The hippocampal sparing subtype of Alzheimer's disease assessed in neuropathology and in vivo tau positron emission tomography: a systematic review

Neuropathology and neuroimaging studies have identified several subtypes of Alzheimer's disease (AD): hippocampal sparing AD, typical AD, and limbic predominant AD. An unresolved question is whether hippocampal sparing AD cases can present with neurofibrillary tangles (NFT) in association cortices while completely sparing the hippocampus. To address that question, we conducted a systematic review and performed original analyses on tau positron emission tomography (PET) data. We searched EMBASE, PubMed, and Web of Science databases until October 2022. We also implemented several methods for AD subtyping on tau PET to identify hippocampal sparing AD cases. Our findings show that seven out of the eight reviewed neuropathologic studies included cases at Braak stages IV or higher and therefore, could not identify hippocampal sparing cases with NFT completely sparing the hippocampus. In contrast, tau PET did identify AD participants with tracer retention in the association cortex while completely sparing the hippocampus. We conclude that tau PET can identify hippocampal sparing AD cases with NFT completely sparing the hippocampus. Based on the accumulating data, we suggest two possible pathways of tau spread: (1) a canonical pathway with early involvement of transentorhinal cortex and subsequent involvement of limbic regions and association cortices, and (2) a less common pathway that affects association cortices with limbic involvement observed at end stages of the disease or not at all.

Cholinergic white matter pathways along the Alzheimer's disease continuum

Previous studies have shown that the cholinergic nucleus basalis of Meynert and its white matter projections are affected in Alzheimer’s disease (AD) dementia and mild cognitive impairment (MCI). However, it is still unknown if these alterations can be found in individuals with subjective cognitive decline (SCD), and whether they are more pronounced than changes found in conventional brain volumetric measurements. To address these questions, we investigated microstructural alterations of two major cholinergic pathways in individuals along the AD continuum using an in vivo model of the human cholinergic system based on neuroimaging.

We included 405 participants (53 AD, 66 MCI, 174 SCD, and 112 healthy controls) from the Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE) Longitudinal Cognitive Impairment and Dementia Study (DELCODE). We modelled the cholinergic white matter pathways with an enhanced diffusion neuroimaging pipeline that included probabilistic fiber-tracking methods and prior anatomical knowledge. The integrity of the cholinergic white matter pathways was compared between stages of the AD continuum, in the whole cohort and in a CSF amyloid-beta stratified subsample. The discriminative power of the integrity of the pathways was compared to the conventional volumetric measures of hippocampus and nucleus basalis of Meynert, using a receiver operating characteristics analysis. A multivariate model was employed to investigate the role of these pathways in relation to cognitive performance.

We found that the integrity of the cholinergic white matter pathways was significantly reduced in all stages of the AD continuum, including individuals with SCD. The differences involved posterior cholinergic white matter in the SCD stage and extended to anterior frontal white matter in MCI and AD dementia stages. Both cholinergic pathways and conventional volumetric measures showed higher predictive power in the more advanced stages of the disease, i.e., MCI and AD dementia. In contrast, the integrity of cholinergic pathways was more informative in distinguishing SCD from healthy controls, as compared with the volumetric measures. The multivariate model revealed a moderate contribution of the cholinergic white matter pathways but not of volumetric measures towards memory tests in the SCD and MCI stages.

In conclusion, we demonstrated that cholinergic white matter pathways are altered already in SCD individuals, preceding the more widespread alterations found in MCI and AD. The integrity of the cholinergic pathways identified the early stages of AD better than conventional volumetric measures such as hippocampal volume or volume of cholinergic nucleus basalis of Meynert.

Prevalence and predictors of acquired long QT syndrome in the ER department

Introduction

Long QT syndrome (LQTS) is a rare heterogeneous syndrome that may be congenital or acquired, the latter being more common. Its real-world prevalence remains to be determined. We aimed to determine the prevalence of this syndrome in patients admitted to the emergency room (ER) and characterize the subset of patients with severely prolonged QT.

Methods

A retrospective analysis of ECG of all consecutively admitted patients in the ER of a tertiary hospital between the 28th of January and the 17th of March 2020 was made. All patients with Bazzett corrected QT interval greater than 470ms in men and 480ms in women were included. Repeated ECGs or with bad electrocardiographic quality, congenital LQTS, atrial fibrillation and pacemaker rhythm were excluded. Clinical data with a special focus on QT prolonging drugs and clinical factors were recorded. Statistical comparison was made between the groups with and without QT interval greater than 500ms.

