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1.  Prevalence, Distribution, and Impact of Mild Cognitive Impairment in Latin America, China, and India: A 10/66 Population-Based Study 
PLoS Medicine  2012;9(2):e1001170.
A set of cross-sectional surveys carried out in Cuba, Dominican Republic, Peru, Mexico, Venezuela, Puerto Rico, China, and India reveal the prevalence and between-country variation in mild cognitive impairment at a population level.
Background
Rapid demographic ageing is a growing public health issue in many low- and middle-income countries (LAMICs). Mild cognitive impairment (MCI) is a construct frequently used to define groups of people who may be at risk of developing dementia, crucial for targeting preventative interventions. However, little is known about the prevalence or impact of MCI in LAMIC settings.
Methods and Findings
Data were analysed from cross-sectional surveys established by the 10/66 Dementia Research Group and carried out in Cuba, Dominican Republic, Peru, Mexico, Venezuela, Puerto Rico, China, and India on 15,376 individuals aged 65+ without dementia. Standardised assessments of mental and physical health, and cognitive function were carried out including informant interviews. An algorithm was developed to define Mayo Clinic amnestic MCI (aMCI). Disability (12-item World Health Organization disability assessment schedule [WHODAS]) and informant-reported neuropsychiatric symptoms (neuropsychiatric inventory [NPI-Q]) were measured. After adjustment, aMCI was associated with disability, anxiety, apathy, and irritability (but not depression); between-country heterogeneity in these associations was only significant for disability. The crude prevalence of aMCI ranged from 0.8% in China to 4.3% in India. Country differences changed little (range 0.6%–4.6%) after standardization for age, gender, and education level. In pooled estimates, aMCI was modestly associated with male gender and fewer assets but was not associated with age or education. There was no significant between-country variation in these demographic associations.
Conclusions
An algorithm-derived diagnosis of aMCI showed few sociodemographic associations but was consistently associated with higher disability and neuropsychiatric symptoms in addition to showing substantial variation in prevalence across LAMIC populations. Longitudinal data are needed to confirm findings—in particular, to investigate the predictive validity of aMCI in these settings and risk/protective factors for progression to dementia; however, the large number affected has important implications in these rapidly ageing settings.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Currently, more than 35 million people worldwide have dementia, a group of brain disorders characterized by an irreversible decline in memory, problem solving, communication, and other “cognitive” functions. Dementia, the commonest form of which is Alzheimer's disease, mainly affects older people and, because more people than ever are living to a ripe old age, experts estimate that, by 2050, more than 115 million people will have dementia. At present, there is no cure for dementia although drugs can be used to manage some of the symptoms. Risk factors for dementia include physical inactivity, infrequent participation in mentally or socially stimulating activities, and common vascular risk factors such as high blood pressure, diabetes, and smoking. In addition, some studies have reported that mild cognitive impairment (MCI) is associated with an increased risk of dementia. MCI can be seen as an intermediate state between normal cognitive aging (becoming increasingly forgetful) and dementia although many people with MCI never develop dementia, and some types of MCI can be static or self-limiting. Individuals with MCI have cognitive problems that are more severe than those normally seen in people of a similar age but they have no other symptoms of dementia and are able to look after themselves. The best studied form of MCI—amnestic MCI (aMCI)—is characterized by memory problems such as misplacing things and forgetting appointments.
Why Was This Study Done?
Much of the expected increase in dementia will occur in low and middle income countries (LAMICs) because these countries have rapidly aging populations. Given that aMCI is frequently used to define groups of people who may be at risk of developing dementia, it would be useful to know what proportion of community-dwelling older adults in LAMICs have aMCI (the prevalence of aMCI). Such information might help governments plan their future health care and social support needs. In this cross-sectional, population-based study, the researchers estimate the prevalence of aMCI in eight LAMICs using data collected by the 10/66 Dementia Research Group. They also investigate the association of aMCI with sociodemographic factors (for example, age, gender, and education), disability, and neuropsychiatric symptoms such as anxiety, apathy, irritability, and depression. A cross-sectional study collects data on a population at a single time point; the 10/66 Dementia Research Group is building an evidence base to inform the development and implementation of policies for improving the health and social welfare of older people in LAMICs, particularly people with dementia.
What Did the Researchers Do and Find?
In cross-sectional surveys carried out in six Latin American LAMICS, China, and India, more than 15,000 elderly individuals without dementia completed standardized assessments of their mental and physical health and their cognitive function. Interviews with relatives and carers provided further details about the participant's cognitive decline and about neuropsychiatric symptoms. The researchers developed an algorithm (set of formulae) that used the data collected in these surveys to diagnose aMCI in the study participants. Finally, they used statistical methods to analyze the prevalence, distribution, and impact of aMCI in the eight LAMICs. The researchers report that aMCI was associated with disability, anxiety, apathy, and irritability but not with depression and that the prevalence of aMCI ranged from 0.8% in China to 4.3% in India. Other analyses show that, considered across all eight countries, aMCI was modestly associated with being male (men had a slightly higher prevalence of aMCI than women) and with having fewer assets but was not associated with age or education.
What Do These Findings Mean?
These findings suggest that aMCI, as diagnosed using the algorithm developed by the researchers, is consistently associated with higher disability and with neuropsychiatric symptoms in the LAMICs studied but not with most sociodemographic factors. Because prevalidated and standardized measurements were applied consistently in all the countries and a common algorithm was used to define aMCI, these findings also suggest that the prevalence of aMCI varies markedly among LAMIC populations and is similar to or slightly lower than the prevalence most often reported for European and North American populations. Although longitudinal studies are now needed to investigate the extent to which aMCI can be used as risk marker for further cognitive decline and dementia in these settings, the large absolute numbers of older people with aMCI in LAMICs revealed here potentially has important implications for health care and social service planning in these rapidly aging and populous regions of the world.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001170.
Alzheimer's Disease International is the international federation of Alzheimer associations around the world; it provides links to individual associations, information about dementia, and links to three World Alzheimer Reports; information about the 10/66 Dementia Research Group is also available on this web site
The Alzheimer's Society provides information for patients and carers about dementia, including information on MCI and personal stories about living with dementia
The Alzheimer's Association also provides information for patients and carers about dementia and about MCI, and personal stories about dementia
A BBC radio program that includes an interview with a man with MCI is available
MedlinePlus provides links to further resources about MCI and dementia (in English and Spanish)
doi:10.1371/journal.pmed.1001170
PMCID: PMC3274506  PMID: 22346736
2.  Cholinesterase Inhibitors in Mild Cognitive Impairment: A Systematic Review of Randomised Trials 
PLoS Medicine  2007;4(11):e338.
Background
Mild cognitive impairment (MCI) refers to a transitional zone between normal ageing and dementia. Despite the uncertainty regarding the definition of MCI as a clinical entity, clinical trials have been conducted in the attempt to study the role of cholinesterase inhibitors (ChEIs) currently approved for symptomatic treatment of mild to moderate Alzheimer disease (AD), in preventing progression from MCI to AD. The objective of this review is to assess the effects of ChEIs (donepezil, rivastigmine, and galantamine) in delaying the conversion from MCI to Alzheimer disease or dementia.
