Blood pressure variability and structural brain changes: a systematic review

Higher blood pressure variability during hospitalization is associated with lower cerebral white matter integrity in COVID-19 patients

BACKGROUND

High blood pressure variability (BPV) is associated with cerebrovascular damage and dementia, but it is unknown whether short-term BPV during hospitalization is also associated with cerebral white matter (WM) damage. We examined whether BPV, measured in-hospital using continuous monitoring, is associated with WM microstructural integrity in COVID-19 patients.

METHODS

We included hospitalized COVID-19 patients from the CORONavirus and Ischemic Stroke (CORONIS) study who underwent continuous vital signs monitoring using a wearable device during hospital admission and had MRI shortly after discharge. Systolic BPV was calculated as Average Real Variability (ARV) and Coefficient of Variation (CV) with 1-, 5- and 20-minute intervals. We used diffusion tensor imaging (DTI) to assess fractional anisotropy (FA) and peak width of skeletonized mean diffusivity (PSMD) as markers of WM integrity. Associations between BPV and WM integrity were examined with linear regression adjusted for age, mean systolic blood pressure, number of blood pressure measurements and type of respiratory support.

RESULTS

We included 47 COVID-19 patients (mean age: 59.6 years). Blood pressure was measured 6306 ± 4343 times per patient (median admission: 11 days [IQR 7.5-15.0]). Both higher ARV and CV were associated with lower WM microstructural integrity, reflected by lower FA (ARV: β=-0.40, p = 0.010; CV: β=-0.33, p = 0.026) and higher PSMD (CV: β = 0.28, p = 0.038) after adjustment for confounders. Correction for WM hyperintensities did not change these results.

CONCLUSIONS

High BPV during hospitalization is associated with lower WM integrity in COVID-19 patients, although causality needs to be demonstrated. Our findings need validation in hospitalized patients without COVID-19 to examine generalizability.

Beat-to-beat blood pressure variability, hippocampal atrophy, and memory impairment in older adults

Visit-to-visit blood pressure variability (BPV) predicts age-related hippocampal atrophy, neurodegeneration, and memory decline in older adults. Beat-to-beat BPV may represent a more reliable and efficient tool for prospective risk assessment, but it is unknown whether beat-to-beat BPV is similarly associated with hippocampal neurodegeneration, or with plasma markers of neuroaxonal/neuroglial injury. Independently living older adults without a history of dementia, stroke, or other major neurological disorders were recruited from the community (N = 104; age = 69.5 ± 6.7 (range 55-89); 63% female). Participants underwent continuous blood pressure monitoring, brain MRI, venipuncture, and cognitive testing over two visits. Hippocampal volumes, plasma neurofilament light, and glial fibrillary acidic protein levels were assessed. Beat-to-beat BPV was quantified as systolic blood pressure average real variability during 7-min of supine continuous blood pressure monitoring. The cross-sectional relationship between beat-to-beat BPV and hippocampal volumes, cognitive domain measures, and plasma biomarkers was assessed using multiple linear regression with adjustment for demographic covariates, vascular risk factors, and average systolic blood pressure. Elevated beat-to-beat BPV was associated with decreased left hippocampal volume (P = .008), increased plasma concentration of glial fibrillary acidic protein (P = .006), and decreased memory composite score (P = .02), independent of age, sex, average systolic blood pressure, total intracranial volume, and vascular risk factor burden. In summary, beat-to-beat BPV is independently associated with decreased left hippocampal volume, increased neuroglial injury, and worse memory ability. Findings are consistent with prior studies examining visit-to-visit BPV and suggest beat-to-beat BPV may be a useful marker of hemodynamic brain injury in older adults.

Hypertension and Cognitive Disorders

Systemic hypertension is possibly the most important modifiable risk factor for the development of cognitive decline, both for mild cognitive impairment (MCI) and dementia. For effective blood pressure (BP) control, it requires proper assessment, using brachial, central, and ambulatory measurements, and monitoring with a focus on different BP parameters. Different BP parameters like pulse pressure, mean arterial pressure, BP variability, and circadian parameters, like nondippers and early morning surge, should be considered in the evaluation for the risk of cognitive decline due to hypertension in middle age and older adults. Chronic hypertension causes vascular remodeling in the brain and leads to brain failure or cognitive decline. Achieving specific BP goals can improve clinical outcomes and possibly slow down cognitive decline for patients with comorbid hypertension and cognitive impairment.

