To identify factors influencing age at symptom onset and disease course in autosomal dominant Alzheimer disease (ADAD), and develop evidence-based criteria for predicting symptom onset in ADAD.
We have collected individual-level data on ages at symptom onset and death from 387 ADAD pedigrees, compiled from 137 peer-reviewed publications, the Dominantly Inherited Alzheimer Network (DIAN) database, and 2 large kindreds of Colombian (PSEN1 E280A) and Volga German (PSEN2 N141I) ancestry. Our combined dataset includes 3,275 individuals, of whom 1,307 were affected by ADAD with known age at symptom onset. We assessed the relative contributions of several factors in influencing age at onset, including parental age at onset, age at onset by mutation type and family, and APOE genotype and sex. We additionally performed survival analysis using data on symptom onset collected from 183 ADAD mutation carriers followed longitudinally in the DIAN Study.
We report summary statistics on age at onset and disease course for 174 ADAD mutations, and discover strong and highly significant (p < 10−16, r2 > 0.38) correlations between individual age at symptom onset and predicted values based on parental age at onset and mean ages at onset by mutation type and family, which persist after controlling for APOE genotype and sex.
Significant proportions of the observed variance in age at symptom onset in ADAD can be explained by family history and mutation type, providing empirical support for use of these data to estimate onset in clinical research.
Recent studies show that cerebral β-amyloid (Aβ) deposition is associated with blood pressure and measures of arterial stiffness in nondemented individuals.
To examine the association between measures of arterial stiffness and change in Aβ deposition over time.
DESIGN, SETTING, AND PARTICIPANTS
Deposition of Aβ was determined in a longitudinal observational study of aging by positron emission tomography using the Pittsburgh compound B twice 2 years apart in 81 nondemented individuals 83 years and older. Arterial stiffness was measured with a noninvasive and automated waveform analyzer at the time closest to the second positron emission tomography scan. All measures were performed under standardized conditions. Pulse wave velocity (PWV) was measured in the central (carotid-femoral and heart-femoral PWV), peripheral (femoral-ankle PWV), and mixed (brachial-ankle PWV) vascular beds.
MAIN OUTCOMES AND MEASURES
The change in Aβ deposition over 2 years was calculated from the 81 individuals with repeat Aβ-positron emission tomography.
The proportion of Aβ-positive individuals increased from 48% at baseline to 75% at follow-up. Brachial-ankle PWV was significantly higher among Aβ-positive participants at baseline and follow-up. Femoral-ankle PWV was only higher among Aβ-positive participants at follow-up. Measures of central stiffness and blood pressure were not associated with Aβ status at baseline or follow-up, but central stiffness was associated with a change in Aβ deposition over time. Each standard deviation increase in central stiffness (carotid-femoral PWV, P = .001; heart-femoral PWV, P = .004) was linked with increases in Aβ deposition over 2 years.
CONCLUSIONS AND RELEVANCE
This study showed that Aβ deposition increases with age in nondemented individuals and that arterial stiffness is strongly associated with the progressive deposition of Aβ in the brain, especially in this age group. The association between Aβ deposition changes over time and generalized arterial stiffness indicated a relationship between the severity of subclinical vascular disease and progressive cerebral Aβ deposition.
Dementia with Lewy bodies; Treatment; Cholinesterase inhibitors; Parkinson's disease dementia; Antipsychotic; Dysautonomia; REM sleep behavior disorder
Autosomal dominant Alzheimer disease (ADAD) is caused by rare genetic
mutations in three specific genes, in contrast to late-onset Alzheimer
Disease (LOAD), which has a more polygenetic risk profile.
Design, Setting, and Participants
We analyzed functional connectivity in multiple brain resting state
networks (RSNs) in a cross-sectional cohort of ADAD (N=79) and LOAD (N=444)
human participants using resting state functional connectivity MRI
(rs-fcMRI) at multiple international academic sites.
Main Outcomes and Measures
For both types of AD, we quantified and compared functional
connectivity changes in RSNs as a function of dementia severity as measured
by clinical dementia rating (CDR). In ADAD, we qualitatively investigated
functional connectivity changes with respect to estimated years from onset
of symptoms within five RSNs.
