Tanno and Sobetsu Studies

The Tanno and Sobetsu study was started by Osamu Iimura and currently is being handed down to Kazuaki Shimamoto. Lecturer Shigeyuki Saito is the current leader.

The study was of two towns in northeastern Hokkaido and began in 1975. The national census at that time showed a population of 5,568 in Tanno (2,732 men, 2,836 women), and 4,447 in Sobetsu (2,156 men, 2,291 women). Both towns were agriculturally based, with Tanno involved in field cropping and Sobetsu in fruit cultivation. The cohort study involved, in the first year, randomly sampling the people aged 40-64 in each town. This resulted in a study population of 1,996 from Tanno (475 men, 521 women, average age 51.1?6.3), and 1,000 from Sobetsu (469 men, 531 women, average age 51.1?6.3). Both cohort groups had similar composition with regard to sex, average age, and age distribution, and 40-64 year olds represented approximately 30% of the town’s population.

Data collection for the cohort study for Tanno started in 1977, and Sobetsu in 1978. Data were collected in summer and winter biannually for the first ten years and every year subsequently. Epidemiological data were collected on past medical history, family history, diet, blood pressure, body mass index, blood cholesterol levels, uric acid, glucose tolerance test, echocardiogram, chest x-ray, and if indicated, endocrinological function tests or other special tests. If a participant was to develop a disease or die, information was gathered from family members and a public health nurse, and a questionnaire sent to the participant’s doctor regarding disease onset, history of presenting complaint, and laboratory test results to obtain an accurate diagnosis of each participant.

The Tanno and Sobetsu study was a rare example of a Japanese epidemiological study done by an internal medicine department.

Results of the Study

1. When comparing hypertension “developers and non-developers,” the developers were more likely to have high initial blood pressure measurements, see bigger changes with age, and have blood pressure tracking than non-developers.
2. When comparing 10-year averages of obesity, subcutaneous fat, blood uric acid, total protein, total cholesterol and serum triglyceride between those who developed hypertension or did not, those of hypertensives had significantly higher levels than those of non-hypertensives. The laboratory findings suggest this was a result of excess dietary calorie consumption.
3. Even when multivariate analysis was done to revise influences of age and initial blood pressure measurement, obesity and fasting blood glucose levels were better predictors of hypertension predisposition.
4. People diagnosed with diabetes or impaired glucose tolerance by glucose tolerance test, were more predisposed to hypertension, and people with hypertension were more likely to develop diabetes or impaired glucose tolerance.
5. Even with normal or slightly elevated blood pressure levels, people who had coexisting impaired glucose tolerance had poorer prognosis.

Due to the long-term follow up of the Tanno and Sobetsu study, there were people over the age of 80 participating in the study. From these participants, the study can look into other areas such as activity of daily life and quality of life. (H.Ueshima)