Longitudinal effect of age and smoking cessation on pulmonary function.

Although it is well known that pulmonary function declines with age and that this decline is accelerated by cigarette smoking, it is not as clear what effect smoking cessation has on pulmonary function. The Normative Aging Study, a longitudinal aging study of 2,280 men, has assessed this question. Longitudinal data on smoking and pulmonary function were available on 850 healthy men. Of 452 who smoked at entry to the study, 98 quit during a 5-yr period. There were no significant differences between current and ex-smokers in FVC (p = 0.12) and FEV1 (p = 0.66) at entry into the study. However, significant differences were observed during the 5-yr period in FVC and FEV1 decline between current, former, and never smokers, after adjusting for age and initial pulmonary function. The decrease in FVC for men who quit smoking was significantly less than that for current smokers (p = 0.02). Similarly, FEV1 for former smokers decreased significantly less than for current smokers (p less than 0.001). When multiple regression was performed among former smokers, no significant effects of years since quitting on rate of decrease in FVC and FEV1 were seen. This study suggested a definite and rapid beneficial effect of smoking cessation.