Methods and Findings
The terms “donepezil”, “rivastigmine”, “galantamine”, and “mild cognitive impairment” and their variants, synonyms, and acronyms were used as search terms in four electronic databases (MEDLINE, EMBASE, Cochrane, PsycINFO) and three registers: the Cochrane Collaboration Trial Register, Current Controlled Trials, and ClinicalTrials.gov. Published and unpublished studies were included if they were randomized clinical trials published (or described) in English and conducted among persons who had received a diagnosis of MCI and/or abnormal memory function documented by a neuropsychological assessment. A standardized data extraction form was used. The reporting quality was assessed using the Jadad scale. Three published and five unpublished trials met the inclusion criteria (three on donepezil, two on rivastigmine, and three on galantamine). Enrolment criteria differed among the trials, so the study populations were not homogeneous. The duration of the trials ranged from 24 wk to 3 y. No significant differences emerged in the probability of conversion from MCI to AD or dementia between the treated groups and the placebo groups. The rate of conversion ranged from 13% (over 2 y) to 25% (over 3 y) among treated patients, and from 18% (over 2 y) to 28% (over 3 y) among those in the placebo groups. Only for two studies was it possible to derive point estimates of the relative risk of conversion: 0.85 (95% confidence interval 0.64–1.12), and 0.84 (0.57–1.25). Statistically significant differences emerged for three secondary end points. However, when adjusting for multiple comparisons, only one difference remained significant (i.e., the rate of atrophy in the whole brain).
Conclusions
The use of ChEIs in MCI was not associated with any delay in the onset of AD or dementia. Moreover, the safety profile showed that the risks associated with ChEIs are not negligible. The uncertainty regarding MCI as a clinical entity raises the question as to the scientific validity of these trials.
A systematic review of trials of cholinesterase inhibitors for preventing transition of mild cognitive impairment (MCI) to dementia, conducted by Roberto Raschetti and colleagues, found no difference between treatment and control groups and concluded that uncertainty regarding the definition of MCI casts doubts on the validity of such trials.
Editors' Summary
Background.
Worldwide, more than 24 million people have dementia, a group of brain disorders characterized by an irreversible decline in memory, problem solving, communication, and other “cognitive” functions. The commonest form of dementia is Alzheimer disease (AD). The risk of developing AD increases with age—AD is rare in people younger than 65 but about half of people over 85 years old have it. The earliest symptom of AD is usually difficulty in remembering new information. As the disease progresses, patients may become confused and have problems expressing themselves. Their behavior and personality can also change. In advanced AD, patients need help with daily activities like dressing and eating, and eventually lose their ability to recognize relatives and to communicate. There is no cure for AD but a class of drugs called “cholinesterase inhibitors” can sometimes temporarily slow the worsening of symptoms. Three cholinesterase inhibitors—donepezil, rivastigmine, and galantamine—are currently approved for use in mild-to-moderate AD.
Why Was This Study Done?
Some experts have questioned the efficacy of cholinesterase inhibitors in AD, but other experts and patient support groups have called for these drugs to be given to patients with a condition called mild cognitive impairment (MCI) as well as to those with mild AD. People with MCI have memory problems that are more severe than those normally seen in people of their age but no other symptoms of dementia. They are thought to have an increased risk of developing AD, but it is not known whether everyone with MCI eventually develops AD, and there is no standardized way to diagnose MCI. Despite these uncertainties, several clinical trials have investigated whether cholinesterase inhibitors prevent progression from MCI to AD. In this study, the researchers have assessed whether the results of these trials provide any evidence that cholinesterase inhibitors can prevent MCI progressing to AD.
What Did the Researchers Do and Find?
The researchers conducted a systematic review of the medical literature to find trials that had addressed this issue, which met criteria that they had defined clearly in advance of their search. They identified three published and five unpublished randomized controlled trials (studies in which patients randomly receive the test drug or an inactive placebo) that investigated the effect of cholinesterase inhibitors on the progression of MCI. The researchers obtained the results of six of these trials—four examined the effect of cholinesterase inhibitors on the conversion of MCI to clinically diagnosed AD or dementia (the primary end point); all six examined the effect of the drugs on several secondary end points (for example, individual aspects of cognitive function). None of the drugs produced a statistically significant difference (a difference that is unlikely to have happened by chance) in the probability of progression from MCI to AD. The only statistically significant secondary end point after adjustment for multiple comparisons (when many outcomes are considered, false positive results can occur unless specific mathematical techniques are used to prevent this problem) was a decrease in the rate of brain shrinkage associated with galantamine treatment. More patients treated with cholinesterase inhibitors dropped out of trials because of adverse effects than patients given placebo. Finally, in the one trial that reported all causes of deaths, one participant who received placebo and six who received galantamine died.
What Do These Findings Mean?
These findings suggest that the use of cholinesterase inhibitors is not associated with any delay in the onset of clinically diagnosed AD or dementia in people with MCI. They also show that the use of these drugs has no effect on most surrogate (substitute) indicators of AD but that the risks associated with their use are not negligible. However, because MCI has not yet been clearly defined as a clinical condition that precedes dementia, some (even many) of the patients enrolled into the trials that the researchers assessed may not actually have had MCI. Thus, further clinical trials are needed to clarify whether cholinesterase inhibitors can delay the progression of MCI to dementia, but these additional trials should not be done until the diagnosis of MCI has been standardized.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0040338.
An essay by Matthews and colleagues, in the October 2007 issue of PLoS Medicine, discusses how mild cognitive impairment is currently diagnosed
The US Alzheimer's Association provides information about all aspects of Alzheimer disease, including fact sheets on treatments for Alzheimer disease and on mild cognitive impairment
The UK Alzheimer's Society provides information for patients and caregivers on all aspects of dementia, including drug treatments and mild cognitive impairment
The UK charity DIPEx provides short video clips of personal experiences of care givers of people with dementia
doi:10.1371/journal.pmed.0040338
PMCID: PMC2082649  PMID: 18044984
3.  Longitudinal progression of Alzheimer's-like patterns of atrophy in normal older adults: the SPARE-AD index 
Brain  2009;132(8):2026-2035.
A challenge in developing informative neuroimaging biomarkers for early diagnosis of Alzheimer's disease is the need to identify biomarkers that are evident before the onset of clinical symptoms, and which have sufficient sensitivity and specificity on an individual patient basis. Recent literature suggests that spatial patterns of brain atrophy discriminate amongst Alzheimer's disease, mild cognitive impairment (MCI) and cognitively normal (CN) older adults with high accuracy on an individual basis, thereby offering promise that subtle brain changes can be detected during prodromal Alzheimer's disease stages. Here, we investigate whether these spatial patterns of brain atrophy can be detected in CN and MCI individuals and whether they are associated with cognitive decline. Images from the Alzheimer's Disease Neuroimaging Initiative (ADNI) were used to construct a pattern classifier that recognizes spatial patterns of brain atrophy which best distinguish Alzheimer's disease patients from CN on an individual person basis. This classifier was subsequently applied to longitudinal magnetic resonance imaging scans of CN and MCI participants in the Baltimore Longitudinal Study of Aging (BLSA) neuroimaging study. The degree to which Alzheimer's disease-like patterns were present in CN and MCI subjects was evaluated longitudinally in relation to cognitive performance. The oldest BLSA CN individuals showed progressively increasing Alzheimer's disease-like patterns of atrophy, and individuals with these patterns had reduced cognitive performance. MCI was associated with steeper longitudinal increases of Alzheimer's disease-like patterns of atrophy, which separated them from CN (receiver operating characteristic area under the curve equal to 0.89). Our results suggest that imaging-based spatial patterns of brain atrophy of Alzheimer's disease, evaluated with sophisticated pattern analysis and recognition methods, may be useful in discriminating among CN individuals who are likely to be stable versus those who will show cognitive decline. Future prospective studies will elucidate the temporal dynamics of spatial atrophy patterns and the emergence of clinical symptoms.