Results

A total of 6280 ECGs of 5056 patients were analysed. After evaluation, 390 ECGs from 387 different patients were considered. Prevalence of LQTS at admission was 7.95%. Patients were more commonly men (53.1%) with an average age of 73.6±14.7 years old and mean QTc interval of 502.14±32.2ms. Only 20% of the patients were symptomatic, with the most common form of presentation being syncope (50%). No ventricular arrhythmias were recorded.

Regarding patients with a QT interval greater than 500ms, these were more frequently female (59.9% vs 37.2%, p<0.001), were more frequently on QT prolonging drugs (77.8% vs 67.3%; p=0.002). Presence of clinical risk factors was not a risk factor per se (p=0.811) but a greater number of risk factors was linked to more severely prolonged QT (p=0.040). The main contributing factor was intake of antibiotics (odds ratio (OR) 3.497; CI 95% 1.074–11.321; p=0.038) followed by female gender (OR 2.518; CI 95% 1.668–3.800; p<0.001) and use of antipsychotics (OR 1.960; CI 95% 1.159–3.316; p=0.012).

Conclusions

Acquired LQTS is particularly prevalent in the ER setting. The complex interaction of clinical factors and drug iatrogenesis and the unpredictability of its manifestations render its management and recognition difficult but essential. Female patients on antibiotics and antipsychotics are at particularly high risk. Efforts must be made in order to avoid, detect and treat acquired LQTS as early as possible.

Funding Acknowledgement

Type of funding sources: None.

Management of Refractory Status Epilepticus: An International Cohort Study (MORSE CODe) Analysis of Patients Managed in the ICU

BACKGROUND AND OBJECTIVES

Status epilepticus that continues after the initial benzodiazepine and a second anticonvulsant medication is known as refractory status epilepticus (RSE). Management is highly variable because adequately powered clinical trials are missing. We aimed to determine whether propofol and midazolam were equally effective in controlling RSE in the intensive care unit, focusing on management in resource-limited settings.

METHODS

Patients with RSE treated with midazolam or propofol between January 2015 and December 2018 were retrospectively identified among 9 centers across 4 continents from upper-middle-income economies in Latin America and high-income economies in North America, Europe, and Asia. Demographics, Status Epilepticus Severity Score, etiology, treatment details, and discharge modified Rankin Scale (mRS) were collected. The primary outcome measure was good functional outcome defined as a mRS score of 0-2 at hospital discharge.

RESULTS

Three hundred eighty-seven episodes of RSE (386 patients) were included, with 162 (42%) from upper-middle-income and 225 (58%) from high-income economies. Three hundred six (79%) had acute and 79 (21%) remote etiologies. Initial RSE management included midazolam in 266 (69%) and propofol in 121 episodes (31%). Seventy episodes (26%) that were initially treated with midazolam and 42 (35%) with propofol required the addition of a second anesthetic to treat RSE. Baseline characteristics and outcomes of patients treated with midazolam or propofol were similar. Breakthrough (odds ratio [OR] 1.6, 95% CI 1.3-2.0) and withdrawal seizures (OR 2.0, 95% CI 1.7-2.5) were associated with an increased number of days requiring continuous intravenous anticonvulsant medications (cIV-ACMs). Prolonged EEG monitoring was associated with fewer days of cIV-ACMs (1-24 hours OR 0.5, 95% CI 0.2-0.9, and >24 hours OR 0.7, 95% CI 0.5-1.0; reference EEG <1 hour). This association was seen in both, high-income and upper-middle-income economies, but was particularly prominent in high-income countries. One hundred ten patients (28%) were dead, and 80 (21%) had good functional outcomes at hospital discharge.

DISCUSSION

Outcomes of patients with RSE managed in the intensive care unit with propofol or midazolam infusions are comparable. Prolonged EEG monitoring may allow physicians to decrease the duration of anesthetic infusions safely, but this will depend on the implementation of RSE management protocols. Goal-directed management approaches including EEG targets may hold promise for patients with RSE.

CLASSIFICATION OF EVIDENCE

This study provides Class III data that propofol and midazolam are equivalently efficacious for RSE.

Parent-reported toothbrushing behaviour in the Portuguese preschool population

PURPOSE

Study toothbrushing behaviours and associated factors in a Portuguese preschool population.