Visit-to-visit blood pressure variability and progression of white matter hyperintensities over 14 years

Purpose: There is evidence that blood pressure variability (BPV) is associated with cerebral small vessel disease (SVD) and may therefore increase the risk of stroke and dementia. It remains unclear if BPV is associated with SVD progression over years. We examined whether visit-to-visit BPV is associated with white matter hyperintensity (WMH) progression over 14 years and MRI markers after 14 years.

Materials and methods: We included participants with SVD from the Radboud University Nijmegen Diffusion tensor Magnetic resonance-imaging Cohort (RUNDMC) who underwent baseline assessment in 2006 and follow-up in 2011, 2015 and 2020. BPV was calculated as coefficient of variation (CV) of BP at all visits. Association between WMH progression rates over 14 years and BPV was examined using linear-mixed effects (LME) model. Regression models were used to examine association between BPV and MRI markers at final visit in participants.

Results: A total of 199 participants (60.5 SD 6.6 years) who underwent four MRI scans and BP measurements were included, with mean follow-up of 13.7 (SD 0.5) years. Systolic BPV was associated with higher progression of WMH (β = 0.013, 95% CI 0.005 - 0.022) and higher risk of incident lacunes (OR: 1.10, 95% CI 1.01-1.21). There was no association between systolic BPV and grey and white matter volumes, Peak Skeleton of Mean Diffusivity (PSMD) or microbleed count after 13.7 years.

Conclusions: Visit-to-visit systolic BPV is associated with increased progression of WMH volumes and higher risk of incident lacunes over 14 years in participants with SVD. Future studies are needed to examine causality of this association.

Neural correlates of the revised reinforcement sensitivity theory: A cross-sectional structural neuroimaging study in middle-aged adults

The revised reinforcement sensitivity theory (RST) proposes that neurobiological systems control behavior: the fight-flight-freeze (FFFS) for avoidance of threat; behavioral approach/activation (BAS) for approach to rewards; and behavioral inhibition (BIS) for conflict resolution when avoidance and approach are possible. Neuroimaging studies have confirmed some theoretical associations between brain structures and the BAS and BIS; however, little representative population data are available for the FFFS. We investigated the neural correlates of the revised RST in a sample of 404 middle-aged adults (Mage = 47.18 (SD = 1.38); 54.5% female). Participants underwent structural magnetic resonance imaging and completed health questionnaires and the BIS/BAS/FFFS scales. We used multiple regression analyses to investigate the association between scale scores and volumes of a priori theoretically linked regions of interest while controlling for sex, age, intracranial volume, and cardio-metabolic variables; and conducted exploratory analyses on cortical thickness. The BIS was negatively associated with hippocampus laterality. At standard significance levels, the fear component of the FFFS was positively associated with anterior cingulate cortex; the BAS was positively associated with bilateral caudate; and the BIS was positively associated with posterior cingulate cortex volume. Furthermore, these neurobiological systems showed distinct patterns of association with cortical thickness though future work is needed. Our results showed that the neurobiological systems of the revised RST characterized in rodents can also be identified in the human brain.

Safety and feasibility of transcranial direct current stimulation in end-stage renal disease patients undergoing hemodialysis: an exploratory study

INTRODUCTION

Patients with end-stage renal disease often face a challenging routine of hemodialysis, dietary restrictions, and multiple medications, which can affect their hemodynamic function. Home-based, safe, and nonpharmacological approaches such as transcranial direct current stimulation (tDCS) should be combined with conventional treatment.

OBJECTIVE

To assess the safety and feasibility of tDCS on blood pressure and heart rate in patients with end-stage renal disease undergoing hemodialysis.

METHOD

This is a parallel, randomized, sham-controlled trial. Patients undergoing hemodialysis for more than three months were included. The patients received ten non-consecutive 2mA tDCS sessions on the primary motor cortex . Each session lasted 20 minutes. At baseline and after each of the ten sessions, blood pressure and heart rate of the patients were measured hourly for four hours.

RESULTS

Thirty patients were randomized to the active or sham group. The mean difference between the groups was calculated as the mean value of the sham group minus the mean value of the active group. Despite there were no statistical changes for all outcomes considering all 10 sessions, we found differences between groups for systolic -10.93 (-29.1;7.2), diastolic -3.63 (-12.4; 5.1), and mean blood pressure -6.0 (-16.3; 4.2) and hear rate 2.26 (-2.5; 7.1). No serious adverse events were found. The active group showed higher blood pressure values at all points, while heart rate was lower in the active group.

