Impact of cigarette smoking on pulmonary function in non-allergic subjects.

BACKGROUND: Cigarette smokers have been shown to have a greater tendency to develop respiratory allergies than non-smokers. Since the early obstructive airway changes seen in respiratory allergy and smoking are similar, the early airway changes seen in populations of young smokers might be attributed to the fact that a proportion of smokers are allergic. We therefore studied the effects of smoking on non-allergic individuals. METHODS: Forced expiratory spirograms and peak expiratory flows were measured in a population of asymptomatic non-allergic male medical students, 59 smokers and 110 non-smokers. They had between 2 and 5 examinations performed serially over a period of 4 years. RESULTS: Smoking had a negative impact on pulmonary function. Analysis of covariance and multiple regression analysis using age, height gain and weight change as covariables showed that smokers, when compared to non-smokers, had a significantly greater percentage decline in the forced expiratory volume in one second expressed as a fraction of the forced vital capacity (4.01 +/- 4.6 v. 1.52 +/- 5.84), the forced expiratory flow in the middle half of the forced vital capacity (FEF25%-75%; 11.36 +/- 15.09 v. 5.3 +/- 17.58) and the ratio of the FEF25%-75% to the forced vital capacity (FEF/FVC; 14.06 +/- 14.45 v. 6.95 +/- 17.94). CONCLUSIONS: Our results suggest that young smokers, within a few years of starting to smoke, develop changes in pulmonary function indicating early peripheral airway narrowing, and that these effects worsen progressively with continued smoking.