Blood pressure rhythms in early school-age children of normotensive and hypertensive parents: a replication study.

The purpose of this study was to reexamine blood pressure rhythms in children and the relationships among rhythmicity and age, gender, race, height, weight, and parental blood pressure status. The sample consisted of 60 healthy children between 7 to 9 years old; 30 had a parental history of hypertension and 30 did not. Blood pressure was measured in the child's home every hour, day and night, for three 24-hour periods. Linear regression of logarithmically transformed data demonstrated statistically significant rhythms for systolic and diastolic pressures in 37 of the 60 subjects. Spectral analyses revealed that these rhythms were ultradian, with predominantly 3-hour cycles. Children who exhibited significant systolic and diastolic pressure rhythms differed significantly from those who did not with respect to weight and height but not in age, race, gender, or parental blood pressure status.