doi:10.1093/brain/awp091
PMCID: PMC2714059  PMID: 19416949
early Alzheimer's disease; mild cognitive impairment; neuroimaging; ageing; SPARE-AD
4.  Neuropsychiatric symptoms in MCI subtypes: the importance of executive dysfunction 
Objective
Mild cognitive impairment (MCI) is a syndrome thought to be a prodrome of dementia for some patients. One subtype, amnestic MCI, may be specifically predispose patients to develop Alzheimer’s Dementia (AD). Since dementia has been associated with a range of neuropsychiatric symptoms (NPS), we sought to examine the prevalence of NPS in MCI and its subtypes.
Methods
1779 participants in the National Alzheimer Coordinating Center (NACC) with MCI were included in this study. All participants were evaluated systematically with a thorough cognitive battery, clinical interview, and consensus diagnoses, and subtyped as: 1) amnestic (aMCI) (single- or multiple-domain) vs. non-amnestic (non-aMCI); 2) executive dysfunction-MCI (exMCI) (single- or multiple-domain) vs. no executive dysfunction-MCI (non-exMCI); 3) both aMCI and exMCI; 4) and neither aMCI nor exMCI. Additionally , aMCI vs. nonaMCI and exMCI vs. non-exMCI dichotomies were explored. NPS were assessed with the Neuropsychiatric Inventory (NPI-Q) and Geriatric Depression Scale (GDS).
Results
1379 participants (77.5%) met criteria for aMCI and 616 (34.6%) for exMCI. No differences were observed in the prevalence of NPS between aMCI vs. non-aMCI. However, exMCI was associated with greater severity of depression, anxiety, agitation, disinhibition, irritability, and sleep problems, although these differences do not persist after adjustment for several variables. .
Conclusions
While there were few associations between aMCI and NPS, the presence of executive dysfunction in MCI was associated with greater severity of symptoms and specifically with depression (evidenced by GDS score) and anxiety. These findings may have implications for MCI prognosis and need to be explored in longitudinal studies.
doi:10.1002/gps.2535
PMCID: PMC3204866  PMID: 20845402
Mild Cognitive Impairment; Depression; Executive Dysfunction; Neuropsychiatric symptoms
5.  Electrophysiological Correlates of Amnestic Mild Cognitive Impairment in a Simon Task 
PLoS ONE  2013;8(12):e81506.
Amnestic mild cognitive impairment (aMCI) represents a prodromal stage of Alzheimer`s disease (AD), especially when additional cognitive domains are affected (Petersen et al., 2009). Thus, single-domain amnestic MCI (sdaMCI) and multiple-domain-amnestic MCI (mdaMCI) biomarkers are important for enabling early interventions to help slow down progression of the disease. Recording event-related potentials (ERPs) is a non-invasive and inexpensive measure of brain activity associated with cognitive processes, and it is of interest from a clinical point of view. The ERP technique may also be useful for obtaining early sdaMCI and mdaMCI biomarkers because ERPs are sensitive to impairment in processes that are not manifested at behavioral or clinical levels. In the present study, EEG activity was recorded in 25 healthy participants and 30 amnestic MCI patients (17 sdaMCI and 13 mdaMCI) while they performed a Simon task. The ERPs associated with visuospatial (N2 posterior-contralateral – N2pc -) and motor (lateralized readiness potential – LRP –) processes were examined. The N2pc amplitude was smaller in participants with mdaMCI than in healthy participants, which indicated a decline in the correlates of allocation of attentional resources to the target stimulus. In addition, N2pc amplitude proved to be a moderately good biomarker of mdaMCI subtype (0.77 sensitivity, 0.76 specificity). However, the LRP amplitude was smaller in the two MCI groups (sdaMCI and mdaMCI) than in healthy participants, revealing a reduction in the motor resources available to execute the response in sdaMCI and mdaMCI patients. Furthermore, the LRP amplitude proved to be a valid biomarker (0.80 sensitivity, 0.92 specificity) of both amnestic MCI subtypes.
doi:10.1371/journal.pone.0081506
PMCID: PMC3855269  PMID: 24339941
6.  Familiarity-based memory as an early cognitive marker of preclinical and prodromal AD 
Neuropsychologia  2013;51(6):1094-1102.
There is great interest in the development of cognitive markers that differentiate “normal” age-associated cognitive change from that of Alzheimer's disease (AD) in its prodromal (i.e., mild cognitive impairment; MCI) or even preclinical stages. Dual process models posit that recognition memory is supported by the dissociable processes of recollection and familiarity. Familiarity-based memory has generally been considered to be spared during normal aging, but it remains controversial whether this type of memory is impaired in early AD. Here, we describe findings of estimates of recollection and familiarity in young adults (YA), cognitively normal older adults (CN), and patients with amnestic-MCI (a-MCI). These measures in the CN and a-MCI patients were then related to a structural imaging biomarker of AD that has previously been demonstrated to be sensitive to preclinical and prodromal AD, the Cortical Signature of AD (ADsig). Consistent with much work in the literature, recollection, but not familiarity, was impaired in CN versus YA. Replicating our prior findings, a-MCI patients displayed impairment in both familiarity and recollection. Finally, the familiarity measure was correlated with the ADsig biomarker across the CN and a-MCI group, as well as within the CN adults alone. No other standard psychometric measure was as highly associated with the ADsig, suggesting that familiarity may be a sensitive biomarker of AD-specific brain changes in preclinical and prodromal AD and that it may offer a qualitatively distinct measure of early AD memory impairment relative to normal age-associated change.
doi:10.1016/j.neuropsychologia.2013.02.014
PMCID: PMC3742759  PMID: 23474075
Memory; Recollection; Familiarity; Alzheimer's disease; Medial temporal lobe; Preclinical Alzheimer's disease; Mild cognitive impairment
7.  Relationships between Personality Traits, Medial Temporal Lobe Atrophy, and White Matter Lesion in Subjects Suffering from Mild Cognitive Impairment 
Mild cognitive impairment (MCI) is a heterogeneous cognitive status that can be a prodromal stage of Alzheimer’s disease (AD). It is particularly relevant to focus on prodromal stages of AD such as MCI, because patho-physiological abnormalities of AD start years before the dementia stage. Medial temporal lobe (MTL) atrophy resulting from AD lesions and cerebrovascular lesions [i.e., white matter lesions (WML), lacunar strokes, and strokes] are often revealed concurrently on magnetic resonance imaging (MRI) in MCI subjects. Personality changes have been reported to be associated with MCI status and early AD. More specifically, an increase in neuroticism and a decrease in conscientiousness have been reported, suggesting that higher and lower scores, respectively, in neuroticism and conscientiousness are associated with an increased risk of developing the disease. However, personality changes have not been studied concomitantly with pathological structural brain alterations detected on MRI in patients suffering from MCI. Therefore, the objective of the present study was to assess the relationship between MTL atrophy, WML, lacunar strokes, and personality traits in such patients. The severity of WML was strongly associated with lower levels of conscientiousness and higher levels of neuroticism. Conversely, no association was detected between personality traits and the presence of lacunar strokes or MTL atrophy. Altogether, these results strongly suggest that personality changes occurring in a MCI population, at high risk of AD, are associated with WML, which can induce executive dysfunctions, rather than with MTL atrophy.
doi:10.3389/fnagi.2014.00195
PMCID: PMC4114211  PMID: 25120483
conscientiousness; neuroticism; Alzheimer; mild cognitive impairment; medial temporal lobe; WML; leukoaraiosis
8.  CCL2 Is Associated with a Faster Rate of Cognitive Decline during Early Stages of Alzheimer's Disease 
PLoS ONE  2012;7(1):e30525.
