Postural changes in blood pressure and pulse rate among black adolescents and white adolescents: the Minneapolis Children's Blood Pressure Study.

Because studies have suggested a possible relation between vascular responsiveness to postural changes and risk of subsequent myocardial infarction, the reactivity of blood pressure and pulse rate to change from supine to standing positions was examined in 158 black males, 144 black females, 342 white males, and 272 white females aged 14-16 years. The study was part of the Minneapolis Children's Blood Pressure Study and was conducted during October to December 1985. Two blood pressure readings and one pulse reading were taken after five minutes of supine rest, immediately upon standing, and five minutes after standing. After adjustment for body mass index, mean systolic blood pressure decreased, and fourth- and fifth-phase diastolic blood pressures and pulse rate increased from supine to standing positions in all race and sex groups. Black males had significantly larger changes in systolic pressure than did white males (-5.9 vs. -4.1 mmHg), and males had significantly larger changes in fourth- and fifth-phase diastolic pressures compared with females of the same race (fourth-phase diastolic pressure, 8.0 vs. 4.1 mmHg for blacks and 10.0 vs. 4.8 mmHg for whites). Fifth-phase diastolic pressure increased more than did fourth-phase diastolic pressure in all groups. No race or sex differences were seen for pulse changes. For all race-sex groups, decreases in systolic pressure were positively correlated with initial levels of supine systolic pressure, whereas increases in fourth- and fifth-phase diastolic pressures were negatively correlated with corresponding initial levels. Measurement of postural changes may provide a clinically simple and reproducible way of testing for abnormalities in blood pressure and may better discriminate those at high risk of hypertension and its cardiovascular complications than would the commonly used single-seated blood pressure measurement.