Professional driving, smoking, and lung cancer: a case referent study.

In a case referent study of about 600 cases of male lung cancer in northern Sweden the risk in professional drivers was specifically studied. Data concerning occupations, time and type of employment, and smoking habits were collected by questionnaires directed to close relatives. On average, professional drivers were heavier smokers and this was the chief cause of a slightly increased crude risk ratio in the study as a whole. Smoking drivers in an upper age group (70 and over) had a high relative risk of lung cancer, whereas in a lower age group (under 70) no significant increase was found. The relative risk in non-smoking drivers in the upper age group was moderately raised with borderline statistical significance. The high relative risk estimated for smoking drivers in the upper age group suggests a synergistic effect between smoking and occupational exposure.