Relations of arterial stiffness and endothelial function to brain aging in the community

Exercise Improves Vascular Function, but does this Translate to the Brain?

The number of adults with Alzheimer’s disease (AD) or related dementia is expected to increase exponentially. Interventions aimed to reduce the risk and progression of AD and dementia are critical to the prevention and treatment of this devastating disease. Aging and cardiovascular disease risk factors are associated with reduced vascular function, which can have important clinical implications, including brain health. The age-associated increase in blood pressure and impairment in vascular function may be attenuated or even reversed through lifestyle behaviors. Greater volumes of habitual exercise and higher cardiorespiratory fitness are associated with beneficial effects on vascular health and cognition. Exercise and cardiorespiratory fitness may be most important during midlife, as physical activity and cardiorespiratory fitness during the middle-aged years are associated with future cognitive function. The extent to which exercise, and more specifically aerobic exercise, influences the cerebral circulation is not well established. In this review, we present our working hypothesis showing how cerebrovascular function may be a mediating factor underlying the association between exercise and cognition, as well as discuss recent studies evaluating the effect of exercise interventions on the cerebral circulation.

Arterial stiffness and white matter integrity in the elderly: A diffusion tensor and magnetization transfer imaging study

BACKGROUND AND PURPOSE

The stiffness of large arteries and increased pulsatility can have an impact on the brain white matter (WM) microstructure, however those mechanisms are still poorly understood. The aim of this study was to investigate the association between central artery stiffness, axonal and myelin integrity in 54 cognitively unimpaired elderly subjects (65-75 years old).

METHODS

The neuronal fiber integrity of brain WM was assessed using diffusion tensor metrics and magnetization transfer imaging as measures of axonal organization (Fractional anisotropy, Radial diffusivity) and state of myelination (Myelin volume fraction). Central artery stiffness was measured by carotid-femoral pulse wave velocity (cfPWV). Statistical analyses included 4 regions (the corpus callosum, the internal capsule, the corona radiata and the superior longitudinal fasciculus) which have been previously denoted as vulnerable to increased central artery stiffness.

RESULTS

cfPWV was significantly associated with fractional anisotropy and radial diffusivity (p < 0.05, corrected for multiple comparisons) but not with myelin volume fraction. Findings from this study also show that improved executive function performance correlates with Fractional anisotropy positively (p < 0.05 corrected) as well as with myelin volume fraction and radial diffusivity negatively (p < 0.05 corrected).

CONCLUSIONS

These findings suggest that arterial stiffness is associated with axon degeneration rather than demyelination. Controlling arterial stiffness may play a role in maintaining the health of WM axons in the aging brain.

Examining the relationship between nutrition and cerebral structural integrity in older adults without dementia

The proportion of adults aged 60 years and over is expected to increase over the coming decades. This ageing of the population represents an important health issue, given that marked reductions to cerebral macro- and microstructural integrity are apparent with increasing age. Reduced cerebral structural integrity in older adults appears to predict poorer cognitive performance, even in the absence of clinical disorders such as dementia. As such, it is becoming increasingly important to identify those factors predicting cerebral structural integrity, especially factors that are modifiable. One such factor is nutritional intake. While the literature is limited, data from available cross-sectional studies indicate that increased intake of nutrients such as B vitamins (for example, B6, B12 and folate), choline, n-3 fatty acids and vitamin D, or increased adherence to prudent whole diets (for example, the Mediterranean diet) predicts greater cerebral structural integrity in older adults. There is even greater scarcity of randomised clinical trials investigating the effects of nutritional supplementation on cerebral structure, though it appears that supplementation with B vitamins (B6, B12 and folic acid) or n-3 fatty acids (DHA or EPA) may be beneficial. The current review presents an overview of available research examining the relationship between key nutrients or adherence to select diets and cerebral structural integrity in dementia-free older adults.

Aortic stiffness and brain integrity in elderly patients with cognitive and functional complaints

Purpose

Cerebral white matter lesions (WML) and brain atrophy are frequent in older persons and are associated with adverse outcomes. It has been suggested that aortic stiffness plays a role in the pathogenesis of WML and gray matter (GM) loss. There is, however, little evidence on the association between aortic stiffness and brain integrity in older patients. In this study, we investigated whether aortic stiffness is associated with WML and GM volume in older patients with cognitive and functional complaints.

Patients and methods

Fazekas score was used to analyze WML on brain imaging data of 84 persons; in a subanalysis on 42 MRI scans, the exact volume of white matter hyperintensities (WMH) and GM was determined using a brain-tissue and WMH tool. Aortic stiffness, measured as aortic pulse wave velocity (aPWV) and central pulse pressure (cPP), and blood pressure levels were non-invasively measured by the Mobil-O-Graph.

Results

Mean age was 76.6 (±6.8) years. Age was correlated with cPP (Spearman's ρ =0.296, P=0.008), aPWV (r ²=0.785, P<0.001) and WMH volume (r ²=0.297, P<0.001). cPP did not differ between categories of Fazekas, whereas aPWV increased with increasing Fazekas score (P for trend <0.001). After additional adjustment for age, levels of aPWV did not differ between categories. Both cPP and aPWV were associated with WMH volumes (lnB 0.025, P=0.055 and lnB 0.405, P<0.001, respectively); after additional adjustment for age, estimates were less consistent. Both cPP and aPWV were negatively associated with GM volumes in multivariate analysis (B=2.805, P=0.094 and B=111.052, P=0.032).

Conclusion

Higher aortic stiffness was partly associated with increased volume of WMH and decreased volume of GM and slightly influenced by blood pressure. Age also plays a role in this association in older patients.

Arterial Stiffness and Cerebral Small Vessel Disease

Background and Objective: Studies on relations between arterial stiffness and full spectrum of radiological features of cerebral small vessel disease (CSVD) are scarce. We aim to investigate the association of arterial stiffness with lacunes, white matter hyperintensities (WMH), microbleeds (CMBs), dilated perivascular spaces (PVS), and brain atrophy in a community-based sample.

Methods: A total of 953 participants (55.7 ± 9.4 years) who underwent brachial-ankle pulse wave velocity (baPWV) and brain magnetic resonance imaging were included. Lacunes, CMBs, and PVS were visually rated. Brain structure and WMH were automatically segmented. Brain parenchyma fraction (BPF), a surrogate index of brain atrophy, was calculated as a ratio of brain parenchyma volume to total intracranial volume. Multivariable logistic and linear regressions were used to investigate the associations between baPWV and CSVD. Subsequently, we explored these associations in strata of age.

Results: Increased baPWV was associated with severe PVS in white matter (OR, 1.09; 95%CI, 1.01–1.17; p = 0.022), larger WMH volume (β, 0.08; 95%CI, 0.04–0.12; p < 0.001), lower BPF (β, −0.09; 95%CI, −0.15– −0.03; p = 0.007), and marginally associated with strictly lobar CMBs (OR, 1.11; 95%CI, 1.00–1.23; p = 0.055), but not with lacunes. WMH volume mediated the relation between baPWV and BPF. In age subgroup analysis, the association of baPWV with PVS in white matter was stronger among those aged <55 years, whereas the association with brain atrophy was more prominent among those aged ≥55 years. Increased baPWV was associated with larger WMH volume in both younger and older individuals.

Conclusions: Increased arterial stiffness was associated with most of imaging markers of CSVD, including PVS in white matter, larger WMH volume, strictly lobar CMBs, and brain atrophy, but not lacunes. The mechanisms underlying these associations and their potential clinical significances warrant further investigations.

Cerebrovascular Reactivity and Central Arterial Stiffness in Habitually Exercising Healthy Adults

Reduced cerebrovascular reactivity to a vasoactive stimulus is associated with age-related diseases such as stroke and cognitive decline. Habitual exercise is protective against cognitive decline and is associated with reduced stiffness of the large central arteries that perfuse the brain. In this context, we evaluated the age-related differences in cerebrovascular reactivity in healthy adults who habitually exercise. In addition, we sought to determine the association between central arterial stiffness and cerebrovascular reactivity. We recruited 22 young (YA: age = 27 ± 5 years, range 18–35 years) and 21 older (OA: age = 60 ± 4 years, range 56–68 years) habitual exercisers who partake in at least 150 min of structured aerobic exercise each week. Middle cerebral artery velocity (MCAv) was recorded using transcranial Doppler ultrasound. In order to assess cerebrovascular reactivity, MCAv, end-tidal carbon dioxide (ETCO₂), and mean arterial pressure (MAP) were continuously recorded at rest and during stepwise elevations of 2, 4, and 6% inhaled CO₂. Cerebrovascular conductance index (CVCi) was calculated as MCAv/MAP. Central arterial stiffness was assessed using carotid–femoral pulse wave velocity (PWV). Older adults had higher PWV (YA: 6.2 ± 1.2 m/s; OA: 7.5 ± 1.3 m/s; p < 0.05) compared with young adults. MCAv and CVCi reactivity to hypercapnia were not different between young and older adults (MCAv reactivity, YA: 2.0 ± 0.2 cm/s/mmHg; OA: 2.0 ± 0.2 cm/s/mmHg; p = 0.77, CVCi reactivity, YA: 0.018 ± 0.002 cm/s/mmHg²; OA: 0.015 ± 0.001 cm/s/mmHg²; p = 0.27); however, older adults demonstrated higher MAP reactivity to hypercapnia (YA: 0.4 ± 0.1 mmHg/mmHg; OA: 0.7 ± 0.1 mmHg/mmHg; p < 0.05). There were no associations between PWV and cerebrovascular reactivity (range: r = 0.00–0.39; p = 0.07–0.99). Our results demonstrate that cerebrovascular reactivity was not different between young and older adults who habitually exercise; however, MAP reactivity was augmented in older adults. This suggests an age-associated difference in the reliance on MAP to increase cerebral blood flow during hypercapnia.