Chemokine (C-C motif) receptor 2 (CCR2)-signaling can mediate accumulation of microglia at sites affected by neuroinflammation. CCR2 and its main ligand CCL2 (MCP-1) might also be involved in the altered metabolism of beta-amyloid (Aβ) underlying Alzheimer's disease (AD). We therefore measured the levels of CCL2 and three other CCR2 ligands, i.e. CCL11 (eotaxin), CCL13 (MCP-4) and CCL26 (eotaxin-3), in the cerebrospinal fluid (CSF) and plasma of 30 controls and 119 patients with mild cognitive impairment (MCI) at baseline. During clinical follow-up 52 MCI patients were clinically stable for five years, 47 developed AD (i.e. cases with prodromal AD at baseline) and 20 developed other dementias. Only CSF CCL26 was statistically significantly elevated in patients with prodromal AD when compared to controls (p = 0.002). However, in patients with prodromal AD, the CCL2 levels in CSF at baseline correlated with a faster cognitive decline during follow-up (rs = 0.42, p = 0.004). Furthermore, prodromal AD patients in the highest tertile of CSF CCL2 exhibited a significantly faster cognitive decline (p<0.001) and developed AD dementia within a shorter time period (p<0.003) compared to those in the lowest tertile. Finally, in the entire MCI cohort, CSF CCL2 could be combined with CSF Tau, P-tau and Aβ42 to predict both future conversion to AD and the rate of cognitive decline. If these results are corroborated in future studies, CCL2 in CSF could be a candidate biomarker for prediction of future disease progression rate in prodromal AD. Moreover, CCR2-related signaling pathways might be new therapeutic targets for therapies aiming at slowing down the disease progression rate of AD.
doi:10.1371/journal.pone.0030525
PMCID: PMC3268759  PMID: 22303443
9.  Using Voxel-Based Morphometry to Examine the Relationship between Regional Brain Volumes and Memory Performance in Amnestic Mild Cognitive Impairment 
Alzheimer’s disease (AD) is a slowly progressive neurodegenerative disorder, in which morphological alterations of brain tissue develop many years before the first neuropsychological and clinical changes occur. Among the first and most prominent symptoms are deficiencies of declarative memory functions. This stage of precursory symptoms to AD has been described as amnestic mild cognitive impairment (aMCI) and is discussed as a potential AD prodrome. As therapy in the later stages of AD has been shown to be of limited impact, aMCI would be the key target for early intervention. For that purpose a comprehensive neuropsychological and anatomical characterization of this group is necessary. Previous neuropsychological investigations identified tests which are highly sensitive in diagnosing aMCI and very early AD. However, the sensitivity of those neuropsychological tests to the particular structural neuropathology in aMCI remains to be specified. To this end, we investigated 25 patients with single-domain aMCI. All participants underwent extensive neuropsychological testing and anatomical scanning with structural magnetic resonance imaging. Voxel-based morphometry (VBM) was performed to identify brain regions that show a significant correlation between regional brain volume and behavioral measures of memory and executive functioning. We found that performance in a variety of mnemonic tests was directly related to the integrity of the medial temporal lobe cortex (MTLC). Moreover, impairment of memory sub-functions in aMCI might be detected earlier than overt structural damage. By this, these findings contribute to the identification of cerebral structures associated with memory deficits in aMCI.
doi:10.3389/fnbeh.2013.00089
PMCID: PMC3719379  PMID: 23888131
voxel-based morphometry; amnestic mild cognitive impairment; neuropsychological tests; medial temporal lobe; episodic memory; semantic memory
10.  Identifying Informative Imaging Biomarkers via Tree Structured Sparse Learning for AD Diagnosis 
Neuroinformatics  2014;12(3):381-394.
Neuroimaging provides a powerful tool to characterize neurodegenerative progression and therapeutic efficacy in Alzheimer’s disease (AD) and its prodromal stage—mild cognitive impairment (MCI). However, since the disease pathology might cause different patterns of structural degeneration, which is not pre-known, it is still a challenging problem to identify the relevant imaging markers for facilitating disease interpretation and classification. Recently, sparse learning methods have been investigated in neuroimaging studies for selecting the relevant imaging biomarkers and have achieved very promising results on disease classification. However, in the standard sparse learning method, the spatial structure is often ignored, although it is important for identifying the informative biomarkers. In this paper, a sparse learning method with tree-structured regularization is proposed to capture patterns of pathological degeneration from fine to coarse scale, for helping identify the informative imaging biomarkers to guide the disease classification and interpretation. Specifically, we first develop a new tree construction method based on the hierarchical agglomerative clustering of voxel-wise imaging features in the whole brain, by taking into account their spatial adjacency, feature similarity and discriminability. In this way, the complexity of all possible multi-scale spatial configurations of imaging features can be reduced to a single tree of nested regions. Second, we impose the tree-structured regularization on the sparse learning to capture the imaging structures, and then use them for selecting the most relevant biomarkers. Finally, we train a support vector machine (SVM) classifier with the selected features to make the classification. We have evaluated our proposed method by using the baseline MR images of 830 subjects from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database, which includes 198 AD patients, 167 progressive MCI (pMCI), 236 stable MCI (sMCI), and 229 normal controls (NC). Our experimental results show that our method can achieve accuracies of 90.2 %, 87.2 %, and 70.7 % for classifications of AD vs. NC, pMCI vs. NC, and pMCI vs. sMCI, respectively, demonstrating promising performance compared with other state-of-the-art methods.
doi:10.1007/s12021-013-9218-x
PMCID: PMC4058415  PMID: 24338729
Alzheimer’s disease diagnosis; Tree-structured sparse learning; Biomarker identification; Mild cognitive impairment; Group sparse learning
11.  Multi-Atlas Based Representations for Alzheimer’s Disease Diagnosis 
Human brain mapping  2014;35(10):5052-5070.
