The influence of smoking and other etiopathogenetic factors on the incidence of bronchogenic carcinoma and chronic nonspecific respiratory diseases.

In the longterm epidemiological studies carried out in the Kol ín District, Czechoslovak Socialist Republic, in the course of the past 20 years, the importance of cigarette smoking as a risk factor of bronchogenic carcinoma and chronic bronchitis has been confirmed. The proportion of cigarette smokers in the population of the district under study, aged 15 years and over, was 57% for males and 14% females. The incidence of bronchogenic carcinoma, proved by histological or cytological examination, was approximately 50 times higher in males from 40 to 64 years of age, who had smoked 200 000 cigarettes and over, than in non-smokers. In cigarette smokers who had not smoked as much, the incidence was 10 times higher then in non-smokers. The frequency of new cases of bronchogenic carcinoma was much higher in males with chronic respiratory symptoms and with tuberculous or posttuberculous fibrotic lesions in the lungs. The prevalence of chronic bronchitis in 1972 was 13% for males and 4% for females, in the total of all age groups over 15 years of age. In the group of smokers who had smoked 100 000 cigarettes, 28% of males and 20% of females had symptoms suggestive of chronic bronchitis. In the group of non-smokers, 5% of males and 3% of females had such symptoms. The incidence of bronchogenic carcinoma and chronic nonspecific respiratory diseases can be raised by the interaction of two or more risk factors.