Book Review

Pathophysiology of Hypertension in Blacks

N Engl J Med 1993; 329:1823-1824December 9, 1993

Article

Pathophysiology of Hypertension in Blacks
(Clinical Physiology Series.) Edited by John C.S. Fray and Janice G. Douglas. 299 pp. New York, Oxford University Press, 1993. $85. ISBN: 0-19-506720-7

This is the third book on hypertension in blacks published in the past eight years. It reflects a growing recognition that the pathogenesis of hypertension in blacks may well differ from that in whites in ways that could account for its greater prevalence and severity. Just as health problems of Native Americans and Hispanics have come under recent scrutiny, so has hypertension in blacks assumed investigative legitimacy.

This book is multiauthored and is edited by John Fray and Janice Douglas, both of whom have important credentials in laboratory investigation. It is a helpful textbook because it is provocative and has an extensive bibliography.

The foreword is by A. Clifford Barger, and the 12 chapters are grouped into 5 sections. In the introduction (part I) Fray puts forth his concept that hypertension in blacks is initiated by psychosocial stress that, in turn, causes the release of “stress response molecules” such as serotonin, corticotropin, cortisol, catecholamines, renin, and angiotensin II. These produce organ and vascular responses that induce hypertension by increasing intracellular calcium levels. This “equilibrium model” of hypertension focuses on a stable physical equilibrium of arteriolar smooth muscle.

Two chapters make up part II. In the first, Grim and Wilson explain their theory that the physical conditions and diseases on the slave ships allowed the survival of black Africans who had the most efficient salt-retaining mechanisms. These mechanisms have been passed on to subsequent generations and are now expressed as salt-sensitive hypertension. In the other chapter, Falkner discusses her studies of hypertension in black children and adolescents. She concludes that the primary genetic defect is in insulin-mediated glucose uptake, with resultant hyperinsulinemia. This in turn stimulates adrenergic nervous-system activity, causes sodium retention, and serves as a growth factor for vascular smooth muscle.

Part III has three chapters. In the first, Dressler discusses how social and cultural influences “can link social profiles of hypertension, such as differences in population average blood pressure by type of society, with individual-level processes, such as the presentation of self in mundane social interaction and the physiological responses that might accompany that interaction.” Myers and McClure present evidence of the interaction of a number of psychosocial stressors in the production of hypertension in socially and financially deprived black Americans. The third chapter summarizes the large body of data on differences in cardiovascular reactivity between blacks and whites. This section of the book is particularly helpful to physicians who have no easy access to the psychology literature.

With part IV, physicians are once again in familiar territory. Mufunda and Sparks discuss salt sensitivity not only in African Americans, but also in African Africans. Sowers and colleagues present their work and that of others on nutritional factors and dietary intake of ions, with a particular emphasis on calcium. Cooper and Borke summarize data on differences in intracellular ion concentrations and ion transmembrane transport systems between blacks and whites -- mostly in red cells -- and Fray discusses renin formation and release in hypertension in blacks and in other conditions in which plasma renin activity is low.

In the first of the two chapters making up part V, Fray expands on his equilibrium model. In the second chapter, Wright and Douglas summarize what we know about effective antihypertensive therapy for African Americans.

I found the book helpful because the chapters have excellent bibliographies. But the hypotheses troubled me because I found them simplistic. Relating the high prevalence and severity of hypertension in African Americans almost solely to psychosocial stress fails to take into consideration the fact that not all people affected by such stress are hypertensive and that those who maintain normal pressure under such conditions should be studied just as carefully and in large enough numbers to serve as adequate controls. Furthermore, this theory fails to account for the fact, as shown by analyses of the Hypertension Detection and Follow-up data, that low socioeconomic status and a poor education account for only a portion of the differences in the prevalence and severity of hypertension between blacks and whites.

Harriet P. Dustan, M.D.
28 Hagan Dr., Essex, VT 05452