CONCLUSION

tDCS is safe and feasible for patients with end-stage renal disease undergoing hemodialysis. Future studies should investigate whether tDCS could potentially induce a hypotensive protective effect during hemodialysis.

Gray matter volume mediates the association of long-term blood pressure variability with cognitive function in an adult population

INTRODUCTION

We delineated the associations among long-term blood pressure variability (BPV), brain structure, and cognitive function.

METHODS

We included 1254 adult participants from the Kailuan study. BPV was calculated from 2006 to 2020. Brain magnetic resonance imaging (MRI) and Montreal Cognitive Assessment (MoCA) were conducted in 2020.

RESULTS

Higher systolic BPV (SBPV) and diastolic BPV (DBPV) were associated with lower total and frontal gray matter (GM) volume, and higher SBPV was associated with lower temporal GM volume. Elevated DBPV was associated with lower volume of total brain and parietal GM, and higher white matter hyperintensity (WMH) volume. Higher SBPV and DBPV were associated with lower MoCA scores. Decreased total and regional GM volume and increased WMH volume were associated with lower MoCA scores. The association between SBPV and cognitive function was mediated by total, frontal, and temporal GM volume.

DISCUSSION

GM volume may play key roles in the association between SBPV and cognitive function.

HIGHLIGHTS

SBPV and DBPV were negatively associated with total and regional brain volume. SBPV and DBPV were negatively associated with cognitive function. Decreased brain volume was associated with cognitive decline. GM volume mediated the negative association between SBPV and cognitive function.

Under pressure: A systematic review of the association between blood pressure variability with depression and anxiety

Blood pressure variability (BPV) impacts brain health by influencing brain structure and cerebrovascular pathologies, though the mechanisms are poorly understood. Changes in the cerebrovasculature may lead to late-onset depression, cognitive impairment, and dementia, however the relationship between BPV with depression and anxiety remains unclear, due to methodological differences and inconsistencies in past research. This review aims to clarify the association between BPV with depression and anxiety in adults to inform understandings of the mechanisms implicating BPV in cognitive health. A systematic search from inception through to January 2024 was performed on Embase, PubMed, PsycINFO, and Web of Science. Studies that assessed BPV quantified by beat-to-beat, 24-hour, or visit-to-visit were eligible if the standardised assessment of depression and/or anxiety were reported as a linear association, or mean differences across control and affect groups. A total of 14 articles reporting on 13 samples and N = 5055 persons met the inclusion criteria (median female proportion = 61 %, range 0 % - 76 %). A meta-analysis was not possible due to methodological heterogeneity in BPV measurements and metrics across studies. Mixed results were observed across depression studies with inconsistencies and variation in the direction, strength of association, and BPV metric. There was weak evidence from only three studies to support a linear association between systolic coefficient of variation and anxiety. Collectively, the findings contribute to understanding the association between BPV and brain health, suggesting that any relationship between BPV and brain structures critical for cognitive function are independent of depression and only modestly implicate anxiety.

Short-term blood pressure variability and brain functional network connectivity in older adults

Background

Blood pressure variability is increasingly linked with cerebrovascular disease and Alzheimer's disease, independent of mean blood pressure levels. Elevated blood pressure variability is also associated with attenuated cerebrovascular reactivity, which may have implications for functional hyperemia underpinning brain network connectivity. It remains unclear whether blood pressure variability is related to functional network connectivity. We examined relationships between beat-to-beat blood pressure variability and functional connectivity in brain networks vulnerable to aging and Alzheimer's disease.

Methods

53 community-dwelling older adults (mean [SD] age = 69.9 [7.5] years, 62.3% female) without history of dementia or clinical stroke underwent continuous blood pressure monitoring and resting state fMRI scan. Blood pressure variability was calculated as variability independent of mean. Functional connectivity was determined by resting state fMRI for several brain networks: default, salience, dorsal attention, fronto-parietal, and language. Multiple linear regression examined relationships between short-term blood pressure variability and functional network connectivity.

Results

Elevated short-term blood pressure variability was associated with lower functional connectivity in the default network (systolic: standardized ß = -0.30 [95% CI -0.59, -0.01], p = .04). There were no significant associations between blood pressure variability and connectivity in other functional networks or between mean blood pressure and functional connectivity in any network.