METHODS

The study population was the parents of children attending Portuguese kindergartens. The data on sociodemographic and toothbrushing behaviours, at home and at school, were collected by an online questionnaire. The data analysis was performed using Chi-square, Fisher, Mann-Whitney and Kruskal-Wallis tests (α = 0.05).

RESULTS

The sample included 711 parents. Most of the children brushed their teeth at home at least twice-a-day (65.3%), with the help of an adult (62.9%). The majority of the children did not brush their teeth at school (71.2%); however, only 9.9% of the parents reported that they don't/wouldn't authorise it. Considering both toothbrushing, at home and at school, 75% of the children brushed their teeth twice-a-day. However, only 7.8% of the children performed all the correct toothbrushing related procedures. Toothbrushing at school was more frequent in private kindergartens (p < 0.001). A higher level of education was associated with non-authorisation of toothbrushing at school (p = 0.019) and with performing the correct toothbrushing related procedures (p = 0.007). Attending an oral health professional appointment was also associated with performing the correct toothbrushing related procedures (p = 0.005).

CONCLUSION

Toothbrushing twice-a-day was frequent in the studied population, however, the percentage of children who brushed at school was low, as well as the percentage of children who performed all the correct toothbrushing related procedures. Toothbrushing at school was more likely in private kindergartens. Performing correct toothbrushing related procedures was more frequent in children who had a previous oral health appointment and whose parents had a higher education level.

Multi-cohort and longitudinal Bayesian clustering study of stage and subtype in Alzheimer's disease

Understanding Alzheimer's disease (AD) heterogeneity is important for understanding the underlying pathophysiological mechanisms of AD. However, AD atrophy subtypes may reflect different disease stages or biologically distinct subtypes. Here we use longitudinal magnetic resonance imaging data (891 participants with AD dementia, 305 healthy control participants) from four international cohorts, and longitudinal clustering to estimate differential atrophy trajectories from the age of clinical disease onset. Our findings (in amyloid-β positive AD patients) show five distinct longitudinal patterns of atrophy with different demographical and cognitive characteristics. Some previously reported atrophy subtypes may reflect disease stages rather than distinct subtypes. The heterogeneity in atrophy rates and cognitive decline within the five longitudinal atrophy patterns, potentially expresses a complex combination of protective/risk factors and concomitant non-AD pathologies. By alternating between the cross-sectional and longitudinal understanding of AD subtypes these analyses may allow better understanding of disease heterogeneity.

Association of Cerebrovascular and Alzheimer Disease Biomarkers With Cholinergic White Matter Degeneration in Cognitively Unimpaired Individuals

OBJECTIVES

Several pathological processes might contribute to the degeneration of the cholinergic system in aging. We aimed to determine the contribution of amyloid, tau, and cerebrovascular biomarkers towards the degeneration of cholinergic white matter (WM) projections in cognitively unimpaired individuals.

METHODS

The contribution of amyloid and tau pathology was assessed through cerebrospinal fluid (CSF) levels of the Aβ_42/40 ratio and phosphorylated tau (p-tau). CSF Aβ₃₈ levels were also measured. Cerebrovascular pathology was assessed using automatic segmentations of WM lesions on magnetic resonance imaging (MRI). Cholinergic WM projections (i.e., cingulum and external capsule pathways) were modeled using tractography based on diffusion tensor imaging data. Sex and APOE 𝜀4 carriership were also included in the analysis as variables of interest.

RESULTS

We included 203 cognitively unimpaired individuals from the H70 Gothenburg Birth Cohort Studies (all individuals 70 years old, 51% female). WM lesion burden was the most important contributor to the degeneration of both cholinergic pathways (Increase in mean square error (IncMSE)=98.8% in external capsule pathway and IncMSE=93.3% in the cingulum pathway). Levels of Aβ₃₈ and p-tau also contributed to cholinergic white matter degeneration, especially in the external capsule pathway (IncMSE=28.4% and IncMSE=23.4%, respectively). The Aβ_42/40 ratio did not contribute notably to the models (IncMSE<3.0%). APOE 𝜀4 carriers showed poorer integrity in the cingulum pathway (IncMSE=21.33%). Women showed poorer integrity of the external capsule pathway (IncMSE=21.55%), which was independent of amyloid status as reflected by the non-significant differences in integrity when comparing amyloid positive versus amyloid negative women participants (T₂₀₁=-1.55; p=0.123).