Long-Term Blood Pressure Level and Variability From Midlife to Later Life and Subsequent Cognitive Change: The ARIC Neurocognitive Study

Background To understand how blood pressure ( BP ) from midlife and beyond is related to cognition in older age, a lifespan approach is needed. We assessed the associations of BP levels and variability from midlife on with subsequent cognitive change. Methods and Results The ARIC (Atherosclerosis Risk in Communities) Study participants underwent 4 clinic BP measurements (visit 1, 2, 3, and 4 BP s) between 1987 and 1998, and their mean levels and average real variability ( ARV ) were assessed as exposures. A global cognitive z score, estimated from the Delayed Word Recall Test, Digit Symbol Substitution Test, and Word Fluency Test scores, was calculated at 1996 to 1998 (visit 4) and 2011 to 2013 (visit 5). Among 11 408 participants (mean age, 54 years; 56% women; 21% black race), mean systolic BP ( SBP )/diastolic BP ( DBP ) level was 123/72 mm Hg, and ARVSBP / ARVDBP was 11/7 mm Hg. With linear mixed models, 1- SD increases of ARVSBP (standardized regression coefficient [95% confidence interval], -0.03 [-0.04 to -0.01] points) and ARVDBP (standardized regression coefficient [95% confidence interval], -0.02 [-0.03 to -0.002] points; both P<0.05), but not mean SBP or DBP levels, were associated with lower global cognitive z scores at visit 4. In contrast, mean SBP (standardized regression coefficient [95% confidence interval], -0.04 [-0.06 to -0.02] points) or DBP (standardized regression coefficient [95% confidence interval], 0.04 [0.02-0.06] points; both P<0.001) level, but not ARVSBP or ARVDBP , was associated with change in global cognitive z scores from visits 4 to 5. Conclusions Greater visit-to-visit SBP or DBP variability from midlife on is modestly associated with lower cognitive function, whereas higher mean SBP and lower DBP levels from midlife to later life are modestly associated with cognitive decline in later life.

Urbanization as a risk factor for aortic stiffness in a cohort in India

Urbanization is associated with higher prevalence of cardiovascular disease worldwide. Aortic stiffness, as measured by carotid-femoral pulse wave velocity is a validated predictor of cardiovascular disease. Our objective was to determine the association between urbanization and carotid-femoral pulse wave velocity. The analysis included 6166 participants enrolled in an ongoing population-based study (mean age 42 years; 58% female) who live in an 80 × 80 km region of southern India. Multiple measures of urbanization were used and compared: 1) census designations, 2) satellite derived land cover (crops, grass, shrubs or trees as rural; built-up areas as urban), and 3) distance categories based on proximity to an urban center. The association between urbanization and carotid-femoral pulse wave velocity was tested in sex-stratified linear regression models. People residing in urban areas had significantly (p < 0.05) elevated mean carotid-femoral pulse wave velocity compared to non-urban populations after adjustment for other risk factors. There was also an inverse association between distance from the urban center and mean carotid-femoral pulse wave velocity: each 10 km increase in distance was associated with a decrease in mean carotid-femoral pulse wave velocity of 0.07 m/s (95% CI: -0.09, -0.06 m/s). The association was stronger among older participants, among smokers, and among those with other cardiovascular risk factors. Further research is needed to determine which components in the urban environment are associated with higher carotid-femoral pulse wave velocity.

Large Vessel Disease Modifies the Relationship Between Kidney Injury and Cerebral Small Vessel Disease

Background: Recent studies have shown that renal disease is associated with magnetic resonance imaging (MRI) markers of cerebral small vessel disease (CSVD), independent of traditional vascular risk factors. Although large artery lesions might be involved in the cerebrorenal association, evidence has been lacking.

Methods: A total of 928 participants from a population-based cohort study were included. Kidney injury measurements included urinary albumin-to-creatinine ratio (ACR) and estimated glomerular filtration rate (eGFR). CSVD was assessed on MRI by white matter hyperintensity volume (WMHV), lacunes, brain parenchymal fraction (BPF), cerebral microbleeds (CMBs), and perivascular space. Carotid plaques and brachial-ankle pulse wave velocity (baPWV) were used to assess large artery atherosclerosis and stiffness. Multivariable linear and logistic regression and additional interaction models were used for statistical analysis.

Results: Individuals with elevated ACR had higher prevalence of lacunes and more WMHV (p = 0.001 and 0.000, respectively), those with decreased eGFR had smaller brain volume, higher prevalence of lacunes and deep CMBs (p = 0.009, p = 0.017) and p = 0.010 respectively). Interaction analysis revealed that carotid plaque and baPWV significantly enhanced the association between eGFR and BPF (p = 0.001 and p = 0.002, respectively), that is, the association of eGFR with BPF was only significant among participants with carotid plaque and higher baPWV. In addition, carotid plaque enhanced the association between ACR and WMHV (p = 0.034) and baPWV enhanced the association between ACR and the presence of lacunes (p = 0.027). Modifying effect of large vessel disease markers on the association between kidney injury measurements and CMBs was not significant.

Conclusion: Evaluation of subclinical CVSD in individuals with kidney injury is warranted, especially in those with combined large artery disease.

The Glymphatic System and Waste Clearance with Brain Aging: A Review

The glymphatic system is a glial-dependent waste clearance pathway in the brain, in place of lymphatic vessels, dedicated to drain away soluble waste proteins and metabolic products. Specifically, the glymphatic network serves as a "front end" for waste clearance, and is connected downstream to an authentic lymphatic network, associated with dura covering the brain as well as cranial nerves and large vessels at the skull exits. The anatomical and functional interconnections between these two networks are not completely understood. Several key physiological processes have been identified that control glymphatic transport function and waste clearance from brain. In this review, we aim to provide an overview and discussion of the concept behind the glymphatic system, current evidence, and controversies, while specifically focusing on the consequences of aging and evidence of its existence in human brain. Discovering novel strategies for optimizing and maintaining efficient brain waste clearance across the lifespan may in the future prove to be important for preventing cognitive decline and sustaining healthy aging.

Age and sex-specific associations of carotid pulsatility with small vessel disease burden in transient ischemic attack and ischemic stroke

Background Although large artery stiffness has been implicated in the pathogenesis of cerebral small vessel disease, whether carotid pulsatility, a convenient surrogate marker of arterial stiffness, is similarly associated with global burden of small vessel disease is unknown. Aims To determine the age and sex-specific associations of carotid pulsatility with global burden of small vessel disease. Methods We studied consecutive patients with transient ischemic attack or non-disabling ischemic stroke from the Oxford Vascular Study who had a brain MRI and carotid duplex ultrasound during 2002-2014. We determined clinical correlates of common carotid artery (CCA) and internal carotid artery (ICA) pulsatility index (PI) and their associations with the total small vessel disease score on MRI, stratified by age (median = 72). Results In 587 patients, correlates of CCA and ICA-PI were both independently associated with age, diabetes, and premorbid mean pulse pressure after adjustment for age, sex, and cardiovascular risk factors (all p < 0.05). ICA-PI was strongly associated with small vessel disease markers and burden, particularly lacunes, in patients aged<70 (age and sex-adjusted odds ratio of top vs. bottom pulsatility index quartile: 5.35, 1.95-14.70, p = 0.001; increasing small vessel disease score: 2.30, 1.01-5.25, p = 0.048), but not in patients aged ≥ 70 ( p > 0.05). No associations between CCA-PI with small vessel disease score were noted at any age. In 94 consecutive patients who also received transcranial Doppler ultrasound, strong associations between middle cerebral artery (MCA)-PI and an increasing small vessel disease score were noted (unadjusted OR-MCA: 4.26, 1.45-12.55, p = 0.009; ICA: 2.37, 0.81-6.87, p = 0.11; CCA: 1.33, 0.45-3.96, p=0.61). Conclusions ICA and MCA-PI are associated with global small vessel disease burden, especially in individuals aged<70 and may be causally related.

