Different aspects of failing to recover from proactive semantic interference predicts rate of progression from amnestic mild cognitive impairment to dementia

Introduction

This study investigated the role of proactive semantic interference (frPSI) in predicting the progression of amnestic Mild Cognitive Impairment (aMCI) to dementia, taking into account various cognitive and biological factors.

Methods

The research involved 89 older adults with aMCI who underwent baseline assessments, including amyloid PET and MRI scans, and were followed longitudinally over a period ranging from 12 to 55 months (average 26.05 months).

Results

The findings revealed that more than 30% of the participants diagnosed with aMCI progressed to dementia during the observation period. Using Cox Proportional Hazards modeling and adjusting for demographic factors, global cognitive function, hippocampal volume, and amyloid positivity, two distinct aspects of frPSI were identified as significant predictors of a faster decline to dementia. These aspects were fewer correct responses on a frPSI trial and a higher number of semantic intrusion errors on the same trial, with 29.5% and 31.6 % increases in the likelihood of more rapid progression to dementia, respectively.

Discussion

These findings after adjustment for demographic and biological markers of Alzheimer's Disease, suggest that assessing frPSI may offer valuable insights into the risk of dementia progression in individuals with aMCI.

Semantic intrusion errors are associated with plasma Ptau-181 among persons with amnestic mild cognitive impairment who are amyloid positive

Introduction

Semantic intrusion errors (SI) have distinguished between those with amnestic Mild Cognitive Impairment (aMCI) who are amyloid positive (A+) versus negative (A-) on positron emission tomography (PET).

Method

This study examines the association between SI and plasma - based biomarkers. One hundred and twenty-eight participants received SiMoA derived measures of plasma pTau-181, ratio of two amyloid-β peptide fragments (Aβ42/Aβ40), Neurofilament Light protein (NfL), Glial Fibrillary Acidic Protein (GFAP), ApoE genotyping, and amyloid PET imaging.

Results

The aMCI A+ (n = 42) group had a higher percentage of ApoE ɛ4 carriers, and greater levels of pTau-181 and SI, than Cognitively Unimpaired (CU) A- participants (n = 25). CU controls did not differ from aMCI A- (n = 61) on plasma biomarkers or ApoE genotype. Logistic regression indicated that ApoE ɛ4 positivity, pTau-181, and SI were independent differentiating predictors (Correct classification = 82.0%; Sensitivity = 71.4%; Specificity = 90.2%) in identifying A+ from A- aMCI cases.

Discussion

A combination of plasma biomarkers, ApoE positivity and SI had high specificity in identifying A+ from A- aMCI cases.

Multi-ancestry genome-wide meta-analysis of 56,241 individuals identifies LRRC4C, LHX5-AS1 and nominates ancestry-specific loci PTPRK , GRB14 , and KIAA0825 as novel risk loci for Alzheimer's disease: the Alzheimer's Disease Genetics Consortium

Limited ancestral diversity has impaired our ability to detect risk variants more prevalent in non-European ancestry groups in genome-wide association studies (GWAS). We constructed and analyzed a multi-ancestry GWAS dataset in the Alzheimer's Disease (AD) Genetics Consortium (ADGC) to test for novel shared and ancestry-specific AD susceptibility loci and evaluate underlying genetic architecture in 37,382 non-Hispanic White (NHW), 6,728 African American, 8,899 Hispanic (HIS), and 3,232 East Asian individuals, performing within-ancestry fixed-effects meta-analysis followed by a cross-ancestry random-effects meta-analysis. We identified 13 loci with cross-ancestry associations including known loci at/near CR1 , BIN1 , TREM2 , CD2AP , PTK2B , CLU , SHARPIN , MS4A6A , PICALM , ABCA7 , APOE and two novel loci not previously reported at 11p12 ( LRRC4C ) and 12q24.13 ( LHX5-AS1 ). Reflecting the power of diverse ancestry in GWAS, we observed the SHARPIN locus using 7.1% the sample size of the original discovering single-ancestry GWAS (n=788,989). We additionally identified three GWS ancestry-specific loci at/near ( PTPRK ( P =2.4×10 -8 ) and GRB14 ( P =1.7×10 -8 ) in HIS), and KIAA0825 ( P =2.9×10 -8 in NHW). Pathway analysis implicated multiple amyloid regulation pathways (strongest with P adjusted =1.6×10 -4 ) and the classical complement pathway ( P adjusted =1.3×10 -3 ). Genes at/near our novel loci have known roles in neuronal development ( LRRC4C, LHX5-AS1 , and PTPRK ) and insulin receptor activity regulation ( GRB14 ). These findings provide compelling support for using traditionally-underrepresented populations for gene discovery, even with smaller sample sizes.

