Pulse pressure correlates with leukoaraiosis in Alzheimer disease

Reduced Cerebral Blood Flow in Mild Cognitive Impairment Assessed Using Phase-Contrast MRI

There is increasing evidence of a vascular contribution to Alzheimer's disease (AD). In some cases, prior work suggests that chronic brain hypoperfusion could play a prime pathogenic role contributing to the accumulation of amyloid-β,while other studies favor the hypothesis that vascular dysfunction and amyloid pathology are independent, although synergistic, mechanisms contributing to cognitive impairment. Vascular dysfunction can be evaluated by assessing cerebral blood flow impairment. Phase contrast velocity mapping by MRI offers a non-invasive means of quantifying the total inflow of blood to the brain. This quantitative parameter could be a sensitive indicator of vascular disease at early stages of AD. In this work, phase contrast MRI was used to evaluate cerebral hemodynamics in patients with subjective memory complaints, amnestic mild cognitive impairment, and mild to moderate AD, and compare them with control subjects. Results showed that blood flow and velocity were decreased in the patients with cognitive dysfunction and the decrease correlated with the degree of cognitive impairment as assessed by means of neuropsychological tests. Total cerebral blood flow measurements were clearly reduced in AD patients, but more importantly appeared to be sensitive enough to distinguish between healthy subjects and those with mild cognitive impairment. A quantitative measurement of total brain blood flow could potentially predict vascular dysfunction and compromised brain perfusion in early stages of AD.

A U-shaped Association Between Blood Pressure and Cognitive Impairment in Chinese Elderly

OBJECTIVES

Higher or lower blood pressure may relate to cognitive impairment, whereas the relationship between blood pressure and cognitive impairment among the elderly is not well-studied. The study objective was to determine whether blood pressure is associated with cognitive impairment in the elderly, and, if so, to accurately describe the association.

DESIGN

Cross-sectional data from the sixth wave of the Chinese Longitudinal Healthy Longevity Survey (CLHLS) conducted in 2011.

SETTING

Community-based setting in longevity areas in China.

PARTICIPANTS

A total of 7144 Chinese elderly aged 65 years and older were included in the sample.

MEASURES

Systolic blood pressures (SBP) and diastolic blood pressures (DBP) were measured, pulse pressure (PP) was calculated as (SBP) - (DBP) and mean arterial pressures (MAP) was calculated as 1/3(SBP) + 2/3(DBP). Cognitive function was assessed via a validated Mini-Mental State Examination (MMSE).

RESULTS

Based on the results of generalized additive models (GAMs), U-shaped associations were identified between cognitive impairment and SBP, DBP, PP, and MAP. The cutpoints at which risk for cognitive impairment (MMSE <24) was minimized were determined by quadratic models as 141 mm Hg, 85 mm Hg, 62 mm Hg, and 103 mm Hg, respectively. In the logistic models, U-shaped associations remained for SBP, DBP, and MAP but not PP. Below the identified cutpoints, each 1-mm Hg decrease in blood pressure corresponded to 0.7%, 1.1%, and 1.1% greater risk in the risk of cognitive impairment, respectively. Above the cutpoints, each 1-mm Hg increase in blood pressure corresponded to 1.2%, 1.8%, and 2.1% greater risk of cognitive impairment for SBP, DBP, and MAP, respectively.

CONCLUSION

A U-shaped association between blood pressure and cognitive function in an elderly Chinese population was found. Recognition of these instances is important in identifying the high-risk population for cognitive impairment and to individualize blood pressure management for cognitive impairment prevention.

