EFFECTS OF SMOKING AND SMOKING CESSATION ON LONGITUDINAL DECLINE IN PULMONARY-FUNCTION

Effects of cigarette smoking and smoking cessation on rate of FEV(1) d ecline over 6 yr were examined in 4,451 Japanese-American men from the Honolulu Heart Program who were 45 to 68 yr of age at baseline (1965- 1968). Within-person regression was used to calculate annual change in FEV(1). Rates of FEV(1) decline varied strongly with smoking status a nd increased significantly with age. Overall, men who continued to smo ke experienced steeper rates of decline compared with men who never sm oked (-33 ml/yr versus -22 ml/yr, respectively; p = 0.0001). Rates of decline for those who quit smoking during the first 2 yr (-32 ml/yr) w ere nearly the same as those who continued smoking (-34 ml/yr). After quitting, their rates of decline diminished to a level (-19 ml/yr) sim ilar to that of men who had never smoked (-21 ml/yr). FEV(1) decline i n continuing smokers was significantly associated with duration of smo king, whereas associations with intensity and pack-years were of borde rline significance. Among 216 men with impaired pulmonary function, th ose who quit smoking had significantly slower rates of FEV(1) decline than did those who continued smoking. Potential reasons for quitting i ncluded respiratory conditions and stroke. These results extend previo us reports of accelerated rates of FEV(1) decline in the persons who c ontinue to smoke, and they indicate that smoking cessation leads to le ss steep rates of decline in pulmonary function over a short period of time in middle-aged men, as well as in men with established pulmonary impairment.