Joint effect of mid- and late-life blood pressure on the brain: the AGES-Reykjavik study

[Small vessel cerebrovascular disease]

Small vessel vascular disease is a spectrum of different conditions that includes lacunar infarction, alteration of deep white matter, or microbleeds. Hypertension is the main risk factor, although the atherothrombotic lesion may be present, particularly in large-sized lacunar infarctions along with other vascular risk factors. MRI findings are characteristic and the lesions authentic biomarkers that allow differentiating the value of risk factors and defining their prognostic value.

Association of diastolic blood pressure with cardiovascular events in older people varies upon cardiovascular history

BACKGROUND

In older age, a low DBP has been associated with increased risk of cardiovascular events, especially in frail older people. We tested the hypothesis that low DBP is associated with a high risk of cardiovascular events in people with a previous history of cardiovascular disease, as a proxy of vascular impairment.

METHODS

We included 5804 participants (mean age 75 years) from the PROspective Study of Pravastatin in the Elderly at Risk (PROSPER) who as part of the trial were intensively monitored for an average period of 3.2 years. DBP was categorized in low (<70 mmHg), normal (70-90 mmHg) or high (>90 mmHg). Cox proportional hazards analyses were used to estimate hazard ratio with 95% confidence intervals (CI); analyses were stratified for cardiovascular history.

RESULTS

Participants with low DBP had a 1.24-fold (1.04; 1.49) increased risk of cardiovascular events compared with those with normal DBP. After further adjusting for cardiovascular factors, this association attenuated to 1.05 (0.86; 1.28). A previous history of cardiovascular disease significantly modified the relation between DBP and risk of cardiovascular events (P-interaction 0.042). In participants without a history of cardiovascular disease, DBP was marginally significantly associated with an increased event risk (hazard ratio (95% CI) per 10 mmHg increase in DBP 1.08 (0.99; 1.18), P value = 0.07), whereas in participants with a history of cardiovascular disease, higher DBP was associated with a decreased risk of cardiovascular events (hazard ratio (95% CI) per 10 mmHg increase in DBP 0.92 (0.85; 0.99, P value = 0.018). These risk estimates were independent of potential confounders, including classical cardiovascular risk factors.

CONCLUSION

The association of DBP with cardiovascular events in older people varies upon their previous history, showing that in participants with preexisting cardiovascular diseases, a higher DBP associates with a decreased risk of future cardiovascular events.

Blood pressure from mid- to late life and risk of incident dementia

OBJECTIVE

To determine the association between blood pressure during midlife (40-64 years) to late life (≥65 years) and risk of incident dementia.

METHODS

This study included 1,440 (758 women, mean age 69 ± 6 years) Framingham Offspring participants who were free of dementia and attended 5 consecutive examinations at 4-year intervals starting at midlife (1983-1987, mean age 55 years) until late life (1998-2001, mean 69 years) and subsequently were followed up for incident dementia (mean 8 years). We determined the effect of midlife hypertension (≥140/90 mm Hg), late life hypertension, lower late life blood pressure (<100/70 mm Hg), persistence of hypertension during mid- to late life, and steep decline in blood pressure from mid- to late life over an 18-year exposure period.

RESULTS

During the follow-up period, 107 participants (71 women) developed dementia. Using multivariable Cox proportional hazards models, we found that midlife systolic hypertension (hazard ratio [HR] 1.57, 95% confidence interval [CI] 1.05-2.35) and persistence of systolic hypertension into late life (HR 1.96, 95% CI 1.25-3.09) were associated with an elevated risk of incident dementia. However, in individuals with low to normal blood pressure (≤140/90 mm Hg) at midlife, a steep decline in systolic blood pressure during mid- to late life was also associated with a >2-fold increase in dementia risk (HR 2.40, 95% CI 1.39-4.15).

