To reveal the underlying mechanisms responsible for the regional vulnerability to amyloid-β (Aβ) accumulation prior to the development of Alzheimer’s disease, we studied distribution of Aβ, apolipoprotein E (apoE), synaptic markers, and other molecules involved in Aβ metabolism in multiple brain areas of non-demented individuals. Twelve brain regions including neocortical, limbic, and subcortical areas were dissected from brains of non-demented individuals and extracted according to increasing insolubility by a sequential three-step method. The levels of Aβ40, Aβ42, apoE, APP, APP-CTFβ, BACE1, presenilin-1, neprilysin, insulysin, LRP1, LDLR, synaptophysin, PSD95, GFAP, and lactate were determined by ELISAs or enzymatic assays. The regional distribution of apoE showed moderate-to-strong inverse correlation with levels of Aβ, especially insoluble Aβ40. On the other hand, the regional distributions of synaptic markers, particularly PSD95, showed moderate-to-strong positive correlation with levels of Aβ, especially soluble Aβ40. The regional correlations between Aβ and LRP1, GFAP, or lactate were mild-to-moderate. Moderate-to-strong positive regional correlations were observed between apoE and GFAP or lactate and between PSD95 and LRP1. No significant regional correlations were detected between Aβ and APP, APP-CTFβ, BACE1, or presenilin-1, those involved in Aβ production. There were no significant negative regional correlations between Aβ and two major Aβ degrading enzymes, neprilysin and insulysin. These regional correlations remained consistent regardless of the degree of Aβ accumulation. The regional vulnerability to Aβ accumulation may be due to a net balance between two competing processes: (1) synapses involved in promoting the initial Aβ accumulation and (2) astrocyte-derived apoE involved in preventing Aβ accumulation.
Alzheimer’s disease; Amyloid-β; Regional vulnerability; Apolipoprotein E; Synapses
The new criteria for preclinical Alzheimer’s Disease (AD) proposed 3 stages: abnormal levels of β-amyloid (stage 1); stage 1 plus evidence of brain injury (stage 2); and stage 2 plus subtle cognitive changes (stage 3). However, a large group of subjects with normal β-amyloid biomarkers have evidence of brain injury; we labeled them as “suspected non-Alzheimer pathway” (sNAP) group. The characteristics of the sNAP group are poorly understood.
Using the preclinical AD classification, 430 cognitively normal subjects from the Mayo Clinic Study of Aging who underwent brain MR, 18fluorodeoxyglucose (FDG) and Pittsburgh compound B (PiB) positron emission tomography (PET) were evaluated with FDG PET regional volumetrics, MR regional brain volumetrics, white matter hyperintensity (WMH) volume and number of infarcts. We examined cross-sectional associations across AD preclinical stages, those with all biomarkers normal, and the sNAP group.
The sNAP group had a lower proportion (14%) with APOE ε4 genotype than the preclinical AD stages 2 + 3. The sNAP group did not show any group differences compared to stages 2 + 3 of the preclinical AD group on measures of FDG PET regional hypometabolism, MR regional brain volume loss, cerebrovascular imaging lesions, vascular risk factors, imaging changes associated with α-synucleinopathy or physical findings of parkinsonism.
Cognitively normal persons with brain injury biomarker abnormalities, with or without abnormal levels of β-amyloid, were indistinguishable on a variety of imaging markers, clinical features and risk factors. The initial appearance of brain injury biomarkers that occurs in cognitively normal persons with preclinical AD may not depend on β-amyloidosis.
Alzheimer’s disease; PET imaging; MR imaging; Epidemiology
We analyzed the baseline and 3-year T1-weighted magnetic resonance imaging data of 110 amnestic mild cognitive impairment (MCI) participants with minimal hippocampal atrophy at baseline from the Alzheimer’s Disease Cooperative Study group (ADCS) MCI Donepezil/Vitamin E trial. 46 subjects converted to AD (MCIc) while 64 remained stable (MCInc). We used the radial distance technique to examine the differences in lateral ventricle shape and size between MCIc and MCInc and the associations between ventricular enlargement and cognitive decline.
MCIc group had significantly larger frontal and right body/occipital horns relative to MCInc at baseline and significantly larger bilateral frontal, body/occipital and left temporal horns at follow-up. Global cognitive decline measured with ADAScog and MMSE and decline in activities of daily living (ADL) were associated with posterior lateral ventricle enlargement. Decline in ADAScog and ADL were associated with left temporal and decline in MMSE with right temporal horn enlargement. After correction for baseline hippocampal volume decline in ADL showed a significant association with right frontal horn enlargement. Executive decline was associated with right frontal and left temporal horn enlargement.
Alzheimer’s disease; AD; mild cognitive impairment; MCI; imaging; MRI; brain atrophy; ventricular enlargement
Non-amnestic mild cognitive impairment (naMCI), a putative precursor of vascular and other non-Alzheimer’s disease dementias, is hypothesized to have a vascular etiology. We investigated the association of cardiac disease with amnestic (aMCI) and non-amnestic (naMCI) MCI.
