A case-control study on risk factors for leukemia in a district of Japan.

A case control study was performed with 142 leukemia patients and 284 controls matched for age and sex. Occupation, birth order, past medical history, and drinking and smoking habits were compared in these two groups. Persons born first or fourth were found to have a higher incidence of leukemia. History of a fracture was one of the risk factors for acute leukemia, and a history of gastroduodenal ulcer was a risk factor for chronic leukemia. This may suggest that extensive exposure to X-rays in diagnosis and treatment is a risk factor for leukemia. There was a significant dose-response relationship between the amount of smoking and the incidence of acute nonlymphocytic leukemia, but not between the amount of alcohol consumption and the incidence of leukemia. Thus, smoking was one of the risk factors for acute leukemia.