CONCLUSIONS

Elevated blood pressure during midlife, persistence of elevated blood pressure into late life, and, among nonhypertensives, a steep decline in blood pressure during mid- to late life were associated with an increased dementia risk in a community-based cohort. Our data highlight the potential sustained cognitive benefits of lower blood pressures in midlife but also suggest that declining blood pressure in older adults with prehypertension or normotension, but not in those with hypertension, may be a risk marker for dementia.

Defining the Relationship Between Hypertension, Cognitive Decline, and Dementia: a Review

Hypertension is a highly prevalent condition which has been established as a risk factor for cardiovascular and cerebrovascular disease. Although the understanding of the relationship between cardiocirculatory dysfunction and brain health has improved significantly over the last several decades, it is still unclear whether hypertension constitutes a potentially treatable risk factor for cognitive decline and dementia. While it is clear that hypertension can affect brain structure and function, recent findings suggest that the associations between blood pressure and brain health are complex and, in many cases, dependent on factors such as age, hypertension chronicity, and antihypertensive medication use. Whereas large epidemiological studies have demonstrated a consistent association between high midlife BP and late-life cognitive decline and incident dementia, associations between late-life blood pressure and cognition have been less consistent. Recent evidence suggests that hypertension may promote alterations in brain structure and function through a process of cerebral vessel remodeling, which can lead to disruptions in cerebral autoregulation, reductions in cerebral perfusion, and limit the brain's ability to clear potentially harmful proteins such as β-amyloid. The purpose of the current review is to synthesize recent findings from epidemiological, neuroimaging, physiological, genetic, and translational research to provide an overview of what is currently known about the association between blood pressure and cognitive function across the lifespan. In doing so, the current review also discusses the results of recent randomized controlled trials of antihypertensive therapy to reduce cognitive decline, highlights several methodological limitations, and provides recommendations for future clinical trial design.

Home blood pressure monitoring among adults-American Heart Association Cardiovascular Health Consumer Survey, 2012

Home blood pressure monitoring (HBPM) among hypertensive adults was assessed using the 2012 American Heart Association Cardiovascular Health Consumer Survey. The prevalence of hypertension was 25.5% and 53.8% of those reported HBPM. Approximately 63% of hypertensive adults 65 years and older reported HBPM followed by 51% and 34.6% (35-64 and 18-34 years, respectively; P=.001). Those who had seen a healthcare professional within a year reported HBPM compared with those who had not (54.8% vs 32.8%, P=.047). Those who believed that lowering blood pressure can reduce risk of heart attack and stroke had a higher percentage of HBPM compared with those who did not (55.5% vs 33.1%, P=.01). Age and the belief that lowering blood pressure could reduce cardiovascular disease risk were significant factors associated with HBPM. Half of the adult hypertensive patients reported HBPM and its use was greater among those who reported a positive attitude toward lowering blood pressure to reduce cardiovascular disease risk.

Hypertension, cerebrovascular impairment, and cognitive decline in aged AβPP/PS1 mice

Cardiovascular risk factors, especially hypertension, are also major risk factors for Alzheimer's disease (AD). To elucidate the underlying vascular origin of neurodegenerative processes in AD, we investigated the relation between systolic blood pressure (SBP) cerebral blood flow (CBF) and vasoreactivity with brain structure and function in a 16-18 months old double transgenic AβPP_swe/PS1_dE9 (AβPP/PS1) mouse model for AD. These aging AβPP/PS1 mice showed an increased SBP linked to a declined regional CBF. Furthermore, using advanced MRI techniques, decline of functional and structural connectivity was revealed in the AD-like mice coupled to impaired cognition, increased locomotor activity, and anxiety-related behavior. Post mortem analyses demonstrated also increased neuroinflammation, and both decreased synaptogenesis and neurogenesis in the AβPP/PS1 mice. Additionally, deviant levels of fatty acids and sterols were present in the brain tissue of the AβPP/PS1 mice indicating maladapted brain fatty acid metabolism. Our findings suggest a link between increased SBP, decreased cerebral hemodynamics and connectivity in an AD mouse model during aging, leading to behavioral and cognitive impairments. As these results mirror the complex clinical symptomatology in the prodromal phase of AD, we suggest that this AD-like murine model could be used to investigate prevention and treatment strategies for early AD patients. Moreover, this study helps to develop more efficient therapies and diagnostics for this very early stage of AD.