A prospective, population-based, cohort study with a median 4.0 years of follow-up.
Olmsted County, Minnesota.
Participants were evaluated at baseline and every 15 months using the Clinical Dementia Rating scale, a neurological evaluation, and neuropsychological testing. A diagnosis of normal cognition, MCI, or dementia was made by consensus. Cardiac disease at baseline was assessed from the participant’s medical records.
Main outcome measures
Incident MCI, aMCI, naMCI.
Among 1,450 subjects free of MCI or dementia at baseline, 366 developed MCI. Cardiac disease was associated with an increased risk of naMCI (hazard ratio [HR] 95% confidence interval; 1.77 [1.16–2.72]). However, the association varied by sex (P for interaction = .02). Cardiac disease was associated with an increased risk of naMCI (HR, 3.07 [1.58–5.99]) in women, but not in men (HR, 1.16 [0.68–1.99]. Cardiac disease was not associated with any MCI or aMCI.
Cardiac disease is an independent risk factor for naMCI, within sex comparisons showed a stronger association in women. Prevention and management of cardiac disease and vascular risk factors may reduce the risk of naMCI.
Maintaining and improving quality of life has become a major focus in geriatric medicine, but the oldest old have received limited attention in clinical investigations. We aimed to investigate the relationship between self-perceived and caregiver-perceived quality of life (QOL), cognitive functioning, and depressive symptoms in the oldest old.
This IRB-approved prospective study recruited community dwellers aged 90–99 years old. Collected data included neurological evaluation, DSM III-R criteria for dementia, Mini-Mental State Examination (MMSE), Dementia Rating Scale (DRS), Geriatric Depression Scale (GDS), Record of Independent Living (ROIL), and QOL assessment using the Linear Analogue Self Assessment (LASA).
Data on 144 subjects (56 cognitively normal (normal), 13 mild cognitive impairment (MCI), 41 dementia (DEM), 34 dementia with stroke and parkinsonism (DEMSP)) over a three-year period were analyzed. Mean ages ranged from 93 to 94 years, and the majority were female with at least high school education. Overall functional ability was higher in groups without dementia (p < 0.0001). All subjects reported high overall QOL (range 6.76–8.3 out of 10), regardless of cognitive functioning. However, caregivers perceived the subjects’ overall QOL to be lower with increasing severity of cognitive impairment (p < 0.0001). Lower GDS scores correlate with higher self-perceived overall QOL (ρ = −0.38, p < 0.0001).
In our community sample of the oldest old, there was a fairly high level of overall QOL, whether or not cognitive impairment exists. Individuals perceive their QOL better than caregivers do, and the difference in subjects’ and caregivers’ perception is more pronounced for the groups with dementia. QOL is more strongly correlated with depressive symptoms than with dementia severity.
geriatric; well being; cognition; depression; dementia; stroke; parkinsonism; MCI
We aimed to determine if there is an association between teaching and the development of progressive speech and language disorders (SLDs). Occupation was compared between 100 patients with a progressive SLD, 404 Alzheimer’s dementia patients, and the 2008 US census. In SLDs the most common occupation was teacher (22%), versus 8% in Alzheimer’s dementia. The odds ratio of being a teacher in SLDs compared to Alzheimer’s dementia was 3.4 (95% CI=1.87, 6.17). No differences were observed in the frequency of other occupations. The frequency of teachers was higher in SLDs compared to the US census; odds ratio of 6.9 (95% CI=4.3, 11.1). Farming, forestry and fishing occupations were more frequent in SLDs compared to the US census. We identified an association between progressive SLDs and the occupation of teaching. Since teaching is a communication demanding occupation, teachers may be more sensitive to the development of speech and language impairments.
Alzheimer’s; dementia; aphasia; teacher; occupation
We aimed to assess associations between clinical, imaging, pathological and genetic features and frontal lobe asymmetry in behavioral variant frontotemporal dementia (bvFTD). Volumes of the left and right dorsolateral, medial and orbital frontal lobes were measured in 80 bvFTD subjects and subjects were classified into three groups according to the degree of asymmetry (asymmetric left, asymmetric right, symmetric) using cluster analysis. The majority of subjects were symmetric (65%), with 20% asymmetric left and 15% asymmetric right. There were no clinical differences across groups, although there was a trend for greater behavioral dyscontrol in right asymmetric compared to left asymmetric subjects. More widespread atrophy involving the parietal lobe was observed in the symmetric group. Genetic features differed across groups with symmetric frontal lobes associated with C9ORF72 and tau mutations, while asymmetric frontal lobes were associated with progranulin mutations. These findings therefore suggest that neuroanatomical patterns of frontal lobe atrophy in bvFTD are influenced by specific gene mutations.