Functional connectivity decreases with increasing CDR were similar
for both LOAD and ADAD in multiple RSNs. Ordinal logistic regression models
constructed in each type of AD accurately predicted CDR stage in the other,
further demonstrating similarity of functional connectivity loss in each
disease type. Among ADAD participants, functional connectivity in multiple
RSNs appeared qualitatively lower in asymptomatic mutation carriers near
their anticipated age of symptom onset compared to asymptomatic mutation
Conclusions and Relevance
rs-fcMRI changes with progressing AD severity are similar between
ADAD and LOAD. Rs-fcMRI may be a useful endpoint for LOAD and ADAD therapy
trials. ADAD disease process may be an effective model for LOAD disease
Resting-state functional connectivity; autosomal dominant Alzheimer's disease; late-onset Alzheimer's disease; default mode network; apolipoprotein E (APOE)
To determine arterial stiffness and β-amyloid (Aβ) deposition in the brain of dementia-free older adults.
We studied a cohort of 91 dementia-free participants aged 83–96 years. In 2009, participants completed brain MRI and PET imaging using Pittsburgh compound B (PiB; a marker of amyloid plaques in human brain). In 2011, we measured resting blood pressure (BP), mean arterial pressure (MAP), and arterial stiffness by pulse wave velocity (PWV) in the central, peripheral, and mixed (e.g., brachial ankle PWV [baPWV]) vascular beds, using a noninvasive and automated waveform analyzer.
A total of 44/91 subjects were Aβ-positive on PET scan. Aβ deposition was associated with mixed PWV, systolic BP, and MAP. One SD increase in baPWV resulted in a 2-fold increase in the odds of being Aβ-positive (p = 0.007). High white matter hyperintensity (WMH) burden was associated with increased central PWV, systolic BP, and MAP. Compared to Aβ-negative individuals with low WMH burden, each SD increase in PWV was associated with a 2-fold to 4-fold increase in the odds of being Aβ-positive and having high WMH.
Arterial stiffness was associated with Aβ plaque deposition in the brain, independent of BP and APOE ε4 allele. The associations differed by type of brain abnormality and vascular bed measured (e.g., WMH with central stiffness and Aβ deposition and mixed stiffness). Arterial stiffness was highest in individuals with both high Aβ deposition and WMH, which has been suggested to be a “double hit” contributing to the development of symptomatic dementia.
Many people with REM sleep behavior disorder have an underlying synucleinopathy, the most common of which is Lewy body disease. Identifying additional abnormal clinical features may help in identifying those at greater risk of evolving to a more severe syndrome. As gait disorders are common in the synucleinopathies, early abnormalities in gait in those with REM sleep behavior disorder could help in identifying those at increased risk of developing overt parkinsonism and/or cognitive impairment.
We identified 42 probable REM sleep behavior disorder subjects and 492 controls using the Mayo Sleep Questionnaire and assessed gait velocity, cadence and stride dynamics with an automated gait analysis system.
Cases and controls were similar in age (79.9 ± 4.7 & 80.1 ± 4.7, p= 0.74), UPDRS score (3.3 ± 5.5 & 1.9 ± 4.1, p=0.21) and Mini-Mental State Examination scores (27.2 ± 1.9 & 27.7 ± 1.6, p=0.10). A diagnosis of probable REM sleep behavior disorder was associated with decreased velocity (−7.9 cm/sec, 95%CI −13.8 to −2.0, p<0.01), cadence (−4.4 steps/min, 95%CI −7.6 to −1.3, p<0.01), and significantly increased double limb support variability (30%, 95%CI 6 – 60, p=0.01), greater stride time variability (29%, 95%CI 2 – 63, p=0.03) and swing time variability (46%, 95%CI 15 – 84, p<0.01).
Probable REM sleep behavior disorder is associated with subtle gait changes prior to overt clinical parkinsonism. Diagnosis of probable REM sleep behavior disorder supplemented by gait analysis may help as a screening tool for disorders of α-synuclein.