CONCLUSIONS

In cognitively unimpaired older individuals, WM lesions play a central role in the degeneration of cholinergic pathways. Our findings highlight the importance of WM lesion burden in the elderly population, which should be considered in the development of prevention programs for neurodegeneration and cognitive impairment.

Neuropathologic Features of Antemortem Atrophy-Based Subtypes of Alzheimer Disease

BACKGROUND AND OBJECTIVES

To investigate whether antemortem MRI-based atrophy subtypes of Alzheimer disease (AD) differ in neuropathologic features and comorbid non-AD pathologies at postmortem.

METHODS

From the Alzheimer's Disease Neuroimaging Initiative cohort, we included individuals with antemortem MRI evaluating brain atrophy within 2 years before death, antemortem diagnosis of AD dementia/mild cognitive impairment, and postmortem-confirmed AD neuropathologic change. Antemortem atrophy subtypes were modeled as continuous phenomena based on a recent conceptual framework: typicality (spanning limbic-predominant AD to hippocampal-sparing AD) and severity (spanning typical AD to minimal atrophy AD). Postmortem neuropathologic evaluation included AD hallmarks, β-amyloid, and tau as well as non-AD pathologies, alpha-synuclein and TAR DNA-binding protein 43 (TDP-43). We also investigated the overall concomitance across these pathologies. Partial correlations assessed the associations between antemortem atrophy subtypes and postmortem neuropathologic outcomes.

RESULTS

In 31 individuals (26 AD dementia/5 mild cognitive impairment, mean age = 80 years, 26% females), antemortem typicality was significantly negatively associated with neuropathologic features, including β-amyloid (rho = -0.39 overall), tau (rho = -0.38 regionally), alpha-synuclein (rho = -0.39 regionally), TDP-43 (rho = -0.49 overall), and concomitance of pathologies (rho = -0.59 regionally). Limbic-predominant AD was associated with higher Thal phase, neuritic plaque density, and presence of TDP-43 compared with hippocampal-sparing AD. Regionally, limbic-predominant AD showed a higher presence of tau and alpha-synuclein pathologies in medial temporal structures, a higher presence of TDP-43, and concomitance of pathologies subcortically/cortically compared with hippocampal-sparing AD. Antemortem severity was significantly negatively associated with concomitance of pathologies (rho = -0.43 regionally), such that typical AD showed higher concomitance of pathologies than minimal atrophy AD.

DISCUSSION

We provide a direct antemortem-to-postmortem validation, highlighting the importance of understanding atrophy-based heterogeneity in AD relative to AD and non-AD pathologies. We suggest that (1) typicality and severity in atrophy reflect differential aspects of susceptibility of the brain to AD and non-AD pathologies; and (2) limbic-predominant AD and typical AD subtypes share similar biological pathways, making them more vulnerable to AD and non-AD pathologies compared with hippocampal-sparing AD, which may follow a different biological pathway. Our findings provide a deeper understanding of associations of atrophy subtypes in AD with different pathologies, enhancing the prevailing knowledge of biological heterogeneity in AD and could contribute toward tracking disease progression and designing clinical trials in the future.

Clinical outcome measures in dementia with Lewy bodies trials: critique and recommendations

The selection of appropriate outcome measures is fundamental to the design of any successful clinical trial. Although dementia with Lewy bodies (DLB) is one of the most common neurodegenerative conditions, assessment of therapeutic benefit in clinical trials often relies on tools developed for other conditions, such as Alzheimer's or Parkinson's disease. These may not be sufficiently valid or sensitive to treatment changes in DLB, decreasing their utility. In this review, we discuss the limitations and strengths of selected available tools used to measure DLB-associated outcomes in clinical trials and highlight the potential roles for more specific objective measures. We emphasize that the existing outcome measures require validation in the DLB population and that DLB-specific outcomes need to be developed. Finally, we highlight how the selection of outcome measures may vary between symptomatic and disease-modifying therapy trials.

Timed Up and Go in People with Subjective Cognitive Decline Is Associated with Faster Cognitive Deterioration and Cortical Thickness

INTRODUCTION

Early markers of neurodegeneration provide an opportunity to detect, monitor, and initiate interventions in individuals who have an increased risk of developing dementia. Here, we investigated whether the Timed Up and Go (TUG) test is associated with early brain neurodegeneration and whether the TUG test could be a marker of cognitive decline in people with subjective cognitive decline (SCD).