Hypertension, brain damage and cognitive decline

Loss of cognitive function is one the most devastating manifestations of ageing and vascular disease. Cognitive decline is rapidly becoming an important cause of disability worldwide and contributes significantly to increased mortality. There is growing evidence that hypertension is the most important modifiable vascular risk factor for development and progression of both cognitive decline and dementia. High blood pressure contributes to cerebral small and large vessel disease resulting in brain damage and dementia. A decline in cerebrovascular reserve capacity and emerging degenerative vascular wall changes underlie complete and incomplete brain infarcts, haemorrhages and white matter hyperintensities. This review discusses the complexity of factors linking hypertension to brain functional and structural changes, and to cognitive decline and dementia. The evidence for possible clinical markers useful for prevention of decreased cognitive ability, as well as recent data on vascular mechanism in the pathogenesis of cognitive decline, and the role of antihypertensive therapies in long-term prevention of late-life cognitive decline will be reviewed.

Aggregate effects of vascular risk factors on cerebrovascular changes in autopsy-confirmed Alzheimer's disease

We examined the relationships of antemortem vascular risk factors to postmortem cerebrovascular and Alzheimer's disease (AD) pathologies. Eighty-four AD patients underwent an assessment of vascular risk (blood pressure, cholesterol, smoking, cardiovascular disease, diabetes, atrial fibrillation, transient ischemic attack [TIA], or stroke) and later underwent brain autopsy. Given our aim to examine mild cerebrovascular changes (CVCs), individuals were excluded if autopsy revealed large stroke. The most common forms of CVC were circle of Willis atherosclerosis followed by arteriosclerosis, lacunes, and microinfarcts. Excluding the history of TIA/clinical stroke, individual vascular risk factors were not associated with CVC. However, the presence of multiple vascular risk factors was associated with CVC. Furthermore, the presence of CVC was associated with lower Braak and Braak stage. These findings highlight the importance of aggregate risk in the vascular contribution to dementia. Interventions designed to maintain cerebrovascular health may represent important opportunities for preventing or delaying dementia, even when AD is the dominant pathology.

Association between risk factors for vascular dementia and adiponectin

Vascular dementia is caused by various factors, including increased age, diabetes, hypertension, atherosclerosis, and stroke. Adiponectin is an adipokine secreted by adipose tissue. Adiponectin is widely known as a regulating factor related to cardiovascular disease and diabetes. Adiponectin plasma levels decrease with age. Decreased adiponectin increases the risk of cardiovascular disease and diabetes. Adiponectin improves hypertension and atherosclerosis by acting as a vasodilator and antiatherogenic factor. Moreover, adiponectin is involved in cognitive dysfunction via modulation of insulin signal transduction in the brain. Case-control studies demonstrate the association between low adiponectin and increased risk of stroke, hypertension, and diabetes. This review summarizes the recent findings on the association between risk factors for vascular dementia and adiponectin. To emphasize this relationship, we will discuss the importance of research regarding the role of adiponectin in vascular dementia.

Comprehensive analysis of clinico-pathological data reveals heterogeneous relations between atherosclerosis and cancer

AIMS

Atherosclerosis and cancer share common risk factors and involve similar molecular pathomechanisms. Most clinical and epidemiological studies show a positive correlation between atherosclerosis and smoking-related cancers and heterogeneous results for non-smoking-related cancers. However, up-to-date large-scale autopsy studies including a detailed analysis of cancer types are lacking. Therefore, we sought to investigate the relation between major cancer types and the grade of atherosclerosis in a recent well-powered autopsy cohort.

METHODS

In 2101 patients, both autopsy data and clinical data including demographics, disease groups, tumour type, cause of death and grade of atherosclerosis were reviewed and statistically analysed.

