Impact of hypertension and apolipoprotein E4 on poststroke cognition in subjects >75 years of age

APOE ɛ4 Carriers Show Delayed Recovery of Verbal Memory and Smaller Entorhinal Volume in the First Year After Ischemic Stroke

BACKGROUND

The apolipoprotein E (APOE) gene ɛ4 allele is a risk factor for Alzheimer's disease and cardiovascular disease. However, its relationship with cognition and brain volume after stroke is not clear.

OBJECTIVE

We compared cognition and medial temporal lobe volumes in APOEɛ4 carriers and non-carriers in the first year after ischemic stroke.

METHODS

We sampled 20 APOEɛ4 carriers and 20 non-carriers from a larger cohort of 135 ischemic stroke participants in the longitudinal CANVAS study. Participants were matched on a range of demographic and stroke characteristics. We used linear mixed-effect models to compare cognitive domain z-scores (attention, processing speed, executive function, verbal and visual memory, language, visuospatial function) and regional medial temporal lobe volumes (hippocampal, entorhinal cortex) between groups at each time-point (3, 12-months post-stroke), and within groups across time-points. APOE gene single nucleotide polymorphisms (SNPs; rs7412, rs429358) were genotyped on venous blood.

RESULTS

APOEɛ4 carriers and non-carriers did not differ on any demographic, clinical, or stroke variable. Carriers performed worse than non-carriers in verbal memory at 3 months post-stroke (p = 0.046), but were better in executive function at 12 months (p = 0.035). Carriers demonstrated a significant improvement in verbal memory (p = 0.012) and executive function (p = 0.015) between time-points. Non-carriers demonstrated a significant improvement in visual memory (p = 0.0005). Carriers had smaller bilateral entorhinal cortex volumes (p < 0.05), and larger right sided and contralesional hippocampal volumes, at both time-points (p < 0.05).

CONCLUSION

APOE ɛ4 is associated with delayed recovery of verbal memory function and reduced entorhinal cortex volumes in the first year after ischemic stroke.

Vascular Cellular Adhesion Molecule-1 (VCAM-1) and Memory Impairment in African-Americans after Small Vessel-Type Stroke

BACKGROUND

African-Americans (AA) are 3 times more likely to have small-vessel-type ischemic strokes (SVS) than Whites. Small vessel strokes are associated with cognitive impairment, a relationship incompletely explained by white matter hyperintensity (WMH) burden. We examined whether inflammatory/endothelial dysfunction biomarkers are associated with cognition after SVS in AAs.

METHODS

Biomarkers were obtained in 24 subjects (median age 56.5 years, 54% women, median 12 years education). Cognition was assessed more than 6 weeks poststroke using the memory composite score (MCS), which was generated using recall from the Hopkins Verbal Learning Test-II and Brief Visuospatial Memory Test-Revised. A semi-automated, volumetric protocol was used to quantify WMH volume (WMHv) on clinical MRI scans. Potential biomarkers including vascular cell adhesion molecule-1 (VCAM-1), interleukin-1 receptor antagonist, interleukin-6, interleukin-8, interleukin-10, interferon gamma, and thrombin-antithrombin (TAT) were log-transformed and correlated with MCS with adjustment for potential confounders.

RESULTS

Among serum biomarkers, only VCAM-1-correlated with poorer memory based on the MCS (r = -.659; P = .0006). VCAM-1 (r = .554; P = .005) and age (r = .479; P = .018) correlated with WMHv; VCAM-1 was independently associated with MCS after adjustment for WMHv, age, and education (P = .023).

CONCLUSIONS

The findings of this exploratory analysis suggest that endothelial dysfunction and inflammation as reflected by VCAM-1 levels may play a role in poststroke cognitive impairment. Additional studies are needed to validate this observation and to evaluate this relationship in non-AAs and with other stroke types and compare this finding to cognitive impairment in nonstroke populations.

Progression of cognitive decline before and after incident stroke

OBJECTIVE

To determine the trajectory of cognitive decline before and after incident stroke.

