In the northeastern region of Japan there is from old times as expression "attata" meaning "was being affected by". It seems to be "apoplexy" which has been observed since the Greek era. With regards to the diseases of circulatory system in Japan, especially cerebrovascular diseases, it is known that there are various features in comparison with other countries. That is, mortality rate of cerebrovascular diseases is high, particularly in the Northeast Japan. The mortality rate is significant in young people and middle age. The cause od death is mainly hemorrhage, and there are seasonal changes: it is high in winter and low in summer.

For the explication of the nation-wide difference in the mortality from cerebral apoplexy and in the blood pressure levels of the inhabitants, the author reported the quantity of salt intake is the most influencial factors from the standpoint of retrospective epidemiological studies.

From the global epidemiological point of view the correlation between the level and distributions of blood pressure and daily salt intake is striking. The blood pressure level appears to be already high in a younger age group in areas with salt intake of more than 10 g per day for a person with subsequent rise of blood pressure upon aging. In areas with intake of less than 5 g on the other hand, the blood pressure is low at a younger age and no rise is noted with advance in age.

In order to acrutinize the relation between the blood pressure levels and occurence of death from cerebrovascular diseases in the population, follow-up studies were made in the Northeast.

According to the results obtained in the person-years of observation at every 10 mmHg level of systolic and diastolic blood pressure, it becomes obvious that person whose blood pressure were around 120 mmHg for the systolic and around 70 mmHg for the diastolic were lowest in the death rates. The death rates from cerebrovascular diseases showed "smooth" increment in the same proprtion as the rise of systolic and diastolic blood pressure levels.

Also the results of epidemiological studies on blood pressure of the inhabitants in the Northeast suggested that interaction between genetic and enviromental factors play an important role in the causation of human hypertension.

According to the results of intervention studies on the hypertension-control by reducing high salt intake the changes of the levels and frequency distribution of blood pressure and the changes of way of living such as traditional high salt intakes is the inhabitants of Northeast Japan were observed.