RESULTS

We found cancer in general is associated with less atherosclerosis (OR 0.60, p<0.0001). In particular, haematological neoplasm and sarcomas were associated with much less atherosclerosis (OR=0.45, p<0.0001 and OR=0.43, p=0.087), while carcinomas were associated with moderately less atherosclerosis (OR=0.72, p=0.002). Furthermore, non-smoking-related cancers were associated with much less atherosclerosis (OR=0.41, p<0.0001), while possibly smoking-related cancer and smoking-related cancer showed no significant association. In a comprehensive analysis of 21 cancer types, biliary tract cancer, lymphomas/lymphoid leukaemias and kidney cancer were associated with much less atherosclerosis (OR=0.19, p<0.0001; OR=0.41, p<0.0001; and OR=0.48, p=0.029). In an exploratory analysis of treatment strategies, we found that tumours with a recommendation of oxazaphosphorines and pyrimidine antagonist treatment were significantly associated with less atherosclerosis (OR=0.33, p=0.0068 and OR=0.58, p=0.012).

CONCLUSIONS

In conclusion, the study showed an inverse association between cancer and atherosclerosis postmortem that depends on the cancer type and suggests a possible impact of chemotherapy regimens.

Cerebrovascular atherosclerosis correlates with Alzheimer pathology in neurodegenerative dementias

A growing body of evidence demonstrates an association between vascular risk factors and Alzheimer's disease. This study investigated the frequency and severity of atherosclerotic plaques in the circle of Willis in Alzheimer's disease and multiple other neurodegenerative diseases. Semi-quantitative data from gross and microscopic neuropathological examinations in 1000 cases were analysed, including 410 with a primary diagnosis of Alzheimer's disease, 230 with synucleinopathies, 157 with TDP-43 proteinopathies, 144 with tauopathies and 59 with normal ageing. More than 77% of subjects with Alzheimer's disease had grossly apparent circle of Willis atherosclerosis, a percentage that was significantly higher than normal (47%), or other neurodegenerative diseases (43-67%). Age- and sex-adjusted atherosclerosis ratings were highly correlated with neuritic plaque, paired helical filaments tau neurofibrillary tangle and cerebral amyloid angiopathy ratings in the whole sample and within individual groups. We found no associations between atherosclerosis ratings and α-synuclein or TDP-43 lesion ratings. The association between age-adjusted circle of Willis atherosclerosis and Alzheimer's disease-type pathology was more robust for female subjects than male subjects. These results provide further confirmation and specificity that vascular disease and Alzheimer's disease are interrelated and suggest that common aetiologic or reciprocally synergistic pathophysiological mechanisms promote both vascular pathology and plaque and tangle pathology.

Antemortem pulse pressure elevation predicts cerebrovascular disease in autopsy-confirmed Alzheimer's disease

Elevated pulse pressure (PP) is associated with cognitive decline and increased risk of Alzheimer's disease (AD) in older adults, although the mechanisms behind these associations remain unclear. To address this question, we examined whether antemortem late-life PP elevation predicted vascular or AD pathology in autopsy-confirmed AD patients. Sixty-five elderly patients (mean age 74.2 years) clinically diagnosed with possible or probable AD underwent neuropsychological testing and blood pressure examinations. Postmortem histopathological measures of cerebrovascular disease (CVD) and AD neuropathology were later obtained on these same patients. We expected that antemortem PP elevation, but not standard blood pressure measures such as systolic or diastolic blood pressure, would predict the autopsy-based presence of CVD, and possibly AD pathology, in elderly AD patients. Results demonstrated that antemortem PP elevation was associated with the presence and severity of CVD at autopsy. For every 5 mmHg increase in antemortem PP there was an estimated 36% increase in the odds of having CVD at autopsy. Additionally, PP accounted for 12% of variance in CVD severity. No significant associations were present for cerebral amyloid angiopathy or Braak and Braak staging of the severity of AD pathology. Other standard blood pressure measures also did not significantly predict neuropathology. The association between antemortem PP and CVD at autopsy suggests that in older adults with AD, PP elevation may increase the risk of CVD. These findings may have treatment implications since some antihypertensive medications specifically address the pulsatile component of blood pressure (e.g., renin-angiotensin system inhibitors, calcium channel blockers).