REM Sleep Behavior Disorder; gait; gait variability
To evaluate the proton MR spectroscopy (1H MRS) changes in carriers of a novel octapeptide repeat insertion in the Prion Protein Gene (PRNP) and family history of frontotemporal dementia with ataxia. Four at-risk mutation carriers and 13 controls were compared using single voxel, short TE, 1H MRS from the posterior cingulate gyrus. The mutation carriers had an increased choline/creatine, p=0.003 and increased myoinositol/creatine ratio, p=0.003. 1H MRS identified differences in markers of glial activity and choline metabolism in pre- and early symptomatic carriers of a novel PRNP gene octapeptide insertion. These findings expand the possible diagnostic utility of 1H MRS in familial prion disorders.
MRS; MRI; familial prion disorders; frontotemporal dementia
This study examined amyloid-β (Aβ) deposition in 190 non-demented subjects aged 82 and older to determine the proportion of Aβ-positive scans and associations with cognition, APOE status, brain volume, and Ginko biloba (Gb) treatment.
Subjects who agreed to participate had a brain MRI and positron emission tomography scan with 11C-labeled Pittsburgh compound B (PiB) following completion of a Gb treatment clinical trial. The youngest subject in this imaging study was 82, and the mean age of the subjects was 85.5 at the time of the scans;152 (80%) were cognitively normal and 38 (20%) were diagnosed with mild cognitive impairment (MCI)at the time of the PiB study.
A high proportion of the cognitively normal subjects (51%) and MCI subjects (68%) were PiB-positive. The APOE*4 allele was more prevalent in PiB-positive than in PiB-negative subjects (30% vs 6%). Measures of memory, language and attentional functions were worse in PiB-positive than in PiB-negative subjects, when both normal and MCI cases were analyzed together; however no significant associations were observed within either normal or MCI subject groups alone. There was no relationship between Gb treatment and Aβ deposition as determined by PiB.
The data revealed a 55% prevalence of PiB-positivity in non-demented subjects age >80 and 85% PiB-positivity in the APOE*4 non-demented elderly subjects. The findings also showed that long-term exposure to Gb did not affect the prevalence of cerebral Aβ deposition.
An important research application of amyloid imaging with positron emission tomography (PET) is detection of the earliest evidence of fibrillar amyloid-beta (Aβ) deposition. Use of amyloid PET for this purpose, requires a reproducible method for defining a cutoff that separates individuals with no significant Aβ deposition from those in which Aβ deposition has begun. We previously reported the iterative outlier approach (IO) for the analysis of Pittsburgh Compound-B (PiB) PET data. Developments in amyloid imaging since the initial report of IO have led us to re-examine the generalizability of this method. IO was developed using full-dynamic atrophy-corrected PiB PET data obtained from a group of control subjects with a fairly distinct separation between PiB-positive [PiB(+)] and PiB-negative [PiB(−)] subjects.
We tested the performance of IO using late-summed tissue ratio data with atrophy correction or with an automated template method without atrophy correction and tested the robustness of the method when applied to a cohort of older subjects in which separation between PiB(+) and PiB(−) subjects was not so distinct.
The IO method did not perform consistently across analyses and performed particularly poorly when separation was less clear. We found that a sparse k-means (SKM) cluster analysis approach performed significantly better; performing more consistently across methods and subject cohorts. We also compared SKM to a consensus visual read approach and found very good correspondence.
The visual read and SKM methods, applied together, may optimize the identification of early Aβ deposition. These methods have the potential to provide a standard approach to the detection of PiB-positivity that is generalizable across centers.
Amyloid; Positron Emission Tomography; Pittsburgh Compound B; Visual Read; Cluster analysis
The authors sought to determine the effects of conventional and atypical antipsychotic use on time to nursing home admission and time to death in a group of outpatients with mild to moderate probable Alzheimer’s disease.
The authors examined time to nursing home admission and time to death in 957 patients with the diagnosis of probable Alzheimer’s disease who had at least one follow-up evaluation (mean follow-up time, 4.3 years [SD=2.7]; range, 0.78–18.0 years) using Cox proportional hazard models adjusted for age, gender, education level, dementia severity, hypertension, diabetes mellitus, heart disease, extrapyramidal signs, depression, psychosis, aggression, agitation, and dementia medication use.
