Visit-to-Visit Blood Pressure Variability and CSF Alzheimer Disease Biomarkers in Cognitively Unimpaired and Mildly Impaired Older Adults

Longitudinal trajectories of Alzheimer's disease CSF biomarkers and blood pressure in cognitively healthy subjects

INTRODUCTION

We examined whether hypertension (HTN) was associated with Alzheimer's disease-related biomarkers in cerebrospinal fluid (CSF) and how changes in blood pressure (BP) related to changes in CSF biomarkers over time.

METHODS

A longitudinal observation of cognitively healthy normotensive subjects (n = 134, BP < 140/90, with no antihypertensive medication), controlled HTN (n = 36, BP < 140/90, taking antihypertensive medication), and 35 subjects with uncontrolled HTN (BP ≥ 140/90). The follow-up range was 0.5to15.6 years.

RESULTS

Total tau (T-tau) and phospho-tau181 (P-tau 181) increased in all but controlled HTN subjects (group×time interaction: p < 0.05 for both), but no significant Aβ42 changes were seen. Significant BP reduction was observed in uncontrolled HTN, and it was related to increase in T-tau (p = 0.001) and P-tau 181 (p < 0.001).

DISCUSSION

Longitudinal increases in T-tau and P-tau 181 were observed in most subjects; however, only uncontrolled HTN had both markers increase alongside BP reductions. We speculate cumulative vascular injury renders the brain susceptible to relative hypoperfusion with BP reduction.

HIGHLIGHTS

Over the course of the study, participants with uncontrolled HTN at baseline showed greater accumulation of CSF total tau and phospho-tau181 (P-tau 181) than subjects with normal BP or with controlled HTN. In the group with uncontrolled HTN, increases in total tau and P-tau 181 coincided with reduction in BP. We believe this highlights the role of HTN in vascular injury and suggests decline in cerebral perfusion resulting in increased biomarker concentrations in CSF. Medication use was the main factor differentiating controlled from uncontrolled HTN, indicating that earlier treatment was beneficial for preventing accumulations of pathology.

Potential role of blood pressure variability and plasma neurofilament light in the mechanism of comorbidity between Alzheimer's disease and cerebral small vessel disease

INTRODUCTION

Long-term blood pressure variability (BPV) and plasma neurofilament light (pNfL) have been identified as potential biomarkers for Alzheimer's disease (AD) and cerebral small vessel disease (CSVD). However, the relationship between BPV, pNfL, and their association with the comorbidity of AD and CSVD remains unknown.

METHODS

Participants with normal cognition and mild cognitive impairment from the Alzheimer's Disease Neuroimaging Initiative study were included in the data analysis. Linear mixed-effects regression models and causal mediation analyses were conducted to investigate the relationship among BPV, pNfL, comorbidity-related brain structural changes (hippocampal atrophy and white matter hyperintensities [WMH]), and cognitive function.

RESULTS

BPV was associated with pNfL, volumes of hippocampus and WMH, and cognition. pNfL mediated the effects of BPV on brain structural changes and cognition.

DISCUSSION

Our findings suggest a potential role of BPV and pNfL in the mechanism of comorbidity between AD and CSVD, underscoring the importance of BPV intervention in the general population.

HIGHLIGHTS

Individuals with both Alzheimer's disease (AD) and cerebral small vessel disease (CSVD) pathologies had elevated blood pressure variability (BPV) and plasma neurofilament light (pNfL). The association between different components of BPV and brain structural changes may vary. BPV was associated with pNfL levels independent of average blood pressure. pNfL mediated the effects of BPV on comorbidity-related brain structural changes and cognitive performance.

Central autonomic network dysfunction and plasma Alzheimer's disease biomarkers in older adults

BACKGROUND

Higher order regulation of autonomic function is maintained by the coordinated activity of specific cortical and subcortical brain regions, collectively referred to as the central autonomic network (CAN). Autonomic changes are frequently observed in Alzheimer's disease (AD) and dementia, but no studies to date have investigated whether plasma AD biomarkers are associated with CAN functional connectivity changes in at risk older adults.