Stress, exercise, and Alzheimer's disease: a neurovascular pathway

Genetic factors are known to play a role in Alzheimer's disease (AD) vulnerability, yet less than 1% of incident AD cases are directly linked to genetic causes, suggesting that environmental variables likely play a role in the majority of cases. Several recent human and animal studies have examined the effects of behavioral factors, specifically psychological stress and exercise, on AD vulnerability. Numerous animal studies have found that, while stress exacerbates neuropathological changes associated with AD, exercise reduces these changes. Some human studies suggest that psychological stress can increase the risk of developing AD, while other studies suggest that exercise can significantly reduce AD risk. Most animal studies investigating the mechanisms responsible for the effects of these behavioral factors have focused on neuronal processes, including the effects of stress hormones and neurotrophic factors on the neuropathological hallmarks of AD, namely amyloid-beta (Aβ) deposition and tau-phosphorylation. However, cumulative evidence indicates that, in humans, AD is associated with the presence of cerebrovascular disease, and cardiovascular risk factors are associated with increased risk of developing AD. There is an extensive literature demonstrating that behavioral factors, particularly stress and exercise, can powerfully modulate the pathophysiology of vascular disease. Thus, the following model proposes that the influence of stress and exercise on AD risk may be partially due to the effects of these behavioral factors on vascular homeostasis and pathology. These effects are likely due to both indirect modification of AD risk through alterations in vascular risk factors, such as hypertension, diabetes, and aortic stiffening, as well as direct influence on the cerebrovasculature, including changes in cerebral blood flow, angiogenesis, and vascular disease. Future studies examining the effects of behavioral factors on AD risk should incorporate measures of both peripheral and cerebral vascular function to further our understanding of the mechanisms by which behavior can modify AD susceptibility. Greater knowledge of the molecular mechanisms behind these behavioral effects would further our understanding of the disease and lead to innovative treatment and preventive approaches.

The relationship between pulse pressure and leukoaraiosis in the elderly

Leukaraiosis and a higher level of pulse pressure are well-recognized as associated with cardiovascular disease, vascular angiopathy, and geriatric syndrome. A cross-sectional study was conducted to examine the relation between pulse pressure and leukoaraiosis based on brain magnetic resonance imaging (MRI) scans in the apparently healthy elderly (147 men aged 60-84 years and 89 women aged 60-82 years). The odds ratios (OR) and 95% confidence interval (CI) for leukoaraiosis were calculated using multivariate logistic regression analyses according to each quartile of pulse pressure. The percentage of leukoaraiosis gradually increased in accordance with pulse pressure quartiles: 5.1%, 8.6%, 16.1%, and 26.2% for men, and 4.5%, 8.7%, 13.0%, and 23.8% for women. In comparison with subjects in the lowest quartile, the OR (95%CI) for leukoaraiosis in the highest quartile was 6.80 (1.20-38.45) in men after adjusting for age, body mass index, fasting plasma glucose, HDL-cholesterol, triglyceride (TG), smoking status, and current drinking. However, the relationship was not evident in women after adjusting for the same co-variables. In conclusion, pulse pressure was found to be independently associated with leukoaraiosis regardless of classical cardiovascular risk factors in elderly men.

Elevated pulse pressure is associated with age-related decline in language ability

Recent research suggests that pulse pressure (PP), a putative marker of vascular integrity, may be associated with brain microvascular damage and age-related cognitive decline. Thus, the present study examined the relationship between PP and cognition in a sample of healthy nondemented older adults. One hundred nine participants were administered neurological and neuropsychological evaluations and determined to be nondemented. Regression analyses were used to examine the relationships among pulse pressure (PP) [systolic blood pressure (SBP)--diastolic blood pressure (DBP)], age, and cognition. PP and related measures were inversely correlated with global cognitive functioning and scores on a composite measure of language function, even after adjusting for age, education, and relevant vascular risk factors. Results indicate that increases in the pulsatile component of blood pressure may convey added risk of global cognitive decline and specific impairment in language abilities.