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

Greater aortic stiffness and pulse pressure are associated with cerebrovascular remodeling, reduced white matter microstructure, and cognitive performance with aging in humans. However, it is unclear whether aortic stiffness and pulse pressure are associated with reduced basal global cerebral blood flow (CBF) and cerebrovascular reserve among older adults. Global CBF was quantified in 205 adults (range, 19-87 years; mean±SE: 30.6±1.3 years) using quantitative [¹⁵O]water brain positron emission tomography imaging. In a subset of older adults (n=24; 70.0±2.0 years), aortic stiffness (carotid femoral pulse wave velocity) and cerebrovascular reserve (change in global CBF after intravenous infusion of acetazolamide) were assessed. In the entire cohort, global CBF was lower in older compared with young adults (36.5±1.1 versus 50.5±0.7 mL/min per 100 mL; P<0.001). Global CBF was higher in young women compared with young men (51.0±0.30 versus 47.4±0.03 mL/min per 100 mL; P<0.001) but did not differ between older women and men (P=0.63). In older adults, greater carotid femoral pulse wave velocity was associated with lower cerebrovascular reserve (r=-0.68; P=0.001 adjusted for age, sex, and mean arterial pressure) but not global CBF (r=0.13; P=0.60). Brachial pulse pressure was not associated with lower cerebrovascular reserve (r=-0.37; P=0.159) when adjusted for age and sex. These data indicate that the age-related increases in aortic stiffness may contribute, in part, to the brain's impaired ability to augment blood flow in response to a stimulus with aging in humans.

Impact of Aging on Endurance and Neuromuscular Physical Performance: The Role of Vascular Senescence

The portion of society aged ≥60 years is the fastest growing population in the Western hemisphere. Aging is associated with numerous changes to systemic physiology that affect physical function and performance. We present a narrative review of the literature aimed at discussing the age-related changes in various metrics of physical performance (exercise economy, anaerobic threshold, peak oxygen uptake, muscle strength, and power). It also explores aging exercise physiology as it relates to global physical performance. Finally, this review examines the vascular contributions to aging exercise physiology. Numerous studies have shown that older adults exhibit substantial reductions in physical performance. The process of decline in endurance capacity is particularly insidious over the age of 60 years and varies considerably as a function of sex, task specificity, and individual training status. Starting at the age of 50 years, aging also implicates an impressive deterioration of neuromuscular function, affecting muscle strength and power. Muscle atrophy, together with minor deficits in the structure and function of the nervous system and/or impairments in intrinsic muscle quality, plays an important role in the development of neuromotor senescence. Large artery stiffness increases as a function of age, thus triggering subsequent changes in pulsatile hemodynamics and systemic endothelial dysfunction. For this reason, we propose that vascular senescence has a negative impact on cerebral, cardiac, and neuromuscular structure and function, detrimentally affecting physical performance.

Vascular Function Is Improved After an Environmental Enrichment Program

Environmental enrichment may slow cognitive decay possibly acting through an improvement in vascular function. Aim of the study was to assess the effects of a 7-month cognitive, social, and physical training program on cognitive and vascular function in patients with mild cognitive impairment. In a single-center, randomized, parallel-group study, 113 patients (age, 65–89 years) were randomized to multidomain training (n=55) or usual care (n=58). All participants underwent neuropsychological tests and vascular evaluation, including brachial artery flow-mediated dilation, carotid–femoral pulse wave velocity, carotid distensibility, and assessment of circulating hematopoietic CD34+ and endothelial progenitor cells. At study entry, an age-matched control group (n=45) was also studied. Compared with controls, patients had at study entry a reduced flow-mediated dilation (2.97±2.14% versus 3.73±2.06%; P =0.03) and hyperemic stimulus (shear rate area under the curve, 19.1±15.7 versus 25.7±15.1×10 −3 ; P =0.009); only the latter remained significant after adjustment for confounders ( P =0.03). Training improved Alzheimer disease assessment scale cognitive (training, 14.0±4.8 to 13.1±5.5; nontraining, 12.1±3.9 to 13.2±4.8; P for interaction visit×training=0.02), flow-mediated dilation (2.82±2.19% to 3.40±1.81%, 3.05±2.08% to 2.24±1.59%; P =0.006; P =0.023 after adjustment for diameter and shear rate area under the curve), and circulating hematopoietic CD34 + cells and prevented the decline in carotid distensibility (18.4±5.3 to 20.0±6.6, 23.9±11.0 to 19.5±7.1 Pa −1 ; P =0.005). The only clinical predictor of improvement of cognitive function after training was established hypertension. There was no correlation between changes in measures of cognitive and vascular function. In conclusion, a multidomain training program slows cognitive decline, especially in hypertensive individuals. This effect is accompanied by improved systemic endothelial function, mobilization of progenitor CD34 + cells, and preserved carotid distensibility.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT01725178.

Mitochondria-targeted antioxidant therapy with MitoQ ameliorates aortic stiffening in old mice

Aortic stiffening is a major independent risk factor for cardiovascular diseases, cognitive dysfunction, and other chronic disorders of aging. Mitochondria-derived reactive oxygen species are a key source of arterial oxidative stress, which may contribute to arterial stiffening by promoting adverse structural changes-including collagen overabundance and elastin degradation-and enhancing inflammation, but the potential for mitochondria-targeted therapeutic strategies to ameliorate aortic stiffening with primary aging is unknown. We assessed aortic stiffness [pulse-wave velocity (aPWV)], ex vivo aortic intrinsic mechanical properties [elastic modulus (EM) of collagen and elastin regions], and aortic protein expression in young (~6 mo) and old (~27 mo) male C57BL/6 mice consuming normal drinking water (YC and OC) or water containing mitochondria-targeted antioxidant MitoQ (250 µM; YMQ and OMQ) for 4 wk. Both baseline and postintervention aPWV values were higher in OC vs. YC (post: 482 ± 21 vs. 420 ± 5 cm/s, P < 0.05). MitoQ had no effect in young mice but decreased aPWV in old mice (OMQ, 426 ± 20, P < 0.05 vs. OC). MitoQ did not affect age-associated increases in aortic collagen-region EM, collagen expression, or proinflammatory cytokine expression, but partially attenuated age-associated decreases in elastin region EM and elastin expression. Our results demonstrate that MitoQ reverses in vivo aortic stiffness in old mice and suggest that mitochondria-targeted antioxidants may represent a novel, promising therapeutic strategy for decreasing aortic stiffness with primary aging and, possibly, age-related clinical disorders in humans. The destiffening effects of MitoQ treatment may be at least partially mediated by attenuation/reversal of age-related aortic elastin degradation. NEW & NOTEWORTHY We show that 4 wk of treatment with the mitochondria-specific antioxidant MitoQ in mice completely reverses the age-associated elevation in aortic stiffness, assessed as aortic pulse-wave velocity. The destiffening effects of MitoQ treatment may be at least partially mediated by attenuation of age-related aortic elastin degradation. Our results suggest that mitochondria-targeted therapeutic strategies may hold promise for decreasing arterial stiffening with aging in humans, possibly decreasing the risk of many chronic age-related clinical disorders.

Brain Arterial Diameters and Cognitive Performance: The Northern Manhattan Study

OBJECTIVES

To test the hypothesis that brain arterial diameters are associated with cognitive performance, particularly in arteries supplying domain-specific territories.

METHODS

Stroke-free participants in the Northern Manhattan Study were invited to have a brain MRI from 2003-2008. The luminal diameters of 13 intracranial arterial segments were obtained using time-of-flight magnetic resonance angiogram (MRA), and then averaged and normalized into a global score and region-specific arterial diameters. Z-Scores for executive function, semantic memory, episodic memory and processing speed were obtained at MRI and during follow-up. Adjusted generalized additive models were used to assess for associations.

RESULTS

Among the 1034 participants with neurocognitive testing and brain MRI, there were non-linear relationships between left anterior (ACA) and middle cerebral artery (MCA) diameter and semantic memory Z-scores (χ2=10.00; DF=3; p=.019), and left posterior cerebral artery (PCA) and posterior communicating artery (Pcomm) mean diameter and episodic memory Z-scores (χ2=9.88; DF=3; p=.020). Among the 745 participants who returned for 2nd neuropsychological testing, on average 5.0±0.4 years after their MRI, semantic memory change was associated non-linearly with the left PCA/Pcomm mean diameter (χ2=13.09; DF=3; p=.004) and with the right MCA/ACA mean diameter (χ2=8.43; DF=3; p=.03). In both cross-sectional and longitudinal analyses, participants with the larger brain arterial diameters had more consistently lower Z-scores and greater decline than the rest of the participants.

CONCLUSIONS

Brain arterial diameters may have downstream effects in brain function presenting as poorer cognition. Identifying the mechanisms and the directionality of such interactions may increase the understanding of the vascular contribution to cognitive impairment and dementia. (JINS, 2018, 24, 335-346).

Glycerophospholipid Supplementation as a Potential Intervention for Supporting Cerebral Structure in Older Adults

Modifying nutritional intake through supplementation may be efficacious for altering the trajectory of cerebral structural decline evident with increasing age. To date, there have been a number of clinical trials in older adults whereby chronic supplementation with B vitamins, omega-3 fatty acids, or resveratrol, has been observed to either slow the rate of decline or repair cerebral tissue. There is also some evidence from animal studies indicating that supplementation with glycerophospholipids (GPL) may benefit cerebral structure, though these effects have not yet been investigated in adult humans. Despite this paucity of research, there are a number of factors predicting poorer cerebral structure in older humans, which GPL supplementation appears to beneficially modify or protect against. These include elevated concentrations of homocysteine, unbalanced activity of reactive oxygen species both increasing the risk of oxidative stress, increased concentrations of pro-inflammatory messengers, as well as poorer cardio- and cerebrovascular function. As such, it is hypothesized that GPL supplementation will support cerebral structure in older adults. These cerebral effects may influence cognitive function. The current review aims to provide a theoretical basis for future clinical trials investigating the effects of GPL supplementation on cerebral structural integrity in older adults.

