[Epidemiological investigation of senile dementia at home--with special reference to incidence and prevalence rate in Miki-cho, Kagawa Prefecture].

Epidemiological investigation of senile dementia was performed in 1987 and 1988 on all the aged at home (3,754 persons at the ages of 65 years or more) in Miki-cho (M-cho), Kagawa Prefecture. The composition of the population in M-cho is similar to that in Kagawa Prefecture. M-cho has the most population among the towns or villages in Kagawa Prefecture. Urban areas, rural areas, and middle areas are distributed evenly in respect to the size in M-cho. Thus, it was possible to carry out the investigation reflecting the situation in Kagawa Prefecture. The results of the present investigation were as follows. 1) The prevalence rate was 4.1% in both the first year (1987) and the second year (1988). 2) The incidence rate was 1.01%. 3) The proportion of Alzheimer type dementia to cerebrovascular type dementia was 0.98 in the first year and 1.00 in the second year. 4) Although no statistically significant difference in the prevalence rate was noted between males and females, the prevalence rate of males was higher than that of females in the first half of senility, and the prevalence rate of females was higher than that of males in the second half of senility. 5) Although no statistically significant difference in the prevalence rate was noted between Alzheimer type dementia and cerebrovascular type dementia, the prevalence rate of cerebrovascular type was higher than that of Alzheimer type in the first half of senility, and the prevalence rate of Alzheimer type was higher than that of cerebrovascular type in the second half of senility. The epidemiological investigations of senile dementia have been often reported in all over the world. However, most of the investigations were made on nothing but the calculation of the prevalence rate of senile dementia, while the investigation of the incidence rate was hardly carried out. In respect to the incidence rate, it is desirable that the subjects should be more than 1,000 in number. When the number of subjects is less than 1,000, the occurrence of senile dementia will be noted yearly in approximately 10 cases. If the number of patients with senile dementia increases or decreases even by one, therefore, the incidence rate differs to a great extent. The past reports on the incidence rate were made in subjects of less than 1,000 in number. Accordingly, it may be possible to say that the present investigation was made by the exact methods accompanied by less errors.(ABSTRACT TRUNCATED AT 400 WORDS)