Higher Aortic Stiffness Is Associated With Lower Global Cerebrovascular Reserve Among Older Humans

Peripheral vascular dysfunction and the aging brain

Aging is the greatest non-modifiable risk factor for most diseases, including cardiovascular diseases (CVD), which remain the leading cause of mortality worldwide. Robust evidence indicates that CVD are a strong determinant for reduced brain health and all-cause dementia with advancing age. CVD are also closely linked with peripheral and cerebral vascular dysfunction, common contributors to the development and progression of all types of dementia, that are largely driven by excessive levels of oxidative stress (e.g., reactive oxygen species [ROS]). Emerging evidence suggests that several fundamental aging mechanisms (e.g., "hallmarks" of aging), including chronic low-grade inflammation, mitochondrial dysfunction, cellular senescence and deregulated nutrient sensing contribute to excessive ROS production and are common to both peripheral and cerebral vascular dysfunction. Therefore, targeting these mechanisms to reduce ROS-related oxidative stress and improve peripheral and/or cerebral vascular function may be a promising strategy to reduce dementia risk with aging. Investigating how certain lifestyle strategies (e.g., aerobic exercise and diet modulation) and/or select pharmacological agents (natural and synthetic) intersect with aging "hallmarks" to promote peripheral and/or cerebral vascular health represent a viable option for reducing dementia risk with aging. Therefore, the primary purpose of this review is to explore mechanistic links among peripheral vascular dysfunction, cerebral vascular dysfunction, and reduced brain health with aging. Such insight and assessments of non-invasive measures of peripheral and cerebral vascular health with aging might provide a new approach for assessing dementia risk in older adults.

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.

Impact of arterial stiffness on cerebrovascular function: a review of evidence from humans and preclincal models

With advancing age, the cerebral vasculature becomes dysfunctional, and this dysfunction is associated with cognitive decline. However, the initiating cause of these age-related cerebrovascular impairments remains incompletely understood. A characteristic feature of the aging vasculature is the increase in stiffness of the large elastic arteries. This increase in arterial stiffness is associated with elevated pulse pressure and blood flow pulsatility in the cerebral vasculature. Evidence from both humans and rodents supports that increases in large elastic artery stiffness are associated with cerebrovascular impairments. These impacts on cerebrovascular function are wide-ranging and include reductions in global and regional cerebral blood flow, cerebral small vessel disease, endothelial cell dysfunction, and impaired perivascular clearance. Furthermore, recent findings suggest that the relationship between arterial stiffness and cerebrovascular function may be influenced by genetics, specifically APOE and NOTCH genotypes. Given the strength of the evidence that age-related increases in arterial stiffness have deleterious impacts on the brain, interventions that target arterial stiffness are needed. The purpose of this review is to summarize the evidence from human and rodent studies, supporting the role of increased arterial stiffness in age-related cerebrovascular impairments.

Emerging Links between Cerebral Blood Flow Regulation and Cognitive Decline: A Role for Brain Microvascular Pericytes

Cognitive impairment associated with vascular etiology has been of considerable interest in the development of dementia. Recent studies have started to uncover cerebral blood flow deficits in initiating cognitive deterioration. Brain microvascular pericytes, the only type of contractile cells in capillaries, are involved in the precise modulation of vascular hemodynamics due to their ability to regulate resistance in the capillaries. They exhibit potential in maintaining the capillary network geometry and basal vascular tone. In addition, pericytes can facilitate better blood flow supply in response to neurovascular coupling. Their dysfunction is thought to disturb cerebral blood flow causing metabolic imbalances or structural injuries, leading to consequent cognitive decline. In this review, we summarize the characteristics of microvascular pericytes in brain blood flow regulation and outline the framework of a two-hit hypothesis in cognitive decline, where we emphasize how pericytes serve as targets of cerebral blood flow dysregulation that occurs with neurological challenges, ranging from genetic factors, aging, and pathological proteins to ischemic stress.

