Linear dynamic features of ambulatory blood pressure in a population-based study

Background: The objective of the present study was to characterize inter-individual variation in traits that measure linear dynamic features of ambulatory blood pressure (BP) measurements that may be used in future population studies to investigate the relationships between variation in genetic and environmental factors that influence BP regulation and risk of hypertension, and among hypertensives, provide new insights into variation in risk of target organ damage. Design: We obtained ambulatory BP measurements every 10 min over a 24-h period in 199 healthy non-Hispanic Whites (84 females, 115 males) from Rochester, Minnesota, USA. Methods: We then used the autocorrelation function (ACF) to measure linear dynamic features of the daytime and night-time observations in females and males separately. Re-sampling procedures were used to test whether these individuals had significant linear dependencies. Results: We found that systolic and diastolic ambulatory BP measurements in our sample have statistically significant linear dependencies and that the ACFs are approximately normally distributed among individuals. In addition, we found that the distributions of the ACF traits among individuals are not significantly correlated with the mean of the ambulatory BP measurements, are different in men and women, and are different during the daytime versus the night-time. Conclusions: We conclude that ACF traits are different measures of BP than the mean that capture information about the biology of BP regulation reflected in the dynamics of a person's minute-to-minute and hour-to-hour BP phenotype. Studies of measures of linear dynamic features of BP are likely to offer new insights into the genetic and environmental factors that contribute to inter-individual variation in BP regulation and risk of future hypertension as well as new insights into the causes of variation in risk of target organ damage in individuals with established hypertension.