A-214 A Novel Computerized Cognitive Test for the Detection of MCI and its Association with Neurodegeneration in Alzheimer’s Disease Prone Brain Regions

Objective: First, to determine whether a digitized cognitive stress test, the Loewenstein-Acevedo Scales for Sematic Interference and Learning, Brief Computerized Version (LASSI-BC) could differentiate between Cognitively Unimpaired (CU) and amnestic Mild Cognitive Impairment (aMCI) groups. Second, to correlate LASSI-BC performance to volumetric reductions in Alzheimer’s disease (AD)-prone regions.

Methods: 111 elders underwent a clinical and neuropsychological evaluation, along with the LASSI-BC. All participants were independent community-dwellers, had knowledgeable informants, and did not meet DSM-V criteria for any active neuropsychiatric disorder, Mood Disorder or Psychotic Disorder. Eighty-seven participants (51 CU; 36 aMCI) underwent MRI imaging. The volumes of 12 AD-prone regions were related to LASSI-BC and other memory indices correcting for False Discovery Rate (FDR).

Results: After adjusting for initial learning ability, the failure to recover from proactive semantic interference (frPSI) of LASSI-BC successfully differentiated between groups. Measures of frPSI were associated with volumetric reductions in AD-prone regions (hippocampus, amygdala, inferior temporal-lobes, precuneus and posterior cingulate) in aMCI cohort. A combination of maximum learning capacity and frPSI on the LASSI-BC yielded an area under ROC curve of 0.876 with greater sensitivity and specificity when compared to other traditional tests (e.g., HVLT).

Conclusions: Performance on the LASSI-BC successfully discriminated between diagnostic groups and is significantly associated with volumetric loss among aMCI individuals. This is significant as diagnostic cognitive tests of preclinical and prodromal AD should also be required to exhibit sensitivity to biomarkers of AD (e.g., amyloid, tau, and neurodegeneration in AD-prone regions), which may address some of the most critical challenges facing clinical trials.

Persistent Failure to Recover from Proactive Semantic Interference on the Cognitive Stress Test Differentiates Between Amnestic Mild Cognitive Impairment, Pre-Mild Cognitive Impairment, and Cognitively Unimpaired Older Adults

BACKGROUND

Susceptibility to proactive semantic interference (PSI) and the inability to ameliorate these difficulties with one additional learning trial have repeatedly been implicated as early features of incipient Alzheimer's disease (AD). Unfortunately, persistent failure to recover from PSI (frPSI) after repeated learning trials, are not captured by existing memory measures, or been examined in pre-mild cognitive impairment (PreMCI).

OBJECTIVE

A novel Cognitive Stress Test (CST) was employed to measure the impact of PSI, initial failure to recover from PSI and persistent effects of PSI, despite multiple learning trials of the new to-be-remembered material (pfrPSI). We hypothesized that PSI deficits on the CST would persist in both PreMCI and amnestic MCI (aMCI) groups over repeated learning trials when compared to cognitively unimpaired (CU) older adults.

METHODS

One hundred fifty older adults (69 CU, 31 PreMCI, and 50 aMCI) underwent a standardized clinical and neuropsychological evaluation. The CST was independent of diagnostic classification.

RESULTS

Even after adjusting for strength of initial learning, aMCI and PreMCI groups demonstrated greater persistent PSI (pfrPSI) relative to the CU group despite repeated learning trials of List B. Further, the aMCI group made a higher number of semantic intrusion errors relative to the PreMCI and CU groups on all List B Cued Recall trials.