METHODS

Independently living older adults (N = 122) without major neurological or psychiatric disorder were recruited from the community. Participants underwent resting-state brain fMRI and a CAN network derived from a voxel-based meta-analysis was applied for overall, sympathetic, and parasympathetic CAN connectivity using the CONN Functional Toolbox. Sensorimotor network connectivity was studied as a negative control. Plasma levels of amyloid (Aβ42, Aβ40), neurofilament light chain (NfL), and glial fibrillary acidic protein (GFAP) were assessed using digital immunoassay. The relationship between plasma AD biomarkers and within-network functional connectivity was studied using multiple linear regression adjusted for demographic covariates and Apolipoprotein E (APOE) genotype. Interactive effects with APOE4 carrier status were also assessed.

RESULTS

All autonomic networks were positively associated with Aβ42/40 ratio and remained so after adjustment for age, sex, and APOE4 carrier status. Overall and parasympathetic networks were negatively associated with GFAP. The relationship between the parasympathetic CAN and GFAP was moderated by APOE4 carrier status, wherein APOE4 carriers with low parasympathetic CAN connectivity displayed the highest plasma GFAP concentrations (B = 910.00, P = .004). Sensorimotor connectivity was not associated with any plasma AD biomarkers, as expected.

CONCLUSION

The present study findings suggest that CAN function is associated with plasma AD biomarker levels. Specifically, lower CAN functional connectivity is associated with decreased plasma Aβ42/40, indicative of cerebral amyloidosis, and increased plasma GFAP in APOE4 carriers at risk for AD. These findings could suggest higher order autonomic and parasympathetic dysfunction in very early-stage AD, which may have clinical implications.

The interactive effect of intra-beat and inter-beat blood pressure variability on neurodegeneration in older adults

Blood pressure variability (BPV) and arterial stiffness are age-related hemodynamic risk factors for neurodegenerative disease, but it remains unclear whether they exert independent or interactive effects on brain health. When combined with high inter-beat BPV, increased intra-beat BPV indicative of arterial stiffness could convey greater pressure wave fluctuations deeper into the cerebrovasculature, exacerbating neurodegeneration. This interactive effect was studied in older adults using multiple markers of neurodegeneration, including medial temporal lobe (MTL) volume, plasma neurofilament light (NfL) and glial fibrillary acidic protein (GFAP). Older adults (N=105) without major neurological or systemic disease were recruited and underwent brain MRI and continuous BP monitoring to quantify inter-beat BPV through systolic average real variability (ARV) and intra-beat variability through arterial stiffness index (ASI). Plasma NfL and GFAP were assessed. The interactive effect of ARV and ASI on MTL atrophy, plasma NfL, and GFAP was studied using hierarchical linear regression. Voxel-based morphometry (VBM) was used to confirm region-of-interest analysis findings. The interaction between higher ARV and higher ASI was significantly associated with left-sided MTL atrophy in both the region-of-interest and false discovery rate-corrected VBM analysis. The interactive effect was also significantly associated with increased plasma NfL, but not GFAP. The interaction between higher ARV and higher ASI is independently associated with increased neurodegenerative markers, including MTL atrophy and plasma NfL, in independently living older adults. Findings could suggest the increased risk for neurodegeneration associated with higher inter-beat BPV may be compounded by increased intra-beat variability due to arterial stiffness.

Hypertension, Neurodegeneration, and Cognitive Decline

Elevated blood pressure is a well-established risk factor for age-related cognitive decline. Long linked to cognitive impairment on vascular bases, increasing evidence suggests a potential association of hypertension with the neurodegenerative pathology underlying Alzheimer disease. Hypertension is well known to disrupt the structural and functional integrity of the cerebral vasculature. However, the mechanisms by which these alterations lead to brain damage, enhance Alzheimer pathology, and promote cognitive impairment remain to be established. Furthermore, critical questions concerning whether lowering blood pressure by antihypertensive medications prevents cognitive impairment have not been answered. Recent developments in neurovascular biology, brain imaging, and epidemiology, as well as new clinical trials, have provided insights into these critical issues. In particular, clinical and basic findings on the link between neurovascular dysfunction and the pathobiology of neurodegeneration have shed new light on the overlap between vascular and Alzheimer pathology. In this review, we will examine the progress made in the relationship between hypertension and cognitive impairment and, after a critical evaluation of the evidence, attempt to identify remaining knowledge gaps and future research directions that may advance our understanding of one of the leading health challenges of our time.

