Short History of Epidemiology for Noninfectious Diseases in Japan. Part 2: Epidemiology of Stroke and Hypertension up to 1970

INTRODUCTION The mortality due to stroke had been around 170 per 100,000 population in 1930s in Japan, ranking second only to that from tuberculosis. According to Aizawa, only a few studies were reported on the topic of stroke at scientific meetings of internal medicine. In those days, it was only an occasional topic of discussion among the clinical specialists at the cerebrovascular sections of the Japanese Society of Circulation and Neurological Society, indicating a paucity of general interest in this disease entity. This was an era when average life expectancy was only slightly over 40 years; mortality for young and middle-aged adults was very high; the middle-aged and aged population rarely visited medical institutions; diseases were often diagnosed after they had advanced to a grave state; and effective therapies were relatively rare. Sasaki stated that in the 1930s, few medical researchers focused on the mortality from cerebral apoplexy and did not note its seriousness until Sadamu Watanabe called their attention to it. Under the war-time regime, the Ministry of Health and Welfare was newly established. The medical insurance system was reinforced and a health screening system was initiated at some work places. Subsequently, more patients sought medical attention for stroke and the significance of this illness began to be recognized. The Life Insurance Association had initiated a study on stroke. Realizing the significance of this trend, it offered a research fund amounting to 30,000 yen for a period of 3 years to the Japan Society for the Promotion of Science to organize a research group. The proposal was accepted and in April 1941, the 43rd Subcommittee for the study of Prevention of Cerebral Apoplexy of the Japan Society for the Promotion of Science was organized. This subcommittee was composed of the following 12 members, with the selection of Professor Chujiro Nishino as its Committee Chairperson: Tsugitake Isshiki, Chuji Ito, Seizo Katsunuma, Otoya Kimura, Yasutoshi Furuse, Takayuki Sasa, Takao Takada, Chujiro Nishino, Goichi Hiramitsu, Shunichi Mashita, Terasu Mozai, and Sadamu Watanabe. It was reported that this research group was scheduled to conduct discussions while representing both universities and insurance companies. They deliberated on the results from statistical, clinical and histopathological studies, collected pertinent literature, and while placing particular emphasis on the relationship between blood pressure and cerebral apoplexy, delved into topics that included specific factors (i.e., risk factors, heredity, specific somatotypes, environmental elements, prevention and measures to reduce the mortality of stroke). One may get an impression this the academic study on stroke was initiated in a somewhat unorthodox manner in Japan. During this period, the word epidemiology was rarely used in relation to non-infectious chronic diseases. In the category of circulatory diseases, Naosuke Sasaki published a study in 1952 entitled “Epidemiology of Apoplexy” and in 1958, the 29th Congress of the Japanese Society for Hygiene hosted a symposium that focused on the epidemiology of hypertension. In the following year, at the 16th Symposium on Hypertension (chairperson, Fusakichi Nakazawa) of the Japanese Medical Association, Noboru Kimura and Katsuya Itahara presented a speech entitled “An Epidemiologic Study of Hypertension”. It appears that those researchers who returned from studies in the United States began to start using the word epidemiology then. With a grant from the Ministry of Education, a group led by Shigeo Okinaka started a study in 1962 and published “An Epidemiologic Study of Apoplexy.” The 1966 ABCC (Atomic Bomb Casualty Commission) Symposium held in Hiroshima selected “Epidemiology of Coronary Artery Diseases and Apoplexy” as its major theme. It appears that the word epidemiology was firmly established in Japan in the 1960s; therefore a historical overview of epidemiologic studies on apoplexy and hypertension up to the 1960s must include those represented by topics such as hygienic and public health studies, statistical observations, regional or geographical studies, surveys on population groups and etiological investigations. After the 1970s, studies on circulatory diseases made