Brain morphometry based classification from magnetic resonance (MR) acquisitions has been widely investigated in the diagnosis of Alzheimer’s disease (AD) and its prodromal stage, i.e., mild cognitive impairment (MCI). In the literature, a morphometric representation of brain structures is obtained by spatial normalization of each image into a common space (i.e., a pre-defined atlas) via non-linear registration, thus the corresponding regions in different brains can be compared. However, representations generated from one single atlas may not be sufficient to reveal the underlying anatomical differences between the groups of disease-affected patients and normal controls (NC). In this article, we propose a different methodology, namely the multi-atlas based morphometry, which measures morphometric representations of the same image in different spaces of multiple atlases. Representations generated from different atlases can thus provide the complementary information to discriminate different groups, and also reduce the negative impacts from registration errors. Specifically, each studied subject is registered to multiple atlases, where adaptive regional features are extracted. Then, all features from different atlases are jointly selected by a correlation and relevance based scheme, followed by final classification with the support vector machine (SVM). We have evaluated the proposed method on 459 subjects (97 AD, 117 progressive-MCI (p-MCI), 117 stable-MCI (s-MCI), and 128 NC) from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database, and achieved 91.64% for AD/NC classification and 72.41% for p-MCI/s-MCI classification. Our results clearly demonstrate that the proposed multi-atlas based method can significantly outperform the previous single-atlas based methods.
doi:10.1002/hbm.22531
PMCID: PMC4169318  PMID: 24753060
multi-atlas based morphometry; AD diagnosis; brain classification
12.  Multimodal Classification of Alzheimer’s Disease and Mild Cognitive Impairment 
NeuroImage  2011;55(3):856-867.
Effective and accurate diagnosis of Alzheimer’s disease (AD), as well as its prodromal stage (i.e., mild cognitive impairment (MCI)), has attracted more and more attentions recently. So far, multiple biomarkers have been shown sensitive to the diagnosis of AD and MCI, i.e., structural MR imaging (MRI) for brain atrophy measurement, functional imaging (e.g., FDG-PET) for hypometabolism quantification, and cerebrospinal fluid (CSF) for quantification of specific proteins. However, most existing research focuses on only a single modality of biomarkers for diagnosis of AD and MCI, although recent studies have shown that different biomarkers may provide complementary information for diagnosis of AD and MCI. In this paper, we propose to combine three modalities of biomarkers, i.e., MRI, FDG-PET, and CSF biomarkers, to discriminate between AD (or MCI) and healthy controls, using a kernel combination method. Specifically, ADNI baseline MRI, FDG-PET, and CSF data from 51 AD patients, 99 MCI patients (including 43 MCI converters who had converted to AD within 18 months and 56 MCI non-converters who had not converted to AD within 18 months), and 52 healthy controls are used for development and validation of our proposed multimodal classification method. In particular, for each MR or FDG-PET image, 93 volumetric features are extracted from the 93 regions of interest (ROIs), automatically labeled by an atlas warping algorithm. For CSF biomarkers, their original values are directly used as features. Then, a linear support vector machine (SVM) is adopted to evaluate the classification accuracy, using a 10-fold cross-validation. As a result, for classifying AD from healthy controls, we achieve a classification accuracy of 93.2% (with a sensitivity of 93% and a specificity of 93.3%) when combining all three modalities of biomarkers, and only 86.5% when using even the best individual modality of biomarkers. Similarly, for classifying MCI from healthy controls, we achieve a classification accuracy of 76.4% (with a sensitivity of 81.8% and a specificity of 66%) for our combined method, and only 72% even using the best individual modality of biomarkers. Further analysis on MCI sensitivity of our combined method indicates that 91.5% of MCI converters and 73.4% of MCI non-converters are correctly classified. Moreover, we also evaluate the classification performance when employing a feature selection method to select the most discriminative MR and FDG-PET features. Again, our combined method shows considerably better performance, compared to the case of using an individual modality of biomarkers.
doi:10.1016/j.neuroimage.2011.01.008
PMCID: PMC3057360  PMID: 21236349
Alzheimer’s disease (AD); MCI; Multimodal classification; AD biomarkers; MRI; PET; CSF
13.  Functional impairment in elderly patients with mild cognitive impairment and mild Alzheimer's disease 
Archives of general psychiatry  2011;68(6):617-626.
CONTEXT
The original mild cognitive impairment (MCI) criteria exclude substantial functional deficits, but recent reports suggest otherwise. Identifying the extent, severity, type, and correlates of functional deficits that occur in MCI and mild Alzheimer’s disease (AD) can aid in early detection of incipient dementia and identify potential mechanistic pathways to disrupted instrumental activities of daily living (IADLs).
OBJECTIVES
To examine the number, type, and severity of functional impairments and identify the clinical characteristics associated with functional impairment across individuals with amnestic MCI (aMCI) and those with mild AD.
DESIGN
The study uses baseline data from the Alzheimer’s Disease Neuroimaging Initiative.
SETTING
Data from the Alzheimer’s Disease Neuroimaging Initiative was collected at multiple research sites in the US and Canada.
PATIENTS
The samples included 229 controls, 394 aMCI, and 193 AD patients.
MAIN OUTCOME MEASURE
The 10-item Pfeffer Functional Activities Questionnaire (FAQ) assessed function.
RESULTS
Informant-reported FAQ deficits were common in patients with aMCI (72.3%) and AD (97.4%) but were rarely self-reported by controls (7.9%). The average severity per FAQ deficit did not differ between patients with aMCI and controls; both were less impaired than patients with AD (P < .001). Two FAQ items (remembering appointments, family occasions, holidays, and medications; assembling tax records, business affairs, or other papers) were specific (0.95) in differentiating controls from the combined aMCI and AD groups (only 34.0% of patients with aMCI and 3.6% of patients with AD had no difficulty with these 2 items). The severity of FAQ deficits in the combined aMCI and AD group was associated with worse Trailmaking Test A scores and smaller hippocampal volumes (P < .001). Within the aMCI group, functionally intact individuals had greater hippocampal volumes and better Auditory Verbal Learning Test 30-minute delay and Trailmaking Test A (P < .001) scores compared with those with moderate or severe FAQ deficits. Patients with a high number of deficits were more likely to express the APOE ε4 allele (63.8%) compared with patients with no (46.8%) or few (48.4%) functional deficits.
CONCLUSIONS
Mild IADL deficits are common in individuals with aMCI and should be considered in MCI criteria. Two IADLs, remembering appointments, family occasions, holidays, and medications and assembling tax records, business affairs, or other papers, appear to be characteristic of clinically significant cognitive impairment. In patients with aMCI, impairment in memory and processing speed and greater medial temporal atrophy were associated with greater IADL deficits
doi:10.1001/archgenpsychiatry.2011.57
PMCID: PMC3682408  PMID: 21646578
14.  Requiring an amyloid-β1-42 biomarker for prodromal Alzheimer’s disease or mild cognitive impairment does not lead to more efficient clinical trials 
Background
Low cerebrospinal fluid (CSF) amyloid-β1-42 concentration and high total-tau/Aβ1-42 ratio have been recommended to support the diagnosis of prodromal Alzheimer’s disease (AD) in patients with amnestic mild cognitive impairment (aMCI) and also to select patients for clinical trials.
Methods
We tested this recommendation with clinical trials simulations using patients from the Alzheimer Disease Neuroimaging Initiative who fulfilled the following entry criteria: (1) aMCI, (2) aMCI with CSF Aβ1-42 ≤192 mg/mL, (3) and aMCI with total-tau/Aβ1-42 >.0.39. For each criterion, we randomly resampled the database obtaining samples for 1000 trials for each trial scenario, planning for 1 or 2 year trials with samples from 50 to 400 patients per treatment or placebo group, with up to 40% dropouts, outcomes after using the AD assessment scale-cognitive subscale and clinical dementia rating scale with effect sizes ranging from 0.15 to 0.75, and calculated statistical power.
