BACKGROUND:

Hypertension related diseases are major causes of morbidity and mortality among United States Blacks. Among Blacks and whites, lower levels of education are associated with higher levels of blood pressure, stroke, and coronary heart disease mortality. High levels of blood pressure in United States Blacks compared to United States whites persist even after controlling for education. Furthermore, it has been demonstrated that individuals living in the southeastern part of the United States continue to have higher stroke and coronary heart disease mortality rates than those living in most other areas of the United States. The number of upwardly mobile Blacks, based on education and occupation, has been increasing in the United States yet relatively little is known about the relationships of improvements in socioeconomic status and cardiovascular risk factors, particularly blood pressure.

In Africa, for over four decades, hypertension has been regarded as a rare disease among the Black Africans. However, recent evidence from hospital and community based populations suggests that hypertension is the most prevalent cardiovascular disease among Africans and constitutes a major public health problem, particularly in West Africa. Furthermore, stroke is an increasing health problem.

DESIGN NARRATIVE:

In this longitudinal study, the United States students were recruited and followed annually for three years. The African students were followed for two years. At the initial clinic visit blood pressure, heart rate and anthropometric measurements were obtained and questionnaires completed concerning socioeconomic status, family and medical history, dietary practices, and smoking and drinking habits. One out of every four students had blood pressure measurements reassessed. Each participant collected an overnight urine sample for analysis of sodium and potassium. Fifty percent of the population wore a physical activity monitor for two days. Approximately ten percent of the students' families were studied to validate the hypertensive status and medical history of the parent as reported by the students and to assess known cardiovascular risk factors including obesity, smoking, alcohol intake, physical activity, and behavioral factors. Univariate analyses were conducted to assess the association between the dependent variable of blood pressure and each of the independent variables including age, body mass index, height, sodium and potassium. T-tests were used to analyze the dichotomous variables such as sex, race, and geographic location. Stratification was used to examine blood pressure levels for Blacks and whites by socioeconomic status. Multiple regression models were used to determine whether physiological or psychosocial variables were more predictive of cardiovascular risk.