Microvascular endothelial function and cognitive performance: The ELSA-Brasil cohort study

Impaired microvascular endothelial function may be implicated in the etiology of cognitive decline. Yet, current data on this association are inconsistent. Our objective is to investigate the relation of microvascular endothelial function to cognitive performance in the ELSA-Brasil cohort study. A total of 1521 participants from ELSA-Brasil free of dementia underwent peripheral arterial tonometry (PAT) to quantify microvascular endothelial function (PAT-ratio and mean baseline pulse amplitude (BPA)) and cognitive tests that covered the domains of memory, verbal fluency, and executive function at baseline. Cognitive tests in participants aged 55 years old and above were repeated during the second examination (mean follow-up: 3.5 (0.3) years). Linear regression and generalized linear models were used to evaluate the association between endothelial function, global cognitive performance, and performance on specific cognitive domains. In unadjusted cross-sectional analyses, we found that BPA and PAT-ratio were associated with worse global cognitive performance (mean difference for BPA: -0.07, 95% CI: -0.11; -0.03, p<0.01; mean difference for PAT-ratio: 0.11, 95% CI: 0.01; 0.20, p=0.02), worse performance on learning, recall, and word recognition tests (BPA: -0.87, 95% CI: -1.21; -0.52, p<0.01; PAT-ratio: 1.58, 95% CI: 0.80; 2.36, p<0.01), and only BPA was associated with worse performance in verbal fluency tests (-0.70, 95% CI: -1.19; -0.21, p<0.01). Adjustments for age, sex, and level of education rendered the associations statistically non-significant. Longitudinally, there was no association between microvascular endothelial and cognitive functions. The associations between microvascular endothelial function and cognition are explained by age, sex, and educational level. Measures of microvascular endothelial function may be of limited value with regard to preclinical cognitive deficits.

Impact of pulse pressure on cerebrovascular events leading to age-related cognitive decline

Aging is a modern concept: human life expectancy has more than doubled in less than 150 yr in Western countries. Longer life span, however, reveals age-related diseases, including cerebrovascular diseases. The vascular system is a prime target of aging: the "wear and tear" of large elastic arteries exposed to a lifelong pulsatile pressure causes arterial stiffening by fragmentation of elastin fibers and replacement by stiffer collagen. This arterial stiffening increases in return the amplitude of the pulse pressure (PP), its wave penetrating deeper into the microcirculation of low-resistance, high-flow organs such as the brain. Several studies have associated peripheral arterial stiffness responsible for the sustained increase in PP, with brain microvascular diseases such as cerebral small vessel disease, cortical gray matter thinning, white matter atrophy, and cognitive dysfunction in older individuals and prematurely in hypertensive and diabetic patients. The rarefaction of white matter is also associated with middle cerebral artery pulsatility that is strongly dependent on PP and artery stiffness. PP and brain damage are likely associated, but the sequence of mechanistic events has not been established. Elevated PP promotes endothelial dysfunction that may slowly develop in parallel with the accumulation of proinflammatory senescent cells and oxidative stress, generating cerebrovascular damage and remodeling, as well as brain structural changes. Here, we review data suggesting that age-related increased peripheral artery stiffness may promote the penetration of a high PP to cerebral microvessels, likely causing functional, structural, metabolic, and hemodynamic alterations that could ultimately promote neuronal dysfunction and cognitive decline.

Brain Tissue Pulsatility is Increased in Midlife Depression: a Comparative Study Using Ultrasound Tissue Pulsatility Imaging

Cerebrovascular disease (CVD) is consistently associated with late-life depression but poorly documented in midlife depression. It can be hypothesized that the relatively low sensitivity of conventional neuroimaging techniques does not allow the detection of subtle CVD in midlife depression. We used tissue pulsatility imaging (TPI), a novel ultrasound (US) neuroimaging technique that has demonstrated good sensitivity to detect changes in the pulsatility of small brain volumes, to identify early and subtle changes in brain vascular function in midlife depression. We compared the maximum and mean brain tissue pulsatility (MaxBTP and MeanBTP), as identified by TPI, between three groups of middle-aged females matched for age: patients with depression (n=25), patients with remitted depression (n=24) and community controls (n=25). MRI arterial spin labeling, white matter hyperintensities (WMHs) and transcranial doppler (TCD) were used as control conventional markers for CVD. We found no difference in the MRI and TCD measures among the three groups. In contrast, depressive patients showed an increased BTP related to the mean global brain pulsatility (MeanBTP) and no change related to large vessels (MaxBTP) in comparison with the remitted and control groups. US neuroimaging is a highly accurate method to detect brain pulsatility changes related to cerebrovascular functioning, and TPI identified an increased BTP in midlife depressed patients, suggesting early and subtle vascular impairments in this population at risk for CVD such as stroke or WMHs. Because high pulsatility could represent prodromal cerebrovascular changes that damage the brain over time, this paper provides a potential target for blocking the progression of CVD.

Visit-to-Visit Blood Pressure Variability in Young Adulthood and Hippocampal Volume and Integrity at Middle Age: The CARDIA Study (Coronary Artery Risk Development in Young Adults)

The aims of this study are to assess the relationships of visit-to-visit blood pressure (BP) variability in young adulthood to hippocampal volume and integrity at middle age. We used data over 8 examinations spanning 25 years collected in the CARDIA study (Coronary Artery Risk Development in Young Adults) of black and white adults (age, 18-30 years) started in 1985 to 1986. Visit-to-visit BP variability was defined as by SDBP and average real variability (ARVBP, defined as the absolute differences of BP between successive BP measurements). Hippocampal tissue volume standardized by intracranial volume (%) and integrity assessed by fractional anisotropy were measured by 3-Tesla magnetic resonance imaging at the year-25 examination (n=545; mean age, 51 years; 54% women and 34% African Americans). Mean systolic BP (SBP)/diastolic BP levels were 110/69 mm Hg at year 0 (baseline), 117/73 mm Hg at year 25, and ARVSBP and SDSBP were 7.7 and 7.9 mm Hg, respectively. In multivariable-adjusted linear models, higher ARVSBP was associated with lower hippocampal volume (unstandardized regression coefficient [standard error] with 1-SD higher ARVSBP: -0.006 [0.003]), and higher SDSBP with lower hippocampal fractional anisotropy (-0.02 [0.01]; all P<0.05), independent of cumulative exposure to SBP during follow-up. Conversely, cumulative exposure to SBP and diastolic BP was not associated with hippocampal volume. There was no interaction by sex or race between ARVSBP or SDSBP with hippocampal volume or integrity. In conclusion, visit-to-visit BP variability during young adulthood may be useful in assessing the potential risk for reductions in hippocampal volume and integrity in midlife.

Pulse Pressure Is Associated With Early Brain Atrophy and Cognitive Decline: Modifying Effects of APOE-ε4

We investigated whether midlife pulse pressure is associated with brain atrophy and cognitive decline, and whether the association was modified by apolipoprotein-E ε4 (APOE-ε4) and hypertension. Participants (549 stroke-free and dementia-free Framingham Offspring Cohort Study participants, age range=55.0 to 64.9 y) underwent baseline neuropsychological and magnetic resonance imaging (subset, n=454) evaluations with 5- to 7-year follow-up. Regression analyses investigated associations between baseline pulse pressure (systolic-diastolic pressure) and cognition, total cerebral volume and temporal horn ventricular volume (as an index of smaller hippocampal volume) at follow-up, and longitudinal change in these measures. Interactions with APOE-ε4 and hypertension were assessed. Covariates included age, sex, education, assessment interval, and interim stroke. In the total sample, baseline pulse pressure was associated with worse executive ability, lower total cerebral volume, and greater temporal horn ventricular volume 5 to 7 years later, and longitudinal decline in executive ability and increase in temporal horn ventricular volume. Among APOE-ε4 carriers only, baseline pulse pressure was associated with longitudinal decline in visuospatial organization. Findings indicate arterial stiffening, indexed by pulse pressure, may play a role in early cognitive decline and brain atrophy in mid to late life, particularly among APOE-ε4 carriers.

Vascular Aging and Cognitive Dysfunction: Silent Midlife Crisis in the Brain

Background

Vascular aging may cause cerebral microvascular damage and cognitive dysfunction. There is incremental evidence that consistently implicates arterial stiffness being involved in the manifestation of cognitive impairment in the elderly. However, few investigations have examined the relationship between arterial stiffness and cognitive impairment in midlife.

Summary

Past studies inconsistently showed improved cognitive outcomes after antihypertensive therapy in elderly populations. Nevertheless, recent findings revealed that blood-pressure-lowering treatment in young adults might eliminate or halt the progression of the detrimental effects related to arterial stiffness, indicating that younger adults may have more favorable outcomes in cognition than their older counterparts if early intervention is conducted at the subclinical stage. Stiffening of the aorta may lead to an excessive flow pulsatility in the brain that may cause microvascular structural brain damage and worse cognitive performance. Recent investigations have suggested that arterial stiffness is likely to trigger initial silent brain damage, possibly preceding midlife, while the manifestation of cognitive decline and deterioration can be foreseen in the subsequent life span.