METHODS

By using data from the English Longitudinal Study of Ageing, we studied 9,278 participants without dementia with no history of stroke who underwent cognitive assessment at baseline (wave 1) and at least 1 other time point (waves 2-7). We used linear mixed models to analyze repeated measures and longitudinal data.

RESULTS

Among the 9,278 participants (56.8% women, mean age 63.1 ± 10.3 years), 471 (5.1%) incident stroke events were identified. Compared with stroke-free participants, multivariable-adjusted rates of prestroke cognitive decline in global cognition, memory, semantic fluency, and temporal orientation of participants who later experienced an incident stroke were increased by -0.029 , -0.016, -0.022, and -0.024 SD/y, respectively. Among the 471 stroke survivors, the multivariable-adjusted acute changes in the 4 cognitive domains were -0.257, -0.150, -0.121, and -0.272 SD, respectively. In the years after stroke, global cognition declined over time and was steeper than its prestroke slope, that is, by -0.064 SD/y after multivariable adjustment. The rates of memory, semantic fluency, and temporal orientation decline were -0.046, -0.033, and -0.037 SD/y, respectively.

CONCLUSIONS

Accelerated prestroke cognitive decline and poststroke cognitive decline were associated with incident stroke over a follow-up period of 12 years. Attention should be paid to the long-term cognitive problems of stroke survivors, and intervention and management of major vascular risk factors should start from early life or midlife to reduce the risk of cerebrovascular disease and the associated cognitive impairment.

A Quarter Century of APOE and Alzheimer's Disease: Progress to Date and the Path Forward

Alzheimer's disease (AD) is considered a polygenic disorder. This view is clouded, however, by lingering uncertainty over how to treat the quasi "monogenic" role of apolipoprotein E (APOE). The APOE4 allele is not only the strongest genetic risk factor for AD, it also affects risk for cardiovascular disease, stroke, and other neurodegenerative disorders. This review, based mostly on data from human studies, ranges across a variety of APOE-related pathologies, touching on evolutionary genetics and risk mitigation by ethnicity and sex. The authors also address one of the most fundamental question pertaining to APOE4 and AD: does APOE4 increase AD risk via a loss or gain of function? The answer will be of the utmost importance in guiding future research in AD.

Associations between ApoE gene and psychological consequences post stroke in a Bahraini cohort

BACKGROUND

The contribution of genetic factors such as the presence of ApoE allele e4 and its association with psychological consequences post stroke remains unknown within Middle-Eastern regions. This study examined the association of ApoE genotype with cognitive impairment and mood in stroke patients and compare with healthy older adults in Bahrain.

METHOD

A prospective sample of n = 62 stroke patients (case group) and n = 53 healthy ageing individuals (control group) were eligible to participate in the study. A neuropsychological battery of cognitive assessments were conducted on all participants, and then stratified by cognitive function: no cognitive impairment, mild cognitive impairment and moderate to severe cognitive impairment. Anxiety and depression were assessed using the Hospital Anxiety and Depression Scale (HADS).

RESULTS

Most frequent ApoE genotype was e2/e3 in case (44%) and control groups (63%). ApoE allele e3 had the highest frequency for both groups with all stroke patients presenting with this allele and 86% for the control group (χ²  = 12.14, p < .0001). Stroke patients' non-carriers for ApoE allele e4 performed better on all cognitive measures but differences were not statistically significant (ns). Carriers of ApoE allele e2 in both groups had less mood symptoms compared to non-carriers.

DISCUSSION

ApoE genotype e3/e4 and e4/e4 was low in this Bahraini cohort explaining why there may been no significant associations found for this genotype variant with cognitive impairment. Further investigation of cognitive impairment and mood dysregulation with the different variants of the ApoE gene in general ageing and stroke populations is required from different ethno-cultural groups and geographical regions globally.