The Association of Tacrolimus Formulation on Cerebral Blood Flow and Cognitive Function

Calcineurin inhibitors are inherent vasoconstrictors. Cerebral vasoconstriction can reduce cerebral blood flow (CBF), and negatively impact cerebrovascular response (CVR) to exercise, and cognitive function. The once-daily extended-release (LCP) tacrolimus has fewer side effects than the immediate-release (IR) tacrolimus. The role of calcineurin inhibitors on CBF and the impact of specific formulations of tacrolimus on CBF, CVR, and cognitive function are unknown. In this pilot study, we evaluated whether changing from IR tacrolimus to LCP tacrolimus modulates CBF, CVR, or cognitive function in kidney transplant (KT) recipients.

Methods

We randomized (2:1) 30 stable KT recipients on IR tacrolimus to intervention (switch to LCP tacrolimus) and control (continue IR tacrolimus) arms. We measured CBF, CVR, and cognitive function at baseline and at 12 wk. We used ANCOVA to evaluate changes in outcome variables, with baseline values and study arm as covariates. We used descriptive statistics with mean changes in outcome variables to compare the 2 groups.

Results

Participants were 51 ± 13 y old. There was no difference in plasma tacrolimus levels at baseline and at 12 wk in the 2 arms. The changes in CBF, resting middle cerebral artery velocity, CVR, and cognitive function were more favorable in the intervention arm than in the control group.

Conclusions

Changing IR tacrolimus to LCP tacrolimus may improve CBF, cerebrovascular dynamics, and cognitive function in KT recipients. Larger studies are needed to confirm these results.

Pathophysiological Association of Alzheimer's Disease and Hypertension: A Clinical Concern for Elderly Population

Alzheimer's disease (AD), the most common cause of dementia and the fifth leading cause of death in the adult population has a complex pathophysiological link with hypertension (HTN). A growing volume of published literature on a parallel elevation of blood pressure (BP), amyloid plaques, and neurofibrillary tangles formation in post-middle of human brain cells has developed new, widely accepting foundations on this association. In particular, HTN in elderly life mediates cerebral blood flow dysfunction, neuronal dysfunction, and significant decline in cognitive impairment, primarily in the late-life populace, governing the onset of AD. Thus, HTN is an established risk factor for AD. Considering the impact of AD, 1.89 million deaths annually, and the failure of palliative therapies to cure AD, the scientific research community is looking to adopt integrated approaches to target early modified risk factors like HTN to reduce AD burden. The current review highlights the significance and impact of HTN-based prevention in lowering the AD burden in the elderly by providing a comprehensive overview of the physiological relationship between AD and HTN with an in-detail explanation of the role and applications of pathological biomarkers in this clinical association. The review will gain worth in presenting new insights and providing inclusive discussion on the correlation between HTN and cognitive impairment. It will increase across a wider scientific audience to expand understanding of this pathophysiological association.

Sex-specific associations of reservoir-excess pressure parameters with age and subclinical vascular remodeling

OBJECTIVE

Central artery reservoir pressure and excess pressure (XSP) are associated with cardiovascular disease (CVD) events and mortality. However, sex differences in the trajectory of central reservoir pressure and XSP with advancing age and their relations with vascular markers of subclinical CVD risk are incompletely understood. Therefore, we tested the hypothesis that central reservoir pressure and XSP would be positively associated with advancing age and vascular markers of subclinical CVD risk in men and women.

METHOD

Healthy adults ( n  = 398; aged 18-80 years, 60% female individuals) had central (carotid) artery pressure waveforms acquired by applanation tonometry. Reservoir pressure and XSP peaks and integrals were derived retrospectively from carotid pressure waveforms using custom written software. Carotid artery intimal-medial thickness (IMT) was measured by ultrasonography, and aortic stiffness was determined from carotid-femoral pulse wave velocity (cfPWV).

