Nocturnal blood pressure dip and morning blood pressure surge: A 24-hour ambulatory blood pressure monitoring study

Abstract

Abnormal nocturnal blood pressure (BP) dip as well as the morning BP surge have been found to be predictors of risk for cerebrovascular accidents (CVA). The purpose of this study was to investigate if there is a correlation between the nocturnal BP dip and the morning BP surge determined by ambulatory BP monitor. We studied 19 consecutive hypertensive patients referred to our hypertension clinic for the performance of ambulatory BP monitoring. There were 8 male and 11 female patients. Their ages ranged between 46 to 87 years of age (mean 65.2 ± 13 years). These patients were all taking BP medicines, but were not adequately controlled. There were 8 normal dippers and 11 abnormal dippers. The mean value of the dipping status was 7.2 ± 6.4 (SD) mmHg. The morning BP surge was calculated using the formula introduced by Kario et al in a recent communication. We determined the high morning systolic BP in the 2 hours following awakening. The low systolic BP was obtained from the average of the lower systolic BP during sleep and the immediate before and after systolic BP. The morning BP surge was obtained by the subtraction of the high morning systolic BP from the lower systolic BP. The mean value for the morning BP surge for this group of patients was 16.7 ± 13.1 (SD) mmHg. The calculated Pearson's coefficient of correlation was 0.644, the SE was 5 mmHg and this correlation was significant at the p=0.01 (2 tailed). We concluded from this study that abnormal nocturnal BP dip has a significant correlation with morning BP surge and is probably a co-contributor in the increased risk for cerebrovascular accidents. Further studies are needed in patients with significant risk factors for the production of CVAs to see if these variables, systolic nocturnal BP dip and morning systolic BP surge, are predictive for increased risk of cerebrovascular accidents.