Frontotemporal dementia; frontal lobes; MRI; asymmetry; microtubule associated protein tau; progranulin; C9ORF72; pathology
Four subtypes of frontotemporal lobar degeneration with TDP-43 immunoreactive inclusions have been described (types A–D). Of these four subtypes, motor neuron disease is more commonly associated with type B pathology, but has also been reported with type A pathology. We have noted, however, the unusual occurrence of cases of type C pathology having corticospinal tract degeneration. We aimed to assess the severity of corticospinal tract degeneration in a large cohort of cases with type C (n = 31). Pathological analysis included semi-quantitation of myelin loss of fibres of the corticospinal tract and associated macrophage burden, as well as axonal loss, at the level of the medullary pyramids. We also assessed for motor cortex degeneration and fibre loss of the medial lemniscus/olivocerebellar tract. All cases were subdivided into three groups based on the degree of corticospinal tract degeneration: (i) no corticospinal tract degeneration; (ii) equivocal corticospinal tract degeneration; and (iii) moderate to very severe corticospinal tract degeneration. Clinical, genetic, pathological and imaging comparisons were performed across groups. Eight cases had no corticospinal tract degeneration, and 14 cases had equivocal to mild corticospinal tract degeneration. Nine cases, however, had moderate to very severe corticospinal tract degeneration with myelin and axonal loss. In these nine cases, there was degeneration of the motor cortex without lower motor neuron degeneration or involvement of other brainstem tracts. These cases most commonly presented as semantic dementia, and they had longer disease duration (mean: 15.3 years) compared with the other two groups (10.8 and 9.9 years; P = 0.03). After adjusting for disease duration, severity of corticospinal tract degeneration remained significantly different across groups. Only one case, without corticospinal tract degeneration, was found to have a hexanucleotide repeat expansion in the C9ORF72 gene. All three groups were associated with anterior temporal lobe atrophy on MRI; however, the cases with moderate to severe corticospinal tract degeneration showed right-sided temporal lobe asymmetry and greater involvement of the right temporal lobe and superior motor cortices than the other groups. In contrast, the cases with no or equivocal corticospinal tract degeneration were more likely to show left-sided temporal lobe asymmetry. For comparison, the corticospinal tract was assessed in 86 type A and B cases, and only two cases showed evidence of corticospinal tract degeneration without lower motor neuron degeneration. These findings confirm that there exists a unique association between frontotemporal lobar degeneration with type C pathology and corticospinal tract degeneration, with this entity showing a predilection to involve the right temporal lobe.
TDP-43 type C; corticospinal tract; MRI; semantic dementia; right temporal lobe
In 2010, the authors published a hypothetical model of the major biomarkers of Alzheimer’s disease (AD). The model was received with interest because we described the temporal evolution of AD biomarkers in relation to each other and to the onset and progression of clinical symptoms. In the interim, evidence has accumulated that supports the major assumptions of this model. Evidence has also appeared that challenges some of the assumptions underlying our original model. Recent evidence has allowed us to modify our original model. Refinements include indexing subjects by time rather than clinical symptom severity; incorporating inter-subject variability in cognitive response to the progression of AD pathophysiology; modifications of the specific temporal ordering of some biomarkers; and, recognition that the two major proteinopathies underlying AD biomarker changes, Aβ and tau, may be initiated independently in late onset AD where we hypothesize that an incident Aβopathy can accelerate an antecedent tauopathy.
In a population-based case-control study, we examined whether moderate and high caloric intakes are differentially associated with the odds of having mild cognitive impairment (MCI). The sample was derived from the Mayo Clinic Study of Aging in Olmsted County, Minnesota. Non-demented study participants aged 70–92 years (1,072 cognitively normal persons and 161 subjects with MCI) reported their caloric consumption within 1 year of the date of interview by completing a Food Frequency Questionnaire. An expert consensus panel classified each subject as either cognitively normal or having MCI based on published criteria. We conducted multivariable logistic regression analyses to compute odds ratios (OR) and 95% confidence intervals (95% CI) after adjusting for age, sex, education, depression, medical comorbidity, and body mass index. We also conducted stratified analyses by apolipoprotein E ε4 genotype status. Analyses were conducted in tertiles of caloric intake: 600 to <1,526 kcals per day (reference group); 1,526 to 2,143 kcals per day (moderate caloric intake group); and >2,143 kcals per day (high caloric intake group). In the primary analysis, there was no significant difference between the moderate caloric intake group and the reference group (OR 0.87, 95% CI 0.53–1.42, p = 0.57). However, high caloric intake was associated with a nearly two-fold increased odds of having MCI (OR 1.96, 95% CI 1.26–3.06, p = 0.003) as compared to the reference group. Therefore, high caloric intake was associated with MCI but not moderate caloric intake. This association is not necessarily a cause-effect relationship.
aging; APOE ε4 genotype; caloric intake; mild cognitive impairment; population-based
The clinical features of dementia with Lewy bodies (DLB) during wakefulness are well known. Other than REM sleep behavior disorder (RBD), only limited data exists on other sleep disturbances and disorders in DLB. We sought to characterize the polysomnographic (PSG) findings in a series of DLB patients with sleep-related complaints.