A total of 241 patients (25%) were exposed to antipsychotics at some time during follow-up (conventional, N=138; atypical, N=95; both, N=8). Nursing home admission (63% compared with 23%) and death (69% compared with 34%) were more frequent in individuals taking conventional than atypical antipsychotics. In amodel that included demographic and cognitive variables, hypertension, diabetes mellitus, heart disease, incident strokes, and extrapyramidal signs, only conventional antipsychotic use was associated with time to nursing home admission. However, the association was no longer significant after adjustment for psychiatric symptoms. Psychosis was strongly associated with nursing home admission and time to death, but neither conventional nor atypical antipsychotics were associated with time to death.
The use of antipsychotic medications, both conventional and atypical, was not associated with either time to nursing home admission or time to death after adjustment for relevant covariates. Rather, it was the presence of psychiatric symptoms, including psychosis and agitation, that was linked to increased risk of institutionalization and death after adjustment for exposure to antipsychotics.
To determine whether a high prevalence (55%) of Aβ deposition in a cohort of individuals remaining dementia-free into their 9th and 10th decades is associated with cognitive decline prior to imaging.
A total of 194 participants (mean age 85.5 years, range 82–95) who completed the Ginkgo Evaluation of Memory Study (GEMS) and remained dementia-free subsequently completed Pittsburgh compound B–PET imaging. We examined cross-sectional associations between Aβ status and performance on a broad neuropsychological test battery completed at GEMS entry 7–9 years prior to neuroimaging. We also longitudinally examined cognition over annual evaluations using linear mixed models.
At GEMS screening (2000–2002), participants who were Aβ-positive in 2009 had lower performance on the Stroop test (p < 0.01) and Raven's Progressive Matrices (p = 0.05), with trend level difference for Block Design (p = 0.07). Longitudinal analyses showed significant slope differences for immediate and delayed recall of the Rey-Osterrieth figure, semantic fluency, and Trail-Making Test parts A and B, indicating greater performance decline prior to neuroimaging for Aβ-positive relative to Aβ-negative participants (ps < 0.05).
Highly prevalent Aβ deposition in oldest-older adults is associated with cognitive decline in visual memory, semantic fluency, and psychomotor speed beginning 7–9 years prior to neuroimaging. Mean differences in nonmemory domains, primarily executive functions, between Aβ-status groups may be detectable 7–9 years before neuroimaging.
To investigate default mode network (DMN) functional connectivity MRI (fcMRI) in a large cross-sectional cohort of subjects from families harboring pathogenic presenilin-1 (PSEN1), presenilin-2 (PSEN2), and amyloid precursor protein (APP) mutations participating in the Dominantly Inherited Alzheimer Network.
Eighty-three mutation carriers and 37 asymptomatic noncarriers from the same families underwent fMRI during resting state at 8 centers in the United States, United Kingdom, and Australia. Using group-independent component analysis, fcMRI was compared using mutation status and Clinical Dementia Rating to stratify groups, and related to each participant's estimated years from expected symptom onset (eYO).
We observed significantly decreased DMN fcMRI in mutation carriers with increasing Clinical Dementia Rating, most evident in the precuneus/posterior cingulate and parietal cortices (p < 0.001). Comparison of asymptomatic mutation carriers with noncarriers demonstrated decreased fcMRI in the precuneus/posterior cingulate (p = 0.014) and right parietal cortex (p = 0.0016). We observed a significant interaction between mutation carrier status and eYO, with decreases in DMN fcMRI observed as mutation carriers approached and surpassed their eYO.
Functional disruption of the DMN occurs early in the course of autosomal dominant Alzheimer disease, beginning before clinically evident symptoms, and worsening with increased impairment. These findings suggest that DMN fcMRI may prove useful as a biomarker across a wide spectrum of disease, and support the feasibility of DMN fcMRI as a secondary endpoint in upcoming multicenter clinical trials in Alzheimer disease.
Objectives and Methods:
The purpose of this study was to examine the incidence of mild cognitive impairment (MCI) and patterns of progression from incident MCI to dementia in 285 cognitively normal subjects (mean age, 78.9 years) in the Cardiovascular Health Study–Cognition Study from 1998–1999 to 2010–2011.