Discussion

Older adults with elevated short-term blood pressure variability exhibit lower resting state functional connectivity in the default network. Findings support the role of blood pressure variability in neurovascular dysfunction and Alzheimer's disease. Blood pressure variability may represent an understudied early vascular risk factor for neurovascular dysfunction relevant to Alzheimer's disease, with potential therapeutic implications.

Nocturnal blood pressure dipping, blood pressure variability, and cognitive function in early and middle-aged adults

Higher nighttime blood pressure (BP), less BP dipping, and higher BP variability have been linked with worse cognitive function in the elderly. The goal of this study is to explore whether this relationship already exists in early and middle adulthood. We further examined whether ethnic differences between African Americans and European Americans in BP parameters can explain ethnic differences in cognitive function. 24-h ambulatory BP monitoring and cognitive function were obtained from 390 participants (average age: 37.2 years with a range of 25-50; 54.9% African Americans; 63.6% females). We observed that higher nighttime BP, decreased dipping, and higher variability were significantly associated with lower scores on the Picture Sequence Memory Test. Significant negative associations between variability and overall composite scores were also observed. No significant associations between average 24-h or daytime BP and cognitive function were observed. Ethnic differences in nighttime diastolic pressures and dipping can explain 6.81% to 10.8% of the ethnicity difference in the score of the Picture Sequence Memory Test (ps < .05). This study suggests that the associations of nighttime BP, dipping, and variability with cognitive function already exist in young and middle-aged adults. Ethnic differences in nighttime BP and dipping can at least partially explain ethnic differences in cognitive function. The stronger association of these parameters with cognitive function than daytime or average BP in this age range raises the importance of using ambulatory BP monitoring for more precise detection of abnormal BP patterns in young adulthood.

Effect of blood pressure variability on hypertensive retinopathy

PURPOSE

This study intends to investigate the correlation between blood pressure variability (BPV) levels and the use of optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) to measure retinal microvasculature in hypertensive patients.

METHODS

All individuals in the study had 24-hour ambulatory blood pressure monitoring and bilateral OCT and OCTA exams, and only data from the right eye were analyzed statistically.

RESULTS

The study included 170 individuals, with 60 in the control group. The experimental group was separated into two groups based on the average real variability (ARV) median, with 55 in the low ARV group and 55 in the high ARV group. The mean thicknesses of the Retinal Nerve Fiber Layer (RNFL), internal limiting membrane-retinal pigment epithelial cell layer (ILM-RPE), vessel density (VD), and perfusion density (PD) in the high-ARV group were substantially lower in the low-ARV and control groups (p＜0.05). Multiple linear regression analysis revealed that disease duration, age, and 24 h diastolic standard deviation all affected RNFL mean thickness (p＜0.05). VD and PD were influenced by disease duration, systolic-ARV, daytime systolic blood pressure, intraocular pressure(IOP), and best-corrected visual acuity (BCVA) (p＜0.05). And the change in VD was connected to best-corrected visual acuity.

CONCLUSION

Hypertensive retinopathy is related to BPV. In clinical practice, we can assess the degree of BPV and retinopathy in hypertensive patients to track the progression of hypertension-mediated organ damage (HMOD). Correction of BPV may help treat or postpone the progression of HOMD.

Cross-sectional associations between short and mid-term blood pressure variability, cognition, and vascular stiffness in older adults

Background

High blood pressure variability (BPV), particularly in older age, appears to be an independent risk factor for incident dementia. The current study aimed to investigate the association between different BPV measures (short- and mid-term BPV including circadian patterns) and cognitive functioning as well as vascular stiffness measures to better understand the role that BPV plays in cognitive impairment.

Methods

70 older adults (60-80-year-olds) without dementia completed a cognitive test battery and had their blood pressure (BP) assessed via a 24-hour ambulatory BP monitor (divided into sleep and wake for short-term BPV) and 4-day morning and evening home-based BP monitor (for day-to-day BPV). Arterial stiffness was evaluated via pulse wave analysis and pulse wave velocity (PWV) and cerebrovascular pulsatility was assessed via transcranial doppler sonography of the middle cerebral arteries.

