Infant blood pressure and heart rate: relation to ethnic group (black or white), nutrition and electrolyte intake.

Blood pressure (BP) and heart rate were measured during non-rapid-eye-movement sleep in 392 full-term newborns and in 318 of these infants at age six months. Two-day records of food intake were collected at age six months for 150 infants. Black babies did not differ substantially in BP from white babies either at birth or at six months. The earliest BP tracking was from age six to 15 months (systolic (SBP): r = .29, p less than .001; diastolic:r = .45, p less than .001). No relationship was found between BP at six months and breast- or bottle-feeding, infant weight or weight change, or nutrient intake. The relationship between parental BP, on the one hand, and infant electrolyte intake and BP on the other, suggested that electrolyte intake was related to BP in the six-month-old infant, and that the relationship was different in white babies than in black babies. Among 56 white infants whose mother's mean BP was above the median for this population, infant sodium intake correlated with infant SBP (r = .31, p less than .009). Among 32 black infants, regardless of parents' BP, sodium intake was negatively correlated with SBP (r = -.36, p less than .021).