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.

Evaluating the Role of Reduced Oxygen Saturation and Vascular Damage in Traumatic Brain Injury Using Magnetic Resonance Perfusion-Weighted Imaging and Susceptibility-Weighted Imaging and Mapping

The cerebral vasculature, along with neurons and axons, is vulnerable to biomechanical insult during traumatic brain injury (TBI). Trauma-induced vascular injury is still an underinvestigated area in TBI research. Cerebral blood flow and metabolism could be important future treatment targets in neural critical care. Magnetic resonance imaging offers a number of key methods to probe vascular injury and its relationship with traumatic hemorrhage, perfusion deficits, venous blood oxygen saturation changes, and resultant tissue damage. They make it possible to image the hemodynamics of the brain, monitor regional damage, and potentially show changes induced in the brain's function not only acutely but also longitudinally following treatment. These methods have recently been used to show that even mild TBI (mTBI) subjects can have vascular abnormalities, and thus they provide a major step forward in better diagnosing mTBI patients.

The association between pulse pressure change and cognition in late life: Age and where you start matters

INTRODUCTION

Variations across studies in the association between blood pressure (BP) and cognition might be explained partly by duration of exposure to hypertension and partly by nonrandom attrition over time. Pulse pressure (PP) reflects arterial stiffness which may better reflect chronicity of hypertension.

METHODS

Over six annual cycles, 1954 individuals aged 65+ years from a prospective population-based cohort underwent BP measurements and cognitive evaluations. We examined the relationship of change in five cognitive domains to longitudinal PP patterns across the late-life age spectrum, before and after stratifying by baseline systolic blood pressure (SBP) and adjusting for attrition.

RESULTS

There were four longitudinal PP patterns: stable normal, stable high, increasing, and decreasing. Those with lower baseline SBP and an increasing or stable high PP had less decline in cognition, an effect that was attenuated with aging. Among those with higher baseline SBP, there were no differences across PP groups, but increasing age was consistently associated with greater cognitive decline.

DISCUSSION

The effect of PP on cognitive decline depends on age, baseline SBP, and the trajectory of PP change. Cardiovascular mechanisms underlying cognitive aging should be recognized as nuanced and dynamic processes when exploring prevention and treatment targets in the elderly, so that the optimal timing and type of intervention can be identified.

Life-course blood pressure in relation to brain volumes

INTRODUCTION

The impact of blood pressure on brain volumes may be time-dependent or pattern-dependent.

METHODS

Of 1678 participants from the Atherosclerosis Risk in Communities Neurocognitive Study, we quantified the association between measures and patterns of blood pressure over three time points (∼24 or ∼15 years prior and concurrent with neuroimaging) with late life brain volumes.

RESULTS

Higher diastolic blood pressure ∼24 years prior, higher systolic and pulse pressure ∼15 years prior, and consistently elevated or rising systolic blood pressure from ∼15 years prior to concurrent with neuroimaging, but not blood pressures measured concurrent with neuroimaging, were associated with smaller volumes. The pattern of hypertension ∼15 years prior and hypotension concurrent with neuroimaging was associated with smaller volumes in regions preferentially affected by Alzheimer's disease (e.g., hippocampus: -0.27 standard units, 95% CI: -0.51, -0.03).

DISCUSSION

Hypertension 15 to 24 years prior is relevant to current brain volumes. Hypertension followed by hypotension appears particularly detrimental.

