Hypertension and Ischemic Heart Disease in Hiroshima, Japan

Abstract

A random sampling of Hiroshima residents, comprising 1,051 males and 1,872 females, has been studied with respect to the interrelations of hypertension, ischemic heart disease, blood lipid levels, and ionizing irradiation experienced during the atom bombing of 1945. No significant effect of ionizing irradiation upon the cardiovascular system has been detected. No major difference in age-sex specific mean blood pressures between Hiroshima residents and a suitable white American comparison group was found. Dissimilarities noted with other groups compared are considered due to the sum of sampling bias, varying technics, and coincidental environmental factors rather than a true racial difference. Blood pressure levels, stable from puberty through young adulthood, begin to rise early in middle age and continue to rise into old age. As a result, hypertension as clinically defined (140/90), is common in middle-aged and elderly Japanese. In 94.4 per cent of instances, or more, a demonstrable etiology for hypertension could not be found; these are considered to represent essential hypertension. An accelerated course with fulminating vascular deterioration was suspected in only 1 per cent of the hypertensive subjects. As a result, advanced retinopathy and renal failure were rarely seen. Electrocardiographic evidence of left ventricular hypertrophy occurred in 7.2 per cent of the hypertensive Japanese in this study, and was readily correlated with the ambient systolic blood pressure. Evidence of ischemic heart disease and congestive failure is rare and distinctly less common than in American males unselected as to blood pressure levels. In contrast, mortality statistics indicate cerebrovascular disease to be at least as common in Japan as in the U. S. Japanese exhibit low serum cholesterol concentrations by Western standards and elevated levels are predominantly limited to the obese. Both factors appear of importance in the occasional hypertensive Japanese with ischemic heart disease. The therapeutic implication of this observation is briefly discussed.