Retrospective study of patients with DLB who underwent clinical PSG at Mayo Clinic Rochester or Mayo Clinic Jacksonville over an almost 11 year span for evaluation of dream enactment behavior, excessive nocturnal movements, sleep apnea, hypersomnolence, or insomnia. The following variables were analyzed: respiratory disturbance index (RDI) in disordered breathing events/hour, periodic limb movement arousal index (PLMAI), arousals for no apparent reason (AFNAR), total arousal index (TAI), presence of REM sleep without atonia (RSWA), and percent sleep efficiency (SE).
Data on 78 patients (71M, 7F) were analyzed. The mean age was 71 ± 8 years. Seventy-five (96%) patients had histories of recurrent dream enactment during sleep with 83% showing confirmation of RSWA +/- dream enactment during PSG. Mean RDI = 11.9 ± 5.8, PLMAI = 5.9 ± 8.5, AFNARI = 10.7 ± 12.0, and TAI = 26.6 ± 17.4. SE was <80% in 72% of the sample, <70% in 49%, and <60% in 24%. In patients who did not show evidence of significant disordered breathing (23 with RDI<5), 62% of arousals were AFNARs. In those patients who had significant disordered breathing (55 with RDI ≥ 5), 36% of arousals were AFNARs. Six patients underwent evaluations with PSG plus MSLT. Two patients had mean initial sleep latencies less than five minutes, and both had RDI<5. No patient had any sleep onset rapid eye movement periods. Nineteen patients have undergone neuropathologic examination, and 18 have had limbic- or neocortical-predominant Lewy body pathology. One had progressive supranuclear palsy, but no REM sleep was recorded in prior PSG.
In patients with DLB and sleep-related complaints, several sleep disturbances in addition to RBD are frequently present. In this sample, about three quarters had a significant number of arousals not accounted for by a movement or breathing disturbance, and the primary sleep disorders do not appear to entirely account for the poor sleep efficiency in DLB, especially in those without a significant breathing disorder. Further studies are warranted to better understand the relationship between disturbed sleep, arousal and DLB; such characterization may provide insights into potential avenues of treatment of symptoms which could impact quality of life.
Sleep disorders; REM sleep behavior disorder; dementia with Lewy bodies; synucleinopathy
Recently, we evaluated two patients with corticobasal syndrome (CBS) who reported symptom onset after limb immobilization. Our objective was to investigate the association between trauma, immobilization and CBS.
The charts of forty-four consecutive CBS patients seen in the Mayo Clinic Alzheimer Disease Research Center were reviewed with attention to trauma and limb immobilization.
10 CBS patients (23%) had immobilization or trauma on the most affected limb preceding the onset or acceleration of symptoms. The median age at onset was 61. Six patients manifested their first symptoms after immobilization from surgery or fracture with one after leg trauma. Four patients had pre-existing symptoms of limb dysfunction but significantly worsened after immobilization or surgery.
23 percent of patients had immobilization or trauma of the affected limb. This might have implications for management of CBS, for avoiding injury, limiting immobilization and increasing movement in the affected limb.
Corticobasal syndrome; plasticity; immobilization
Memory deficits are prominent features of mild cognitive impairment (MCI) and Alzheimer’s disease (AD). The genetic architecture underlying these memory deficits likely involves the combined effects of multiple genetic variants operative within numerous biological pathways. In order to identify functional pathways associated with memory impairment, we performed a pathway enrichment analysis on genome-wide association data from 742 Alzheimer’s Disease Neuroimaging Initiative (ADNI) participants. A composite measure of memory was generated as the phenotype for this analysis by applying modern psychometric theory to item-level data from the ADNI neuropsychological test battery. Using the GSA-SNP software tool, we identified 27 canonical, expertly-curated pathways with enrichment (FDR-corrected p-value < 0.05) against this composite memory score. Processes classically understood to be involved in memory consolidation, such as neurotransmitter receptor-mediated calcium signaling and long-term potentiation, were highly represented among the enriched pathways. In addition, pathways related to cell adhesion, neuronal differentiation and guided outgrowth, and glucose- and inflammation-related signaling were also enriched. Among genes that were highly-represented in these enriched pathways, we found indications of coordinated relationships, including one large gene set that is subject to regulation by the SP1 transcription factor, and another set that displays co-localized expression in normal brain tissue along with known AD risk genes. These results 1) demonstrate that psychometrically-derived composite memory scores are an effective phenotype for genetic investigations of memory impairment and 2) highlight the promise of pathway analysis in elucidating key mechanistic targets for future studies and for therapeutic interventions.
memory; psychometrics; Alzheimer’s disease; mild cognitive impairment; pathway analysis; genome-wide association study
To investigate the effect of intellectual and physical activity on biomarkers of Alzheimer’s disease (AD) pathophysiology and cognition in a non-demented elderly population. The biomarkers evaluated were brain Aβ-amyloid load via PIB-PET, neuronal dysfunction via FDG-PET and neurodegeneration via Structural-MRI.