Hypertension and cognitive function

Cumulative evidence implicates hypertension in the pathogenesis of Alzheimer disease. Although it may not presently be possible to completely differentiate the effects of treatment and control of hypertension itself from those of the medication used to achieve such treatment goals, efforts directed at the treatment and control of hypertension can have significant public health impact.

High blood pressure, hypertension, and high pulse pressure are associated with poorer cognitive function in persons aged 60 and older: the Third National Health and Nutrition Examination Survey

OBJECTIVES

To test the hypothesis that hypertension, high blood pressure, and high pulse pressure (PP) are independently associated with lower cognitive function.

DESIGN

Cross-sectional study of persons examined in 1988 to 1994.

SETTING

U.S. noninstitutionalized population.

PARTICIPANTS

Six thousand one hundred sixty-three men and women aged 60 and older who participated in the Third National Health and Nutrition Examination Survey (NHANES III).

MEASUREMENTS

Measurements included blood pressure, short-portable Mini-Mental State Examination (sp-MMSE), self-reported history of hypertension, diagnosis, and treatment.

RESULTS

In the initial bivariate analysis within age groups of 60 to 64, 65 to 69, and 70 to 74, optimal blood pressure (< 120/80 mmHg) was associated with best cognitive performance; the severe hypertension group had the poorest performance in all age groups except the very old (> or = 80), where the pattern was reversed, showing poorest performance in the optimal blood pressure group and best in the group with moderate hypertension. This pattern changed slightly in multiple regression analyses modeling sp-MMSE as the outcome variable. Higher stage of hypertension according to the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure and higher PP were associated with worse cognitive performance than normal blood pressure at ages 70 to 79 and 80 and older. No significant negative association was seen in subjects aged 60 to 69. Subjects with treated but uncontrolled hypertension had significantly lower sp-MMSE scores than those without hypertension or with controlled hypertension after controlling for age, sex, ethnicity, income, and PP.

CONCLUSION

At age 70 and older, high blood pressure, hypertension, and uncontrolled blood pressure are associated with poorer cognitive function than normal blood pressure. Optimal control of blood pressure may be useful in preserving neurocognitive loss as the population ages.

Alzheimer’s disease in late-life dementia: A minor toxic consequence of devastating cerebrovascular dysfunction

Alzheimer's disease (AD) is thought to be the most common cause of late-life dementia. But pure AD is infrequent whereas AD pathology is often insufficient to explain dementia in the elderly. Conversely, cerebrovascular disease is omnipresent and the crucial role of microvascular alterations increasingly recognized in late dementia or "Alzheimer syndrome". Pathomechanisms of vascular cognitive impairment are still debated but recent data indicate that the initial concept of chronic low grade cerebral hypoxia should not have been abandoned. Thus, it is proposed that windkessel dysfunction is the missing link between vascular and craniospinal senescence on the one hand, and chronic low grade cerebral hypoxia, "senile brain degeneration" and "Alzheimer syndrome" on the other hand. An age-related decrease in the buffering capacity of both the vessels and the craniospinal cavity favours cerebral hypoxia; due to increased capillary pulsatility with disturbances in capillary exchanges or due to a marked reduction in craniospinal compliance with a mechanical reduction in cerebral arterial inflow. "Invisible" windkessel dysfunction, most often related to "hardening of the arteries" may be the most frequent pathomechanism of late-onset dementia whereas associated mild or moderate AD may be merely a toxic manifestation of a primarily hypoxic disease. Structural patterns of arteriosclerotic dementia fit well with an underlying arterial windkessel dysfunction: with secondary mechanical damage to the cerebral small vessels and the brain and predominantly deep hypoxia. The clinical significance of leukoaraïosis, small foci of necrosis, ventricular dilatation, hippocampal and cortical atrophy is in good agreement with their value as indirect markers of windkessel dysfunction. An age-related "invisible" reduction in craniospinal compliance may also contribute to the associations between heart failure, arterial hypotension and cognitive impairment in the elderly and to the high percentage of dementia of unknown origin in the very old. Both neuropathological and clinical overlap between AD and windkessel dysfunction can explain that cerebrovascular dysfunction remains misdiagnosed for AD in the elderly. Evidence of the key role of cerebrovascular dysfunction should markedly facilitate and widen therapeutic research in late-life dementia. Routine MRI including direct assessment of intracranial dynamics should be increasingly used to define etiological subtypes of the "Alzheimer syndrome" and develop a well-targeted therapeutic strategy.

