Stomach cancer in New Zealand: time trends, ethnic group differences and a cancer registry-based case-control study

Stomach cancer trends in New Zealand were examined. Age-standardized mortality and incidence rates have declined over the past four decades, as in other countries. Rates have been consistently higher for men, and for Maori. A cancer registry-based case-control study of 1016 male stomach cancer cases and 19,042 male controls with other cancers was also conducted, to evaluate the relationships between stomach cancer and specific occupations. Adjustment was made for age, ethnicity, socioeconomic level, and smoking status. When 22 occupational groups were examined, adjusted odds ratios (ORs) and 95% confidence intervals (95% Cls) were elevated above unity for only one group: forestry workers (OR 1.83, 95% Cl 1.01-3.32). When two large, heterogeneous groups were broken down into 15 subgroups, adjusted ORs and 95% Cls elevated above unity were found for three sub-groups: grain millers and related workers; brewers, wine and beverage makers; and field crop workers. These findings may be because of the multiple comparisons and subgroup analyses undertaken. Men who had ever smoked cigarettes were found to have an increased stomach cancer risk compared to those who had never smoked (adjusted OR 1.36, 95% Cl 1.15-1.60).