The Multiscale Dynamics of Beat-to-Beat Blood Pressure Fluctuation Links to Functions in Older Adults

Abstract

BackgroundThe blood pressure (BP) is regulated by multiple neurophysiologic elements over multiple temporal scales. The multiscale dynamics of continuous beat-to-beat BP series, which can be characterized by “BP complexity”, may, thus, capture the subtle changes of those elements, and be associated with the level of functional status in older adults. We aimed to characterize the relationships between BP complexity and several important functions in older adults and to understand the underlying factors contributing to BP complexity.MethodA total of 400 older adults completed a series of clinical and functional assessments, a finger BP assessment of at least 10 min, and blood sample and vessel function tests. Their hypertensive characteristics, cognitive function, mobility, functional independence, blood composition, arterial stiffness, and endothelial function were assessed. The complexity of systolic (SBP) and diastolic (DBP) BP series was measured using multiscale entropy.ResultsWe observed that lower SBP and DBP complexity was significantly associated with poorer functional independence (β > 0.17, p < 0.005), cognitive function (β > 0.45, p = 0.01), and diminished mobility (β < −0.57, p < 0.003). Greater arterial stiffness (β < −0.48, p = 0.02), decreased endothelial function (β > 0.42, p < 0.03), and excessed level of blood lipids (p < 0.03) were the main contributors to BP complexity.ConclusionBlood pressure complexity is closely associated with the level of multiple functional statuses and cardiovascular health in older adults with and without hypertension, providing novel insights into the physiology underlying BP regulation. The findings suggest that this BP complexity metric would serve as a novel marker to help characterize and manage the functionalities in older adults.

The alterations in multiple neurophysiological procedures are associated with frailty phenotype in older adults

“…Following this idea, by uniquely quantifying the complex dynamics of vascular system using BP complexity, we here observed that lower BP complexity is significantly associated with greater odds of being pre-frail and frail. This is also consistent with our recent study showing that compared to robust, older adults in pre-frail and frail had significantly lower BP complexity, and more interestingly, such BP complexity mediated the relationship between arterial stiffness and frailty (Jiang et al, 2022a). Additionally, numerous studies showed that this complexity metric, which characterizing the dynamics of a given neurophysiological procedure [e.g., the heartbeat fluctuation (Toosizadeh et al, 2021)] over multiple scales of time or space, can better capture subtle changes in this system that cannot be appropriately captured by traditional single-scale measures (e.g., mean or variability) (Lipsitz, 2002;Thijssen et al, 2011;Manor and Lipsitz, 2013;Jiang et al, 2021Jiang et al, , 2022b.…”

“…We measured the complexity of beat-to-beat BP fluctuation (i.e., BP complexity), and the arterial stiffness using brachial-ankle pulse wave velocity (baPWV) ( Yamashina et al, 2002 ). In previous studies from our group and others, both BP complexity and baPWV were closely associated with the frailty status ( Amarasekera et al, 2021 ; Jiang et al, 2022a ).…”

“…Therefore, the dynamics of the beat-to-beat BP fluctuation is complex, and the complexity in BP fluctuation contains important information of the neurophysiology in vascular system. Studies have shown that the BP complexity, which can be quantified by using multiscale entropy (MSE) ( Costa et al, 2002 , 2005 ), is an appropriate marker to capture the subtle functional changes vascular system and closely associated with frailty ( Jiang et al, 2021 , 2022a , b ). We here followed the protocol that was used in the previous work to record the continuous beat-to-beat BP series of 10–15 min and quantified the complexity of systolic (SBP) and diastolic (DBP) BP using MSE.…”

“…Specifically, to obtain an appropriate estimate of entropy, the number of data points in the largest-scale coarse-grained series should at least be 10 m to 17 m ; therefore, the appropriate number on the largest scale would be 100∼289 when using m of 2. We thus chose to calculate the MSE over Scale 1 to 5 following our previous work ( Jiang et al, 2021 , 2022a , b ) and the well-established procedure ( Costa et al, 2005 ). The complexity of SBP and DBP was then defined as the averaged entropy across five scales, and lower averaged entropy reflected lower complexity.…”

Effects of endurance exercise on physiologic complexity of the hemodynamics in prefrontal cortex

“…Numerous studies have demonstrated that aging and/or age-related conditions often alter the multiscale regulation of the biophysiological system/procedures of humans, leading to the diminished capacity of the system to adapt to stressors or perturbations, which can be captured by a decreased physiologic complexity in the systems' output fluctuation. [49][50][51] On the other hand, evidence has also shown that such a loss of complexity is not obligatory, but it can be restored or improved via appropriate strategies. For example, Zhou et al 52 showed that applying subsensory vibratory random stimuli on foot soles can increase the complexity of the standing postural sway in older adults and such an increase of complexity is associated with the improvement of mobility.…”