Circle of Willis atherosclerosis: association with Alzheimer's disease, neuritic plaques and neurofibrillary tangles

The role of intracranial atherosclerosis in Alzheimer's disease (AD) has been a subject of debate since the first decade of the last century. The initial "vascular hypothesis" of AD was rejected after a series of mid-twentieth century gross anatomical postmortem studies that showed an inconstant relationship between intracranial atherosclerosis and senile dementia. These early studies did not utilize statistical methods, however, and the investigators did not appear to consider the possibility that intracranial atherosclerosis might have a probabilistic, rather than an absolute, effect on AD risk. Recent studies by three independent groups have found a significant statistical association between postmortem measures of circle of Willis atherosclerosis and AD. The present study was undertaken to further address the validity of this association in a large autopsy series, including cases diagnosed neuropathologically with vascular dementia (VaD) and non-AD dementias. Postmortem gross anatomical grading of circle of Willis atherosclerosis was performed in 397 subjects classified by neuropathological diagnosis, including 92 non-demented elderly controls, 215 with AD, 30 with VaD and 60 with non-AD dementias. Circle of Willis atherosclerosis was more severe in subjects with AD and VaD than in control subjects, while it was equivalent between control subjects and subjects with non-AD dementias. Increasing atherosclerotic grade increased the odds ratios (OR) for the diagnoses of both AD and VaD and also increased the ORs for both increased neuritic plaque density and higher Braak neurofibrillary tangle stage. The significance of these associations was retained after consideration of the effects of age, gender and the apolipoprotein E-epsilon4 allele. The results suggest that the statistical association between intracranial atherosclerosis and AD is not an artifact of diagnostic misclassification or of unequal distribution of the apolipoprotein E-epsilon4 allele.

Interaction of cardiovascular disease and neurodegeneration: transcranial Doppler ultrasonography and Alzheimer's disease

OBJECTIVE

Recent post-mortem studies have reported that the severity of atheromatous deposits in the circle of Willis is significantly greater, relative to non-demented (ND) elderly persons, in subjects with neuropathologically diagnosed Alzheimer's disease (AD). Additionally, the severity of intracranial atherosclerosis correlates significantly with the densities of neuritic plaques and neurofibrillary tangles. In this study, we examine the arteries of the circle of Willis by transcranial Doppler (TCD) ultrasonography.

METHODS

TCD was used to measure, in 25 AD patients and 30 ND elderly subjects, mean flow velocities and pulsatility indices in 16 different segments of the circle of Willis. The data were compared with and without adjustment for age, gender and systolic blood pressure.

RESULTS

The AD patients had systematically higher pulsatility indices (p<0.005) than the ND group. Incremental increases of pulsatility indices in these segments had odds ratios ranging from 1.8 to 48 for the presence of AD when adjusted for age, gender and systolic blood pressure. The left internal carotid artery siphon and the left posterior cerebral artery were the two vessels that were strongly associated with AD diagnosis. Mean flow velocities were generally lower in patients with AD but the differences did not reach the significance level.

DISCUSSION

The pulsatility indices of the arteries of AD patients were generally greater than those of similarly-aged ND subjects. This difference is most likely due to increased arterial wall rigidity imposed by atherosclerotic changes. Atherosclerotic disease of intracranial arteries may be a risk factor for AD.