CONCLUSION

Persistent PSI appears to be a common feature of aMCI and PreMCI. The possible theoretical mechanisms and empirical implications of these new findings are discussed.

Amnestic Mild Cognitive Impairment is Characterized by the Inability to Recover from Proactive Semantic Interference across Multiple Learning Trials

BACKGROUND

Difficulties in inhibition and self-monitoring are early features of incipient Alzheimer's disease and may manifest as susceptibility to proactive semantic interference. However, due to limitations of traditional memory assessment paradigms, recovery from interference effects following repeated learning opportunities has not been explored.

OBJECTIVE

This study employed a novel computerized list learning test consisting of repeated learning trials to assess recovery from proactive and retroactive semantic interference.

DESIGN

The design was cross-sectional.

SETTING

Participants were recruited from the community as part of a longitudinal study on normal and abnormal aging.

PARTICIPANTS

The sample consisted of 46 cognitively normal individuals and 30 participants with amnestic mild cognitive impairment.

MEASUREMENTS

Participants were administered the Cognitive Stress Test and traditional neuropsychological measures. Step-wise logistic regression was applied to determine which Cognitive Stress Test measures best discriminated between diagnostic groups. This was followed by receiver operating characteristic analyses.

RESULTS

Cued A3 recall, Cued B3 recall and Cued B2 intrusions were all independent predictors of diagnostic status. The overall predictive utility of the model yielded 75.9% sensitivity, 91.1% specificity, and an overall correct classification rate of 85.1%. When these variables were jointly entered into receiver operating characteristic analyses, the area under the curve was .923 (p<.001).

CONCLUSIONS

This novel paradigm's use of repeated learning trials offers a unique opportunity to assess recovery from proactive and retroactive semantic interference. Participants with mild cognitive impairment exhibited a continued failure to recover from proactive interference that could not be explained by mere learning deficits.

Intrusion Errors and Progression of Cognitive Deficits in Older Adults with Mild Cognitive Impairment and PreMCI States

INTRODUCTION

Among persons with amnestic mild cognitive impairment (aMCI), intrusion errors on subscales that measure proactive semantic interference (PSI) may be among the earliest behavioral markers of elevated Alzheimer's disease brain pathology. While there has been considerable cross-sectional work in the area, it is presently unknown whether semantic intrusion errors are predictive of progression of cognitive impairment in aMCI or PreMCI (not cognitively normal but not meeting full criteria for MCI).

METHODS

This study examined the extent to which the percentage of semantic intrusion errors (PIE) based on total responses on a novel cognitive stress test, the Loewenstein-Acevedo Scales for Semantic Interference and Learning (LASSI-L), could predict clinical/cognitive outcomes over an average 26-month period in older adults initially diagnosed with aMCI, PreMCI, and normal cognition.

RESULTS

On the LASSI-L subscale sensitive to PSI, a PIE cut point of 44% intrusion errors distinguished between those at-risk individuals with PreMCI who progressed to MCI over time compared to individuals with PreMCI who reverted to normal on longitudinal follow-up. Importantly, PIE was able to accurately predict 83.3% of aMCI individuals who later progressed to dementia.

DISCUSSION

These preliminary findings indicate that PIE on LASSI-L subscales that measure PSI may be a useful predictor of clinical progression overtime in at-risk older adults.

A Novel Computerized Cognitive Stress Test to Detect Mild Cognitive Impairment

BACKGROUND

The Loewenstein Acevedo Scales of Semantic Interference and Learning (LASSI-L) is a novel and increasingly employed instrument that has outperformed widely used cognitive measures as an early correlate of elevated brain amyloid and neurodegeneration in prodromal Alzheimer's Disease (AD). The LASSI-L has distinguished those with amnestic mild cognitive impairment (aMCI) and high amyloid load from aMCI attributable to other non-AD conditions. The authors designed and implemented a web-based brief computerized version of the instrument, the LASSI-BC, to improve standardized administration, facilitate scoring accuracy, real-time data entry, and increase the accessibility of the measure.

