Background: The Lung Health Study (LHS), a 5-year, randomized, prospective clinical trial, studied the effects of smoking intervention and therapy with inhaled anticholinergic bronchodilators on FEV(1) in participants who were 35 to 60 years of age and had mild COPD. Participants were randomized into the following three groups: usual care; smoking cessation plus inhaled ipratropium bromide; and smoking cessation plus placebo inhaler. This report evaluates the effects of these interventions, demographic characteristics, smoking status, and FEV(1) changes on airway responsiveness (AR).
Methods and results: Of 5,887 participants, 4,201 underwent methacholine challenge testing both at study entry and study completion. All groups increased AR during the 5-year period. The increase in AR was greatest in continuing smokers and was associated with a greater FEV(1) decline. An intent-to-treat analysis indicated no significant differences in AR changes among the three groups.
Conclusions: Changes in AR over a 5-year period in the LHS were primarily related to changes in the FEV(1). The greater the decline in FEV(1), the greater the increase in AR. Smoking cessation had a small additional benefit in AR beyond its favorable effects on FEV(1) changes.