Abstract
To investigate secular trends in incidence of all stroke, cerebral hemorrhage and cerebral infarction in Japan, morbidity surveillance for men and women aged 40 yr and over was conducted in a northeast rural community between 1964 and 1984. Cross-sectional studies of risk characteristics for men and women were also performed in 1963-1966 and in 1972-1975. To determine risk factors of cerebral infarction, two cohorts of men and women aged 4069 were constructed in 1963-1966 (2, 221 persons) and in 1972-1975 (2, 574 persons) and followed until 1974 and 1984, respectively.
Age-adjusted incidence of all stroke, cerebral hemmorrhage, and cerebral infarction declined significantly in both men and women aged 4069 yr between 1964-1968 and 1979-1984 (p<0.01). Incidence of all stroke did not change significantly for men and women aged 70 and over because of no change in cerebral infarction in spite of a decrease in cerebral hemorrhage.
According to the Cox proportional hazard model, sex (men), age, diastolic blood pressure, and hypertensive and sclerotic changes in fundus were positively associated with incidence of cerebral infarction in early cohort. In later cohort, atrial fibrillation was related to incidence of cerebral infarction as well as sex (men), age, and diastolic blood pressure. Incidence of cerebral infarction was three times higher in persons with atrial fibrillation than in persons without it.
Population attributable risk of cerebral infarction was 42% for hypertension and 48% for funduscopic abnormality in early cohort. The attributable risk declined 40% for hypertension and 61% for funduscopic abnormality from early cohort to later cohort. This substantial decline in the attributable risk was mostly due to a decline in blood pressure levels by improvements of hypertension control and diet and environmental factors. For atrial fibrillation, population attributable risk of cerebral infarction was only 3% because of the low frequency of atrial fibrillation in the population.