Key Message

Despite the recent novel findings, definite conclusions on causality between vascular aging and cognitive dysfunction cannot be drawn at present. Further well-powered longitudinal studies with superior neuroimaging indicator, vascular mechanical biomarkers, and sensitive cognitive assessment tools that examine a broad range of age populations may help extend our understanding of the association between vascular aging and cognitive dysfunction throughout the life span.

Age-related Impairment of Vascular Structure and Functions

Among age-related diseases, cardiovascular and cerebrovascular diseases are major causes of death. Vascular dysfunction is a key characteristic of these diseases wherein age is an independent and essential risk factor. The present work will review morphological alterations of aging vessels in-depth, which includes the discussion of age-related microvessel loss and changes to vasculature involving the capillary basement membrane, intima, media, and adventitia as well as the accompanying vascular dysfunctions arising from these alterations.

Combined Dual-Task Gait Training and Aerobic Exercise to Improve Cognition, Mobility, and Vascular Health in Community-Dwelling Older Adults at Risk for Future Cognitive Decline1

This 6-month experimental case series study investigated the effects of a dual-task gait training and aerobic exercise intervention on cognition, mobility, and cardiovascular health in community-dwelling older adults without dementia. Participants exercised 40 min/day, 3 days/week for 26 weeks on a Biodex GaitTrainer2 treadmill. Participants were assessed at baseline (V0), interim (V1: 12-weeks), intervention endpoint (V2: 26-weeks), and study endpoint (V3: 52-weeks). The study outcomes included: cognition [executive function (EF), processing speed, verbal fluency, and memory]; mobility: usual & dual-task gait (speed, step length, and stride time variability); and vascular health: ambulatory blood pressure, carotid arterial compliance, and intima-media thickness (cIMT). Fifty-six participants [age: 70(6) years; 61% female] were included in this study. Significant improvements following the exercise program (V2) were observed in cognition: EF (p = 0.002), processing speed (p < 0.001), verbal fluency [digit symbol coding (p < 0.001), phonemic verbal fluency (p < 0.001)], and memory [immediate recall (p < 0.001) and delayed recall (p < 0.001)]; mobility: usual & dual-task gait speed (p = 0.002 and p < 0.001, respectively) and step length (p = 0.001 and p = 0.003, respectively); and vascular health: cIMT (p = 0.002). No changes were seen in the remaining outcomes. In conclusion, 26 weeks of dual-task gait training and aerobic exercise improved performance on a number of cognitive outcomes, while increasing usual & dual-task gait speed and step length in a sample of older adults without dementia.

Inter-Relations of Orthostatic Blood Pressure Change, Aortic Stiffness, and Brain Structure and Function in Young Adults

BACKGROUND

Relations of orthostatic change in blood pressure with brain structure and function have not been studied thoroughly, particularly in younger, healthier individuals. Elucidation of factors that contribute to early changes in brain integrity may lead to development of interventions that delay or prevent cognitive impairment.

METHODS AND RESULTS

In a sample of the Framingham Heart Study Third Generation (N=2119; 53% women; mean age±SD, 47±8 years), we assessed orthostatic change in mean arterial pressure (MAP), aortic stiffness (carotid-femoral pulse wave velocity), neuropsychological function, and markers of subclinical brain injury on magnetic resonance imaging. Multivariable regression analyses were used to assess relations between orthostatic change in MAP and brain structural and neuropsychological outcomes. Greater orthostatic increase in MAP on standing was related to better Trails B-A performance among participants aged <49 years (β±SE, 0.062±0.029; P=0.031) and among participants with carotid-femoral pulse wave velocity <6.9 m/s (β±SE, 0.063±0.026; P=0.016). This relation was not significant among participants who were older or had stiffer aortas. Conversely, greater orthostatic increase in MAP was related to larger total brain volume among older participants (β±SE, 0.065±0.029; P=0.023) and among participants with carotid-femoral pulse wave velocity ≥6.9 m/s (β±SE, 0.078±0.031; P=0.011).

CONCLUSIONS

Blunted orthostatic increase in MAP was associated with smaller brain volume among participants who were older or had stiffer aortas and with poorer executive function among persons who were younger or who had more-elastic aortas. Our findings suggest that the brain is sensitive to orthostatic change in MAP, with results dependent on age and aortic stiffness.

Relations of Arterial Stiffness With Postural Change in Mean Arterial Pressure in Middle-Aged Adults: The Framingham Heart Study

Impaired regulation of blood pressure on standing can lead to adverse outcomes, including falls, syncope, and disorientation. Mean arterial pressure (MAP) typically increases on standing; however, an insufficient increase or a decline in MAP on standing may result in decreased cerebral perfusion. Orthostatic hypotension has been reported in older people with increased arterial stiffness, whereas the association between orthostatic change in MAP and arterial stiffness in young- to middle-aged individuals has not been examined. We analyzed orthostatic blood pressure response and comprehensive hemodynamic data in 3205 participants (1693 [53%] women) in the Framingham Heart Study Third Generation cohort. Participants were predominantly middle aged (mean age: 46±9 years). Arterial stiffness was assessed using carotid-femoral pulse wave velocity, forward pressure wave amplitude, and characteristic impedance of the aorta. Adjusting for standard cardiovascular disease risk factors, orthostatic change in MAP (6.9±7.7 mm Hg) was inversely associated with carotid-femoral pulse wave velocity (partial correlation, r_p=-0.084; P<0.0001), forward wave amplitude (r_p=-0.129; P<0.0001), and characteristic impedance (r_p=-0.094; P<0.0001). The negative relation between forward wave amplitude and change in MAP on standing was accentuated in women (P=0.002 for sex interaction). Thus, higher aortic stiffness was associated with a blunted orthostatic increase in MAP, even in middle age. The clinical implications of these findings warrant further study.

Endothelial Function Is Associated with White Matter Microstructure and Executive Function in Older Adults

Age-related declines in endothelial function can lead to cognitive decline. However, little is known about the relationships between endothelial function and specific neurocognitive functions. This study explored the relationship between measures of endothelial function (reactive hyperemia index; RHI), white matter (WM) health (fractional anisotropy, FA, and WM hyperintensity volume, WMH), and executive function (Trail Making Test (TMT); Trail B - Trail A). Participants were 36 older adults between the ages of 59 and 69 (mean age = 63.89 years, SD = 2.94). WMH volume showed no relationship with RHI or executive function. However, there was a positive relationship between RHI and FA in the genu and body of the corpus callosum. In addition, higher RHI and FA were each associated with better executive task performance. Tractography was used to localize the WM tracts associated with RHI to specific portions of cortex. Results indicated that the RHI-FA relationship observed in the corpus callosum primarily involved tracts interconnecting frontal regions, including the superior frontal gyrus (SFG) and frontopolar cortex, linked with executive function. These findings suggest that superior endothelial function may help to attenuate age-related declines in WM microstructure in portions of the corpus callosum that interconnect prefrontal brain regions involved in executive function.

Recent Progress in Vascular Aging: Mechanisms and Its Role in Age-related Diseases

As with many age-related diseases including vascular dysfunction, age is considered an independent and crucial risk factor. Complicated alterations of structure and function in the vasculature are linked with aging hence, understanding the underlying mechanisms of age-induced vascular pathophysiological changes holds possibilities for developing clinical diagnostic methods and new therapeutic strategies. Here, we discuss the underlying molecular mediators that could be involved in vascular aging, e.g., the renin-angiotensin system and pro-inflammatory factors, metalloproteinases, calpain-1, monocyte chemoattractant protein-1 (MCP-1) and TGFβ-1 as well as the potential roles of testosterone and estrogen. We then relate all of these to clinical manifestations such as vascular dementia and stroke in addition to reviewing the existing clinical measurements and potential interventions for age-related vascular dysfunction.

"Do it-yourself": Home blood pressure as a predictor of traditional and everyday cognition in older adults

BACKGROUND

Hypertension guidelines recommend home blood pressure (HBP) monitoring in adjunct to office blood pressure (OBP) for its greater reproducibility and prognostic utility in the prevention of cardiovascular outcomes, especially stroke. To date, the relationship between HBP and cognitive function remains unexplored.

METHODS

We examined HBP as a cognitive predictor in a multi-ethnic group of community-dwelling adults aged 60 and over (N = 133) using neuropsychological measures and analyzed the data using multiple regression analyses. We also employed "everyday cognition" measures that have been found to have higher prognostic utility for real-world functioning than traditional cognitive tasks.

RESULTS

Good to perfect HBP monitoring compliance over seven days was achieved by 88.7% of the participants with superior reliability (ICC≥.96) to office readings. Higher home systolic BP and pulse pressure predicted worse processing speed, executive function, and everyday cognitive function, whereas lower home diastolic BP predicted worse everyday cognition. Office readings were similarly associated with everyday cognitive function but with no other cognitive measures.

