Ambulatory blood pressure patterns in youth.

We examined the influence of sex, race, and age on ambulatory blood pressure (BP) patterns in youths. The subjects were 300 normotensive, healthy adolescents between the ages of 10 and 18 years, including 160 boys and 140 girls, of whom 149 were white and 151 were black. The data were divided into periods of activity (Period I: 8 AM to 10 PM) and inactivity (Period II: 10 PM to 8 AM). Boys had higher systolic BP during both Period I (117 +/- 11 nu 112 +/- 8 mm Hg; P < .05) and Period II (109 +/- 11 nu 106 +/- 10 mm Hg; P < .03). Blacks had higher systolic (108 +/- 10 nu 106 +/- 10 mm Hg; P < .01) and diastolic BP (63 +/- 8 nu 60 +/- 7 mm Hg; P < .003) during Period II. Interactions between race and age were found for both systolic (P < .005) and diastolic (P < .005) BP during Period II. Further analyses indicated associations between age and both systolic (beta = 1.16; P < .001) and diastolic (beta = 1.04; P < .0001) BP in black but not white subjects. An interaction was observed between sex and age for systolic BP during Period II (P < .005), with a relationship for boys (beta = 1.47; P < .001) but not for girls. These results suggest that the black adolescents showed a progressive increase in nocturnal BP with age, a pattern not observed in the white youths. This increased BP load may contribute to the early development of hypertension and BP-induced target organ damage in blacks.