A study on chronologic change of the relationship between cigarette smoking and lung cancer based on autopsy diagnosis.

Human cases autopsied at the Department of Pathology, University of Tokyo, were studied to investigate the chronologic changes in the relationship between cigarette smoking and lung cancer occurrence. The results obtained were as follows: (1) it was confirmed that the incidence of lung cancer was significantly higher among cigarette smokers than among nonsmokers, and that there was a definite dose-response relationship between the quantity of cigarettes smoked and the occurrence of lung cancer; and (2) over the time span studied, the incidence of lung cancer among autopsies showed a remarkable increase. However, this tendency was seen in both cigarette smokers and nonsmokers, and in fact, the increase was comparatively higher in the latter group. It should be stressed that the relative importance of cigarette smoking in human pulmonary carcinogenesis seems to have decreased in the past 40 years or so, and factors other than cigarette smoking seems to have become more important.