokers 35 to 60 years of age with early COPD [defined as a forced expiratory volume in the first second (FEV1) of 55% to 90% of predicted and FEV1/forced vital capacity (FVC) <0.70] were enrolled in a 5-year clinical trial. Two-thirds of participants were randomly assigned to smoking-intervention groups and one-third to a usual-care group. The intervention groups attended 12 intensive smoking-cessation sessions that included behavior modification techniques and the use of nicotine chewing gum. One intervention group was treated with ipratropium bromide by inhaler; the other intervention group received placebo inhalers. The usual-care group was advised to stop smoking. All participants were followed annually. Smoking status was biochemically validated by salivary cotinine measurements or exhaled carbon monoxide values.

Results: Validated 5-year sustained smoking cessation occurred in 22% of participants in the intervention compared with only 5% of participants in the usual-care group. At the end of the study, the prevalence of each of the four symptoms in the two intervention groups was significantly less than in the usual-care group (P <0.0001). For example, among participants who did not report cough at baseline, 15% of those in the intervention groups had cough at least 3 months during the year, compared with 23% of those in usual care. Sustained quitters had the lowest prevalence of all four symptoms, whereas continuous smokers had the greatest prevalence of these symptoms. Changes in symptoms occurred primarily in the first year after smoking cessation. Respiratory symptoms were associated with greater declines in FEV1 during the study (P <0.001). Ipratropium bromide had no long-term effects on respiratory symptoms.

Conclusions: In this prospective randomized trial using an intention-to-treat analysis, smokers with early COPD who were assigned to a smoking-cessation intervention had fewer respiratory symptoms after 5 years of follow-up.