RESULTS

Reservoir pressure peak, reservoir pressure integral and XSP integral were higher with age in both men and women ( P  < 0.05), whereas XSP peak was lower with age in men ( P  < 0.05). In women, both reservoir pressure peak ( β  = 0.231, P  < 0.01) and reservoir pressure integral ( β  = 0.254, P  < 0.01) were associated with carotid artery IMT, and reservoir pressure peak was associated with cfPWV ( β  = 0.120, P  = 0.02) after adjusting for CVD risk factors.

CONCLUSION

Central artery reservoir pressure and XSP were higher with advancing age in men and women, and reservoir pressure peak was associated with both carotid artery wall thickness and aortic stiffness in women but not men. Central reservoir pressure peak may provide some insight into sex differences in vascular remodeling and subclinical CVD risk with advancing age in healthy adults.

Intracranial Carotid Arteriosclerosis Mediates the Association Between Blood Pressure and Cerebral Small Vessel Disease

BACKGROUND

Intracranial arteriosclerosis could explain the association between blood pressure (BP) and cerebral small vessel disease (CSVD). Therefore, we tested whether intracranial carotid artery calcification (ICAC) mediates the association between BP and CSVD and determined pathophysiological mechanisms based on ICAC subtypes.

METHODS

One thousand four hundred fifty-eight stroke-free participants from the Rotterdam Study (mean age, 68 years; 52% women) underwent nonenhanced computed tomography scans to quantify ICAC volume (mm³) between 2003 and 2015. ICAC was categorized into intimal and internal elastic lamina calcifications. CSVD included white matter hyperintensities volume, the presence of lacunes, and cerebral microbleeds visualized on magnetic resonance imaging. Office BP included systolic BP, diastolic BP, pulse pressure, and mean arterial pressure. Mediation analysis included a 2-way decomposition to determine the direct association between BP and CSVD and the indirect or mediated effect (negative or positive mediations expressed in %) of log-ICAC volume on such association.

RESULTS

BP and log-ICAC were correlated and were also associated with CSVD. In all participants, total log-ICAC volume mediated the association of diastolic BP (-14.5%) and pulse pressure (16.5%) with log-white matter hyperintensities. Internal elastic lamina log-ICAC volume mediated -19.5% of the association between diastolic BP and log-white matter hyperintensities; intimal log-ICAC volume did not mediate associations. For lacunes, total and internal elastic lamina log-ICAC volume mediated the association of diastolic BP (-40% and -45.8%) and pulse pressure (26.9% and 18.2%). We did not observe mediations for cerebral microbleeds.

CONCLUSIONS

Intracranial arteriosclerosis mediates the association between BP and CSVD. Internal elastic lamina calcification, considered a proxy of arterial stiffness, is the leading mechanism explaining the link between BP and CSVD.

Is It Good to Have a Stiff Aorta with Aging? Causes and Consequences

Aortic stiffness increases with advancing age, more than doubling during the human life span, and is a robust predictor of cardiovascular disease (CVD) clinical events independent of traditional risk factors. The aorta increases in diameter and length to accommodate growing body size and cardiac output in youth, but in middle and older age the aorta continues to remodel to a larger diameter, thinning the pool of permanent elastin fibers, increasing intramural wall stress and resulting in the transfer of load bearing onto stiffer collagen fibers. Whereas aortic stiffening in early middle age may be a compensatory mechanism to normalize intramural wall stress and therefore theoretically "good" early in the life span, the negative clinical consequences of accelerated aortic stiffening beyond middle age far outweigh any earlier physiological benefit. Indeed, aortic stiffness and the loss of the "windkessel effect" with advancing age result in elevated pulsatile pressure and flow in downstream microvasculature that is associated with subclinical damage to high-flow, low-resistance organs such as brain, kidney, retina, and heart. The mechanisms of aortic stiffness include alterations in extracellular matrix proteins (collagen deposition, elastin fragmentation), increased arterial tone (oxidative stress and inflammation-related reduced vasodilators and augmented vasoconstrictors; enhanced sympathetic activity), arterial calcification, vascular smooth muscle cell stiffness, and extracellular matrix glycosaminoglycans. Given the rapidly aging population of the United States, aortic stiffening will likely contribute to substantial CVD burden over the next 2-3 decades unless new therapeutic targets and interventions are identified to prevent the potential avalanche of clinical sequelae related to age-related aortic stiffness.

