Geographical pattern of malignant neoplasm by cluster analysis using standardized mortality ratios (SMRs) in Ibaraki Prefecture, Japan.

We investigated the geographical patterns of mortality from eight (males)/ten (females) sites of malignant neoplasm, using cluster analysis with Standardized Mortality Ratios (SMRs), and examined the relationship between the mortality structure and urbanization. To explore the geographical tendencies is important for the prevention of cancers; such as noticing risk factors associated with regional variance. The death rates, by site, gender and age from 1990 to 1994 in Japan, were obtained from Vital Statistics. The deaths and population in municipalities were obtained from "Population of Ibaraki Prefecture". These were represented as averaged values in five-year periods. As an indicator of urbanization and mortality structure, the population density of municipalities and the overall rank scores of SMRs were used, respectively. Cluster analysis formed some distinctive structures. For males, Cluster 1 included four municipalities and three of these were located in the mountainous area in northwest Ibaraki, characterized by high SMRs from bone marrow. Cluster 5 consisted of the mid-south areas, characterized by high SMRs from stomach cancer. For females, the clusters seemed to be characterized by SMRs from esophagus cancer. An association between mortality structure and urbanization was found for females, 0.364 (p<0.01), but not for males, 0.162 (p=0.14).