Hippocampal Neurodegenerative Pathology in Post-stroke Dementia Compared to Other Dementias and Aging Controls

Neuroimaging evidence from older stroke survivors in Nigeria and Northeast England showed medial temporal lobe atrophy (MTLA) to be independently associated with post-stroke cognitive impairment and dementia. Given the hypothesis ascribing MTLA to neurodegenerative processes, we assessed Alzheimer pathology in the hippocampal formation and entorhinal cortex of autopsied brains from of post-stroke demented and non-demented subjects in comparison with controls and other dementias. We quantified markers of amyloid β (total Aβ, Aβ-40, Aβ-42, and soluble Aβ) and hyperphosphorylated tau in the hippocampal formation and entorhinal cortex of 94 subjects consisting of normal controls (n = 12), vascular dementia, VaD (17), post-stroke demented, PSD (n = 15), and post-stroke non-demented, PSND (n = 23), Alzheimer's disease, AD (n = 14), and mixed AD and vascular dementia, AD_VAD (n = 13) using immunohistochemical techniques. We found differential expression of amyloid and tau across the disease groups, and across hippocampal sub-regions. Among amyloid markers, the pattern of Aβ-42 immunoreactivity was similar to that of total Aβ. Tau immunoreactivity showed highest expression in the AD and mixed AD and vascular dementia, AD_VaD, which was higher than in control, post - stroke and VaD groups (p < 0.05). APOE ε4 allele positivity was associated with higher expression of amyloid and tau pathology in the subiculum and entorhinal cortex of post-stroke cases (p < 0.05). Comparison between PSND and PSD revealed higher total Aβ immunoreactivity in PSND compared to PSD in the CA1, subiculum and entorhinal cortex (p < 0.05) but no differences between PSND and PSD in Aβ-42, Aβ-40, soluble Aβ or tau immunoreactivities (p > 0.05). Correlation of MMSE and CAMCOG scores with AD pathological measures showed lack of correlation with amyloid species although tau immunoreactivity demonstrated correlation with memory scores (p < 0.05). Our findings suggest hippocampal AD pathology does not necessarily differ between demented and non-demented post-stroke subjects. The dissociation of cognitive performance with hippocampal AD pathological burden suggests more dominant roles for non-Alzheimer neurodegenerative and / or other non-neurodegenerative substrates for dementia following stroke.

Predictors of Vascular Cognitive Impairment Poststroke in a Middle Eastern (Bahrain) Cohort: A Proposed Case-Control Comparison

BACKGROUND

Poststroke dementia and cognitive impairment are associated with poor long-term outcomes after stroke. The contribution of genetic factors such as the presence of apolipoprotein (ApoE) ɛ4 allele and its association with cognitive impairment poststroke remains inconclusive, particularly in Middle Eastern regions.

OBJECTIVE

The aim of this study is to examine all correlates and potential predictors of cognitive impairment including self-awareness and regulation deficits in stroke patients and compare these functions with healthy older adults from a Middle Eastern population.

METHODS

A prospective stroke sample of 200 patients (case group) and 100 healthy aging individuals (control group) will be recruited from the largest medical complex in Bahrain. A neuropsychological battery of cognitive assessments (global, executive, and metacognition) will be conducted on all participants. Participants will be categorized into 4 subgroups (nonvascular cognitive impairment, vascular cognitive impairment with no dementia, vascular dementia, and mixed dementia) using standardized cognitive assessment scores and the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, dementia criteria. Biomarkers will include ApoE genotype, soluble form of receptor for advanced glycation end products, neprilysin, beta-secretase 1, biochemistry, and hematology measurements.

RESULTS

The primary study outcome is to determine early risk factors for cognitive impairment after stroke in a Bahraini cohort. The study has received full ethical approval from the Bahrain Ministry of Health and from the affiliated university.

CONCLUSIONS

With increasing stroke incidence rates in the Middle East, this research study will provide useful biological and epidemiological data for future development and planning of health policies and guidelines for stroke care within the Gulf region.

