Multiple myeloma in Western Australia: a case-control study in relation to occupation, father's occupation, socioeconomic status and country of birth.

A death-certificate-based case-control study was undertaken covering 249 patients with multiple myeloma diagnosed in Western Australia from 1975 to 1984 whose deaths were registered in Western Australia in the same period (73.4% of the total diagnosed) and 996 control decedents who were matched to the cases by age, sex and death registration district. Death from multiple myeloma was associated with both farming [odds ratio (OR) 1.44 with 95% confidence interval (CI) 0.81-2.55] and woodworking (OR 1.70 with 95% CI 0.67-4.31) but not with farming as the father's occupation (OR 0.96 with 95% CI 0.66-1.41). It was also more frequent in migrants to Australia than in native-born Australians (OR 1.31 with 95% CI 0.99-1.74) particularly those born in England (OR 1.57 with 95% CI 1.11-2.42) and Italy (OR 2.02 with 95% CI 1.09-3.74). An apparent excess of multiple myeloma in all rural residents appeared to be due to bias introduced by matching for death registration district, as rural residents dying from multiple myeloma were more likely to die and have their deaths registered in the city than other rural residents. A conditional logistic regression analysis showed the above associations to be substantially independent of one another.