METHODS

This is a longitudinal analysis of the Dementia Disease Initiation Study, a prospective, community-based, cohort study from Norway, designed to investigate early markers of cognitive impairment and dementia. Participants were classified as SCD and healthy controls (HC). The main studied variables were the TUG test and cognition as measured by the Mini-Mental State Examination and the Consortium to Establish a Registry for Alzheimer's Disease memory composite score. Additionally, we investigated the cross-sectional association of brain morphology with the TUG using 1.5T-MRI.

RESULTS

The sample included 45 participants (SCD = 21, HC = 24) followed during a mean time of 1.50 ± 0.70 years. At baseline, the cognitive performance did not differ between the groups, but TUG was longer in SCD. Slower baseline TUG was associated with a faster cognitive decline in both groups and it was also associated with reduced cortical thickness especially in motor, executive, associative, and somatosensory cortical regions in people with SCD.

DISCUSSION/CONCLUSION

TUG predicted cognitive change in individuals with SCD, and there was a negative association between TUG and cortical thickness. TUG is a promising cheap and noninvasive marker of early cognitive decline and may help initiate interventions in individuals who have an increased risk of dementia.

Decreased Electroencephalography Global Field Synchronization in Slow-Frequency Bands Characterizes Synaptic Dysfunction in Amnestic Subtypes of Mild Cognitive Impairment

Background

Mild cognitive impairment (MCI) is highly prevalent in a memory clinic setting and is heterogeneous regarding its clinical presentation, underlying pathophysiology, and prognosis. The most prevalent subtypes are single-domain amnestic MCI (sd-aMCI), considered to be a prodromal phase of Alzheimer’s disease (AD), and multidomain amnestic MCI (md-aMCI), which is associated with multiple etiologies. Since synaptic loss and dysfunction are the closest pathoanatomical correlates of AD-related cognitive impairment, we aimed to characterize it in patients with sd-aMCI and md-aMCI by means of resting-state electroencephalography (EEG) global field power (GFP), global field synchronization (GFS), and novel cerebrospinal fluid (CSF) synaptic biomarkers.

Methods

We included 52 patients with sd-aMCI (66.9 ± 7.3 years, 52% women) and 30 with md-aMCI (63.1 ± 7.1 years, 53% women). All patients underwent a detailed clinical assessment, resting-state EEG recordings and quantitative analysis (GFP and GFS in delta, theta, alpha, and beta bands), and analysis of CSF biomarkers of synaptic dysfunction, neurodegeneration, and AD-related pathology. Cognitive subtyping was based on a comprehensive neuropsychological examination. The Mini-Mental State Examination (MMSE) was used as an estimation of global cognitive performance. EEG and CSF biomarkers were included in a multivariate model together with MMSE and demographic variables, to investigate differences between sd-aMCI and md-aMCI.

Results

Patients with sd-aMCI had higher CSF phosphorylated tau, total tau and neurogranin levels, and lower values in GFS delta and theta. No differences were observed in GFP. The multivariate model showed that the most important synaptic measures for group separation were GFS theta, followed by GFS delta, GFP theta, CSF neurogranin, and GFP beta.

Conclusion

Patients with sd-aMCI when compared with those with md-aMCI have a neurophysiological and biochemical profile of synaptic damage, neurodegeneration, and amyloid pathology closer to that described in patients with AD. The most prominent signature in sd-aMCI was a decreased global synchronization in slow-frequency bands indicating that functional connectivity in slow frequencies is more specifically related to early effects of AD-specific molecular pathology.

Why Do Agroforestry Systems Enhance Biodiversity? Evidence From Habitat Amount Hypothesis Predictions

Considering the present ecological crisis, land use-biodiversity relationships have become a major topic in landscape planning, ecosystem management and ecological restoration. In this scope, consistent patterns of outstanding biodiversity have been identified in agroforestry systems within diverse biogeographic regions and types of management. Empirical work has revealed that agroforestry higher structural complexity, when compared with current simplified agricultural systems, might be partially responsible for the observed patterns. The recently developed Habitat Amount Hypothesis predicts diversity for a local habitat patch, from the amount of the same habitat within the local landscape. We have expanded the previous hypothesis to the landscape level, computing the influence of the dominant land uses on the diversity of coexisting guilds. As a case study, we have considered archetypal landscapes dominated (or co-dominated) by crops or trees, which were compared using normalized diversities. The results obtained show that agroforestry systems substantially increase functional diversity and overall biodiversity within landscapes. We highlight that the normalized values should be parametrized to real conditions where the type of crop, tree and agroecological management will make a difference. Most importantly, our findings provide additional evidence that agroforestry has a critical role in enhancing biodiversity in agricultural landscapes and, in this way, should be regarded as a priority measure in European Agri-environmental funding schemes.