Stroke injury, cognitive impairment and vascular dementia

The global burden of ischaemic strokes is almost 4-fold greater than haemorrhagic strokes. Current evidence suggests that 25–30% of ischaemic stroke survivors develop immediate or delayed vascular cognitive impairment (VCI) or vascular dementia (VaD). Dementia after stroke injury may encompass all types of cognitive disorders. States of cognitive dysfunction before the index stroke are described under the umbrella of pre-stroke dementia, which may entail vascular changes as well as insidious neurodegenerative processes. Risk factors for cognitive impairment and dementia after stroke are multifactorial including older age, family history, genetic variants, low educational status, vascular comorbidities, prior transient ischaemic attack or recurrent stroke and depressive illness. Neuroimaging determinants of dementia after stroke comprise silent brain infarcts, white matter changes, lacunar infarcts and medial temporal lobe atrophy. Until recently, the neuropathology of dementia after stroke was poorly defined. Most of post-stroke dementia is consistent with VaD involving multiple substrates. Microinfarction, microvascular changes related to blood–brain barrier damage, focal neuronal atrophy and low burden of co-existing neurodegenerative pathology appear key substrates of dementia after stroke injury. The elucidation of mechanisms of dementia after stroke injury will enable establishment of effective strategy for symptomatic relief and prevention. Controlling vascular disease risk factors is essential to reduce the burden of cognitive dysfunction after stroke. 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.

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Ischaemic injury is common among long-term stroke survivors

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About 25% stroke survivors develop dementia with a much greater proportion developing cognitive impairment

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Risk factors of dementia after stroke include older age, vascular comorbidities, prior stroke and pre-stroke impairment

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Current imaging and pathological studies suggest 70% of dementia after stroke is vascular dementia

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Severe white matter changes and medial temporal lobe atrophy as sequelae after ischaemic injury are substrates of dementia

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Controlling vascular risk factors and prevention strategies related to lifestyle factors would reduce dementia after stroke

Understanding and preventing the development of post-stroke dementia

Post-stroke dementia (PSD) is a clinical entity but it now appears that most of PSD may be categorized as vascular dementia. The well-established relationship between vascular factors and dementia provides a rationale for the implementation of intervention and prevention efforts. Larger primary prevention trials related to lifestyle factors are warranted in association with dementia. Published clinical trials have not been promising and there is meager information on whether PSD can be prevented through the use of pharmacological agents. Control of vascular disease risk and prevention of recurrent strokes are obviously key to reducing the burden of cognitive decline and dementia after stroke. However, modern imaging and analysis techniques will help to elucidate the mechanism of PSD and establish better treatment.

The association between apolipoprotein E gene polymorphisms and essential hypertension: a meta-analysis of 45 studies including 13,940 cases and 16,364 controls

The apolipoprotein E single-nucleotide polymorphisms are among the potential candidate genes that may serve as modulators in susceptibility to essential hypertension. In an effort to clarify earlier inconclusive results, we performed a meta-analysis of population-based case-control genetic association studies. Random-effects methods were applied on summary data in order to combine the results of the individual studies. We identified in total 45 studies, including 13 940 hypertensive cases and 16 364 controls. The contrast of E4 carriers versus non-carriers yielded an overall odds ratio (OR) of 1.16 (95% confidence interval (CI): 1.02, 1.31), whereas the contrast of E4 allele versus the others in a subtotal of 6617 cases and 7330 controls, yielded an OR of 1.39 (95% CI: 1.12, 1.72). There was moderate evidence of publication bias in both contrasts, which was eliminated after excluding studies not in Hardy-Weinberg equilibrium. Subgroup analyses revealed that significant estimates arose from studies on Asian populations, as opposed to the Caucasian ones. Furthermore, no evidence of publication bias was demonstrated in the comparisons within this subgroup. Our results are consistent with recent meta-analyses but show that the association is weaker than that has been previously demonstrated. Further studies are needed in order to fully address questions about the etiological mechanism of the particular association, as well as to study the effect in populations of African descent.