CONCLUSION

Our findings are the first to validate HBP as a predictor of neuropsychological function in older adults beyond cognitive screening. Differential relationships among blood pressure variables and specific cognitive domains were observed. With proper standardization and training, we demonstrated that HBP can be obtained in a multi-ethnic community-dwelling older adult cohort. Our findings emphasize the importance of employing blood pressure and cognitive measures that are adequately sensitive to detect vascular-related cognitive impairment in a relatively healthy population. Implications regarding proper HBP measurement for hypertension management, cognitive health, and everyday function are discussed.

Association of arterial stiffness with cognition in patients with Lewy body disorder

The brachial-ankle pulse wave velocity (baPWV) is a marker for arterial stiffness, which is associated with cardiovascular diseases. Arterial stiffness is associated with cognitive function in the elderly and patients with Alzheimer's disease (AD). We aimed to investigate the association between arterial stiffness and cognitive function in patients with Lewy body disorder (LBD), including Parkinson's disease (PD) and dementia with Lewy bodies (DLB). We consecutively included 123 patients with PD, 10 patients with DLB, and 27 AD controls. Patients with PD were divided into three groups of normal cognition (PD-NC, n = 63), mild cognitive impairment (PD-MCI, n = 43), and dementia (PD-D, n = 17). Arterial stiffness, measured as baPWV, was compared between the PD-NC, PD-MCI, PD-D, DLB, and AD patients. In LBD, we analyzed the association between arterial stiffness and each cognitive domain with adjustment for covariates. Higher baPWV was significantly associated with cognitive decline in patients with LBD (baPWV in PD-D > PD-MCI > PD-NC; DLB > PD-NC). There was no significant difference in baPWV between PD-D, DLB, and AD patients. In LBD patients, higher baPWV was associated with lower mini mental state examination score (β ± SE = -0.003 ± 0.001, p = 0.007) and more severe dementia. Higher baPWV was also associated with lower performance in attention, language, visuospatial function, memory, and executive function in LBD patients. This suggests that vascular brain injury is associated with cognitive dysfunction in LBD.

Aortic Stiffness, Increased White Matter Free Water, and Altered Microstructural Integrity: A Continuum of Injury

BACKGROUND AND PURPOSE

Previous reports from the Framingham Heart Study have identified cross-sectional associations of arterial stiffness, as reflected by carotid-femoral pulse wave velocity (CFPWV) and systolic blood pressure with vascular brain injury. The purpose of this study is to examine free water (FW), fractional anisotropy (FA), and white matter hyperintensities (WMH) in relation to arterial stiffness among subjects of the Framingham Offspring and Third-Generation cohorts.

METHODS

In 2422 participants aged 51.3±11.6 years, FA, FW, and WMH were related to CFPWV using voxel-based linear and generalized linear regressions, adjusting for relevant covariables. Mean FW, mean FA, and WMH burden (log transformed) were computed within white matter (WM) region and related to systolic blood pressure and CFPWV using multiple mediation analyses.

RESULTS

CFPWV was found to be associated with higher FW, lower FA, and higher WMH incidence in WM areas covering, respectively, 356.1, 211.8, and 10.9 mL of the WM mask. Mediation analyses revealed that the effect of systolic blood pressure on FW was mediated by CFPWV (direct and indirect effects: a=0.040; P<0.001, and a'=0.020; P>0.05). Moreover, the effect of CFPWV on FA was mediated by FW (direct and indirect effects: b=-0.092; P<0.001, and b'=0.012; P>0.05), whose effect on WMH was, in turn, mediated by FA (direct and indirect effects: c=0.246; P<0.001, and c'=0.116; P>0.05).

CONCLUSIONS

From these data, we propose a biomechanical hypothesis designed for future research experiments to explain how hemodynamic alteration may lead to WM injury by impacting cerebral water content and more subtly WM integrity, to finally lead to WMH development.

Olfactory evaluation in Mild Cognitive Impairment: correlation with neurocognitive performance and endothelial function

Mild Cognitive Impairment (MCI) is an intermediate condition between normal aging and dementia, associated with an increased risk of progression into the latter within months or years. Olfactory impairment, a well-known biomarker for neurodegeneration, might be present in the condition early, possibly representing a signal for future pathological onset. Our study aimed at evaluating olfactory function in MCI and healthy controls in relation to neurocognitive performance and endothelial function. A total of 85 individuals with MCI and 41 healthy controls, matched for age and gender, were recruited. Olfactory function was assessed by Sniffin' Sticks Extended Test (Burghart, Medizintechnik, GmbH, Wedel, Germany). A comprehensive neurocognitive assessment was performed. Endothelial function was assessed by flow-mediated dilation (FMD) of the brachial artery by ultrasound. MCI individuals showed an impaired olfactory function compared to controls. The overall olfactory score is able to predict MCI with a good sensitivity and specificity (70.3 and 77.4% respectively). In MCI, olfactory identification score is correlated with a number of neurocognitive abilities, including overall cognitive status, dementia rating, immediate and delayed memory, visuospatial ability and verbal fluency. FMD was reduced in MCI (2.90 ± 2.15 vs. 3.66 ± 1.96%, P = 0.016) and was positively associated with olfactory identification score (ρ_s =0.219, P = 0.025). The association remained significant after controlling for age, gender, and smoking. In conclusion, olfactory evaluation is able to discriminate between MCI and healthy individuals. Systemic vascular dysfunction might be involved, at least indirectly, in olfactory dysfunction in MCI.

Aortic hemodynamics and white matter hyperintensities in normotensive postmenopausal women

Hypertension is associated with development of white matter hyperintensities (WMH) in the brain, which are risk factors for mild cognitive impairment. Hormonal shifts at menopause alter vascular function putting women at risk for both hypertension and WMH. Elevations in aortic hemodynamics precede the appearance of clinically defined hypertension but the relationship of aortic hemodynamics to development of WMH in women is not known. Therefore, this study aimed to characterize aortic hemodynamics in relationship to WMH in postmenopausal women. Aortic systolic and diastolic blood pressure (BP), aortic augmentation index (Alx) and aortic round trip travel time (Aortic T_R) by tonometry were examined in 53 postmenopausal women (age 60 ± 2 years). WMH was calculated from fluid-attenuated inversion recovery MRI using a semi-automated segmentation algorithm. WMH as a fraction of total white matter volume positively associated with aortic systolic BP (regression coefficient = 0.018; p = 0.04) after adjusting for age. In addition, WMH fraction was positively associated with AIx (0.025; p = 0.04), and inversely associated with Aortic T_R (−0.015; p = 0.04) after adjusting for age. Our results suggest that assessing aortic hemodynamics may identify individuals at risk for accelerated development of WMH and guide early treatment to reduce WMH burden and cognitive impairment in the future.

Pulse pressure-dependent cerebrovascular eNOS regulation in mice

Arterial blood pressure is oscillatory; whether pulse pressure (PP) regulates cerebral artery myogenic tone (MT) and endothelial function is currently unknown. To test the impact of PP on MT and dilation to flow (FMD) or to acetylcholine (Ach), isolated pressurized mouse posterior cerebral arteries were subjected to either static pressure (SP) or a physiological PP (amplitude: 30 mm Hg; frequency: 550 bpm). Under PP, MT was significantly higher than in SP conditions ( p < 0.05) and was not affected by eNOS inhibition. In contrast, under SP, eNOS inhibition increased ( p < 0.05) MT to levels observed under PP, suggesting that PP may inhibit eNOS. At a shear stress of 20 dyn/cm², FMD was lower ( p < 0.05) under SP than PP. Under SP, eNOS-dependent [Formula: see text] production contributed to FMD, while under PP, eNOS-dependent NO was responsible for FMD, indicating that PP favours eNOS coupling. Differences in FMD between pressure conditions were abolished after NOX2 inhibition. In contrast to FMD, Ach-induced dilations were higher ( p < 0.05) under SP than PP. Reactive oxygen species scavenging reduced ( p < 0.05) Ach-dependent dilations under SP, but increased ( p < 0.05) them under PP; hence, under PP, Ach promotes ROS production and limits eNOS-derived NO activity. In conclusion, PP finely regulates eNOS, controlling cerebral artery reactivity.