We studied 515 non-demented (428 cognitively normal and 87 MCI) participants in the population based Mayo Clinic Study of Aging who completed a 3T MRI, PET scans, APOE genotype, had lifestyle activity measures and cognition data available. The imaging measures computed were global PiB-PET uptake; global FDG-PET and MRI based hippocampal volume. We consolidated activity variables into lifetime intellectual, current intellectual and current physical activities. We used a global cognitive Z-score as a measure of cognition. We applied two independent methods – partial correlation analysis adjusted for age and gender and path analysis using structural equations to evaluate the associations between lifestyle activities, imaging biomarkers and global cognition.
None of the lifestyle variables correlated with the biomarkers and the path associations between lifestyle variables and biomarkers were not significant (p>0.05). On the other hand, all the biomarkers were correlated with global cognitive Z-score (p<0.05) and the path associations between (lifetime and current) intellectual activities and global Z-score were significant (p<0.01).
Intellectual and physical activity lifestyle factors were not associated with AD biomarkers but intellectual lifestyle factors explained variability in the cognitive performance in this non-demented population. This study provides evidence that lifestyle activities may delay the onset of dementia but do not significantly influence the expression of AD pathophysiology.
Alzheimer’s disease; Imaging biomarkers; Lifestyle Activities
ApoE ε4 is associated with adverse health conditions that negatively impact the quality of life (QOL). The relationship between ApoE ε4 and QOL has not been explored in the oldest old. Our study aimed to examine ApoE in the oldest old, and explore its association with QOL.
Cross-sectional cohort study.
A medium sized community in Olmsted County, Minnesota, USA.
90–99 year old individuals living independently or in long term care environments.
We collected demographic information and measured cognitive function (Short Test of Mental Status [STMS], Mini-Mental State Examination [MMSE], Mattis Dementia Rating Scale [DRS]), QOL (Linear Analogue Self Assessment [LASA]) and ApoE distribution. Subjects were classified as cognitively normal, mild cognitive impairment (MCI), dementia (DEM), or dementia with stroke and/or parkinsonism (DEMSP). Regression model was used to assess the predictors of QOL.
121 subjects (45 cognitively normal, 13 MCI, 34 DEM, 29 DEMSP) aged 90–99,106 (87.6 %) females, were included. Frequency of ApoE ε3 allele was highest [194 (80.2%): ε2/3 18, ε3/3 77, ε3/4 22] followed by ApoE ε4 [25 (10.3%): ε2/4 3, ε3/4 22] and ApoE ε2 [23 (9.5%; ε2/2 1, ε2/3 18, ε2/4 3]. None of the subjects carried ApoE ε4/4 genotype. QOL was similar between ApoE ε4 carrier and non-carriers. Physical well-being, emotional well-being, intellectual well-being, social connectedness and coping ability were positively associated with QOL, whereas male gender, DEMSP, pain frequency and pain severity were negatively associated.
The most common ApoE in the oldest old was ε3/3 genotype and ε3 allele. No association was found between ApoE ε4 and QOL. However, those with high physical, emotional and intellectual well being, social connectedness and coping ability had the highest overall QOL.
Well being; oldest old; apolipoprotein E
Atypical variants of Alzheimer’s disease (AD) have been pathologically defined based on the distribution of neurofibrillary tangles; hippocampal sparing (HpSp) AD shows minimal involvement of the hippocampus and limbic predominant (LP) AD shows neurofibrillary tangles restricted to the medial temporal lobe. We aimed to determine whether MRI patterns of atrophy differ across HpSp AD, LP AD and typical AD, and whether imaging could be a useful predictor of pathological subtype during life.
In this case-control study, we identified 177 patients who had been prospectively followed in the Mayo Clinic Alzheimer’s Disease Research Center, were demented during life, had AD pathology at autopsy (Braak stage ≥ IV, intermediate-high probability AD) and an antemortem MRI. Cases were assigned to one of three pathological subtypes (HpSp n=19, typical n=125, or LP AD n=33) based on neurofibrillary tangle counts and their ratio in association cortices to hippocampus, without reference to neuronal loss. Voxel-based morphometry and atlas-based parcellation were used to compare patterns of grey matter loss across groups, and to controls.
The severity of medial temporal and cortical grey matter atrophy differed across subtypes. The most severe medial temporal atrophy was observed in LP AD, followed by typical AD, and then HpSp AD. Conversely, the most severe cortical atrophy was observed in HpSp AD, followed by typical AD, and then LP AD. A ratio of hippocampal-to-cortical volume provided the best discrimination across all three AD subtypes. The majority of typical AD (98/125;78%) and LP AD (31/33;94%) subjects, but only 8/19 (42%) of the HpSp AD subjects, presented with a dominant amnestic syndrome.
