Studies in hypertension: VI. Differences in the distribution of hypertension in negroes and whites: An appraisal☆

This paper has examined the evidence on differences in the racial distribution of hypertension in Negroes and whites and appraises the hypotheses offered to explain the differences found. 1. a. Despite variations in definition, in procedure, and in sample selection, all studies examined support the conclusion that Negroes in the United States more often have essential hypertension, hypertensive heart disease, hypertensive cardiovascular diseases, or related disorders, than whites. 2. b. The mortality of Negro males and females from hypertension, with or without mention of heart disease, is higher than that of white males and females for every are group between 20 and 48. Between the ages of 30 and 55, the Negro mortality is from five to nine times as high as the white mortality. 3. c. Four hypotheses offered to explain the radical differences are described and evaluated. THese hypotheses were labeled: the genetic hypothesis, the physical exertion hypothesis, the psychosomatic hypothesis, and the associated disorder hypothesis. It can be said that the evidence presented on the occurence and mortality from hypertension among Negroes and whites is generally consistent with all of the major hypotheses which have been advanced. While relating the evidence to the hypotheses does not confirm them, neither does it refute them. Rather, it encourages further study utilizing the observed Negro-white differences as a point of departure. It is clear, first of all, that field research is n eeded to complement laboratory and clinical studies. There is a need for research on representative samples of the population and for research which collects data on nonhypertensives as well as well as on hypertensive subjects. The former is necessary to permit generalizing the findings of research; the latter to make it possible to isolate those characteristics which are unique to the hypertensive. Second, it would seem desirable in formulating research designs to consider ways of testing the interrelationship between sets of hypotheses rather than to focus research on the testing of a single hypothesis. In the present case, for example, any study of the hereditary factor in hypertension should consider at the same time the contribution of social and psychologic factors to the disorder. It is unlikely that either hypothesis can b e confirmed or refused if studied in isolation. Third, investigators should take into account the slow development and chronic character of hypertension and consider the need to establish the temporal factor in any relationship that are discovered. Knowledge, for example, that hypertensive individuals are likely to experience unique psychologic difficulties and, in turn, that Negroes are more likely to have these difficulties than whites is incomplete knowledge. The temporal sequence between the two must also be ascertained. The hypotheses presented in this review are among those to be tested in a long-term study of hypertension, which is outlined in the first of this series of papers.24 Research of this kind which envisions observing a large representaive sample of individuals over a period of time would provide, it is believed, a suitable frame for further study of the N e gro-white differences discussed above. It would require, to be sure, an oversampling of Negroes to make for valid Negro-white comparisons. However, it would provide for the simultaneous testing. of the hypotheses offered to explain these differences. Thus, to test the genetic hypothesis, arrangements could be made to include several generations of the same family in the sample. Regular and systematic observations could be made to measure the amount of physical exertion expanded by each subject. Batteries of psychologic tests could be administered to the subjects, and indices of the social conditions under which they live could be readily obtained. Periotic medical examinations of the sample would provide the kind of data necessary to test the associated disorder hypothesis. Finally, a long-term study could make a significant contribution to the further specification and definition of what hypertension is and what it involves.