Factors associated with cognitive function in older adults in Mexico

Background

As populations age, cognitive decline and dementia pose significant burdens for societies and health care systems, including low- and middle-income countries such as Mexico. Minor age-related declines in cognitive function appear to represent a stable but heterogeneous phase in the continuum between normal cognitive ageing and dementia. Loss of cognitive function has impacts at societal and individual levels and understanding the risk factors can help provide a framework for health policies and interventions to target at-risk groups.

Design

A cohort of older Mexican adults (50+) from the World Health Organization's Study on global AGEing and adult health (WHO SAGE) was used to examine cognitive function, including a total of 2315 respondents, with 325 respondents aged 80 years and older. Cognition was objectively evaluated using verbal recall, verbal fluency, forward digit span and backward digit span, with differences in an overall cognitive score assessed against sociodemographic variables, and associated factors using linear regression.

Results

The most significant predictors of poorer cognitive function were found to be older age (β=−13.88), rural living (β=−2.25), low income (β=−8.28), self-reported severe or extreme memory difficulties (β=−6.62), and difficulty with two or more activities of daily living (β=−2.02).

Conclusions

These findings can inform public health initiatives to address cognitive impairment in ageing populations in Mexico and other middle-income countries.

Hypertension and Its Role in Cognitive Function: Current Evidence and Challenges for the Future

This review summarizes evidence from studies of blood pressure and dementia-related biomarkers into our understanding of cognitive health and highlights the challenges facing studies, particularly randomized trials, of hypertension and cognition. Several lines of research suggest that elevated blood pressure, especially at midlife, is associated with cognitive decline and dementia and that treatment of hypertension could prevent these conditions. Further, studies of hypertension and brain structure show that blood pressure is associated with several forms of small vessel disease that can result in vascular dementia or interact with Alzheimer's pathology to lower the pathologic threshold at which Alzheimer's signs and symptoms manifest. In addition, recent studies of hypertension and Alzheimer's biomarkers show that elevated blood pressure and pulse pressure are associated with the extent of brain beta amyloid (Aβ) deposition and altered cerebral spinal fluid profiles of Aβ and tau indicative of Alzheimer's pathology. However, in spite of strong evidence of biological mechanisms, results from randomized trials of antihypertensive therapy for the prevention of cardiovascular or cerebrovascular disease that include cognitive endpoints do not strongly support the observational evidence that treatment of hypertension should be better for cognition. We propose that future clinical trials should consider including dementia biomarkers and assess genetic and cardiometabolic risk factors that have been associated with progression of the underlying disease pathology to help bridge these gaps.

The role of insulin in the vascular contributions to age-related dementia

In addition to its well-known role in energy metabolism in the body, insulin is a vasoactive hormone that regulates peripheral and cerebral blood flow and neuronal function. Vascular and metabolic dysfunctions are emerging risk factors for Alzheimer's disease (AD) and age-related dementias, and recent evidence suggests that the two pathways are constitutive and interrelated. As a result, an emphasis on correcting metabolic disorders is emerging as an important strategy in the treatment and prevention of age-related cognitive impairment and AD. We review the evidence regarding the unique and interactive effects of vascular and metabolic disorders in pathological brain aging, with special consideration of the role of insulin dysregulation in promoting AD pathologic processes and vascular brain injury. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

The Association of Cardiovascular Disorders and Falls: A Systematic Review

OBJECTIVE

Cardiovascular disorders are recognized as risk factors for falls in older adults. The aim of this systematic review was to identify cardiovascular disorders that are associated with falls, thus providing angles for optimization of fall-preventive care.

DESIGN

Systematic review.

DATA SOURCES

Medline and Embase.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

studies addressing persons aged 50 years and older that described cardiovascular risk factors for falls. Key search terms for cardiovascular abnormalities included all synonyms for the following groups: structural cardiac abnormalities, cardiac arrhythmia, blood pressure abnormalities, carotid sinus hypersensitivity (CSH), orthostatic hypotension (OH), vasovagal syncope (VVS), postprandial hypotension (PPH), arterial stiffness, heart failure, and cardiovascular disease. Quality of studies was assed using the Newcastle-Ottawa Scale.

