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

PURPOSE: To evaluate the effects of randomly assigning smokers who have ear ly chronic obstructive pulmonary disease (COPD) to a smoking-cessation inte rvention on the symptoms of chronic cough, chronic phlegm production, wheez ing and shortness of breath, and to determine the effects of quitting smoki ng on these symptoms. SUBJECTS AND METHODS: A total of 5,887 male and female smokers 35 to 60 yea rs of age with early COPD [defined as a forced expiratory volume in the fir st second (FEV1 of 55% to 90% of predicted and FEV1-forced vital capacity(F VC) <0.70] were enrolled in a 5-year clinical trial. Two-thirds of particip ants 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 u se of nicotine chewing gum. One intervention group was treated with ipratro pium bromide by inhaler; the other intervention group received placebo inha lers. The usual-care group was advised to stop smoking. All participants we re followed annually. Smoking status was biochemically validated by salivar y cotinine measurements or exhaled carbon monoxide values. RESULTS: Validated 5-year sustained smoking cessation occurred in 22% of pa rticipants 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 f our symptoms in the two intervention groups was significantly less than in the usual-care group (P <0.00011. For example, among participants who did n ot report cough at baseline, 15% of those in the intervention groups had co ugh 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, wh ereas continuous smokers had the greatest prevalence of these symptoms. Cha nges in symptoms occurred primarily in the first year after smoking cessati on. Respiratory symptoms were associated with greater declines in FEV, duri ng the study (P <0.001). Ipratropium bromide had no long-term effects on re spiratory symptoms. CONCLUSIONS: In this prospective randomized trial using an intention-to-tre at analysis, smokers with early COPD who were assigned to a smoking-cessati on intervention had fewer respiratory symptoms after 5 years of follow-up. (C) 1999 by Excerpta Medica, Inc.