Findings
Approximately 70% to 74% of aMCI patients with CSF measures met biomarker criteria. The addition of the low Aβ1-42 or high tau/Aβ1-42 requirement resulted in minimal or no increase in the power of the trials compared with enrolling aMCI without requiring the biomarker criteria. Slightly larger mean differences between the placebo and treatment groups fulfilling biomarker criteria were offset by increased outcome variability within the groups.
Interpretations
Although patients with aMCI or patients with prodromal AD meeting CSF biomarkers criteria were slightly more cognitively impaired and showed greater decline than patients with aMCI diagnosed without considering the biomarkers, the requirement of biomarker-positive patients would most likely not result in more efficient clinical trials, and trials would take longer because fewer patients would be available. A CSF Aβ1-42 marker, however, could be useful as an explanatory variable or covariate when warranted by the action of a drug.
doi:10.1016/j.jalz.2010.07.004
PMCID: PMC2947209  PMID: 20813339
Alzheimer disease; Mild cognitive impairment; Biomarkers; Clinical trials; Simulations; Amyloid-beta protein; Alzheimer’s disease neuroimaging initiative (ADNI); Alzheimer’s disease assessment scale; Clinical dementia rating
15.  Microglial activation and amyloid deposition in mild cognitive impairment 
Neurology  2009;72(1):56-62.
Background:
Activated microglia may play a role in the pathogenesis of Alzheimer disease (AD) as they cluster around beta-amyloid (Aβ) plaques. They are, therefore, a potential therapeutic target in both AD and its prodrome amnestic mild cognitive impairment (MCI).
Objective:
To characterize in vivo with 11C-(R)-PK11195 and 11C-PIB PET the distribution of microglial activation and amyloid deposition in patients with amnestic MCI.
Methods:
Fourteen subjects with MCI had 11C-(R)-PK11195 and 11C-PIB PET with psychometric tests.
Results:
Seven out of 14 (50%) patients with MCI had increased cortical 11C-PIB retention (p < 0.001) while 5 out of 13 (38%) subjects with MCI showed increased 11C-(R)-PK11195 uptake. The MCI subgroup with increased 11C-PIB retention also showed increased cortical 11C-(R)-PK11195 binding (p < 0.036) though this increase only remained significant in frontal cortex after a correction for multiple comparisons. There was no correlation between regional levels of 11C-(R)-PK11195 and 11C-PIB binding in individual patients with MCI: only three of the five MCI cases with increased 11C-(R)-PK11195 binding had increased levels of 11C-PIB retention.
Conclusions:
Our findings indicate that, while amyloid deposition and microglial activation can be detected in vivo in around 50% of patients with mild cognitive impairment (MCI), these pathologies can occur independently. The detection of microglial activation in patients with MCI suggests that anti-inflammatory therapies may be relevant to the prevention of AD.
GLOSSARY
= beta-amyloid;
= Alzheimer disease;
= binding potential;
= mild cognitive impairment;
= Mini-Mental State Examination;
= peripheral benzodiazepine binding site;
= region of interest;
= standard deviation;
= simplified reference tissue model.
doi:10.1212/01.wnl.0000338622.27876.0d
PMCID: PMC2817573  PMID: 19122031
16.  Mild cognitive impairment in prediagnosed Huntington disease(e–Pub ahead of print) 
Neurology  2010;75(6):500-507.
Background:
Cognitive decline has been reported in Huntington disease (HD), as well as in the period before diagnosis of motor symptoms (i.e., pre-HD). However, the severity, frequency, and characterization of cognitive difficulties have not been well-described. Applying similar cutoffs to those used in mild cognitive impairment (MCI) research, the current study examined the rates of subtle cognitive dysfunction (e.g., dysfunction that does not meet criteria for dementia) in pre-HD.
Methods:
Using baseline data from 160 non–gene-expanded comparison participants, normative data were established for cognitive tests of episodic memory, processing speed, executive functioning, and visuospatial perception. Cutoff scores at 1.5 standard deviations below the mean of the comparison group were then applied to 575 gene-expanded pre-HD participants from the observational study, PREDICT-HD, who were stratified by motor signs and genetic risk for HD.
Results:
Nearly 40% of pre-HD individuals met criteria for MCI, and individuals closer to HD diagnosis had higher rates of MCI. Nonamnestic MCI was more common than amnestic MCI. Single-domain MCI was more common than multiple-domain MCI. Within the nonamnestic single-domain subtype, impairments in processing speed were most frequent.
Conclusions:
Consistent with the Alzheimer disease literature, MCI as a prodromal period is a valid concept in pre-HD, with nearly 40% of individuals showing this level of impairment before diagnosis. Future studies should examine the utility of MCI as a marker of cognitive decline in pre-HD.
GLOSSARY
= Alzheimer disease;
= Benton Facial Recognition Test;
= Diagnostic Confidence Level;
= Huntington disease;
= Hopkins Verbal Learning Test–Revised;
= mild cognitive impairment;
= Parkinson disease;
= Stroop Color Word Test;
= Symbol Digit Modalities Test;
= Unified Huntington's Disease Rating Scale.
doi:10.1212/WNL.0b013e3181eccfa2
PMCID: PMC2918475  PMID: 20610833
17.  Depressive Symptoms in Mild Cognitive Impairment Predict Greater Atrophy in Alzheimer’s Disease-Related Regions 
Biological Psychiatry  2012;71(9):814-821.
Background
Depression has been associated with higher conversion rates from mild cognitive impairment (MCI) to Alzheimer’s disease (AD) and may be a potential clinical marker of prodromal AD that can be used to identify individuals with MCI who are most likely to progress to AD. Using tensor-based morphometry (TBM), we examined the longitudinal neuroanatomical changes associated with depressive symptoms in MCI.
Methods
243 MCI subjects from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) who had brain MRI scans at baseline and 2-year follow-up were classified into depressed (DEP, n=44), non-depressed with other neuropsychiatric symptoms (OTHER, n=93), and no-symptom (NOSYMP, n=106) groups based on the Neuropsychiatric Inventory Questionnaire (NPI-Q). TBM was used to create individual 3D-maps of 2-year brain changes that were compared between groups.
Results
DEP subjects had more frontal (p=0.024), parietal (p=0.030), and temporal (p=0.038) white matter atrophy than NOSYMP subjects. A subset of DEP subjects whose depressive symptoms persisted over 2-years also had higher conversion to AD and more decline on measures of global cognition, language abilities, and executive functioning compared to stable NOSYMP subjects. OTHER and NOSYMP groups exhibited no differences in rates of atrophy.
Conclusions
Depressive symptoms in MCI subjects were associated with greater atrophy in AD-affected regions, increased cognitive decline, and higher rates of conversion to AD. Depression in individuals with MCI may be associated with underlying neuropathological changes including prodromal AD. Thus, assessment of depressive symptoms may be a potentially useful clinical marker in identifying MCI patients who are most likely to progress to AD.
doi:10.1016/j.biopsych.2011.12.024
PMCID: PMC3322258  PMID: 22322105
Depression; Mild Cognitive Impairment; Alzheimer’s Disease; Neuropsychiatric Symptoms; Tensor-Based Morphometry; White Matter
18.  Visual contrast sensitivity in AD, MCI, & older adults with cognitive complaints 
Neurobiology of aging  2012;34(4):1133-1144.