Effect of diet supplemented with African Star Apple Fruit Pulp on purinergic, cholinergic and monoaminergic enzymes, TNF-α expression and redox imbalance in the brain of hypertensive rats

OBJECTIVE

This study examined whether diet supplemented with African star apple fruit pulp (FP) can mitigate the effect of high blood pressure on brain neurochemicals, histopathology and expression of genes linked with neuroinflammation.

METHODS

Rats were administered with cyclosporine (25 mg/kg.bw) to induce hypertension and were fed with or without FP supplemented diet. Purinergic (Nucleoside triphosphate diphosphohydrolases [NTPdase] and adenosine deaminase [ADA]) cholinergic (acetylcholinesterase [AChE]) and monoaminergic (monoamine oxidase-B) enzymes were assessed in treated and untreated hypertensive rats' brains. Oxidative stress biomarkers (catalase, glutathione-S-transferase, thiols, reactive oxygen species [ROS] and malondialdehyde [MDA]), as well as AChE, tumour necrosis factor and receptor (TNF-α and TNF-α-R) expression, were also determined.

RESULTS

FP supplemented diet significantly reduced NTPdase and ADA activities and increased Na⁺/K+-ATPase activities in hypertensive rats' brains compared to the untreated group. Furthermore, FP reduced acetylcholinesterase and monoamine oxidase-B activities compared to the hypertensive group. Redox imbalance was observed in hypertensive rats with inhibition of antioxidant enzymes and high levels of ROS and MDA. However, FP supplemented diet improved antioxidant enzymes, reduced ROS and MDA production in the brain of hypertensive rats. High blood pressure also triggered upregulation of AChE, TNF-α and TNF-α-R while feeding with FP supplemented diet downregulated the genes.

CONCLUSION

This study demonstrates the neuroprotective role of FP supplemented diet against alterations in neurochemicals associated with Alzheimer's disease, oxidative stress-induced neuronal damage and expression of genes linked with neuroinflammation. Moreover, studies on animal behaviour and human subjects are required to confirm these beneficial effects.

Arterial and Venous Cerebral Blood Flow Velocities and Their Correlation in Healthy Volunteers and Traumatic Brain Injury Patients

BACKGROUND

Few studies have explored the cerebral venous compartment or the correlation between venous and arterial cerebral blood flows. We aimed to correlate cerebral blood flow velocities in the arterial (middle cerebral artery) and venous (straight sinus) compartments in healthy volunteers and traumatic brain injury (TBI) patients. In addition, we determined the normative range of these parameters.

MATERIALS AND METHODS

A total of 122 healthy volunteers and 95 severe TBI patients of both sexes were included and stratified into 3 age groups as follows: group 1 (aged, 18 to 44 y); group 2 (aged, 45 to 64 y); group 3 (older than 65 y). Transcranial Doppler systolic cerebral blood flow velocity, diastolic cerebral blood flow velocity, and mean cerebral blood flow velocity (FVs, FVd, FVm, respectively) were measured in the middle cerebral artery and peak cerebral venous blood flow velocity (FVVs) was measured in the straight sinus. The arteriovenous correlation was assessed on the basis of a positive relationship between FVs and FVVs.

RESULTS

There was an arteriovenous correlation (FVs vs. FVVs) in healthy volunteers (R=0.39, P<0.0001). We found no arteriovenous correlation in the TBI cohort overall, but FVs and FVVs were correlated in age group 1 (R=0.28, P=0.05) and in males (R=0.29, P=0.01). In healthy volunteers, FVs and FVm were significantly higher in males compared with females; and FVs, FVm, FVd, FVVs all increased across the age spectrum. There were no significant differences in any of these parameters in TBI patients.