OBJECTIVE

The psychometric properties and clinical utility of the brief computerized version of the LASSI-L was evaluated, together with its ability to differentiate older adults who are cognitively normal (CN) from those with amnestic Mild Cognitive Impairment (aMCI).

METHODS

After undergoing a comprehensive uniform clinical and neuropsychological evaluation using traditional measures, older adults were classified as cognitively normal or diagnosed with aMCI. All participants were administered the LASSI-BC, a computerized version of the LASSI-L. Test-retest and discriminant validity was assessed for each LASSI-BC subscale.

RESULTS

LASSI-BC subscales demonstrated high test-retest reliability, and discriminant validity was attained.

CONCLUSIONS

The LASSI-BC, a brief computerized version of the LASSI-L is a valid and useful cognitive tool for the detection of aMCI among older adults.

Semantic Intrusion Error Ratio Distinguishes Between Cognitively Impaired and Cognitively Intact African American Older Adults

BACKGROUND

Semantic intrusion errors on memory tests may represent very early cognitive changes associated with elevated Alzheimer's disease pathology within the brain, including amyloid-β (Aβ). Subscales that measure proactive semantic interference (PSI) and intrusions related to PSI on the Loewenstein Acevedo Scales of Semantic Interference and Learning (LASSI-L) have been associated with high levels of brain amyloid load, structural changes on brain MRI in Hispanic and non-Hispanic groups. It is presently unknown whether intrusion errors or other measures of the LASSI-L can differentiate between African-American (AA) older adults diagnosed with amnestic mild cognitive impairment (aMCI) or classified as cognitively normal (CN).

OBJECTIVE

This study examined the extent to which a high percentage of semantic intrusion errors on LASSI-L subscales susceptible to PSI and other LASSI-L measures could differentiate between AA aMCI and CN groups.

METHODS

Forty-eight AA older adults were recruited (27 CN and 21 aMCI) and received a through clinical and neuropsychological evaluation. The LASSI-L was administered independent of diagnostic classification.

RESULTS

With and without statistical adjustment for literacy, AA aMCI participants scored lower on all LASSI-L measures. ROC analyses revealed an area under the curve exceeding 90% and correctly classified 86% of AA aMCI with 82% specificity for AA CN participants.

CONCLUSIONS

Percentage of intrusion errors on the LASSI-L subscales susceptible to PSI differentiated AA aMCI from AA CN. This adds to emerging evidence indicating that the LASSI-L may be culturally appropriate and can differentiate between aMCI and CN in diverse ethnic/cultural groups.

A novel method of evaluating semantic intrusion errors to distinguish between amyloid positive and negative groups on the Alzheimer's disease continuum

BACKGROUND

The development and validation of clinical outcome measures to detect early cognitive decline associated with Alzheimer's disease (AD) biomarkers is imperative. Semantic intrusions on the Loewenstein Acevedo Scales of Semantic Interference and Learning (LASSI-L) has outperformed widely used cognitive measures as an early correlate of elevated brain amyloid in prodromal AD and has distinguished those with amnestic mild cognitive impairment (aMCI) and high amyloid load from aMCI attributable to other non-AD conditions.

METHODS

Since intrusion errors on memory tasks vary widely, we employed a novel method that accounts for the percentage of intrusion errors (PIE) in relation to total responses. Individuals with either high or low amyloid load across the spectrum of aMCI and dementia and amyloid negative cognitively normal older adults (CN) were studied.

RESULTS

Mean PIE on indices sensitive to proactive semantic interference (PSI) and failure to recover from proactive semantic interference (frPSI) could distinguish amyloid positive from amyloid negative aMCI and dementia groups. Number of correct responses alone, while able to differentiate the different diagnostic groups, did not differentiate amyloid positive aMCI from their counterparts without amyloid pathology.