Carotid β-stiffness index is associated with slower processing speed but not working memory or white matter integrity in healthy middle-aged/older adults

Aging is associated with increased carotid artery stiffness, a predictor of incident stroke, and reduced cognitive performance and brain white matter integrity (WMI) in humans. Therefore, we hypothesized that higher carotid stiffness/lower compliance would be independently associated with slower processing speed, higher working memory cost, and lower WMI in healthy middle-aged/older (MA/O) adults. Carotid β-stiffness (P < 0.001) was greater and compliance (P < 0.001) was lower in MA/O (n = 32; 64.4 ± 4.3 yr) vs. young (n = 19; 23.8 ± 2.9 yr) adults. MA/O adults demonstrated slower processing speed (27.4 ± 4.6 vs. 35.4 ± 5.0 U/60 s, P < 0.001) and higher working memory cost (-15.4 ± 0.14 vs. -2.2 ± 0.05%, P < 0.001) vs. young adults. Global WMI was lower in MA/O adults (P < 0.001) and regionally in the frontal lobe (P = 0.020) and genu (P = 0.009). In the entire cohort, multiple regression analysis that included education, sex, and body mass index, carotid β-stiffness index (B = -0.53 ± 0.15 U, P = 0.001) and age group (B = -4.61 ± 1.7, P = 0.012, adjusted R² = 0.4) predicted processing speed but not working memory cost or WMI. Among MA/O adults, higher β-stiffness (B = -0.60 ± 0.18, P = 0.002) and lower compliance (B = 0.93 ± 0.26, P = 0.002) were associated with slower processing speed but not working memory cost or WMI. These data suggest that greater carotid artery stiffness is independently and selectively associated with slower processing speed but not working memory among MA/O adults. Carotid artery stiffening may modulate reductions in processing speed earlier than working memory with healthy aging in humans.NEW & NOTEWORTHY Previously, studies investigating the relation between large elastic artery stiffness, cognition, and brain structure have focused mainly on aortic stiffness in aged individuals with cardiovascular disease risk factors and other comorbidities. This study adds to the field by demonstrating that the age-related increases in carotid artery stiffness, but not aortic stiffness, is independently and selectively associated with slower processing speed but not working memory among middle-aged/older adults with low cardiovascular disease risk factor burden.

Association between central blood pressure, arterial stiffness, and mild cognitive impairment

Background

To determine the relationship between central blood pressure (CBP) indices and mild cognitive impairment (MCI) in adults over the age of 50.

Methods

A cross-sectional study conducted using a non-invasive SphygmoCor XCEL device. CBP indices and brachial blood pressure were measured in 50 inpatients and outpatients. MCI was assessed using the Montreal Cognitive Assessment (MoCA) instrument and by the European Consortium Criteria (ECC).

Results

Seventy-six percent of subjects had hypertension, and 52% were diagnosed as having MCI using the ECC. No significant association was found between any of the measured blood pressure variables and global cognition. A significant relationship was observed between augmentation index (AI) and abnormal clock-drawing (p = 0.04) and language (p = 0.02), and between pulse pressure amplification (PPA) and language (p = 0.03).

Conclusion

CBP indices like AI and PPA, which are markers of vascular stiffness, are associated with poor executive function and language cognitive domain deficits.

Functional vascular contributions to cognitive impairment and dementia: mechanisms and consequences of cerebral autoregulatory dysfunction, endothelial impairment, and neurovascular uncoupling in aging

Increasing evidence from epidemiological, clinical and experimental studies indicate that age-related cerebromicrovascular dysfunction and microcirculatory damage play critical roles in the pathogenesis of many types of dementia in the elderly, including Alzheimer's disease. Understanding and targeting the age-related pathophysiological mechanisms that underlie vascular contributions to cognitive impairment and dementia (VCID) are expected to have a major role in preserving brain health in older individuals. Maintenance of cerebral perfusion, protecting the microcirculation from high pressure-induced damage and moment-to-moment adjustment of regional oxygen and nutrient supply to changes in demand are prerequisites for the prevention of cerebral ischemia and neuronal dysfunction. This overview discusses age-related alterations in three main regulatory paradigms involved in the regulation of cerebral blood flow (CBF): cerebral autoregulation/myogenic constriction, endothelium-dependent vasomotor function, and neurovascular coupling responses responsible for functional hyperemia. The pathophysiological consequences of cerebral microvascular dysregulation in aging are explored, including blood-brain barrier disruption, neuroinflammation, exacerbation of neurodegeneration, development of cerebral microhemorrhages, microvascular rarefaction, and ischemic neuronal dysfunction and damage. Due to the widespread attention that VCID has captured in recent years, the evidence for the causal role of cerebral microvascular dysregulation in cognitive decline is critically examined.

Association of Central Arterial Stiffness and Pressure Pulsatility with Mild Cognitive Impairment and Dementia: The Atherosclerosis Risk in Communities Study-Neurocognitive Study (ARIC-NCS)

BACKGROUND

The association of central arterial stiffness and pressure pulsatility with mild cognitive impairment (MCI) and dementia is not well characterized in the population-based setting.

OBJECTIVE

The aim of this study was to quantify the cross-sectional association of arterial stiffness and pressure pulsatility with MCI and dementia among 4,461 older white and black adults from the population-based Atherosclerosis Risk in Communities Study-Neurocognitive Study.

METHODS

We used race-stratified multinomial logistic regression to evaluate associations of percentile cut points of carotid-femoral pulse wave velocity, central systolic blood pressure, central pulse pressure, and pulse pressure amplification with MCI and dementia versus no cognitive impairment.

RESULTS

Among whites, those with carotid-femoral pulse wave velocity or central systolic blood pressure ≥75th percentile had a higher prevalence of MCI compared to participants <75th percentile (conditional odds ratio (OR); 95% confidence interval (CI): 1.27 (1.02, 1.56) and 1.28 (1.04, 1.57), respectively) and those with central pulse pressure ≥75th percentile had a higher prevalence of MCI (OR 1.27 (95% CI: 1.03, 1.58)) and dementia (OR 1.76 (95% CI: 1.06, 2.92) compared to participants <75th percentile. Also among whites, those with pulse pressure amplification ≤25th percentile had a higher prevalence of dementia compared to participants >25th percentile (OR 1.65; (95% CI: 1.01, 2.70). Weaker associations were seen among black participants.

CONCLUSION

Higher arterial stiffness and pulsatility were associated with MCI and dementia in white participants. Longitudinal characterization of the observed associations is warranted to assess whether arterial stiffness and pressure pulsatility predict MCI and dementia among older adults.

N-Terminal Pro-B-Type Natriuretic Peptide and Subclinical Brain Damage in the General Population

Purpose To investigate the association between N-terminal pro-B-type natriuretic peptide (NT-proBNP), which is a marker of heart disease, and markers of subclinical brain damage on magnetic resonance (MR) images in community-dwelling middle-aged and elderly subjects without dementia and without a clinical diagnosis of heart disease. Materials and Methods This prospective population-based cohort study was approved by a medical ethics committee overseen by the national government, and all participants gave written informed consent. Serum levels of NT-proBNP were measured in 2397 participants without dementia or stroke (mean age, 56.6 years; age range, 45.7-87.3 years) and without clinical diagnosis of heart disease who were drawn from the population-based Rotterdam Study. All participants were examined with a 1.5-T MR imager. Multivariable linear and logistic regression analyses were used to investigate the association between NT-proBNP level and MR imaging markers of subclinical brain damage, including volumetric, focal, and microstructural markers. Results A higher NT-proBNP level was associated with smaller total brain volume (mean difference in z score per standard deviation increase in NT-proBNP level, -0.021; 95% confidence interval [CI]: -0.034, -0.007; P = .003) and was predominantly driven by gray matter volume (mean difference in z score per standard deviation increase in NT-proBNP level, -0.037; 95% CI: -0.057, -0.017; P < .001). Higher NT-proBNP level was associated with larger white matter lesion volume (mean difference in z score per standard deviation increase in NT-proBNP level, 0.090; 95% CI: 0.051, 0.129; P < .001), with lower fractional anisotropy (mean difference in z score per standard deviation increase in NT-proBNP level, -0.048; 95% CI: -0.088, -0.008; P = .019) and higher mean diffusivity (mean difference in z score per standard deviation increase in NT-proBNP level, 0.054; 95% CI: 0.018, 0.091; P = .004) of normal-appearing white matter. Conclusion In community-dwelling persons, higher serum NT-proBNP levels are associated with volumetric and microstructural MR imaging markers of subclinical brain damage. ^© RSNA, 2016 Online supplemental material is available for this article.

Impact of Hypertension on Cognitive Function: A Scientific Statement From the American Heart Association

BACKGROUND

Age-related dementia, most commonly caused by Alzheimer disease or cerebrovascular factors (vascular dementia), is a major public health threat. Chronic arterial hypertension is a well-established risk factor for both types of dementia, but the link between hypertension and its treatment and cognition remains poorly understood. In this scientific statement, a multidisciplinary team of experts examines the impact of hypertension on cognition to assess the state of the knowledge, to identify gaps, and to provide future directions.

METHODS

Authors with relevant expertise were selected to contribute to this statement in accordance with the American Heart Association conflict-of-interest management policy. Panel members were assigned topics relevant to their areas of expertise, reviewed the literature, and summarized the available data.

RESULTS

Hypertension disrupts the structure and function of cerebral blood vessels, leads to ischemic damage of white matter regions critical for cognitive function, and may promote Alzheimer pathology. There is strong evidence of a deleterious influence of midlife hypertension on late-life cognitive function, but the cognitive impact of late-life hypertension is less clear. Observational studies demonstrated a cumulative effect of hypertension on cerebrovascular damage, but evidence from clinical trials that antihypertensive treatment improves cognition is not conclusive.

CONCLUSIONS

After carefully reviewing the literature, the group concluded that there were insufficient data to make evidence-based recommendations. However, judicious treatment of hypertension, taking into account goals of care and individual characteristics (eg, age and comorbidities), seems justified to safeguard vascular health and, as a consequence, brain health.

A comparison between the pathophysiology of multiple sclerosis and normal pressure hydrocephalus: is pulse wave encephalopathy a component of MS?