CONCLUSIONS

There are age and sex differences in arterial and venous cerebral blood flow velocities in healthy volunteers. Arteriovenous correlation is present in healthy volunteers but absent in TBI patients.

Sex Differences in Large Artery Stiffness: Implications for Cerebrovascular Dysfunction and Alzheimer’s Disease

Two in every three Alzheimer’s disease diagnoses are females, calling attention to the need to understand sexual dimorphisms with aging and neurodegenerative disease progression. Dysfunction and damage to the vasculature with aging are strongly linked to Alzheimer’s disease. With aging there is an increase in stiffness of the large elastic arteries, and this stiffening is associated with cerebrovascular dysfunction and cognitive impairment. However, it is unclear how the deleterious effects of arterial stiffness may differ between females and males. While environmental, chromosomal, and sex hormone factors influence aging, there is evidence that the deficiency of estrogen post-menopause in females is a contributor to vascular aging and Alzheimer’s disease progression. The purpose of this mini review is to describe the recent developments in our understanding of sex differences in large artery stiffness, cerebrovascular dysfunction, and cognitive impairment, and their intricate relations. Furthermore, we will focus on the impact of the loss of estrogen post-menopause as a potential driving factor for these outcomes. Overall, a better understanding of how sex differences influence aging physiology is crucial to the prevention and treatment of neurodegenerative diseases.

Sex moderations in the relationship between aortic stiffness, cognition, and cerebrovascular reactivity in healthy older adults

It is well established that sex differences exist in the manifestation of vascular diseases. Arterial stiffness (AS) has been associated with changes in cerebrovascular reactivity (CVR) and cognitive decline in aging. Specifically, older adults with increased AS show a decline on executive function (EF) tasks. Interestingly, the relationship between AS and CVR is more complex, where some studies show decreased CVR with increased AS, and others demonstrate preserved CVR despite higher AS. Here, we investigated the possible role of sex on these hemodynamic relationships. Acquisitions were completed in 48 older adults. Pseudo-continuous arterial spin labeling (pCASL) data were collected during a hypercapnia challenge. Aortic pulse wave velocity (PWV) data was acquired using cine phase contrast velocity series. Cognitive function was assessed with a comprehensive neuropsychological battery, and a composite score for EF was calculated using four cognitive tests from the neuropsychological battery. A moderation model test revealed that sex moderated the relationship between PWV and CVR and PWV and EF, but not between CVR and EF. Together, our results indicate that the relationships between central stiffness, cerebral hemodynamics and cognition are in part mediated by sex.

Arterial Stiffness in Aging: Does It Have a Place in Clinical Practice?: Recent Advances in Hypertension

Aortic stiffness increases markedly with age and is associated with excess risk for various adverse clinical outcomes, including heart disease, dementia, and kidney disease. Although evidence for adverse effects of aortic stiffening is overwhelming, integration of direct and indirect measures of aortic stiffness into routine clinical assessment has lagged behind the science. This brief review will examine recent evidence supporting the value of stiffness as an important new risk factor for hypertension and cardiovascular disease and will offer suggestions for incorporating stiffness measures into routine clinical practice.

Characterizing pulsatility in distal cerebral arteries using 4D flow MRI

Recent reports have suggested that age-related arterial stiffening and excessive cerebral arterial pulsatility cause blood-brain barrier breakdown, brain atrophy and cognitive decline. This has spurred interest in developing non-invasive methods to measure pulsatility in distal vessels, closer to the cerebral microcirculation. Here, we report a method based on four-dimensional (4D) flow MRI to estimate a global composite flow waveform of distal cerebral arteries. The method is based on finding and sampling arterial waveforms from thousands of cross sections in numerous small vessels of the brain, originating from cerebral cortical arteries. We demonstrate agreement with internal and external reference methods and show the ability to capture significant increases in distal cerebral arterial pulsatility as a function of age. The proposed approach can be used to advance our understanding regarding excessive arterial pulsatility as a potential trigger of cognitive decline and dementia.