Two hundred (70%) of the participants progressed to MCI; the age-adjusted incidence of MCI was 111.09 (95% confidence interval, 88.13–142.95) per 1,000 person-years. A total of 107 (53.5%) of the incident MCI subjects progressed to dementia. The mean time from MCI to dementia was 2.8 ± 1.8 years. Forty (20%) of the incident MCI cases had an “unstable” course: 19 (9.5%) converted to MCI and later returned to normal; 10 (5%) converted to MCI, to normal, and later back to MCI; 7 (3.5%) converted to MCI, to normal, to MCI, and later to dementia; and 4 (2%) converted to MCI, to normal, and later to dementia. There was an increased mortality rate among the cognitively normal group (110.10 per 1,000 person-years) compared to those with incident MCI who converted to dementia (41.32 per 1,000 person-years).
The majority of the subjects aged >80 years developed an MCI syndrome, and half of them progressed to dementia. Once the MCI syndrome was present, the symptoms of dementia appeared within 2 to 3 years. Progression from normal to MCI or from normal to MCI to dementia is not always linear; subjects who developed MCI and later returned to normal can subsequently progress to dementia. Competing mortality and morbidity influence the study of incident MCI and dementia in population cohorts.
The Dominantly Inherited Alzheimer Network (DIAN) is a collaborative effort of international Alzheimer disease (AD) centers that are conducting a multifaceted prospective biomarker study in individuals at-risk for autosomal dominant AD (ADAD). DIAN collects comprehensive information and tissue in accordance with standard protocols from asymptomatic and symptomatic ADAD mutation carriers and their non-carrier family members to determine the pathochronology of clinical, cognitive, neuroimaging, and fluid biomarkers of AD. This article describes the structure, implementation, and underlying principles of DIAN, as well as the demographic features of the initial DIAN cohort.
Alzheimer disease; autosomal dominant; biomarkers of Alzheimer disease; PSEN1; PSEN2; APP; amyloid-beta; preclinical Alzheimer disease
The order and magnitude of pathologic processes in Alzheimer’s disease are not well understood, partly because the disease develops over many years. Autosomal dominant Alzheimer’s disease has a predictable age at onset and provides an opportunity to determine the sequence and magnitude of pathologic changes that culminate in symptomatic disease.
In this prospective, longitudinal study, we analyzed data from 128 participants who underwent baseline clinical and cognitive assessments, brain imaging, and cerebrospinal fluid (CSF) and blood tests. We used the participant’s age at baseline assessment and the parent’s age at the onset of symptoms of Alzheimer’s disease to calculate the estimated years from expected symptom onset (age of the participant minus parent’s age at symptom onset). We conducted cross-sectional analyses of baseline data in relation to estimated years from expected symptom onset in order to determine the relative order and magnitude of pathophysiological changes.
Concentrations of amyloid-beta (Aβ)42 in the CSF appeared to decline 25 years before expected symptom onset. Aβ deposition, as measured by positron-emission tomography with the use of Pittsburgh compound B, was detected 15 years before expected symptom onset. Increased concentrations of tau protein in the CSF and an increase in brain atrophy were detected 15 years before expected symptom onset. Cerebral hypometabolism and impaired episodic memory were observed 10 years before expected symptom onset. Global cognitive impairment, as measured by the Mini–Mental State Examination and the Clinical Dementia Rating scale, was detected 5 years before expected symptom onset, and patients met diagnostic criteria for dementia at an average of 3 years after expected symptom onset.
We found that autosomal dominant Alzheimer’s disease was associated with a series of pathophysiological changes over decades in CSF biochemical markers of Alzheimer’s disease, brain amyloid deposition, and brain metabolism as well as progressive cognitive impairment. Our results require confirmation with the use of longitudinal data and may not apply to patients with sporadic Alzheimer’s disease. (Funded by the National Institute on Aging and others; DIAN ClinicalTrials.gov number, NCT00869817.)
Background and Purpose
The cause of initial ischemic stroke in up to 30% of young patients remains unclear. Fabry disease, due to deficient α-galactosidase A (α-Gal A) activity, is a vascular endothelial glycosphingolipid storage disease typically presenting in childhood. With advancing age, patients develop renal, cardiac, and cerebrovascular disease and die prematurely. A European study suggested an increased prevalence of unrecognized Fabry disease in patients with cryptogenic stroke. We hypothesized that α-Gal A deficiency is a rare cause of initial early-onset ischemic stroke in men.