Deficits in contrast sensitivity (CS) have been reported in Alzheimer’s disease (AD). However, the extent of these deficits in prodromal AD stages, including mild cognitive impairment (MCI) or even earlier, has not been investigated. In this study, CS was assessed using frequency doubling technology (FDT) in older adults with AD (n=10), amnestic MCI (n=28), cognitive complaints without performance deficits (CC, n=20), and healthy controls (HC, n=29). The association between CS and cognition was also evaluated. Finally, the accuracy of CS measures for classifying MCI versus HC was evaluated.
CS deficits were found in AD and MCI, while CC showed intermediate performance between MCI and HC. Upper right visual field CS showed the most significant difference among groups. CS was also associated with cognitive performance. Finally, CS measures accurately classified MCI versus HC. The CS deficits in AD and MCI, and intermediate performance in CC, indicate that these measures are sensitive to early AD-associated changes. Therefore, FDT-based measures of CS may have promise as a novel AD biomarker.
doi:10.1016/j.neurobiolaging.2012.08.007
PMCID: PMC3545045  PMID: 23084085
contrast sensitivity (CS); frequency doubling technology (FDT); Alzheimer’s disease (AD); mild cognitive impairment (MCI); cognitive complaints; biomarker; vision
19.  Different Patterns of White Matter Disruption among Amnestic Mild Cognitive Impairment Subtypes: Relationship with Neuropsychological Performance 
Amnestic mild cognitive impairment (aMCI) is recognized as the prodromal phase of Alzheimer’s disease (AD). Evidence showed that patients with multiple-domain (MD) aMCI were at higher risk of converting to dementia and exhibited more severe gray matter atrophy than single-domain (SD) aMCI. The investigation of the microstructural abnormalities of white matter (WM) among different subtypes of aMCI and their relations with cognitive performances can help to understand the variations among aMCI subtypes and to construct potential imaging based biomarkers to monitor the progression of aMCI. Diffusion-weighted MRI data were acquired from 40 patients with aMCI (aMCI-SD: n = 19; aMCI-MD: n= 21) and 37 healthy controls (HC). Voxel-wise and atlas-based analyses of whole-brain WM were performed among three groups. The correlations between the altered diffusion metrics of the WM tracts and the neuropsychological scores in each subtype of aMCI were assessed. The aMCI-MD patients showed disrupted integrity in multiple WM tracts across the whole-brain when compared with HCs or with aMCI-SD. In contrast, only few WM regions with diffusion changes were found in aMCI-SD as compared to HCs and with less significance. For neuropsychological correlations, only aMCI-MD patients exhibited significant associations between disrupted WM connectivity (in the body of the corpus callosum and the right anterior internal capsules) and cognitive impairments (MMSE and Digit Symb-Coding scores), whereas no such correlations were found in aMCI-SD. These findings indicate that the degeneration extensively exists in WM tracts in aMCI-MD that precedes the development of AD, whereas underlying WM pathology in aMCI-SD is imperceptible. The results are consistent with the view that aMCI is not a uniform disease entity and presents heterogeneity in the clinical progression.
doi:10.3233/JAD-122023
PMCID: PMC4085483  PMID: 23603396
Amnestic mild cognitive impairment; diffusion tensor imaging; multiple-domain; single-domain; TBSS; white matter
20.  Recognition memory in amnestic-mild cognitive impairment: insights from event-related potentials 
Episodic memory loss is the hallmark cognitive dysfunction associated with Alzheimer’s disease (AD). Amnestic mild cognitive impairment (a-MCI) frequently represents a transitional stage between normal aging and early AD. A better understanding of the qualitative features of memory loss in a-MCI may have important implications for predicting those most likely to harbor AD-related pathology and for disease monitoring. Dual process models of memory argue that recognition memory is subserved by the dissociable processes of recollection and familiarity. Work studying recognition memory in a-MCI from this perspective has been controversial, particularly with regard to the integrity of familiarity. Event-related potentials (ERPs) offer an alternative means for assessing these functions without the associated assumptions of behavioral estimation methods. ERPs were recorded while a-MCI patients and cognitively normal (CN) age-matched adults performed a recognition memory task. When retrieval success was measured (hits versus correct rejections) in which performance was matched by group, a-MCI patients displayed similar neural correlates to that of the CN group, including modulation of the FN400 and the late positive complex (LPC) which are thought to index familiarity and recollection, respectively. Alternatively, when the integrity of these components was measured based on retrieval attempts (studied versus unstudied items), a-MCI patients displayed a reduced FN400 and LPC. Furthermore, modulation of the FN400 correlated with a behavioral estimate of familiarity and the LPC with a behavioral estimate of recollection obtained in a separate experiment in the same individuals, consistent with the proposed mappings of these indices. These results support a global decline of recognition memory in a-MCI, which suggests that the memory loss of prodromal AD may be qualitatively distinct from normal aging.
doi:10.3389/fnagi.2013.00089
PMCID: PMC3858817  PMID: 24376418
memory; recollection; familiarity; event-related potentials; FN400; LPC; mild cognitive impairment; Alzheimer’s disease
21.  Everyday episodic memory in amnestic mild cognitive impairment: a preliminary investigation 
BMC Neuroscience  2011;12:80.
Background
Decline in episodic memory is one of the hallmark features of Alzheimer's disease (AD) and is also a defining feature of amnestic Mild Cognitive Impairment (MCI), which is posited as a potential prodrome of AD. While deficits in episodic memory are well documented in MCI, the nature of this impairment remains relatively under-researched, particularly for those domains with direct relevance and meaning for the patient's daily life. In order to fully explore the impact of disruption to the episodic memory system on everyday memory in MCI, we examined participants' episodic memory capacity using a battery of experimental tasks with real-world relevance. We investigated episodic acquisition and delayed recall (story-memory), associative memory (face-name pairings), spatial memory (route learning and recall), and memory for everyday mundane events in 16 amnestic MCI and 18 control participants. Furthermore, we followed MCI participants longitudinally to gain preliminary evidence regarding the possible predictive efficacy of these real-world episodic memory tasks for subsequent conversion to AD.
Results
The most discriminating tests at baseline were measures of acquisition, delayed recall, and associative memory, followed by everyday memory, and spatial memory tasks, with MCI patients scoring significantly lower than controls. At follow-up (mean time elapsed: 22.4 months), 6 MCI cases had progressed to clinically probable AD. Exploratory logistic regression analyses revealed that delayed associative memory performance at baseline was a potential predictor of subsequent conversion to AD.
Conclusions
As a preliminary study, our findings suggest that simple associative memory paradigms with real-world relevance represent an important line of enquiry in future longitudinal studies charting MCI progression over time.
doi:10.1186/1471-2202-12-80
PMCID: PMC3160963  PMID: 21816065
22.  Preservation of cortical sortilin protein levels in MCI and Alzheimer’s disease 
Neuroscience letters  2010;471(3):129-133.