RESULTS

Eighty-six studies were included. Of studies that used a control group, most consistent associations with falls were observed for low blood pressure (BP) (4/5 studies showing a positive association), heart failure (4/5), and cardiac arrhythmia (4/6). Higher prevalences of CSH (4/6), VVS (2/2), and PPH (3/4) were reported in fallers compared with controls in most studies, but most of these studies failed to show clear association measures. Coronary artery disease (6/10), orthostatic hypotension (9/25), general cardiovascular disease (4/9), and hypertension (7/25) all showed inconsistent associations with falls. Arterial stiffness was identified as an independent predictor for falls in one study, as were several echocardiographic abnormalities.

CONCLUSION

Several cardiovascular associations with falls were identified, including low BP, heart failure, and arrhythmia. These results provide several angles for optimizing fall-preventive care, but further work on standard definitions, as well as the exact contribution of individual risk factors on fall incidence is now important to find potential areas for preventive interventions.

Prevention and Management of Cerebral Small Vessel Disease

Lacunar infarcts/lacunes, white matter hyperintensities (WMH), and cerebral microbleeds (CMBs) are considered various manifestations of cerebral small vessel disease (SVD). Since the exact mechanisms of these manifestations differ, their associated risk factors differ. High blood pressure is the most consistent risk factor for all of these manifestations. However, a "J curve" phenomenon in terms of blood pressure probably exists for WMH. The association between cholesterol levels and lacunar infarcts/lacunes or WMH was less consistent and sometimes conflicting; a low cholesterol level probably increases the risk of CMBs. Homocysteinemia appears to be associated with WMH. It is noteworthy that the risk factors profile may also differ between different lacunar patterns and CMBs located at different parts of the brain. Thrombolysis, antihypertensives, and statins are used to treat patients with symptomatic lacunar infarction, just as in those with other stroke subtypes. However, it should be remembered that bleeding risks increase in patients with extensive WMH and CMBs after thrombolysis therapy. According to the Secondary Prevention of Small Subcortical Strokes trial results, a blood pressure reduction to <130 mmHg is recommended in patients with symptomatic lacunar infarction. However, an excessive blood pressure decrease may induce cognitive decline in older patients with extensive WMH. Dual antiplatelet therapy (aspirin plus clopidogrel) should be avoided because of the excessive risk of intracerebral hemorrhage. Although no particular antiplatelet is recommended, drugs such as cilostazol or triflusal may have advantages for patients with SVD since they are associated with less frequent bleeding complications than aspirin.

Susceptibility Weighted Imaging and Mapping of Micro-Hemorrhages and Major Deep Veins after Traumatic Brain Injury

Micro-hemorrhages are a common result of traumatic brain injury (TBI), which can be quantified with susceptibility weighted imaging and mapping (SWIM), a quantitative susceptibility mapping approach. A total of 23 TBI patients (five women, 18 men; median age, 41.25 years old; range, 21.69-67.75 years) with an average Glasgow Coma Scale score of 7 (range, 3-15) at admission were recruited at mean 149 d (range, 57-366) after injury. Susceptibility-weighted imaging data were collected and post-processed to create SWIM images. The susceptibility value of small hemorrhages (diameter ≤10 mm) and major deep veins (right septal, left septal, central septal, right thalamostriate, left thalamostriate, internal cerebral, right basal vein of Rosenthal, left basal vein of Rosenthal, and pial veins) were evaluated. Different susceptibility thresholds were tested to determine SWIM's sensitivity and specificity for differentiating hemorrhages from the veins. A total of 253 deep veins and 173 small hemorrhages were identified and evaluated. The mean susceptibility of hemorrhages was 435±206 parts per billion (ppb) and the mean susceptibility of deep veins was 108±56 ppb. Hemorrhages showed a significantly higher susceptibility than all deep veins (p<0.001). With different thresholds (250, 227 and 200 ppb), the specificity was 97%, 95%, and 92%, and the sensitivity was 84%, 90%, and 92%, respectively. These results show that SWIM could be used to differentiate hemorrhages from veins in TBI patients in a semi-automated manner with reasonable sensitivity and specificity. A larger cohort will be needed to validate these findings.