CONCLUSIONS

PIE, a novel and sensitive index of early memory dysfunction, demonstrated high levels of sensitivity and specificity in differentiating CN from amyloid positive persons with preclinical AD. Mean levels of PIE are higher for amyloid positive aMCI and dementia participants relative to their amyloid negative counterparts.

Genetic meta-analysis of diagnosed Alzheimer's disease identifies new risk loci and implicates Aβ, tau, immunity and lipid processing

Risk for late-onset Alzheimer's disease (LOAD), the most prevalent dementia, is partially driven by genetics. To identify LOAD risk loci, we performed a large genome-wide association meta-analysis of clinically diagnosed LOAD (94,437 individuals). We confirm 20 previous LOAD risk loci and identify five new genome-wide loci (IQCK, ACE, ADAM10, ADAMTS1, and WWOX), two of which (ADAM10, ACE) were identified in a recent genome-wide association (GWAS)-by-familial-proxy of Alzheimer's or dementia. Fine-mapping of the human leukocyte antigen (HLA) region confirms the neurological and immune-mediated disease haplotype HLA-DR15 as a risk factor for LOAD. Pathway analysis implicates immunity, lipid metabolism, tau binding proteins, and amyloid precursor protein (APP) metabolism, showing that genetic variants affecting APP and Aβ processing are associated not only with early-onset autosomal dominant Alzheimer's disease but also with LOAD. Analyses of risk genes and pathways show enrichment for rare variants (P = 1.32 × 10-7), indicating that additional rare variants remain to be identified. We also identify important genetic correlations between LOAD and traits such as family history of dementia and education.

A novel cognitive assessment paradigm to detect Pre-mild cognitive impairment (PreMCI) and the relationship to biological markers of Alzheimer's disease

OBJECTIVE

A number of older adults obtain normal scores on formal cognitive tests, but present clinical concerns that raise suspicion of cognitive decline. Despite not meeting full criteria for Mild Cognitive Impairment (MCI), these PreMCI states confer risk for progression to Alzheimer's disease (AD). This investigation addressed a pressing need to identify cognitive measures that are sensitive to PreMCI and are associated with brain biomarkers of neurodegeneration.

METHOD

Participants included 49 older adults with a clinical history suggestive of cognitive decline but normal scores on an array of neuropsychological measures, thus not meeting formal criteria for MCI. The performance of these PreMCI participants were compared to 117 cognitively normal (CN) elders on the LASSI-L, a cognitive stress test that uniquely assesses the failure to recover from proactive semantic interference effects (frPSI). Finally, a subset of these individuals had volumetric analyses based on MRI scans.

RESULTS

PreMCI participants evidenced greater LASSI- L deficits, particularly with regards to frPSI and delayed recall, relative to the CN group. No differences on MRI measures were observed. Controlling for false discovery rate (FDR), frPSI was uniquely related to increased dilatation of the inferior lateral ventricle and decreased MRI volumes in the hippocampus, precuneus, superior parietal region, and other AD prone areas. In contrast, other LASSI-L indices and standard memory tests were not related to volumetric findings.

CONCLUSIONS

Despite equivalent performance on traditional memory measures, the frPSI distinguished between PreMCI and CN elders and was associated with reductions in brain volume in numerous AD-relevant brain regions.

Rare coding variants in PLCG2, ABI3, and TREM2 implicate microglial-mediated innate immunity in Alzheimer's disease

We identified rare coding variants associated with Alzheimer's disease in a three-stage case-control study of 85,133 subjects. In stage 1, we genotyped 34,174 samples using a whole-exome microarray. In stage 2, we tested associated variants (P < 1 × 10-4) in 35,962 independent samples using de novo genotyping and imputed genotypes. In stage 3, we used an additional 14,997 samples to test the most significant stage 2 associations (P < 5 × 10-8) using imputed genotypes. We observed three new genome-wide significant nonsynonymous variants associated with Alzheimer's disease: a protective variant in PLCG2 (rs72824905: p.Pro522Arg, P = 5.38 × 10-10, odds ratio (OR) = 0.68, minor allele frequency (MAF)cases = 0.0059, MAFcontrols = 0.0093), a risk variant in ABI3 (rs616338: p.Ser209Phe, P = 4.56 × 10-10, OR = 1.43, MAFcases = 0.011, MAFcontrols = 0.008), and a new genome-wide significant variant in TREM2 (rs143332484: p.Arg62His, P = 1.55 × 10-14, OR = 1.67, MAFcases = 0.0143, MAFcontrols = 0.0089), a known susceptibility gene for Alzheimer's disease. These protein-altering changes are in genes highly expressed in microglia and highlight an immune-related protein-protein interaction network enriched for previously identified risk genes in Alzheimer's disease. These genetic findings provide additional evidence that the microglia-mediated innate immune response contributes directly to the development of Alzheimer's disease.

