BLOOD-PRESSURE IN 1ST 10 YEARS OF LIFE - THE BROMPTON STUDY

Objectives - To determine the normal range of blood pressure and its pattern of change in the first 10 years of life. To estimate at what age (if any) children consistently appear in one part of the blood pressure distribution and at what age familial correlations in blood pressure become significant. Design - Longitudinal cohort study. Setting - South east England. Subjects - 2088 children of both sexes born consecutively in Farnborough Hospital, Kent, and their parents. Main outcome measure - Blood pressure measured by Doppler ultrasonography and sphygmomanometry. Results - Systolic blood pressure rose from a mean of 88.5 mm Hg at age 6 months to 96-2 mm Hg at 8 years measured with a 8 cm cuff and from 89.1 mm Hg at age 5 years to 94.3 mm Hg at age 10 years measured with a 12 cm cuff. The larger cuff gave blood pressure readings about 6 mm Hg lower. This effect was independent of body weight and arm circumference. Diastolic blood pressure rose from 57.8 mm Hg at 5 years to 61.8 mm Hg at 10 years (12 cm cuff). There was only about 1 mm Hg difference between sexes. Blood pressure was correlated with weight, weight adjusted for height, height, and arm circumference at all ages studied. The correlation coefficient of repeated yearly measurements increased steadily with age from 0.28 at 2 years to 0.59 at 10 years. The correlation coefficients between child's blood pressure and mother's average blood pressure increased from 0.1 at age 1 year to 0.23 at age 10. Conclusions - Blood pressure changes relatively little between the ages of 6 months and 10 years. Yet because of the increasing strength of between occasion and family correlations, children are more consistently occupying a specific part of the blood pressure distribution as they grow older. Studies in children should help determine why some adults have hypertension and others do not.