Short-term and Mid-term Blood Pressure Variability and long-term Mortality: evidence from the Third National Health and Nutrition Examination Study

In considering the impact of blood-pressure variability on health outcomes, two methodological challenges arise: The presence of multiple timescales of variability that may act independently and interactively, and the fairly large stochastic uncertainty that is inevitable in estimates of individual variability based on modest numbers of observations. Here we present an application of Bayesian hierarchical modeling to the problem of estimating the effect of blood pressure (BP) variability on all-cause and cardiovascular mortality with two timescales - short-term variation among multiple measures at one visit, and medium-term variation between the measures at two visits several months apart. We use data from the Third National Health and Nutrition Examination Survey linked with up to 27 years of mortality follow-up. We find that medium-term systolic BP variability had a very significant predictive value for CV and all-cause mortality, around one-third as large as the well-established impact of mean systolic BP. Medium-term diastolic variability had an additional, though smaller, predictive effect. Short-term variability, on the other hand, had little or no measurable predictive value. The medium-term variability effect persisted when controlling for Framingham risk score.