The nerve growth factor (NGF) precursor protein proNGF is the predominant NGF moiety found in the human neocortex and exhibits pro-apoptotic properties when bound to the p75NTR neurotrophin receptor in the presence of sortilin, a Vps10p domain trafficking protein. Recently studies have shown that proNGF levels increase in the cortex of people who died with early stage Alzheimer’s disease (AD) or with mild cognitive impairment (MCI), a putative prodromal AD stage. In contrast, cortical levels of the high-affinity, pro-survival NGF receptor TrkA are reduced in AD despite stable levels of p75NTR. These data suggest a stoichiometric shift in proNGF and its receptors which favors proNGF binding of p75NTR. Whether cortical levels of sortilin are altered during the progression of AD remains unknown. Therefore, we measured sortilin protein levels in postmortem superior frontal and superior temporal cortical tissue derived from Religious Orders Study subjects clinically diagnosed antemortem with no cognitive impairment (NCI), MCI or AD. No changes in frontal or temporal cortical sortilin protein levels occurred across the clinical groups. There was no association between sortilin levels and antemortem cognitive test scores. However, there was a positive association between temporal cortex sortilin levels and severity of neuropathology by Braak and NIA-Reagan diagnoses. The stability of cortical sortilin levels in the face of stable p75NTR, increased proNGF, and reduced TrkA levels may favor pro-apoptotic proNGF:p75NTR:sortilin trimeric interactions within the cortex during the earliest stages of AD. These findings are relevant to the development of NGF drug therapy for the treatment of dementia.
doi:10.1016/j.neulet.2010.01.023
PMCID: PMC2829104  PMID: 20085800
Alzheimer’s disease; mild cognitive impairment; proNGF; receptors; sortilin
23.  Pharmacological Treatment of Mild Cognitive Impairment as a Prodromal Syndrome of Alzheimer´s Disease 
Current Neuropharmacology  2013;11(1):102-108.
Mild cognitive impairment (MCI) is a syndrome which, depending on various neurobiological, psychological and social factors, carries a high risk of developing into dementia. As far as diagnostic uncertainty and the heterogeneous underlying pathophysiological mechanisms are concerned, only limited therapeutic options are currently available. Clinical trials involving a wide range of substances have failed to show efficacy on primary and secondary outcome parameters. Most results reflect not only a lack of effectiveness of drug therapy but also methodological constraints in true prodromal Alzheimer´s disease (AD) based on clinical criteria. Biomarkers may help to identify MCI as a prodromal phase of dementia, so it is important to use them to improve specificity of case selection in future studies. For MCI as a prodromal syndrome of AD, clinical trials with disease modifying drugs that target underlying pathological mechanisms such as amyloid-beta accumulation and neurofibrillary tangle formation may help develop effective treatment options in the future. Alternative pharmacological approaches are currently being evaluated in ongoing phase 1 and phase 2 studies. Nevertheless, a lack of approved pharmacotherapeutic options has led to specific interventions that focus on patient education and life-style related factors receiving increasing attention.
doi:10.2174/157015913804999487
PMCID: PMC3580783  PMID: 23814542
Mild cognitive impairment; Alzheimer’s Dementia; Clinical Trials; Treatment.
24.  Hippocampal Volumes, Proton Magnetic Resonance Spectroscopy Metabolites, and Cerebrovascular Disease in Mild Cognitive Impairment Subtypes 
Archives of neurology  2008;65(12):1621-1628.
Background
Although a majority of patients with amnestic mild cognitive impairment (aMCI) progress to Alzheimer disease, the natural history of nonamnestic MCI (naMCI) is less clear. Noninvasive imaging surrogates for underlying pathological findings in MCI would be clinically useful for identifying patients who may benefit from disease-specific treatments at the prodromal stage of dementia.
Objective
To determine the characteristic magnetic resonance imaging (MRI) and proton MR spectroscopy (1H MRS) profiles of MCI subtypes.
Design
Case-control study.
Setting
Community-based sample at a tertiary referral center.
Patients
Ninety-one patients with single-domain aMCI, 32 patients with multiple-domain aMCI, 20 patients with single- or multiple-domain naMCI, and 100 cognitively normal elderly subjects frequency-matched by age and sex.
Main Outcome Measures
Posterior cingulate gyrus 1H MRS metabolite ratios, hippocampal volumes, and cerebrovascular disease on MRI.
Results
Patients with single-domain aMCI were characterized by small hippocampal volumes and elevated ratios of myo-inositol to creatine levels. Patients with naMCI on average had normal hippocampal volumes and 1H MRS metabolite ratios, but a greater proportion (3 of 20 patients [15%]) had cortical infarctions compared with patients with single-domain aMCI (6 of 91 [7%]). For characterization of MCI subtypes, 1H MRS and structural MRI findings were complementary.
Conclusions
The MRI and 1H MRS findings in singledomain aMCI are consistent with a pattern similar to that of Alzheimer disease. Absence of this pattern on average in patients with naMCI suggests that cerebrovascular disease and other neurodegenerative diseases may be contributing to the cognitive impairment in many individuals with naMCI.
doi:10.1001/archneur.65.12.1621
PMCID: PMC2743393  PMID: 19064749
25.  White matter hyperintensities and amyloid are independently associated with entorhinal cortex volume among individuals with mild cognitive impairment 
Background
Current hypothetical models of Alzheimer’s disease (AD) pathogenesis emphasize the role of beta amyloid, tau deposition, and neurodegenerative changes in the mesial temporal lobe, particularly entorhinal cortex and hippocampus. However, many individuals with clinical AD who come to autopsy also exhibit cerebrovascular disease. The relationship between AD and vascular pathology is unclear, especially whether they represent additive and independent effects on neuronal injury. We used data from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) to 1) confirm whether entorhinal cortex and hippocampal volume is associated with memory among individuals with amnestic mild cognitive impairment (MCI) who are at risk for AD; and 2) determine whether regional white matter hyperintensity (WMH) volume, a radiological marker of small vessel cerebrovascular disease, is associated with entorhinal cortex and hippocampal volume independent of putative AD biomarkers in this group.
Methods
Cognitive test scores, entorhinal cortex volume, hippocampus volume, intracranial volume, and cerebrospinal fluid-derived phosphorylated tau and Aβ1–42 protein levels were measured in 199 subjects with amnestic MCI (mean age=74.89+/−7.47). Lobar WMH volumes were derived from T1-, proton-density-, and T2-weighted MRI scans. We examined the association between entorhinal cortex volume and cognition. Next, we examined the association of tau and Aβ1–42 with entorhinal cortex volume and between lobar WMH and entorhinal cortex volume. Finally, tau, Aβ1–42, and regional WMH volumes were entered simultaneously to predict entorhinal cortex volume. We repeated the analyses with hippocampal volume instead of entorhinal cortex volume. The analyses were also repeated with the sample restricted to those MCI patients who transitioned to AD on subsequent ADNI follow-up visits (n=86).
Results
Larger entorhinal cortex volume was associated with better memory but not with performance on a task of executive functioning. Lower levels of Aβ1–42 and higher temporal WMH volumes were associated with smaller entorhinal cortex volume. When entered simultaneously, temporal lobe WMH volume was more reliably associated with entorhinal cortex volume than was Aβ1–42. The findings were similar for hippocampus volume and when the sample was restricted to MCI patients who subsequently transitioned to AD.
Discussion
The findings confirm the role of entorhinal cortex and hippocampus volume in influencing memory decline in amnestic MCI, and emphasize that even in this nominally AD prodromal condition, WMH may be influencing regional neurodegeneration.
doi:10.1016/j.jalz.2012.11.009
PMCID: PMC3663926  PMID: 23375566
Mild Cognitive Impairment; Alzheimer’s disease; white matter hyperintensities; beta amyloid; tau

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