Parsing heterogeneity within dementia with Lewy bodies using clustering of biological, clinical, and demographic data

BACKGROUND

Dementia with Lewy bodies (DLB) includes various core clinical features that result in different phenotypes. In addition, Alzheimer's disease (AD) and cerebrovascular pathologies are common in DLB. All this increases the heterogeneity within DLB and hampers clinical diagnosis. We addressed this heterogeneity by investigating subgroups of patients with similar biological, clinical, and demographic features.

METHODS

We studied 107 extensively phenotyped DLB patients from the European DLB consortium. Factorial analysis of mixed data (FAMD) was used to identify dimensions in the data, based on sex, age, years of education, disease duration, Mini-Mental State Examination (MMSE), cerebrospinal fluid (CSF) levels of AD biomarkers, core features of DLB, and regional brain atrophy. Subsequently, hierarchical clustering analysis was used to subgroup individuals based on the FAMD dimensions.

RESULTS

We identified 3 dimensions using FAMD that explained 38% of the variance. Subsequent hierarchical clustering identified 4 clusters. Cluster 1 was characterized by amyloid-β and cerebrovascular pathologies, medial temporal atrophy, and cognitive fluctuations. Cluster 2 had posterior atrophy and showed the lowest frequency of visual hallucinations and cognitive fluctuations and the worst cognitive performance. Cluster 3 had the highest frequency of tau pathology, showed posterior atrophy, and had a low frequency of parkinsonism. Cluster 4 had virtually normal AD biomarkers, the least regional brain atrophy and cerebrovascular pathology, and the highest MMSE scores.

CONCLUSIONS

This study demonstrates that there are subgroups of DLB patients with different biological, clinical, and demographic characteristics. These findings may have implications in the diagnosis and prognosis of DLB, as well as in the treatment response in clinical trials.

Harmonizing neuropsychological assessment for mild neurocognitive disorders in Europe

INTRODUCTION

Harmonized neuropsychological assessment for neurocognitive disorders, an international priority for valid and reliable diagnostic procedures, has been achieved only in specific countries or research contexts.

METHODS

To harmonize the assessment of mild cognitive impairment in Europe, a workshop (Geneva, May 2018) convened stakeholders, methodologists, academic, and non-academic clinicians and experts from European, US, and Australian harmonization initiatives.

RESULTS

With formal presentations and thematic working-groups we defined a standard battery consistent with the U.S. Uniform DataSet, version 3, and homogeneous methodology to obtain consistent normative data across tests and languages. Adaptations consist of including two tests specific to typical Alzheimer's disease and behavioral variant frontotemporal dementia. The methodology for harmonized normative data includes consensus definition of cognitively normal controls, classification of confounding factors (age, sex, and education), and calculation of minimum sample sizes.

DISCUSSION

This expert consensus allows harmonizing the diagnosis of neurocognitive disorders across European countries and possibly beyond.

The protective gene dose effect of the APOE ε2 allele on gray matter volume in cognitively unimpaired individuals

INTRODUCTION

Harboring two copies of the apolipoprotein E (APOE) ε2 allele strongly protects against Alzheimer's disease (AD). However, the effect of this genotype on gray matter (GM) volume in cognitively unimpaired individuals has not yet been described.

METHODS

Multicenter brain magnetic resonance images (MRIs) from cognitively unimpaired ε2 homozygotes were matched (1:1) against all other APOE genotypes for relevant confounders (n = 223). GM volumes of ε2 genotypic groups were compared to each other and to the reference group (APOE ε3/ε3).

RESULTS

Carrying at least one ε2 allele was associated with larger GM volumes in brain areas typically affected by AD and also in areas associated with cognitive resilience. APOE ε2 homozygotes, but not APOE ε2 heterozygotes, showed larger GM volumes in areas related to successful aging.

DISCUSSION

In addition to the known resistance against amyloid-β deposition, the larger GM volumes in key brain regions may confer APOE ε2 homozygotes additional protection against AD-related cognitive decline.