BACKGROUND

It has been suggested there is a chronic neurodegenerative disorder, underlying the pathophysiology of multiple sclerosis (MS), which is distinct from the more obvious immune-mediated attack on the white matter. Limited data exists indicating there is an alteration in pulse wave propagation within the craniospinal cavity in MS, similar to the findings in normal pressure hydrocephalus (NPH). It is hypothesized MS may harbor pulse wave encephalopathy. The purpose of this study is to compare blood flow and pulse wave measurements in MS patients with a cohort of NPH patients and control subjects, to test this hypothesis.

METHODS

Twenty patients with MS underwent magnetic resonance (MR) flow quantification techniques. Mean blood flow and stroke volume were measured in the arterial inflow and venous out flow from the sagittal (SSS) and straight sinus (ST). The arteriovenous delay (AVD) was defined. The results were compared with both age-matched controls and NPH patients.

RESULTS

In MS there was a 35 % reduction in arteriovenous delay and a 5 % reduction in the percentage of the arterial inflow returning via the sagittal sinus compared to age matched controls. There was an alteration in pulse wave propagation, with a 26 % increase in arterial stroke volume but 30 % reduction in SSS and ST stroke volume. The AVD and blood flow changes were in the same direction to those of NPH patients.

CONCLUSIONS

There are blood flow and pulsation propagation changes in MS patients which are similar to those of NPH patients. The findings would be consistent with an underlying pulse wave encephalopathy component in MS.

Cerebral Hemodynamics in the Elderly: A Transcranial Doppler Study in the Einstein Aging Study Cohort

OBJECTIVES

We sought to describe the relationship between age, sex, and race/ethnicity with transcranial Doppler hemodynamic characteristics from major intracerebral arterial segments in a large elderly population with varying demographics.

METHODS

We analyzed 369 stroke-free participants aged 70 years and older from the Einstein Aging Study. Single-gate, nonimaging transcranial Doppler sonography, a noninvasive sonographic technique that assesses real-time cerebrovascular hemodynamics, was used to interrogate 9 cerebral arterial segments. Individual Doppler spectra and cerebral blood flow velocities were acquired, and the pulsatility index and resistive index were calculated by the device's automated waveform-tracking function. Multiple linear regression models were used to examine the independent associations of age, sex, and race/ethnicity with transcranial Doppler measures, adjusting for hypertension, history of myocardial infarction or revascularization, and history of diabetes.

RESULTS

Among enrolled participants, 303 individuals had at least 1 vessel insonated (mean age [SD], 80 [6] years; 63% women; 58% white; and 32% black). With age, transcranial Doppler measures of mean blood flow velocity were significantly decreased in the basilar artery (P = .001) and posterior cerebral artery (right, P = .003; left, P = .02). Pulsatility indices increased in the left middle cerebral artery (P = .01) and left anterior cerebral artery (P = .03), and the resistive index was increased in the left middle cerebral artery (P = .007) with age. Women had higher pulsatility and resistive indices compared to men in several vessels.

CONCLUSIONS

We report a decreased mean blood flow velocity and weakly increased arterial pulsatility and resistance with aging in a large elderly stroke-free population. These referential trends in cerebrovascular hemodynamics may carry important implications in vascular diseases associated with advanced age, increased risk of cerebrovascular disease, cognitive decline, and dementia.

Aortic Stiffness and the Risk of Incident Mild Cognitive Impairment and Dementia

BACKGROUND AND PURPOSE

Aortic stiffening increases the transfers of high pressure and flow pulsatility to small cerebral vessels potentially causing the accumulation of vascular brain injury. Our aim was to investigate the prospective association of aortic stiffness with the risks of incident mild cognitive impairment and dementia.

METHODS

We studied 1101 dementia-free Framingham Offspring study participants (mean age, 69±6 years; 54% women). Aortic stiffness was measured as carotid-femoral pulse wave velocity using applanation tonometry and modeled as a linear variable and the top 2 quintiles (>11.4 m/s). Outcomes were the 10-year risk of incident mild cognitive impairment and dementia, including clinically characterized Alzheimer disease. We observed 106, 77, and 59 events of mild cognitive impairment, all-cause dementia, and clinical Alzheimer disease, respectively.

RESULTS

After adjustment for age and sex, higher continuous aortic stiffness predicted an increased risk of mild cognitive impairment (hazard ratio, 1.40 [95% confidence interval, 1.13-1.73]), all-cause dementia (hazard ratio, 1.45 [95% confidence interval, 1.13-1.87]), and Alzheimer disease (hazard ratio, 1.41 [95% confidence interval, 1.06-1.87]). In risk factor-adjusted statistical models, aortic stiffness remained a significant predictor of mild cognitive impairment but not incident dementia. In nondiabetic patients, the top 2 quintiles of aortic stiffness were associated with a higher risk of incident all-cause dementia across all statistical models.

CONCLUSIONS

Aortic stiffness was an independent predictor of incident mild cognitive impairment in the whole sample and with incident dementia in nondiabetic patients. Our findings suggest aortic stiffness as a potentially modifiable risk factor for clinical cognitive impairment and dementia.

Carotid stiffness is associated with impairment of cognitive performance in individuals with and without type 2 diabetes. The Maastricht Study

BACKGROUND AND AIMS

There is increasing evidence linking arterial (mainly aortic) stiffness and type 2 diabetes, a risk factor for arterial stiffness, to cognitive impairment and dementia. However, data on carotid stiffness, which may be especially relevant for cognitive performance, are scarce, and few studies have addressed the interplay between arterial stiffness, type 2 diabetes, and cognitive performance.

METHODS

We studied individuals with (n = 197) and without (n = 528) type 2 diabetes, who completed a neuropsychological test battery and underwent applanation tonometry and vascular ultrasound to evaluate aortic (i.e. carotid-to-femoral pulse wave velocity) and carotid stiffness (i.e. distensibility, compliance and Young's elastic modulus). Linear regression analyses were performed and adjusted for demographics, vascular risk factors, and depression.

RESULTS

Overall, our results showed that carotid, but not aortic, stiffness was associated with worse cognitive performance, primarily in the domains of processing speed (standardized regression coefficient for distensibility -0.083, p = 0.040; compliance -0.077, p = 0.032) and executive function and attention (distensibility -0.133, p = 0.001; compliance -0.090, p = 0.015; Young's elastic modulus -0.081, p = 0.027). These associations did not differ by diabetes status. The differences in cognitive performance between individuals with and without type 2 diabetes (mean difference in domain scores relative to those without diabetes for free recall memory -0.23, processing speed -0.19, executive function and attention -0.23; all p ≤ 0.009 and adjusted for demographics, traditional vascular risk factors, and depression) were not substantially altered after additional adjustment for carotid stiffness.

CONCLUSIONS

Our findings suggest that carotid stiffness is associated with cognitive performance in both individuals with and without diabetes, but does not mediate the relationship between type 2 diabetes and cognitive dysfunction.

Evaluating arterial stiffness in type 2 diabetes patients using ultrasonic radiofrequency

Differences in arterial stiffness between the two sides of the carotid arteries were investigated using ultrasonic radiofrequency in 88 patients with type 2 diabetes and 70 controls. The compliance coefficient (CC), pulse wave velocity (PWV), intima-media thickness (CIMT) and diameter (CCAD) of the common carotid arteries (CCAs) were measured. The ratio of the left to right CCAs was calculated to provide four indexes: CC ratio, PWV ratio, CIMT ratio and CCAD ratio. In the diabetes group, the PWV on the left side was significantly higher than that on the right side, while the CC on the left side was significantly lower than that on the right side. The bilateral CIMT was thicker and CCAD was wider, the left PWV traveled faster, and the right CC was higher in the diabetes group than in the control group. The PWV ratio between the two groups was significantly different and correlated positively with duration of diabetes and systolic blood pressure (SBP). The differences between the two sides of CCAs in patients with diabetes suggested that disease duration and SBP were important risk factors for arterial stiffness. Identifying the difference could potentially lead to the much earlier diagnosis of arteriosclerosis.

Post-exercise pulse pressure is a better predictor of executive function than pre-exercise pulse pressure in cognitively normal older adults

Exercise "stress tests" are widely used to assess cardiovascular function and to detect abnormalities. In line with the view of exercise as a stressor, the present study examined the relationship between cognitive function and cardiovascular activity before and after light physical exercise in a sample of 84 non-demented community-dwelling older adults. Based on known relationships between hypertension, executive function and cerebral white matter changes, we hypothesized that greater post-exercise reactivity, as indexed by higher pulse pressure, would be more related to worse performance on frontal-executive tasks than pre-exercise physiologic measures. All participants were administered a comprehensive neuropsychological battery and underwent a Six Minute Walk Test (6MWT), with blood pressure (BP) measures obtained immediately before and after the walk. Pulse pressure (PP) was derived from BP as an indicator of vascular auto-regulation and composite scores were computed for each cognitive domain assessed. As predicted, worse executive function scores exhibited a stronger relationship with post-exercise PP than pre-exercise PP. Results suggest that PP following system stress in the form of walking may be more reflective of the state of vascular integrity and associated executive dysfunction in older adults than baseline physiologic measures.