Treatment of hypertension reduces cognitive decline in older adults: a systematic review and meta-analysis

OBJECTIVES

To systematically analyse the effect of pharmacological treatment of hypertension (HTN) on cognitive decline in older adults.

METHODS

Randomised, placebo-controlled trials with a prespecified quantitative outcome of cognition and a pharmacological intervention for at least 12 months to treat HTN in older adults (>60 years). Our primary outcome was change in cognition with pharmacological treatment of HTN. Standardised mean difference (SMD) was used to analyse different outcomes reported in the selected studies. We searched PubMed CENTRAL and the Cochrane Library from inception to 6 July 2020. Two independent reviewers assessed trial quality and extracted data. Internal and external validity of the studies was assessed.

RESULTS

Nine randomised controlled trials with 34 994 participants were included in the final analysis. The net SMD for change in cognition was -0.049 (CI: -0.078 to -0.019) indicating that treatment of HTN decreased cognitive decline. Heterogeneity was low with an I² of 6%.

DISCUSSION

Current evidence does not indicate worsening of cognition with treatment of HTN. Treatment of HTN in older adults may reduce cognitive decline. These results have important implications in clinical management of patients at risk for dementia.

PROSPERO REGISTRATION NUMBER

CRD42020139750.

Large artery stiffness and brain health: insights from animal models

There are no effective treatments available to halt or reverse the progression of age-related cognitive decline and Alzheimer's disease. Thus, there is an urgent need to understand the underlying mechanisms of disease etiology and progression to identify novel therapeutic targets. Age-related changes to the vasculature, particularly increases in stiffness of the large elastic arteries, are now recognized as important contributors to brain aging. There is a growing body of evidence for an association between greater large artery stiffness and cognitive impairment among both healthy older adults and patients with Alzheimer's disease. However, studies in humans are limited to only correlative evidence, whereas animal models allow researchers to explore the causative mechanisms linking arterial stiffness to neurocognitive dysfunction and disease. Recently, several rodent models of direct modulation of large artery stiffness and the consequent effects on the brain have been reported. Common outcomes among these models have emerged, including evidence that greater large artery stiffness causes cerebrovascular dysfunction associated with increased oxidative stress and inflammatory signaling. The purpose of this mini-review is to highlight the recent findings associating large artery stiffness with deleterious brain outcomes, with a specific focus on causative evidence obtained from animal models. We will also discuss the gaps in knowledge that remain in our understanding of how large artery stiffness affects brain function and disease outcomes.

Beat-to-Beat Blood Pressure Variability in the First Trimester Is Associated With the Development of Preeclampsia in a Prospective Cohort: Relation With Aortic Stiffness

Women with preeclampsia, a hypertensive disorder of pregnancy, exhibit greater beat-to-beat blood pressure variability (BPV) in the third trimester after clinical onset of the disorder. However, it remains unknown whether elevated BPV precedes the development of preeclampsia. A prospective study cohort of 139 women (age 30.2±4.0 years) were enrolled in early pregnancy (<14 weeks gestation). BPV was quantified by time domain analyses of 10-minute continuous beat-to-beat blood pressure recordings via finger photoplethysmography in the first, second, and third trimesters. Aortic stiffness (carotid-femoral pulse wave velocity) and spontaneous cardiovagal baroreflex sensitivity were also measured each trimester. Eighteen women (13%) developed preeclampsia. Systolic BPV was higher in all trimesters among women who developed versus did not develop preeclampsia (first: 4.8±1.3 versus 3.7±1.2, P=0.001; second: 5.1±1.8 versus 3.8±1.1, P=0.02; third: 5.2±0.8 versus 4.0±1.1 mm Hg, P=0.002). Elevated first trimester systolic BPV was associated with preeclampsia (odds ratio, 1.94 [95% CI, 1.27-2.99]), even after adjusting for risk factors (age, body mass index, systolic blood pressure, history of preeclampsia, and diabetes mellitus) and was a significant predictor of preeclampsia (area under the receiver operator characteristic curve=0.75±0.07; P=0.002). Carotid-femoral pulse wave velocity was elevated in the first trimester among women who developed preeclampsia (5.9±0.8 versus 5.2±0.8 m/s; P=0.002) and was associated with BPV after adjustment for mean blood pressure (r=0.26; P=0.005). First trimester baroreflex sensitivity did not differ between groups (P=0.23) and was not related to BPV (P=0.36). Elevated systolic BPV is independently associated with the development of preeclampsia as early as the first trimester, possibly mediated in part by higher aortic stiffness.

