[Epidemiological study on respiratory effects of smoking in college students]

To study the influence of smoking on the respiratory system in adolescents, we conducted a prospective study to look into the respiratory symptoms, changes in ventilatory function, and levels of expired CO of both smoking and nonsmoking college students. The subjects were 56 male students who entered Akita University in 1986. Thirty of the participants were smokers at entrance whereas the rest who were nonsmokers, served as controls. The smokers started smoking at an average age of 17.6 +/- 0.9 years. Physical examinations at 8 points during the study were performed periodically in May and November for four years, from 1986 to 1989. From these studies, the following conclusions were obtained. 1) The prevalence of respiratory symptoms, especially phlegm, was higher among the smokers compared with the nonsmokers; the differences not being significant. Among both the smokers and nonsmokers, no prevalence of persistent cough and phlegm was observed during the study period. 2) There were no differences in the levels of %FVC and %V50 between the smokers and the nonsmokers at any point during the study period. The FEV1% levels for smokers were decreased progressively, and the differences became significant at the 7th and 8th tests (p < 0.05). After the second test, %V25 levels were lower in the smokers than in the nonsmokers; the differences being significant at the 7th test (p < 0.05). 3) The dose-response relationships between smoking and pulmonary function were not statistically significant in any levels at the 7th and 8th tests. However, %V25 levels of the heavy smokers (15 < or = per a day) were lower than the those of the nonsmokers; the differences being significant at the 7th and 8th tests (p < 0.05). 4) Average expired CO concentrations of the smokers were 2.5-3.5 times higher than those of the nonsmokers during the study period, confirming exposure to tobacco smoke. These observations suggest that young smokers may develop obstructive changes, especially narrowed small airways during the first 5 years of exposure to tobacco smoke.