Amyloid-β and Phosphorylated Tau are the Key Biomarkers and Predictors of Alzheimer's Disease

Alzheimer's disease (AD) is a age-related neurodegenerative disease and is a major public health concern both in Texas, US and Worldwide. This neurodegenerative disease is mainly characterized by amyloid-beta (Aβ) and phosphorylated Tau (p-Tau) accumulation in the brains of patients with AD and increasing evidence suggests that these are key biomarkers in AD. Both Aβ and p-tau can be detected through various imaging techniques (such as positron emission tomography, PET) and cerebrospinal fluid (CSF) analysis. The presence of these biomarkers in individuals, who are asymptomatic or have mild cognitive impairment can indicate an increased risk of developing AD in the future. Furthermore, the combination of Aβ and p-tau biomarkers is often used for more accurate diagnosis and prediction of AD progression. Along with AD being a neurodegenerative disease, it is associated with other chronic conditions such as cardiovascular disease, obesity, depression, and diabetes because studies have shown that these comorbid conditions make people more vulnerable to AD. In the first part of this review, we discuss that biofluid-based biomarkers such as Aβ, p-Tau in cerebrospinal fluid (CSF) and Aβ & p-Tau in plasma could be used as an alternative sensitive technique to diagnose AD. In the second part, we discuss the underlying molecular mechanisms of chronic conditions linked with AD and how they affect the patients in clinical care.

Reliability of beat-to-beat blood pressure variability in older adults

Blood pressure variability (BPV) is emerging as an important risk factor across numerous disease states, including cerebrovascular and neurodegenerative disease in older adults. However, there is no current consensus regarding specific use cases for the numerous available BPV metrics. There is also little published data supporting the ability to reliably measure BPV across metrics in older adults. BPV metrics were derived from continuous beat-to-beat blood pressure monitoring data. Two sequential 7-minute waveforms were analyzed. Absolute and relative reliability testing was performed. Differences between antihypertensive medication users and non-users on BPV metric reliability was also assessed. All sequence and dispersion based BPV metrics displayed good test-retest reliability. A measure of BP instability displayed only moderate reliability. Systolic and diastolic average real variability displayed the highest levels of reliability at ICC= .87 and .82 respectively. Additionally, systolic average real variability was the most reliable metric in both the antihypertensive use group, and the no antihypertensive use group. Beat-to-beat dispersion and sequence-based metrics of BPV can be reliably obtained from older adults using noninvasive continuous blood pressure monitoring. Average real variability may be the most reliable and specific beat-to-beat blood pressure variability metric due to its decreased susceptibility to outliers and low frequency blood pressure oscillations.

Beyond Hypertension: Examining Variable Blood Pressure's Role in Cognition and Brain Structure

Importance

Hypertension is a known risk factor for cognitive decline and structural brain changes in aging and dementia. In addition to high blood pressure (BP), individuals may also experience variable BP, meaning that their BP fluctuates between normal and high. It is currently unclear what the effects of variable BP are on cognition and brain structure.

Objective

To investigate the influence of BP on cognition and brain structure in older adults.

Design Setting and Participants

This longitudinal cohort study included data from the Rush Alzheimer's Disease Center Research Resource Sharing Hub (RUSH) and the Alzheimer's Disease Neuroimaging Initiative (ADNI). Participants from the two studies were included if they had BP measurements and either cognitive scores or MRI scans from at least one visit.

Main Outcomes and Measures

Longitudinal gray matter, white matter, white matter hyperintensity volumes, postmortem neuropathology information, as well as cognitive test scores.

Results

A total of 4606 participants (3429 females, mean age = 76.8) with 32776 follow-ups (mean = 7 years) from RUSH and 2114 participants (1132 females, mean age = 73.3) with 9827 follow-ups (mean = 3 years) from ADNI were included in this study. Participants were divided into one of three groups: 1) normal BP, high BP, or variable BP. Older adults with variable BP exhibited the highest rate of cognitive decline followed by high BP and then normal BP. Increased GM volume loss and WMH burden was also observed in variable BP compared to high and normal BP. With respect to post-mortem neuropathology, both variable and high BP had increased severities compared to normal BP. Importantly, results were consistent across the RUSH and ADNI participants, supporting the generalizability of the findings.