Results

High systolic as well as diastolic short- and mid-term BPV were associated with poorer cognitive functioning, independent of the mean BP. Higher short-term BPV was associated with poorer attention and psychomotor speed, whilst day-to-day BPV was negatively linked with executive functioning. Circadian BP patterns (dipping and morning BP surge) showed no significant relationships with cognition after adjusting for covariates. Higher systolic short-term BPV was associated with higher arterial stiffness (PWV) and higher diastolic day-to-day BPV was linked with lower arterial stiffness. No significant associations between BPV measures and cerebrovascular pulsatility were present.

Conclusion

High BPV, independently of the mean BP, is associated with lower cognitive performance and increased arterial stiffness in older adults without clinically-relevant cognitive impairment. This highlights the role of systolic and diastolic BPV as a potential early clinical marker for cognitive impairment.

The relationship between long-term blood pressure variability and cortical thickness in older adults

High blood pressure variability (BPV) is a risk factor for cognitive decline and dementia, but its association with cortical thickness is not well understood. Here we use a topographical approach, to assess links between long-term BPV and cortical thickness in 478 (54% men at baseline) community dwelling older adults (70-88 years) from the ASPirin in Reducing Events in the Elderly NEURO sub-study. BPV was measured as average real variability, based on annual visits across three years. Higher diastolic BPV was significantly associated with reduced cortical thickness in multiple areas, including temporal (banks of the superior temporal sulcus), parietal (supramarginal gyrus, post-central gyrus), and posterior frontal areas (pre-central gyrus, caudal middle frontal gyrus), while controlling for mean BP. Higher diastolic BPV was associated with faster progression of cortical thinning across the three years. Diastolic BPV is an important predictor of cortical thickness, and trajectory of cortical thickness, independent of mean blood pressure. This finding suggests an important biological link in the relationship between BPV and cognitive decline in older age.

Blood pressure variability in Parkinson's Disease patients - Case control study

Introduction

The cardiovascular risk of Parkinson's Disease (PD) patients is uncertain. Blood pressure variability (BPV) has been associated with cardiovascular and mortality outcomes. We aimed to evaluate blood pressure variability, as a marker of cardiovascular risk, in patients with PD and matched community controls.

Methods

Cross-sectional case-control study was performed. All subjects included in the analysis were clinically evaluated and performed a 24 h ambulatory blood pressure monitoring. BPV was assessed using standard deviations (SDs) of the systolic blood pressure (SBP) and diastolic blood pressure (DBP) for each period - 24 h, daytime, and night-time.

Results

The study included 204 participants, 102 in each group. Mean age 66 years old and 59% man. Most PD patients presented mild symptoms (mean Hoehn&Yahr 2.04). Daytime BPV was significantly higher in PD patients (SD SBP 14.1 mmHg vs 12.96 mmHg and SD DBP 9.39 mmHg vs 8.29 mmHg), but 24 h and night-time BPV were non-significantly increased. PD patients present non-significant higher night-time SBP (114 mmHg vs 110 mmHg) as well as higher frequency of non-dippers or reverse dippers BP profiles (51% vs 36%).

Conclusion

Our exploratory study suggests that PD patients may present a higher blood pressure variability, which may translate in an increased cardiovascular risk. However, further studies are needed to confirm this hypothesis and causality.

Digital Cognitive Biomarker for Mild Cognitive Impairments and Dementia: A Systematic Review

The dementia population is increasing as the world's population is growing older. The current systematic review aims to identify digital cognitive biomarkers from computerized tests for detecting dementia and its risk state of mild cognitive impairment (MCI), and to evaluate the diagnostic performance of digital cognitive biomarkers. A literature search was performed in three databases, and supplemented by a Google search for names of previously identified computerized tests. Computerized tests were categorized into five types, including memory tests, test batteries, other single/multiple cognitive tests, handwriting/drawing tests, and daily living tasks and serious games. Results showed that 78 studies were eligible. Around 90% of the included studies were rated as high quality based on the Newcastle-Ottawa Scale (NOS). Most of the digital cognitive biomarkers achieved comparable or even better diagnostic performance than traditional paper-and-pencil tests. Moderate to large group differences were consistently observed in cognitive outcomes related to memory and executive functions, as well as some novel outcomes measured by handwriting/drawing tests, daily living tasks, and serious games. These outcomes have the potential to be sensitive digital cognitive biomarkers for MCI and dementia. Therefore, digital cognitive biomarkers can be a sensitive and promising clinical tool for detecting MCI and dementia.