Value of repeated blood pressure measurements in children--the Brompton study.

Systolic blood pressure were measured in 1797 infants aged 4 days and then repeated at 6 weeks, 6 months, 1 year and then yearly until 4 years of age. The mean pressure rose from 76 mm Hg at 4 days to 96 mm Hg at 6 weeks but did not vary appreciably between subsequent measurements. Serial correlation coefficients of blood pressure adjusted for weight and degree of consciousness were calculated, comparing measurements at each age. At ages under 1 year the correlation coefficients were relatively weak, though most were significant (r < 0.2). As the children grew older these serial correlations became stronger, so that the correlation coefficient in blood pressure between ages 3 and 4 years was 0.47. These observations suggest that "tracking" for blood pressure starts at about 1 year and is much stronger by 4 years. Taken in conjunction with the findings of other long-term follow-up studies in older children, this suggests that children develop blood pressures indicative of their adult values between 1 and 4 years.