Vascular dementia

The epidemic growth of dementia causes great concern for the society. It is customary to consider Alzheimer's disease (AD) as the most common cause of dementia, followed by vascular dementia (VaD). This dichotomous view of a neurodegenerative disease as opposed to brain damage caused by extrinsic factors led to separate lines of research in these two entities. Indeed, accumulated data suggest that the two disorders have additive effects and probably interact; however it is still unknown to what degree. Furthermore, epidemiological studies have shown "vascular" risk factors to be associated with AD. Therefore, a clear distinction between AD and VaD cannot be made in most cases, and is furthermore unhelpful. In the absence of efficacious treatment for the neurodegenerative process, special attention must be given to the vascular component, even in patients with presumed mixed pathology. Symptomatic treatment of VaD and AD is similar, although the former is less effective. For prevention of dementia it is important to treat all factors aggressively, even in stroke survivors who do not show evidence of cognitive decline. In this review, we will give a clinical and pathological picture of the processes leading to VaD and discuss its interaction with AD.

Cognitive impairment and the role of the ApoE epsilon4-allele after stroke--a 13 months follow-up study

OBJECTIVE

To examine the relationship between the ApoE epsilon4 allele and cognitive impairment 13 months after stroke.

METHODS

One hundred four stroke rehabilitation patients were cognitively tested on average 18 days after hospital admission and again 13 months later with the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). The following potential risk factors for post-stroke cognitive impairment (defined by a RBANS total index score below 77.5 points) at 13 months follow-up were analyzed in bivariate and logistic regression analyses: ApoE-genotype, socio-demographic variables, pre-stroke cognitive reduction (The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE)), vascular factors, lesion characteristics, and neurological impairment (The National Institute of Health Stroke Scale (NIHSS)). Differences in general cognitive performance (pre-stroke, baseline, and follow-up) across patients with different ApoE-genotypes were analyzed, and lastly differences between epsilon4-carriers and non-carriers for changes in performance in various cognitive domains over the 13 months period were examined.

RESULTS

Significant risk factors for cognitive impairment at 13 months were ApoE epsilon4, pre-stroke cognitive reduction (IQCODE 3.44+), previous stroke, and neurological impairment (NIHSS Total Score >5). A significant dose-dependent effect of the ApoE-genotype in relation to overall post-stroke cognitive functioning was found at baseline and follow-up, but not pre-stroke. The epsilon4 carriers showed a significant decline in tests related to verbal learning and memory compared to the non-carriers.

CONCLUSIONS

The ApoE epsilon4-allele constitutes an independent risk factor for cognitive impairment at 13 months post-stroke, and is associated with progression of cognitive decline in tasks related to verbal learning and memory.

Poststroke Urinary Incontinence: One-Year Outcome and Relationships with Measures of Attentiveness

OBJECTIVES

To investigate the prognostic effect of poststroke urinary incontinence (UI) on 1-year outcome in relation to measurements of attention and mental processing speed.

DESIGN

Prospective observational study.

SETTING

Geriatric department (stroke and rehabilitation unit) in a university hospital.

PARTICIPANTS

Two hundred thirty-five previously continent patients (median age 78) with an acute stroke.

MEASUREMENTS

Clinical stroke syndromes, subtypes of UI, pre- and poststroke cognitive function and activities of daily living, computerized assessment of attention and processing speed for 110 of the participants, mortality and accommodation at 1 year.

RESULTS

One hundred seventy patients remained continent, and 65 developed UI (27 with urge UI, 38 with UI with impaired awareness of the need to void (IA-UI). Patients with urge UI had poorer power of attention and speed of memory than continent patients but similar continuity of attention (P<.001, .001, and .07, respectively). Patients with IA-UI performed poorer in all categories than continent and patients with urge UI (all P<.01). In regression analyses, IA-UI was the strongest predictor of mortality and nursing home residence after 1 year (odds ratio=15.7, 95% confidence interval=3.6-69.7). When deaths were excluded, IA-UI and continuity of attention remained independent risk factors.