Conclusion and Relevance

Limited research has examined the long-term impact of variable BP on cognition and brain structure. These findings show the importance that both high and variable BP have on cognitive decline and structural brain changes. Structural damages caused by variable BP may reduce resilience to future dementia-related pathology and increased risk of dementia. Improved treatment and management of variable BP may help reduce cognitive decline in the older adult population.

Blood Pressure Variability and Plasma Alzheimer's Disease Biomarkers in the SPRINT Trial

Background

Recent observational studies suggest higher blood pressure (BP) variability (BPV) is associated with Alzheimer's disease (AD) biomarkers amyloid-beta (Aβ) and tau. Less is known about relationships in interventional cohorts with strictly controlled mean BP levels.

Objective

Investigate the longitudinal relationship between BPV and change in plasma AD biomarkers under standard versus intensive BP treatment.

Methods

In this post hoc analysis of the SPRINT trial, 457 participants (n = 206 in standard group, n = 251 in intensive group) underwent repeated BP measurement between baseline and 12-months follow-up, and venipuncture at baseline and median (IQR) 3.5 (3.0-4.0) years later to determine plasma AD biomarkers total tau and Aβ1-42:Aβ1-40 ratio. BPV was calculated as tertiles of variability independent of mean. Linear mixed models investigated the effect of BPV×time on AD biomarker levels.

Results

Higher BPV was associated with increased levels of total tau in the standard group (β [95% CI] 1st versus 3rd tertiles of BPV: 0.21 [0.02, 0.41], p = 0.035), but not in the intensive group (β [95% CI] 1st versus 3rd tertiles of BPV: -0.02 [-0.19, 0.16], p = 0.843). BPV was not associated with Aβ 1-42:Aβ 1-40 ratio in either group. Mean BP was not associated with biomarkers.

Conclusions

Higher BPV was associated with increased plasma total tau under standard BP treatment. Findings add new evidence to prior observational work linking BPV to AD pathophysiology and suggest that, despite strict control of mean BP, BPV remains a risk for pathophysiological change underlying risk for AD.

Blood Pressure Variability and Plasma Biomarkers of Neuronal Injury and Alzheimer's Disease: A Clinic-Based Study of Patients with Diseases Along the Heart-Brain Axis

 Higher blood pressure variability (BPV) predisposes to cognitive decline. To investigate underlying mechanisms, we measured 24-h ambulatory BPV, nocturnal dipping and orthostatic hypotension in 518 participants with vascular cognitive impairment, carotid occlusive disease, heart failure, or reference participants. We determined cross-sectional associations between BPV indices and plasma biomarkers of neuronal injury (neurofilament light chain) and Alzheimer's disease (phosphorylated-tau-181 and Aβ42/Aβ40). None of the BPV indices were significantly associated with any of the biomarkers. Hence, in patients with diseases along the heart-brain axis, we found no evidence for an association between BPV and selected markers of neuronal injury or Alzheimer's disease.

Association between the blood pressure variability and cognitive decline in Parkinson's disease

OBJECTIVES

High visit-to-visit blood pressure variability (BPV) was found to be associated with cognitive decline in the elderly. This study aimed to investigate the impact of visit-to-visit BPV on cognition in patients with early-stage Parkinson's disease (PD).

DESIGN

This is a retrospective analysis of a prospective cohort.

SETTING AND PARTICIPANTS

A total of 297 patients with early-stage PD (103 mild cognitive impairments [PD-MCI] and 194 normal cognitions [PD-NC] at baseline) were included from the Parkinson's Progression Markers Initiative study.