Patterns of atrophy on MRI differ across the pathological subtypes of AD, suggesting that MR regional volumetrics reliably track the distribution of neurofibrillary tangle pathology and can predict pathological subtype during life.
US National Institutes of Health (National Institute on Aging)
Using data from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) population, we examined (1) cross-sectional relationships between amyloid deposition, hypometabolism, and cognition, and (2) associations between amyloid and hypometabolism measurements and longitudinal cognitive measurements.
We examined associations between mean cortical florbetapir uptake, mean 18F-fluorodeoxyglucose–positron emission tomography (FDG-PET) within a set of predefined regions, and Alzhiemer’s Disease Assessment Scale (ADAS-cog) performance in 426 ADNI participants (126 normal, 162 early mild cognitive impairment [EMCI], 85 late MCI [LMCI], 53 Alzheimer disease [AD] patients). For a subset of these (76 normal, 81 LMCI) we determined whether florbetapir and FDG-PET were associated with retrospective decline in longitudinal ADAS-cog measurements.
Twenty-nine percent of normal subjects, 43% of EMCI patients, 62% of LMCI patients, and 77% of AD patients were categorized as florbetapir positive. Florbetapir was negatively associated with concurrent FDG and ADAS-cog in both MCI groups. In longitudinal analyses, florbetapir-positive subjects in both normal and LMCI groups had greater ongoing ADAS-cog decline than those who were florbetapir negative. However, in normal subjects, florbetapir positivity was associated with greater ADAS-cog decline than FDG, whereas in LMCI, FDG positivity was associated with greater decline than florbetapir.
Although both hypometabolism and β-amyloid (Aβ) deposition are detectable in normal subjects and all diagnostic groups, Aβ showed greater associations with cognitive decline in normal participants. In view of the minimal cognitive deterioration overall in this group, this suggests that amyloid deposition has an early and subclinical impact on cognition that precedes metabolic changes. At moderate and later stages of disease (LMCI/AD), hypometabolism becomes more pronounced and more closely linked to ongoing cognitive decline.
Background and Purpose
This scientific statement provides an overview of the evidence on
vascular contributions to cognitive impairment and dementia. Vascular
contributions to cognitive impairment and dementia of later life are common.
Definitions of vascular cognitive impairment (VCI), neuropathology, basic
science and pathophysiological aspects, role of neuroimaging and vascular
and other associated risk factors, and potential opportunities for
prevention and treatment are reviewed. This statement serves as an overall
guide for practitioners to gain a better understanding of VCI and dementia,
prevention, and treatment.
Writing group members were nominated by the writing group co-chairs
on the basis of their previous work in relevant topic areas and were
approved by the American Heart Association Stroke Council Scientific
Statement Oversight Committee, the Council on Epidemiology and Prevention,
and the Manuscript Oversight Committee. The writing group used systematic
literature reviews (primarily covering publications from 1990 to May 1,
2010), previously published guidelines, personal files, and expert opinion
to summarize existing evidence, indicate gaps in current knowledge, and,
when appropriate, formulate recommendations using standard American Heart
Association criteria. All members of the writing group had the opportunity
to comment on the recommendations and approved the final version of this
document. After peer review by the American Heart Association, as well as
review by the Stroke Council leadership, Council on Epidemiology and
Prevention Council, and Scientific Statements Oversight Committee, the
statement was approved by the American Heart Association Science Advisory
and Coordinating Committee.
The construct of VCI has been introduced to capture the entire
spectrum of cognitive disorders associated with all forms of cerebral
vascular brain injury—not solely stroke—ranging from mild
cognitive impairment through fully developed dementia. Dysfunction of the
neurovascular unit and mechanisms regulating cerebral blood flow are likely
to be important components of the pathophysiological processes underlying
VCI. Cerebral amyloid angiopathy is emerging as an important marker of risk
for Alzheimer disease, microinfarction, microhemorrhage and macrohemorrhage
of the brain, and VCI. The neuropathology of cognitive impairment in later
life is often a mixture of Alzheimer disease and microvascular brain damage,
which may overlap and synergize to heighten the risk of cognitive
impairment. In this regard, magnetic resonance imaging and other
neuroimaging techniques play an important role in the definition and
detection of VCI and provide evidence that subcortical forms of VCI with
white matter hyperintensities and small deep infarcts are common. In many
cases, risk markers for VCI are the same as traditional risk factors for
stroke. These risks may include but are not limited to atrial fibrillation,
hypertension, diabetes mellitus, and hypercholesterolemia. Furthermore,
these same vascular risk factors may be risk markers for Alzheimer disease.
Carotid intimal-medial thickness and arterial stiffness are emerging as
markers of arterial aging and may serve as risk markers for VCI. Currently,
no specific treatments for VCI have been approved by the US Food and Drug
Administration. However, detection and control of the traditional risk
factors for stroke and cardiovascular disease may be effective in the
prevention of VCI, even in older people.