CONCLUSION

Patients with poststroke UI are less attentive than continent patients. Those with IA-UI perform poorest. Sustained attention seems important for outcome and should be taken more into account in the rehabilitation process. In patients who recognize their incontinence, attention-focused training might be the most effective measure of reestablishing bladder control.

Cognitive function following stroke and vascular cognitive impairment

PURPOSE OF REVIEW

This review of the cognitive status following stroke and vascular cognitive impairment starts by questioning the concept of vascular dementia and related concepts. Our position is that in many cases these labels promote a superficial conceptualization of an inherently complex and heterogeneous phenomenon hampering a more detailed understanding.

RECENT FINDINGS

After stroke or disease of the cerebral vasculature, the cognitive and emotional outcome is dependent on a combination of three factors with the relative importance differing between causes. First, focal damage may lead to selective impairments that are dependent on the localization of the (grey matter) lesion. Second, diffuse neuronal dysfunction produces a more uniform profile of a decrease in mental speed, memory problems, and reduced executive functioning. Third, cognitive outcome is further modulated - notably in terms of severity - by patient variables such as age, sex, premorbid level of functioning, and comorbidity (e.g. hypertension).

SUMMARY

The complex character of the cognitive repercussions of stroke can be better harnessed by employing modern neuropsychological assessment procedures. This allows both a detailed categorization of the patients for the selection and effectiveness of therapeutic intervention, as well as the construction of reliable prognostic models.

Vascular cognitive impairment

Cognitive impairment commonly accompanies clinical syndromes associated with vascular disease of the brain. Because of evolving definitional criteria, however, the frequency of cognitive impairment attributable to cerebrovascular disease is difficult to determine. Dementia occurs in up to one-third of elderly patients with stroke, a subset of whom have Alzheimer's disease (AD) rather than a pure vascular dementia syndrome. In fact, pure vascular dementia has been shown to be uncommon in most large autopsy series. A mixed etiology of AD and cerebrovascular disease is thought to become more common with increasing age, although no clinical criteria for the diagnosis of AD with cerebrovascular disease are currently available. Epidemiological studies have implicated subcortical small-vessel disease as a risk factor for cognitive impairment and dementia, but the cognitive expression and clinical significance of MRI white matter changes in individual patients is difficult to establish. The frequency of specific neuropathologic features of vascular cognitive impairment depends largely on study inclusion criteria. Cerebral meningocortical microangiopathies with distinctive clinicopathological profiles are associated with dementia in both sporadic cases and familial syndromes. In patients with AD, the contribution of amyloid-beta protein to the degree of cognitive impairment has not been clearly defined.

Telomere length predicts poststroke mortality, dementia, and cognitive decline

OBJECTIVE

Long-term cognitive development is variable among stroke survivors, with a high proportion developing dementia. Early identification of those at risk is highly desirable to target interventions for secondary prevention. Telomere length in peripheral blood mononuclear cells was tested as prognostic risk marker.

METHODS

A cohort of 195 nondemented stroke survivors was followed prospectively from 3 months after stroke for 2 years for cognitive assessment and diagnosis of dementia and for 5 years for survival. Telomere lengths in peripheral blood mononuclear cells were measured at 3 months after stroke by in-gel hybridization. Hazard ratios for survival in relation to telomere length and odds ratios for dementia were estimated using multivariate techniques, and changes in Mini-Mental State Examination scores between baseline and 2 years were related to telomere length using multivariate linear regression.

RESULTS

Longer telomeres at baseline were associated with reduced risk for death (hazard ratio for linear trend per 1,000 bp = 0.52; 95% confidence interval, 0.28-0.98; p = 0.04, adjusted for age) and dementia (odds ratio for linear trend per 1,000 bp = 0.19; 95% confidence interval, 0.07-0.54; p = 0.002) and less reduction in Mini-Mental State Examination score (p = 0.04, adjusted for baseline score).

INTERPRETATION

Telomere length is a prognostic marker for poststroke cognitive decline, dementia, and death.