METHODS

Variation independent of mean (VIM) of the first year was used as the indicator of BPV. The Montreal Cognitive Assessment (MoCA) was used to assess global cognition. Patients were divided into PD-MCI and PD-NC according to the MoCA score at baseline. Longitudinal cerebrospinal fluid (Aβ-42, Aβ, α-synuclein, neurofilament light protein, tau phosphorylated at the threonine 181 position, total tau, glial fibrillary acidic protein) and serum (neurofilament light protein) biomarkers were assessed. The Bayesian linear growth model was used to evaluate the relationship between baseline BPV and the rate of change in cognition and biomarkers.

RESULTS

Higher systolic VIM of the first year was related to a greater rate of decline in MoCA score in the following years in PD-MCI (β = -.15 [95% CI -.29, -.01]). No association was found between BPV and biomarkers.

CONCLUSION AND IMPLICATIONS

Higher systolic VIM predicted a steeper decline in cognitive tests in PD-MCI independently from the mean value of blood pressure, orthostatic hypotension, and supine hypertension.

Short-term blood pressure variability is inversely related to regional amplitude of low frequency fluctuations in older and younger adults

Blood pressure variability (BPV), independent of mean blood pressure levels, is associated with cerebrovascular disease burden on MRI and postmortem evaluation. However, less is known about relationships with markers of cerebrovascular dysfunction, such as diminished spontaneous brain activity as measured by the amplitude of low frequency fluctuations (ALFF), especially in brain regions with vascular and neuronal vulnerability in aging. We investigated the relationship between short-term BPV and concurrent regional ALFF from resting state fMRI in a sample of community-dwelling older adults (n = 44) and healthy younger adults (n = 49). In older adults, elevated systolic BPV was associated with lower ALFF in widespread medial temporal regions and the anterior cingulate cortex. Higher systolic BPV in younger adults was also related to lower ALFF in the medial temporal lobe, albeit in fewer subregions, and the amygdala. There were no significant associations between systolic BPV and ALFF across the right/left whole brain or in the insular cortex in either group. Findings suggest a possible regional vulnerability to cerebrovascular dysfunction and short-term fluctuations in blood pressure. BPV may be an understudied risk factor for cerebrovascular changes in aging.

Blood Pressure Variability and Cerebral Perfusion Decline: A Post Hoc Analysis of the SPRINT MIND Trial

Background Blood pressure variability (BPV) is predictive of cerebrovascular disease and dementia, possibly though cerebral hypoperfusion. Higher BPV is associated with cerebral blood flow (CBF) decline in observational cohorts, but relationships in samples with strictly controlled blood pressure remain understudied. We investigated whether BPV relates to change in CBF in the context of intensive versus standard antihypertensive treatment. Methods and Results In this post hoc analysis of the SPRINT MIND (Systolic Blood Pressure Intervention Trial-Memory and Cognition in Decreased Hypertension) trial, 289 participants (mean, 67.6 [7.6 SD] years, 38.8% women) underwent 4 blood pressure measurements over a 9-month period after treatment randomization (intensive versus standard) and pseudo-continuous arterial spin labeling magnetic resonance imaging at baseline and ≈4-year follow-up. BPV was calculated as tertiles of variability independent of mean. CBF was determined for whole brain, gray matter, white matter, hippocampus, parahippocampal gyrus, and entorhinal cortex. Linear mixed models examined relationships between BPV and change in CBF under intensive versus standard antihypertensive treatment. Higher BPV in the standard treatment group was associated with CBF decline in all regions (ß comparing the first versus third tertiles of BPV in whole brain: -0.09 [95% CI, -0.17 to -0.01]; P=0.03), especially in medial temporal regions. In the intensive treatment group, elevated BPV was related to CBF decline only in the hippocampus (ß, -0.10 [95% CI, -0.18, -0.01]; P=0.03). Conclusions Elevated BPV is associated with CBF decline, especially under standard blood pressure-lowering strategies. Relationships were particularly robust in medial temporal regions, consistent with prior work using observational cohorts. Findings highlight the possibility that BPV remains a risk for CBF decline even in individuals with strictly controlled mean blood pressure levels. Registration URL: http://clinicaltrials.gov. Identifier: NCT01206062.

