Tracking of 24-hour and casual blood pressure: a 1-year follow-up study in adolescents.

OBJECTIVE: Tracking of blood pressure begins in childhood but the relationship between casual blood pressure in childhood and adult levels is not strong enough to predict adult hypertension. The variability of blood pressure in children might suggest that 24 recordings would have less consistency than casual readings when repeated even a relatively short time later. This study compares the short-term tracking ability of casual versus 24-h blood pressure. DESIGN: An ambulatory blood pressure device was placed on 50 teenagers. Readings were taken at rest and the device was then worn for approximately 24 h, which included the schoolday. The protocol was repeated 1 year later. RESULTS: The correlation coefficient for systolic readings taken 1 year later were: 0.4 for casual, 0.6 for school, 0.6 for home, 0.5 for night-time and 0.8 for 24-h mean systolic blood pressures. When divided into upper and lower tertiles of systolic blood pressure the relationship between tertile ranking 1 year later was stronger for 24-h blood pressure than the casual readings. Casual diastolic pressure was more consistent than the 24-h mean diastolic measurement. CONCLUSIONS: In adolescents, in whom tracking of casual blood pressure has been shown to be poor, 24-h mean systolic blood pressure tracks better than any other time period and significantly better than the casual systolic readings. This study needs to be extended and the ability of 24-h blood pressure to track from childhood to adult life investigated.