Pharmacological Management of Anxiety Disorders in the Elderly

Anxiety disorders are common in the elderly. Additionally, anxiety symptoms often accompany co-morbid psychiatric, medical, as well as neurodegenerative diseases in the older population. Anxiety in the elderly, often accompanied by depression, can lead to worsening physical, cognitive and functional impairments in this vulnerable population. Antidepressants are considered first line treatment. Both SSRIs and SNRIs are efficacious and well-tolerated in the elderly. Some SSRIs are strong inhibitors of the cytochrome P450 hepatic pathway whereas others have less potential for drug interaction. Those antidepressants with more favorable pharmacokinetic profiles should be considered first-line in the treatment of anxiety. Mirtazapine and vortioxetine are also considered safe treatment options. Buspirone may have benefit, but lacks studies in elderly populations. Although tricyclic/tetracyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs) may be effective in the elderly, their side effect and safety profiles are suboptimal and thus are not recommended in late-life. Benzodiazepines and beta blockers should generally be avoided when treating anxiety in the elderly. There is not enough evidence to support the use of antipsychotics or mood stabilizers given their risk of problems in both the long and short term. In addition, antipsychotics have a black box warning for increased mortality in elderly patients with dementia.

Rarity of the Alzheimer disease-protective APP A673T variant in the United States

IMPORTANCE

Recently, a rare variant in the amyloid precursor protein gene (APP) was described in a population from Iceland. This variant, in which alanine is replaced by threonine at position 673 (A673T), appears to protect against late-onset Alzheimer disease (AD). We evaluated the frequency of this variant in AD cases and cognitively normal controls to determine whether this variant will significantly contribute to risk assessment in individuals in the United States.

OBJECTIVE

To determine the frequency of the APP A673T variant in a large group of elderly cognitively normal controls and AD cases from the United States and in 2 case-control cohorts from Sweden.

DESIGN, SETTING, AND PARTICIPANTS

Case-control association analysis of variant APP A673T in US and Swedish white individuals comparing AD cases with cognitively intact elderly controls. Participants were ascertained at multiple university-associated medical centers and clinics across the United States and Sweden by study-specific sampling methods. They were from case-control studies, community-based prospective cohort studies, and studies that ascertained multiplex families from multiple sources.

MAIN OUTCOMES AND MEASURES

Genotypes for the APP A673T variant were determined using the Infinium HumanExome V1 Beadchip (Illumina, Inc) and by TaqMan genotyping (Life Technologies).

RESULTS

The A673T variant genotypes were evaluated in 8943 US AD cases, 10 480 US cognitively normal controls, 862 Swedish AD cases, and 707 Swedish cognitively normal controls. We identified 3 US individuals heterozygous for A673T, including 1 AD case (age at onset, 89 years) and 2 controls (age at last examination, 82 and 77 years). The remaining US samples were homozygous for the alanine (A673) allele. In the Swedish samples, 3 controls were heterozygous for A673T and all AD cases were homozygous for the A673 allele. We also genotyped a US family previously reported to harbor the A673T variant and found a mother-daughter pair, both cognitively normal at ages 72 and 84 years, respectively, who were both heterozygous for A673T; however, all individuals with AD in the family were homozygous for A673.

CONCLUSIONS AND RELEVANCE

The A673T variant is extremely rare in US cohorts and does not play a substantial role in risk for AD in this population. This variant may be primarily restricted to Icelandic and Scandinavian populations.

