Psychophysiology of Cardiovascular Reactivity

BACKGROUND:

Blacks in the United States have a much greater prevalence of essential hypertension than whites. The prevalence of hypertension for adults aged 18-74 has been estimated at 15.7 percent for white women, 18.5 percent for white men, 27.8 percent for Black men and 28.6 percent for Black women. Among adults who underwent screening for the Hypertension Detection and Follow-up Program, 36.2 percent of Black males and 38.2 percent of Black females either had diastolic blood pressures at least as high as 95 mmHg or were taking antihypertensive medications. The Black-white ratio for the prevalence of hypertension in this survey was approximately 2. Reportedly, the prevalence of hypertension among inner city Blacks may be as high as 50 percent. The exact causes of the disparity in hypertension prevalence between Blacks and whites are unknown, but genetic predisposition, psychosocial stress, and life-style factors such as high sodium ingestion and obesity have been implicated. None of these factors alone appears sufficient to account for the difference in the prevalence of hypertension between Blacks and whites, suggesting that multiple factors and/or interactions between factors may be involved.

DESIGN NARRATIVE:

The study is supported by a program project grant and thus includes many subprojects. Projects 1A through 1C were supported beginning in 1986. Project 1A examined the effects of cardiovascular and hormonal responses to standardized laboratory challenges as a function of race, sex, age, and normal blood pressure versus borderline hypertension. The subjects were classified according to four categories: Black or white race; male or female sex; normal or raised blood pressure; and ages 25-39 or 40-54, giving a total of 16 cells with 15 subjects in each. The subjects were given a physical examination, electrocardiogram, blood screening test as well as a battery of special tests including a Structured Interview for Type A behavior pattern, playing a video game, a test designed to elicit anger, and exercise on a bicycle ergometer. During these tasks subjects were monitored for heart rate and blood pressure, and blood was sampled for plasma catecholamines, renin, cortisol, aldosterone, and vasopressin. Various psychological tests were administered including the Cook-Medley hostility scale, the Life Orientation test, a job stress scale, the John Henryism Active Coping Scale and others. Urine samples were collected for electrolyte and catecholamine excretion and ambulatory blood pressure was monitored on a work day and on a non-work day.

Project IB examined the effects of acute sodium loading and depletion on cardiovascular and hormonal reactivity as a function of race and sex. Normotensive subjects were classified according to two categories: Black or white race; male or female sex, with four cells of 15 subjects each. After the initial medical examination, subjects were seen three times at intervals of two weeks. Before each visit three overnight urine collections were made for electrolyte excretion evaluation. On these three visits subjects were randomized to either a control day, a sodium loading day, or sodium depletion day. On each of these days subjects were given three reactivity tests including the video game, exercise test, and speech-stressor task. The same psychological tests as in Project 1A were given on the mornings of the three testing days.