The impact of blood pressure variability on cognition: current limitations and new advances

Dementia is the most common neurodegenerative disease in the aging population. Emerging evidence indicates that blood pressure (BP) variability is correlated with cognitive impairment and dementia independent of mean BP levels. The state-of-the-art review summarizes the latest evidence regarding the impact of BP variability on cognition in cognitively intact populations, patients with mild cognitive impairment, and different dementia types, focusing on the important confounding factors and new advances. This review also summarizes the potential mechanisms underlying the relationship between BP variability and cognitive impairment, and dementia, briefly discussing sex differences in the relationship. At last, current limitations and future perspectives are discussed to optimize BP management in preventing cognitive impairment and dementia.

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 and Cognitive Decline: A Post Hoc Analysis of the SPRINT MIND Trial

BACKGROUND

Blood pressure (BP) variability (BPV) is an emerging risk factor for cognitive impairment and dementia, but relationships with cognition in the context of antihypertensive strategies remain unclear. We examined whether visit-to-visit BPV relates to cognitive change based on antihypertensive treatment type.

METHODS

In this post hoc analysis of the SPRINT MIND trial, 2,348 participants underwent 4 BP measurements over a 9-month period after treatment randomization (standard vs. intensive BP lowering) and ≥ 1 neuropsychological evaluation thereafter. BPV was calculated as tertiles of BP SD. Participants underwent cognitive testing at baseline and every 2 years during the planned 4-year follow-up. Cognitive composite scores were calculated for global cognition, memory, language, executive function, and processing speed. Linear mixed models investigated relationships between BPV, antihypertensive treatment group, and time on cognitive composite scores.

RESULTS

Elevated BPV was associated with the fastest decline in processing speed (ß = -.07 [95% CI -.12, -.01]; P = 0.02) and executive function (ß = -.08 [95% CI -.16, -.006]; P = 0.03) in the standard treatment group only. BPV was not related to cognitive change in the intensive treatment group. Mean/minimum/maximum BP was not associated with cognitive composite scores over time in either antihypertensive treatment group.

CONCLUSIONS

Elevated BPV remains a risk for cognitive decline despite strictly controlled BP levels, in the standard treatment group. Specific declines were observed in processing speed and executive function, domains often impacted by cerebrovascular disease and may underpin risk for dementia and cerebrovascular disease associated with BPV. Clinical trial information: ClinicalTrials.gov; NCT01206062.

Hypertension, Neurovascular Dysfunction, and Cognitive Impairment

Hypertension affects a significant proportion of the adult and aging population and represents an important risk factor for vascular cognitive impairment and late-life dementia. Chronic high blood pressure continuously challenges the structural and functional integrity of the cerebral vasculature, leading to microvascular rarefaction and dysfunction, and neurovascular uncoupling that typically impairs cerebral blood supply. Hypertension disrupts blood-brain barrier integrity, promotes neuroinflammation, and may contribute to amyloid deposition and Alzheimer pathology. The mechanisms underlying these harmful effects are still a focus of investigation, but studies in animal models have provided significant molecular and cellular mechanistic insights. Remaining questions relate to whether adequate treatment of hypertension may prevent deterioration of cognitive function, the threshold for blood pressure treatment, and the most effective antihypertensive drugs. Recent advances in neurovascular biology, advanced brain imaging, and detection of subtle behavioral phenotypes have begun to provide insights into these critical issues. Importantly, a parallel analysis of these parameters in animal models and humans is feasible, making it possible to foster translational advancements. In this review, we provide a critical evaluation of the evidence available in experimental models and humans to examine the progress made and identify remaining gaps in knowledge.

Visit-to-Visit Blood Pressure Variability and Cognitive Decline in Apolipoprotein ɛ4 Carriers versus Apolipoprotein ɛ3 Homozygotes

BACKGROUND

Blood pressure variability (BPV) is associated with cognitive decline and Alzheimer's disease (AD), but relationships with AD risk gene apolipoprotein (APOE) ɛ4 remain understudied.

OBJECTIVE

Examined the longitudinal relationship between BPV and cognitive change in APOE ɛ4 carriers and APOE ɛ3 homozygotes.

