Pathologic Characteristics of Stroke and Myocardial Infarction in Japan

Abstract

The Akita pathology study was conducted to examine risk characteristics of stroke and myocardial infarction, and trends of atherosclerosis in brain and coronary arteries. The subjects were 845 men aged 30 and over, examined among autopsied men admitted to a local hospital of northeast Japan between 1966 and 1984. The overall autopsy rate was 88%. Blood pressure and serum cholesterol at admission was compared according to type of stroke. To elucidate risk characteristics of myocardial infarction in Akita, the infarction cases were compared with those in Osaka (the second largest city in Japan). Grades of atherosclerosis for basal cerebral arteries and coronary arteries and grade of arteriosclerosis for intracerebral small arteries were determined blindly by one pathologist using a method of cross-sectional stenosis scoring. As expected, blood pressure levels were higher in all types of stroke than nonstroke. Serum cholesterol was lower in cerebral hemorrhage than in nonstroke, and was higher in infarction in cortical artery regions than in nonstroke. Cerebral hemorrhage showed the lowest proportion of significant stenosis in both basal and intracerebral penetrating arteries. Myocardial infarction in Akita had a higher prevalence of hypertension and a lower prevalence of high serum cholesterol, the higher proportion of scattered type of infarction (mostly subendocardial infarction) compared with myocardial infarction in Osaka. Age-adjusted mean scores for atherosclerosis in the coronary arteries and basal cerebral arteries declined 30% and 42%, respectively, between 1966-1974 and 1975-1984. There was a decline in age-adjusted blood pressure levels at admission: 10 mmHg for systolic and 4 mmHg for diastolic blood pressure, whereas mean serum cholesterol rose 6 mg/dl. There results indicated that hypertension and low serum cholesterol levels were associated with cerebral hemorrhage, and mostly hypertension with myocardial infarction in Akita. The deline in blood pressure levels between the 1960's and 1980's may have contributed to the decreased atherosclerosis in both brain and coronary arteries. The effect of an increase in serum cholesterol for coronary atherosclerosis was overwhelmed by the large decrease in blood pressure levels.