Education moderates the effects of large central artery aging on cognitive performance in middle-aged and older adults

Central artery aging, including elevated aortic stiffness, central blood pressure (BP), and pulse pressure (PP), is a novel risk factor for the development of age-associated cognitive dysfunction. Individuals with higher educational attainment may develop greater brain pathology prior to the onset of cognitive decline. However, whether education moderates relations between central artery aging and cognitive performance is unknown. We hypothesized that years of formal education would moderate the relation between central artery aging and cognitive performance in middle-aged/older (MA/O) adults (n = 113, age 67.3 ± 0.7 years). Significant interactions between education*central systolic BP (β = .21, p = .02) and education*central PP (β = .22, p = .01) demonstrated weaker associations between central BP and PP with processing speed performance in those with higher education. Similarly, education moderated the relation between aortic stiffness (carotid-femoral pulse wave velocity, cfPWV) and executive function performance (β = .21, p = .02). To test if the relation between central arterial aging and cognitive performance was captured by a predetermined education threshold, MA/O adults were secondarily categorized as ≤high school (HS) (i.e., ≤12 years, n = 36) or >HS (≥13 years, n = 77). Higher central systolic BP was associated with slower processing speed (≤HS: r = -.59, p < .001 vs. >HS: r = -.25, p = .03) and weaker executive function (r = -.39, p = .03 vs. r = -.32, p = .006). Higher cfPWV was selectively correlated with weaker executive function performance (r = -.39, p = .03) in ≤HS only and this association significantly differed between education groups. Educational attainment appears to moderate the adverse effects of central artery aging on cognitive performance among MA/O adults.

Racial disparities in cardiovascular disease risk: mechanisms of vascular dysfunction

Cardiovascular disease (CVD) accounts for a third of all deaths in the United States making it the leading cause of morbidity and mortality. Although CVD affects individuals of all races/ethnicities, the prevalence of CVD is highest in non-Hispanic black (BL) individuals relative to other populations. The mechanism(s) responsible for elevated CVD risk in the BL population remains incompletely understood. However, impaired vascular vasodilator capacity and exaggerated vascular vasoconstrictor responsiveness are likely contributing factors, both of which are present even in young, otherwise healthy BL individuals. Within this review, we highlight some historical and recent data, collected from our laboratories, of impaired vascular function, in terms of reduced vasodilator capacity and heightened vasoconstrictor responsiveness, in the peripheral and cerebral circulations in BL individuals. We provide data that such impairments may be related to elevated oxidative stress and subsequent reduction in nitric oxide bioavailability. In addition, divergent mechanisms of impaired vasodilatory capacity between BL men and women are discussed. Finally, we propose several directions where future research is needed to fill in knowledge gaps, which will allow for better understanding of the mechanisms contributing to impaired vascular function in this population. Ultimately, this information will allow for better lifestyle and therapeutic approaches to be implemented in an effort to minimize the increased CVD burden in the BL population.

Arterial stiffness and brain integrity: A review of MRI findings

BACKGROUND

Given the increasing incidence of vascular diseases and dementia, a better understanding of the cerebrovascular changes induced by arterial stiffness is important for early identification of white and gray matter abnormalities that might antedate the appearance of clinical cognitive symptoms. Here, we review the evidence from neuroimaging demonstrating the impact of arterial stiffness on the aging brain.