METHODS

1,194 Alzheimer's Disease Neuroimaging Initiative participants (554 APOE ɛ4 carriers) underwent 3-4 blood pressure measurements between study baseline and 12-month follow-up. Visit-to-visit BPV was calculated as variability independent of mean over these 12 months. Participants subsequently underwent ≥1 neuropsychological exam at 12-month follow-up or later (up to 156 months later). Composite scores for the domains of memory, language, executive function, and visuospatial abilities were determined. Linear mixed models examined the 3-way interaction of BPV×APOE ɛ4 carrier status x time predicting change in composite scores.

RESULTS

Higher systolic BPV predicted greater decline in memory (+1 SD increase of BPV: β= -0.001, p < 0.001) and language (β= -0.002, p < 0.0001) among APOE ɛ4 carriers, but not APOE ɛ3 homozygotes (memory: +1 SD increase of BPV: β= 0.0001, p = 0.57; language: β= 0.0001, p = 0.72). Systolic BPV was not significantly associated with change in executive function or visuospatial abilities in APOE ɛ4 carriers (ps = 0.08-0.16) or APOE ɛ3 homozygotes (ps = 0.48-0.12).

CONCLUSION

Cognitive decline associated with high BPV may be specifically accelerated among APOE ɛ4 carriers.

Synergistic interaction of high blood pressure and cerebral beta-amyloid on tau pathology

BACKGROUND

Hypertension has been associated with Alzheimer's disease (AD) dementia as well as vascular dementia. However, the underlying neuropathological changes that link hypertension to AD remain poorly understood. In our study, we examined the relationships of a history of hypertension and high current blood pressure (BP) with in vivo AD pathologies including β-amyloid (Aβ) and tau and also investigated whether a history of hypertension and current BP respectively affect the association between Aβ and tau deposition.

METHODS

This cross-sectional study was conducted as part of the Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer's Disease, a prospective cohort study. Cognitively normal older adults who underwent both Aβ and tau positron emission tomography (PET) (i.e., [¹¹C]-Pittsburgh compound B and [¹⁸F] AV-1451 PET) were selected. History of hypertension and current BP were evaluated and cerebral Aβ and tau deposition measured by PET were used as main outcomes. Generalized linear regression models were used to estimate associations.

RESULTS

A total of 68 cognitively normal older adults (mean [SD] age, 71.5 [7.4] years; 40 women [59%]) were included in the study. Neither a history of hypertension nor the current BP exhibited a direct association with Aβ or tau deposition. However, the synergistic interaction effects of high current systolic (β, 0.359; SE, 0.141; p = 0.014) and diastolic (β, 0.696; SE, 0.158; p < 0.001) BP state with Aβ deposition on tau deposition were significant, whereas there was no such effect for a history of hypertension (β, 0.186; SE, 0.152; p = 0.224).

CONCLUSIONS

The findings suggest that high current BP, but not a history of hypertension, synergistically modulate the relationship between cerebral Aβ and tau deposition in late-life. In terms of AD prevention, the results support the importance of strict BP control in cognitively normal older adults with hypertension.

Blood pressure variability and plasma Alzheimer's disease biomarkers in older adults

Blood pressure variability is an emerging risk factor for Alzheimer's disease in older adults, independent of average blood pressure levels. Growing evidence suggests increased blood pressure variability is linked to Alzheimer's disease pathophysiology indexed by cerebrospinal fluid and positron emission tomography markers, but relationships with plasma Alzheimer's disease markers have not been investigated. In this cross-sectional study of 54 community-dwelling older adults (aged 55-88, mean age 69.9 [8.2 SD]), elevated blood pressure variability over 5 min was associated with lower levels of plasma Aβ_1-42 (standardized ß =  - 0.36 [95% CI - 0.61, - 0.12]; p = 0.005; adjusted R² = 0.28) and Aβ_1-42: Aβ_1-40 ratio (ß =  - 0.49 [95% CI - 0.71, - 0.22]; p < 0.001; adjusted R² = 0.28), and higher levels of total tau (ß = 0.27 [95% CI 0.01, 0.54]; p = 0.04; adjusted R² = 0.19) and Ptau₁₈₁:Aβ_1-42 ratio (ß = 0.26 [95% CI 0.02, 0.51]; p = 0.04; adjusted R² = 0.22). Findings suggest higher blood pressure variability is linked to plasma biomarkers of increased Alzheimer's disease pathophysiology.