Effects of multiple genetic loci on age at onset in late-onset Alzheimer disease: a genome-wide association study

IMPORTANCE

Because APOE locus variants contribute to risk of late-onset Alzheimer disease (LOAD) and to differences in age at onset (AAO), it is important to know whether other established LOAD risk loci also affect AAO in affected participants.

OBJECTIVES

To investigate the effects of known Alzheimer disease risk loci in modifying AAO and to estimate their cumulative effect on AAO variation using data from genome-wide association studies in the Alzheimer Disease Genetics Consortium.

DESIGN, SETTING, AND PARTICIPANTS

The Alzheimer Disease Genetics Consortium comprises 14 case-control, prospective, and family-based data sets with data on 9162 participants of white race/ethnicity with Alzheimer disease occurring after age 60 years who also had complete AAO information, gathered between 1989 and 2011 at multiple sites by participating studies. Data on genotyped or imputed single-nucleotide polymorphisms most significantly associated with risk at 10 confirmed LOAD loci were examined in linear modeling of AAO, and individual data set results were combined using a random-effects, inverse variance-weighted meta-analysis approach to determine whether they contribute to variation in AAO. Aggregate effects of all risk loci on AAO were examined in a burden analysis using genotype scores weighted by risk effect sizes.

MAIN OUTCOMES AND MEASURES

Age at disease onset abstracted from medical records among participants with LOAD diagnosed per standard criteria.

RESULTS

Analysis confirmed the association of APOE with earlier AAO (P = 3.3 × 10(-96)), with associations in CR1 (rs6701713, P = 7.2 × 10(-4)), BIN1 (rs7561528, P = 4.8 × 10(-4)), and PICALM (rs561655, P = 2.2 × 10(-3)) reaching statistical significance (P < .005). Risk alleles individually reduced AAO by 3 to 6 months. Burden analyses demonstrated that APOE contributes to 3.7% of the variation in AAO (R(2) = 0.256) over baseline (R(2) = 0.221), whereas the other 9 loci together contribute to 2.2% of the variation (R(2) = 0.242).

CONCLUSIONS AND RELEVANCE

We confirmed an association of APOE (OMIM 107741) variants with AAO among affected participants with LOAD and observed novel associations of CR1 (OMIM 120620), BIN1 (OMIM 601248), and PICALM (OMIM 603025) with AAO. In contrast to earlier hypothetical modeling, we show that the combined effects of Alzheimer disease risk variants on AAO are on the scale of, but do not exceed, the APOE effect. While the aggregate effects of risk loci on AAO may be significant, additional genetic contributions to AAO are individually likely to be small.

How late-life depression affects cognition: neural mechanisms

Late-life depression is a major health problem and a significant cause of dysfunction that warrants closer evaluation and study. In contrast to younger depressed patients, most depressed older adults suffer more severe variants of the disorder, including significant cognitive impairments. These cognitive changes add to the severity of symptoms and disability that older depressed patients face and likely reflect compromise of certain neural circuits, linking cognitive impairment to late-life depression. Studies examining clinical correlates, neuropsychological testing, and functional and anatomic imaging have yielded a clearer understanding of the neural mechanisms underlying cognitive deficits in late-life depression. This article discusses cognitive impairment in geriatric depression and how developing a better understanding of its neural correlates may lead to improved understanding and outcome of this specific disorder.

Psychiatric aspects of mild cognitive impairment

Mild cognitive impairment in the elderly may represent a transitional phase between normal aging and early Alzheimer's disease (AD). It recently has been recognized as a distinct clinical entity with potentially different cognitive subtypes and etiologies. Like AD, studies have shown that psychiatric symptoms are more common than in the cognitively normal geriatric population. Understanding these symptoms has been recognized as important not only because they may impair patient function and caregiver burden, but also these symptoms may be relevant to understanding the development of AD in general. This article presents current information on psychiatric symptoms in mild cognitive impairment, their suggested role in the pathophysiology of AD and future research considerations on the subject.