METHOD

This review presents findings from recent studies examining the association between arterial stiffness, cognitive function, cerebral hypoperfusion, and markers of neuronal fiber integrity using a variety of MRI techniques.

RESULTS

Overall, changes associated with arterial stiffness indicates that the corpus callosum, the internal capsule and the corona radiata may be the most vulnerable regions to microvascular damage. In addition, the microstructural integrity of these regions appears to be associated with cognitive performance. Changes in gray matter structure have also been found to be associated with arterial stiffness and are present as early as the 5th decade. Moreover, low cerebral perfusion has been associated with arterial stiffness as well as lower cognitive performance in age-sensitive tasks such as executive function.

CONCLUSION

Considering the established relationship between arterial stiffness, brain and cognition, this review highlights the need for future studies of brain structure and function in aging to implement measurements of arterial stiffness in parallel with quantitative imaging.

Neurovascular and Cognitive Dysfunction in Hypertension

Hypertension has emerged as a leading cause of age-related cognitive impairment. Long known to be associated with dementia caused by vascular factors, hypertension has more recently been linked also to Alzheimer disease-the major cause of dementia in older people. Thus, although midlife hypertension is a risk factor for late-life dementia, hypertension may also promote the neurodegenerative pathology underlying Alzheimer disease. The mechanistic bases of these harmful effects remain to be established. Hypertension is well known to alter in the structure and function of cerebral blood vessels, but how these cerebrovascular effects lead to cognitive impairment and promote Alzheimer disease pathology is not well understood. Furthermore, critical questions also concern whether treatment of hypertension prevents cognitive impairment, the blood pressure threshold for treatment, and the antihypertensive agents to be used. Recent advances in neurovascular biology, epidemiology, brain imaging, and biomarker development have started to provide new insights into these critical issues. In this review, we will examine the progress made to date, and, after a critical evaluation of the evidence, we will highlight questions still outstanding and seek to provide a path forward for future studies.

Central artery stiffness is related to cerebral oxygenation hemodynamics during executive function tasks in healthy middle-aged and older adults

Age-related decreases in cognitive function, cerebral perfusion, and vascular function increase the risk of dementia. However, the effects of central artery stiffness on cerebral oxygenation hemodynamics during executive function tasks and executive function remain unclear. The aim of this cross-sectional study was to investigate the relationships among central artery stiffness, cerebral oxygenation hemodynamics during executive function tasks, and executive function in middle-aged and older adults. Sixty-two middle-aged and older adults (age range: 51-79 years) were recruited for this study. For each participant, we measured the carotid artery β-stiffness, oxygenated hemoglobin (oxy-Hb) signal change in the prefrontal cortex during the Stroop task, and Stroop interference time. Correlation analyses revealed that the carotid artery β-stiffness was significantly correlated with the Stroop interference time (r = 0.43, P < 0.001) and with the oxy-Hb signal change in the left (r = -0.38, P = 0.002), but not the right, prefrontal cortex. In addition, the Stroop interference time was significantly correlated with the oxy-Hb signal change in the left (r = -0.42, P = 0.001), but not the right, prefrontal cortex. The participants were divided into the low and high arterial stiffness groups according to the median value. We found that the Stroop interference time was significantly shorter (P = 0.006) and the oxy-Hb signal change in the left prefrontal cortex was significantly larger in the low arterial stiffness group than in the high arterial stiffness group (P = 0.011). In the low, but not the high, arterial stiffness group, the oxy-Hb signal change of the left prefrontal cortex during executive function tasks was significantly larger than the oxy-Hb signal change of the right prefrontal cortex (P = 0.014). These results suggest that increases in central artery stiffness are associated with decreases in oxygenation hemodynamics in the left prefrontal cortex during executive function tasks and reductions in executive function.