Vascular contributions to cognitive impairment and dementia are
important. Understanding of VCI has evolved substantially in recent years,
based on preclinical, neuropathologic, neuroimaging, physiological, and
epidemiological studies. Transdisciplinary, translational, and transactional
approaches are recommended to further our understanding of this entity and
to better characterize its neuropsychological profile. There is a need for
prospective, quantitative, clinical-pathological-neuroimaging studies to
improve knowledge of the pathological basis of neuroimaging change and the
complex interplay between vascular and Alzheimer disease pathologies in the
evolution of clinical VCI and Alzheimer disease. Long-term vascular risk
marker interventional studies beginning as early as midlife may be required
to prevent or postpone the onset of VCI and Alzheimer disease. Studies of
intensive reduction of vascular risk factors in high-risk groups are another
important avenue of research.
AHA Scientific Statements; vascular dementia; Alzheimer disease; risk factors; prevention; treatment
Dementia with Lewy bodies (DLB) is the second most common cause of neurodegenerative dementia after Alzheimer's disease (AD). Our objective was to determine whether the 11C–Pittsburgh Compound-B (PiB) retention and regional hypometabolism on PET and regional cortical atrophy on MRI are complementary in characterizing patients with DLB and differentiating them from AD. We studied age, gender and education matched patients with a clinical diagnosis of DLB (n=21), AD (n=21), and cognitively normal subjects (n=42). Hippocampal atrophy, global cortical PiB retention and occipital lobe metabolism in combination distinguished DLB from AD better than any of the measurements alone (area under the receiver operating characteristic=0.98).Five of the DLB and AD patients who underwent autopsy were distinguished through multimodality imaging. These data demonstrate that MRI and PiB PET contribute to characterizing the distinct pathological mechanisms in patients with AD compared to DLB. Occipital and posterior parietotemporal lobe hypometabolism is a distinguishing feature of DLB and this regional hypometabolic pattern is independent of the amyloid pathology.
Dementia with Lewy bodies; MRI; PET; FDG; PiB; Alzheimer's disease
Beta-amyloid (Aβ) is a histopathological hallmark of Alzheimer’s disease dementia, but high levels of Aβ in the brain can also be found in a substantial proportion of nondemented subjects. Here we investigated which 2-year rate of brain and cognitive changes are present in nondemented subjects with high and low Aβ levels, as assessed with cerebrospinal fluid and molecular positron emission tomography (PET)–based biomarkers of Aβ. In subjects with mild cognitive impairment, increased brain Aβ levels were associated with significantly faster cognitive decline, progression of gray matter atrophy within temporal and parietal brain regions, and a trend for a faster decline in parietal Fludeoxyglucose (FDG)-PET metabolism. Changes in gray matter and FDG-PET mediated the association between Aβ and cognitive decline. In contrast, elderly cognitively healthy controls (HC) with high Aβ levels showed only a faster medial temporal lobe and precuneus volume decline compared with HC with low Aβ. In conclusion, the current results suggest not only that both functional and volumetric brain changes are associated with high Aβ years before the onset of dementia but also that HC with substantial Aβ levels show higher Aβ pathology resistance, lack other pathologies that condition neurotoxic effects of Aβ, or accumulated Aβ for a shorter time period.
Aβ; FDG-PET; MCI; PIB-PET
Acetylcholinesterase inhibitors are commonly used to treat patients with dementia with Lewy bodies. Hippocampal atrophy on magnetic resonance imaging and amyloid-β load on positron emission tomography are associated with the Alzheimer’s disease-related pathology in patients with dementia with Lewy bodies. To date, few studies have investigated imaging markers that predict treatment response in patients with dementia with Lewy bodies. Our objective was to determine whether imaging markers of Alzheimer’s disease-related pathology such as hippocampal volume, brain amyloid-β load on 11C Pittsburgh compound B positron emission tomography predict treatment response to acetylcholinesterase inhibitors in patients with dementia with Lewy bodies. We performed a retrospective analysis on consecutive treatment-naive patients with dementia with Lewy bodies (n = 54) from the Mayo Clinic Alzheimer’s Disease Research Centre who subsequently received acetylcholinesterase inhibitors and underwent magnetic resonance imaging with hippocampal volumetry. Baseline and follow-up assessments were obtained with the Mattis Dementia Rating Scale. Subjects were divided into three groups (reliable improvement, stable or reliable decline) using Dementia Rating Scale reliable change indices determined previously. Associations between hippocampal volumes and treatment response were tested with analysis of covariance adjusting for baseline Dementia Rating Scale, age, gender, magnetic resonance field strength and Dementia Rating Scale interval. Seven subjects underwent 11C Pittsburgh compound B imaging within 12 weeks of magnetic resonance imaging. Global cortical 11C Pittsburgh compound B retention (scaled to cerebellar retention) was calculated in these patients. Using a conservative psychometric method of assessing treatment response, there were 12 patients with reliable decline, 29 stable cases and 13 patients with reliable improvement. The improvers had significantly larger hippocampi than those that declined (P = 0.02) and the stable (P = 0.04) group. An exploratory analysis demonstrated larger grey matter volumes in the temporal and parietal lobes in improvers compared with those who declined (P < 0.05). The two patients who had a positive 11C Pittsburgh compound B positron emission tomography scan declined and those who had a negative 11C Pittsburgh compound B positron emission tomography scan improved or were stable after treatment. Patients with dementia with Lewy bodies who do not have the imaging features of coexistent Alzheimer’s disease-related pathology are more likely to cognitively improve with acetylcholinesterase inhibitor treatment.
