A case-control study of multiple myeloma in Japan: association with occupational factors.

Recently the incidence rate of multiple myeloma (MM) has increased in Japan. Epidemiologic efforts have suggested that certain occupational and chemical exposures are likely to increase the risk for MM. We therefore performed a case-control study of MM, examining occupational factors. Data for 57 cases and 57 controls were obtained from Sapporo Medical University Hospital and its affiliated hospitals in Hokkaido. Controls were matched to each case by gender, age (+/- 5 years) and hospital. Detailed information regarding several factors possibly related to MM was obtained by interviews in hospitals. Odds ratios (ORs) and 95% confidence intervals (95%CIs) were calculated with adjustment for cigarette smoking as confounding factor. The occupational category of agriculture and fishery showed a significant association with increased risk (OR = 5.89, 95% CI = 1.24-28.04). Occupational exposure to chemical products including organic solvents or petroleum showed a significant association with increased risk (OR = 8.05, 95% CI = 1.01-64.45). Medical histories of operation for appendicitis and blood transfusion were associated with decreased risk, but not significantly. Our results suggested that occupational exposure to chemicals might play a role in the risk of MM.