Characterizing the white matter hyperintensity penumbra with cerebral blood flow measures

Objective

White matter hyperintensities (WMHs) are common with age, grow over time, and are associated with cognitive and motor impairments. Mechanisms underlying WMH growth are unclear. We aimed to determine the presence and extent of decreased normal appearing white matter (NAWM) cerebral blood flow (CBF) surrounding WMHs to identify ‘WM at risk’, or the WMH CBF penumbra. We aimed to further validate cross-sectional finding by determining whether the baseline WMH penumbra CBF predicts the development of new WMHs at follow-up.

Methods

Sixty-one cognitively intact elderly subjects received 3 T MPRAGE, FLAIR, and pulsed arterial spin labeling (PASL). Twenty-four subjects returned for follow-up MRI. The inter-scan interval was 18 months. A NAWM layer mask, comprised of fifteen layers, 1 mm thick each surrounding WMHs, was generated for periventricular (PVWMH) and deep (DWMH) WMHs. Mean CBF for each layer was computed. New WMH and persistent NAWM voxels for each penumbra layer were defined from follow-up MRI.

Results

CBF in the area surrounding WMHs was significantly lower than the total brain NAWM, extending approximately 12 mm from both the established PVWMH and DWMH. Voxels with new WMH at follow-up had significantly lower baseline CBF than voxels that maintained NAWM, suggesting that baseline CBF can predict the development of new WMHs over time.

Conclusions

A CBF penumbra exists surrounding WMHs, which is associated with future WMH expansion. ASL MRI can be used to monitor interventions to increase white matter blood flow for the prevention of further WM damage and its cognitive and motor consequences.

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We examined cerebral blood flow (CBF) surrounding white matter hyperintensity (WMH) lesions.

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We examined whether low baseline CBF is associated with WMH expansion over time.

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WMH CBF penumbra exists, extending ~12 mm from both periventricular and deep WMH lesions.

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Baseline CBF can predict the development of new WMHs over time.

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ASL MRI can be used to monitor interventions to increase white matter blood flow.

Prevalence and correlates of functional dependence among maintenance dialysis patients

Functional dependence is an important determinant of longevity and quality of life. The purpose of the current study was to determine the prevalence and correlates of functional dependence among patients with end-stage renal disease (ESRD) receiving maintenance dialysis. We enrolled 148 participants with ESRD from five clinics. Functional status, as measured by basic and instrumental activities of daily living (ADL, IADL), was ascertained by validated questionnaires. Functional dependence was defined as needing assistance in at least one of seven IADLs or at least one of four ADLs. Demographic characteristics, chronic health conditions, anthropometric measurements, and laboratories were assessed by a combination of self-report and chart review. Cognitive function was assessed with a neurocognitive battery, and depressive symptoms were assessed by questionnaire. Mean age of the sample was 56.2 ± 14.6 years. Eighty-seven participants (58.8%) demonstrated dependence in ADLs or IADLs, 70 (47.2%) exhibited IADL dependence alone, and 17 (11.5%) exhibited combined IADL and ADL dependence. In a multivariable-adjusted model, stroke, cognitive impairment, and higher systolic blood pressure were independent correlates of functional dependence. We found no significant association between demographic characteristics, chronic health conditions, depressive symptoms or laboratory measurements, and functional dependence. Impairment in executive function was more strongly associated with functional dependence than memory impairment. Functional dependence is common among ESRD patients and independently associated with stroke, systolic blood pressure, and executive function impairment.