dementia with Lewy bodies; acetylcholinesterase inhibitors; MRI; PiB; PET; amyloid
Nicastrin (NCSTN) is a component of the γ-secretase complex and therefore potentially a candidate risk gene for Alzheimer's disease. Here, we have developed a novel functional genomics methodology to express common locus haplotypes to assess functional differences. DNA recombination was used to engineer 5 bacterial artificial chromosomes (BACs) to each express a different haplotype of the NCSTN locus. Each NCSTN-BAC was delivered to knockout nicastrin (Ncstn−/−) cells and clonal NCSTN-BAC+/Ncstn−/− cell lines were created for functional analyses. We showed that all NCSTN-BAC haplotypes expressed nicastrin protein and rescued γ-secretase activity and amyloid beta (Aβ) production in NCSTN-BAC+/Ncstn−/− lines. We then showed that genetic variation at the NCSTN locus affected alternative splicing in human postmortem brain tissue. However, there was no robust functional difference between clonal cell lines rescued by each of the 5 different haplotypes. Finally, there was no statistically significant association of NCSTN with disease risk in the 4 cohorts. We therefore conclude that it is unlikely that common variation at the NCSTN locus is a risk factor for Alzheimer's disease.
Nicastrin; Haplotype variation; Functional genomics; Alzheimer's disease; γ-Secretase complex
The field of aging and dementia research is advancing rapidly toward the stage of earlier identification of clinical symptoms. Ultimately, clinicians would like to be able to identify individuals who are asymptomatic but at risk for developing the disease. In the interim, the construct of mild cognitive impairment (MCI) has come to represent an intermediate clinical state between the cognitive changes of aging and the very earliest features of Alzheimer’s disease. A great deal of research has been generated in the past several years on MCI, and epidemiologic studies are characterizing its frequency in the general population. There are predictors of a more rapid progression from MCI to Alzheimer’s disease, and these studies are suggesting techniques for altering future clinical trials. The neuropathology of MCI is intermediate between the neuropathologic changes of aging and fully developed Alzheimer’s disease. The breadth of research in MCI is expanding and will be reviewed.
Mild cognitive impairment; Alzheimer’s disease; aging
What will it take to develop interventions for the treatment of age-related cognitive decline? Session V of the Summit provided perspectives on the design of clinical trials to evaluate promising but unproven interventions, and some of the steps needed to accelerate the discovery and evaluation of promising treatments. It considered strategies to further characterize the biological and cognitive changes associated with normal aging and their translation into the development of new treatments. It provided regulatory, scientific, and clinical perspectives about neurocognitive aging treatments, their potential benefits and risks, and the strategies and endpoints needed to evaluate them in the most rapid, rigorous, and clinically meaningful way. It considered lessons learned from the study of Alzheimer's disease, the promising roles of biomarkers in neurocognitive aging research, and ways to help galvanize the scientific study and treatment of neurocognitive aging.
Cognition; Clinical trials; Aging
Obsessions and compulsive (OC) behaviors are a frequent feature of behavioral variant frontotemporal dementia (bvFTD), but their structural correlates have not been definitively established.
Patients with bvFTD presenting to the Mayo Clinic Alzheimer’s Disease Research Center were recruited. Each patient’s caregiver was given the Yale-Brown Obsessive-Compulsive scale (YBOCS) to document the type and presence of OC behaviors and to rate their severity. All subjects underwent a standardized MRI which was evaluated using VBM. 17 patients with bvFTD were recruited and 11 were included in the study and compared to 11 age and gender matched controls. Six were excluded for lack of MRI at time of survey or a pre-existing neurodegenerative condition.
Nine of the 11 reported OC behaviors, with the most frequent compulsions being checking, hoarding, ordering/arranging, repeating rituals, and cleaning. In the VBM analysis, total YBOCS score correlated with grey matter loss in the bilateral globus pallidus, left putamen, and in the lateral temporal lobe, particularly the left middle and inferior temporal gyri (p<0.001 uncorrected for multiple comparisons).
Obsessive-compulsive behaviors were frequent among these patients. The correlation with basal ganglia atrophy may point to involvement of frontal subcortical neuronal networks. Left lateral temporal lobe volume loss likely reflects the number of MAPT mutation patients included but also provides additional data implicating temporal lobe involvement in OC behaviors.
Frontotemporal dementia; magnetic resonance imaging; obsessive behavior; compulsive behavior