The Stroke Prevention in Young Men Study enrolled >550 men (15 to 49 years) with first ischemic stroke in the Baltimore–Washington area in 2004 to 2007. Frozen plasma samples were assayed for α-Gal A activity, and DNA from patients with consistently low plasma α-Gal A activities were sequenced.
The study sample consisted of 558 men (42% African-American; median age 44 years). Stroke was cryptogenic in 154 men (40% African-American). In 10 patients with low plasma α-Gal A activities, DNA sequencing identified alterations in the α-Gal A gene in 2 patients. The polymorphism, D313Y, which results in low plasma enzyme activity, but near normal levels of cellular activity was seen in one European-American male. The Fabry disease-causing A143T mutation was seen in an African-American male with cryptogenic stroke (0.18% of all strokes: upper 95% CI=0.53%; 0.65% of cryptogenic strokes: upper 95% CI=1.92%).
In this biracial population, unrecognized Fabry disease is a rare but treatable cause of initial ischemic stroke in young men.
brain infarction; genetic diseases; genetic screening; Fabry disease; stroke; X-linked
REM sleep behavior disorder (RBD) is associated with neurodegenerative disease and particularly with the synucleinopathies. Convenience samples involving subjects with idiopathic RBD have suggested an increased risk of incident mild cognitive impairment (MCI), dementia (usually dementia with Lewy bodies) or Parkinson’s disease (PD). There is no data on such risk in a population-based sample.
Cognitively normal subjects aged 70–89 in a population-based study of aging who screened positive for probable RBD using the Mayo Sleep Questionnaire were followed at 15 month intervals. In a Cox Proportional Hazards Model, we measured the risk of developing MCI, dementia, PD among the exposed (pRBD+) and unexposed (pRBD−) cohorts.
Forty-four subjects with pRBD+ at enrollment (median duration of pRBD features was 7.5 years), and 607 pRBD− subjects, were followed prospectively for a median of 3.8 years. Fourteen of the pRBD+ subjects developed MCI and one developed PD (15/44=34% developed MCI / PD); none developed dementia. After adjustment for age, sex, education, and medical comorbidity, pRBD+ subjects were at increased risk of MCI / PD [Hazard Ratio (HR) 2.2, 95% Confidence Interval (95%CI) 1.3 – 3.9; p=0.005]. Inclusion of subjects who withdrew from the study produced similar results, as did exclusion of subjects with medication-associated RBD. Duration of pRBD symptoms did not predict the development of MCI / PD (HR 1.05 per 10 years, 95%CI 0.84 – 1.3; p=0.68).
In this population-based cohort study, we observed that pRBD confers a 2.2-fold increased risk of developing MCI / PD over four years.
sleep disorders; parasomnias; dementia; Alzheimer’s disease; dementia with Lewy bodies; parkinsonism; synuclein
Purpose of review
This review describes the evolution of the clinical criteria for Alzheimer’s disease over the past 25 years, with special emphasis on those recently published that have incorporated the use of biomarkers.
One of the most important advances in the knowledge of Alzheimer’s disease was the development of cerebrospinal fluid, PET and MRI biomarkers. These have shown that the Alzheimer’s disease is present in cognitively normal individuals, suggesting that there is a long incubation process that precedes the onset of the symptoms. Although there are diagnostic criteria for Alzheimer’s disease, the National Institute on Aging and the Alzheimer’s Association has proposed a set of diagnostic criteria oriented to provide a unified vision of the pathological process from preclinical, to mild cognitive impairment, and to full-blown dementia. These new criteria take advantage of different biomarkers to support the clinical diagnosis of the different stages of the disease.
The new guidelines provide a definition of the dementia syndrome and core diagnostic features to be used in research and clinical practice, although they caution about the use of biomarkers, since they still require validation, and the longitudinal interaction and dynamics of these biomarkers in relationship to the manifestation of the symptoms are not fully understood.
