EFFECT OF WEIGHT-GAIN ON PULMONARY-FUNCTION AFTER SMOKING CESSATION IN THE LUNG HEALTH STUDY

The objective of this study was to determine if the weight gain that a ccompanies smoking cessation is independently associated with reductio ns in FEV1 and NC, using a multicenter randomized intervention trial o f smoking cessation in 10 communities in the United States and Canada. Enrollees were currently smoking women and men 35 to 60 yr of age wit h mild-to-moderate airway obstruction. Participants were randomized to one of three study groups: an intensive smoking cessation program wit h an inhaled bronchodilator (or a placebo), and usual care. Changes in absolute and percent predicted FEV1 and FVC between baseline and fift h annual fellow-up visit were monitored in relation to changes in body weight during the interval. At the baseline examination, percent pred icted FEV1 was maximal at 90 to 100% ideal body weight (IBW) and was l ower as body weight deviated from this range. The FVC decreased linear ly when IBW exceeded 100%. Weight gain was greatest during the first 1 2 mo after smoking cessation. Weight gain was associated with lower fi fth-year FEV1 and FVC in all smoking categories: continuous smokers, i ntermittent smokers, and sustained quitters. The FVC was affected by w eight gain more than was the FEV1, and the FEV1 was affected by smokin g cessation more than FVC. Men showed more impairment of FVC with weig ht gain than did women, possibly because of differential patterns of f at deposition. In sustained quitters, after adjustment for baseline fa ctors, the estimated reduction of FVC was 17.4 ml/kg weight gain for m en and 10.6 ml/kg for women. The estimated loss of FEV1 was 11.1 ml/kg weight gain for men and 5.6 ml/kg for women. Lung function after smok ing cessation is significantly influenced by weight gain and affects m en more than women. The deleterious effects of weight gain are small, however, in comparison with the beneficial effects of smoking cessatio n.