Diurnal blood pressure variation: differences among disparate ethnic groups

We examined the possibility that excess cardiovascular morbidity in American blacks compared with whites might be partly the result of differences in diurnal blood pressure variation. Urban American blacks have higher night-time blood pressures and show a smaller increase in blood pressure during the waking day than whites. This difference is associated with a higher cardiac mass in the blacks and occurs despite similar duration and quality of sleep in blacks and whites. Both groups show similar levels of sympatho-adrenal activity at night, but the diurnal increase is smaller in blacks, paralleling the smaller increase in blood pressure. In Africa blacks show a diurnal pressure pattern similar to American whites. Disparities in cation consumption do not explain the differences in blood pressure variation between these groups.