Alzheimer’s disease; dementia; diagnostic criteria; mild cognitive impairment; preclinical Alzheimer’s disease
To examine default mode and salience network functional connectivity as a function of APOE ε4 status in a group of cognitively normal age, gender and education-matched older adults.
Fifty-six cognitively normal APOE ε4 carriers and 56 age, gender and education-matched cognitively normal APOE ε4 non-carriers.
Main Outcome Measure
Alterations in in-phase default mode and salience network connectivity in APOE ε4 carriers compared to APOE ε4 non-carriers ranging from 63 to 91 years of age.
A posterior cingulate seed revealed decreased in-phase connectivity in regions of the posterior default mode network that included the left inferior parietal lobe, left middle temporal gyrus, and bilateral anterior temporal lobes in the ε4 carriers relative to APOE ε4 non-carriers. An anterior cingulate seed showed greater in-phase connectivity in the salience network, including the cingulate gyrus, medial prefrontal cortex, bilateral insular cortex, striatum, and thalamus in APOE ε4 carriers vs. non-carriers. There were no group-wise differences in brain anatomy.
We found reductions in posterior default mode network connectivity but increased salience network connectivity in elderly cognitively normal APOE ε4 carriers relative to APOE ε4 non-carriers at rest. The observation of functional alterations in connectivity in the absence of structural changes between APOE e4 carriers and non-carriers suggests that alterations in connectivity may have the potential to serve as an early biomarker.
While factor analyses have characterized pace, rhythm and variability as factors that explain variance in gait performance in older adults, comprehensive analyses incorporating many gait parameters have not been undertaken and normative data for many of those parameters are lacking. The purposes of this study were to conduct a factor analysis on nearly two dozen spatiotemporal gait parameters and to contribute to the normative database of gait parameters from healthy, able-bodied men and women over the age of 70. Data were extracted from 294 participants enrolled in the Mayo Clinic Study of Aging. Spatiotemporal gait data were obtained as participants completed two walks across a 5.6-m electronic walkway (GAITRite®). Five primary domains of spatiotemporal gait performance were identified: a “rhythm” domain was characterized by cadence and temporal parameters such as stride time; a “phase” domain was characterized by temporophasic parameters that constitute distinct divisions of the gait cycle; a “variability” domain encompassed gait cycle and step variability parameters; a “pace” domain was characterized by parameters that included gait speed, step length and stride length; and a “base of support” domain was characterized by step width and step width variability. Several domains differed between men and women and differed across age groups. Reference values of 23 gait parameters are presented which researchers or clinicians can use for assessing and interpreting gait dysfunction in aging persons.
Gait; Aging; Sex Characteristics; Reference Values
Frontotemporal dementia-amyotrophic lateral sclerosis (FTD-ALS) is a heritable form of FTD, but the gene(s) responsible for the majority of autosomal dominant FTD-ALS cases have yet to be found. Previous studies have identified a region on chromosome 9p that is associated with FTD and ALS.
The authors report the clinical, volumetric MRI, neuropathological and genetic features of a new chromosome 9p-linked FTD-ALS family, VSM-20.
Ten members of family VSM-20 displayed heterogeneous clinical phenotypes of isolated behavioural-variant FTD (bvFTD), ALS or a combination of the two. Parkinsonism was common, with one individual presenting with a corticobasal syndrome. Analysis of structural MRI scans from five affected family members revealed grey- and white-matter loss that was most prominent in the frontal lobes, with mild parietal and occipital lobe atrophy, but less temporal lobe atrophy than in 10 severity-matched sporadic bvFTD cases. Autopsy in three family members showed a consistent and unique subtype of FTLD-TDP pathology. Genome-wide linkage analysis conclusively linked family VSM-20 to a 28.3 cM region between D9S1808 and D9S251 on chromosome 9p, reducing the published minimal linked region to a 3.7 Mb interval. Genomic sequencing and expression analysis failed to identify mutations in the 10 known and predicted genes within this candidate region, suggesting that next-generation sequencing may be needed to determine the mutational mechanism associated with chromosome 9p-linked FTD-ALS.
Family VSM-20 significantly reduces the region linked to FTD-ALS on chromosome 9p. A distinct pattern of brain atrophy and neuropathological findings may help to identify other families with FTD-ALS caused by this genetic abnormality.