Blood pressure during the first five years of life: relation to ethnic group (black or white) and to parental hypertension.

Blood pressure was measured in 392 healthy, full-term, appropriate-weight infants and was measured again at 6, 15, 24, 36, 48, and 60 months of age. Systolic pressure rose from birth to six months of age, remained at a plateau until 15 months of age, and from 24 to 60 months rose an average of 1 mmHg per year. Diastolic pressure rose from birth to 24 months but showed little change from 24 to 60 months. The correlation of systolic with diastolic pressure decreased seriatim from birth to 60 months. Blood pressure did not vary as a function of ethnic group, sex, or socioeconomic status during the first five years of life. The association of body size with blood pressure was no more than modest during this period, but seemed to be closer for females than for males. A closer child-parent association was found for heart rate than for blood pressure. The child's heart rate was inversely associated with the parent's blood pressure although the child's blood pressure was not associated with the parent's pressure. During the first five years of life, a low heart rate may be a more significant risk factor for adult hypertension than elevated blood pressure.