Based on the death records covering a 15-year period 1971 to 1985, the standardized mortality ratios (SMRs) for selected Cerebro-cardio-vascular diseases were calculated for each of 96 local community units (14 cities, 73 towns and 9 villages) in Kagoshima prefecture. These local communities characterized by the SMRs for different categories of cerebro-cardio-vascular disease were classified by the cluster analysis using the statistical package (Ward) on computer and the geographic difference in the characteristic of death rates from these diseases were explained by the ionic concentrations in local drinking water. Results obtained are as follows; 1) With a criterion of 7.5 in the cluster analysis, the 96 local communities were classified into five regional groups (Group I, II, III, IV and V), each of which could be regarded as the group of local communities with similar characteristics of SMRs for different categories of cerebro-cardio-vascular disease. A total of 33 local communities belonged to Group I, 16 to Group II, 25 to Group III, 11 to Group IV and 11 to Group V, respectively. All the local communities in Group IV were on the remote islands. 2) The values of SMRs for cerebrovascular disease in Groups I, II and III were higher than the expected level of 1 while those in Group IV and V were less than this level. For cerebral hemorrhage, the values of SMRs were higher than 2 in Group II, higher than 1 in Groups I, III and V and below 1 in Group IV. For cerebral infarction, the values of SMRs were higher than 1 in only Group III and less than 1 in the other Groups. For hypertensive disease, the values of SMRs were higher than 2 in Group V, higher than 1 in Group I, II and III, and less than 1 in Group IV. For ischemic heart disease, the values of SMRs were higher than 1 in only Group III and less than 1 in the other Groups. For other heart disease, the values of SMRs were higher than 1 in Groups I, II, III and V and less than 1 in only Group IV. Therefore, the values of SMRs for all of cerebro-cardio-vascular diseases were higher than l in Group III and less than 1 in Group IV . 3) On a Group basis, significant negative correlations were noted between SMRs of cerebrovascular disease and Mg, Ca, Mg + Ca or Ca/K in drinking water, between SMRs of ischemic heart disease and Mg or Mg + Ca, and between SMRs of other heart disease and Na, Mg, Ca, Cl or Mg +Ca. Similar negative correlations existed between SMRs of selected cerebro-cardio-vascular diseases and selected ionic concentrations, on a community basis for the 96 units. 4) Results of the multiple regression analyses showed that Ca and Ca-Na in drinking water were positively associated with deaths from cerebrovascular disease while Cl was negatively associated with that factor. They also showed that Na was negatively associated with deaths from cerebral hemorrhage, K was positively while Cl and Cl/K were negatively associated with deaths from cerebral infarction, Cl was negatively associated with deaths from hypertensive disease, Mg, Ca and Mg/Ca were negatively associated with deaths from ishemic heart disease, and Ca and Na were negatively associated with deaths from other heart disease, respectively.
