Aggregation of blood pressure in infants and their siblings.

Sibling aggregation of blood pressure has been shown in children 2 to 14 years of age. To determine the earliest age at which this finding is detectable, blood pressures were evaluated in 98 siblings from 43 black families with newborns. Variances of blood pressure scores were significantly greater among families than within families for systolic (p less than .025) but not diastolic pressures. Sib-sib intraclass correlation coefficients were .26 (95% two-sided confidence limits .05 to .47) for systolic and .16 (-.06 to .38) for diastolic pressures. When 1-month-old infant pressures were added, significant aggregation was present for systolic (p less than .01) and diastolic (p less than .025) pressures. The intraclass correlation coefficients were .21 (.02 to .38) and .17 (.03 to .34), respectively. When newborn scores were substituted, aggregation was not demonstrable. These data demonstrate a familial influence on blood pressure in infancy by 1 month of age.