Sex differences in Alzheimer's disease and other dementias

Novel Insight in Idiopathic Normal Pressure Hydrocephalus (iNPH) Biomarker Discovery in CSF

Idiopathic normal pressure hydrocephalus (iNPH) is a potentially reversible neurological disease, causing motor and cognitive dysfunction and dementia. iNPH and Alzheimer’s disease (AD) share similar molecular characteristics, including amyloid deposition, t-tau and p-tau dysregulation; however, the disease is under-diagnosed and under-treated. The aim was to identify a panel of sphingolipids and proteins in CSF to diagnose iNPH at onset compared to aged subjects with cognitive integrity (C) and AD patients by adopting multiple reaction monitoring mass spectrometry (MRM-MS) for sphingolipid quantitative assessment and advanced high-resolution liquid chromatography–tandem mass spectrometry (LC–MS/MS) for proteomic analysis. The results indicated that iNPH are characterized by an increase in very long chains Cer C22:0, Cer C24:0 and Cer C24:1 and of acute-phase proteins, immunoglobulins and complement component fragments. Proteins involved in synaptic signaling, axogenesis, including BACE1, APP, SEZ6L and SEZ6L2; secretory proteins (CHGA, SCG3 and VGF); glycosylation proteins (POMGNT1 and DAG1); and proteins involved in lipid metabolism (APOH and LCAT) were statistically lower in iNPH. In conclusion, at the disease onset, several factors contribute to maintaining cell homeostasis, and the protective role of very long chains sphingolipids counteract overexpression of amyloidogenic and neurotoxic proteins. Monitoring specific very long chain Cers will improve the early diagnosis and can promote patient follow-up.

Race-Related Association between APOE Genotype and Alzheimer's Disease: A Systematic Review and Meta-Analysis

BACKGROUND

The global race-dependent association of Alzheimer's disease (AD) and apolipoprotein E (APOE) genotype is not well understood. Transethnic analysis of APOE could clarify the role of genetics in AD risk across populations.

OBJECTIVE

This study aims to determine how race and APOE genotype affect the risks for AD.

METHODS

We performed a systematic search of PubMed, Embase, Web of Science, and the Cochrane Library since 1993 to Aug 25, 2020. A total of 10,395 reports were identified, and 133 were eligible for analysis with data on 77,402 participants. Studies contained AD clinical diagnostic and APOE genotype data. Homogeneous data sets were pooled in case-control analyses. Odds ratios and 95% confidence intervals for developing AD were calculated for populations of different races and APOE genotypes.

RESULTS

The proportion of APOE genotypes and alleles differed between populations of different races. Results showed that APOEɛ4 was a risk factor for AD, whereas APOEɛ2 protected against it. The effects of APOEɛ4 and ɛ2 on AD risk were distinct in various races, they were substantially attenuated among Black people. Sub-group analysis found a higher frequency of APOEɛ4/ɛ4 and lower frequency of APOEɛ3/ɛ3 among early-onset AD than late-onset AD in a combined group and different races.

CONCLUSION

Our meta-analysis suggests that the association of APOE genotypes and AD differ between races. These results enhance our understanding of APOE-related risk for AD across race backgrounds and provide new insights into precision medicine for AD.

Association between dementia and hepatitis B and C virus infection

ABSTRACT

Several viral infections are known to increase the risk of dementia through brain cell damage and systemic infection. The association between hepatitis B and C virus (HBV and HCV) infections and dementia was evaluated using a national sample cohort from South Korea. Using the national cohort study from the Korean National Health Insurance Service, we extracted data for patients with HBV or HCV infection and for matched control participants. The controls were matched to the patients according to age, sex, income, region of residence, and past medical histories. The incidence of HCV infection was higher in the dementia group (1.0% [113/11,228]) than in the control group (0.8% [364/44,912], P = .043). However, there was no difference in the incidence of HBV infection in the dementia and control groups. The adjusted odds ratio (OR) for HCV infection was 1.25 (95% confidence interval [CI] = 1.01-1.54, P = .043) in the dementia group. According to the subgroup analysis by sex, the adjusted ORs for HCV infection were 1.04 (95% CI = 072-1.49, P = .851) in men and 1.38 (95% CI = 1.06-1.79, P = .016) in women. We concluded that the incidence of HCV infection was higher (with a higher OR) in women with dementia than in matched control participants in South Korea.

Specific White Matter Tracts and Diffusion Properties Predict Conversion From Mild Cognitive Impairment to Alzheimer's Disease

Identifying biomarkers that can assess the risk of developing Alzheimer's Disease (AD) remains a significant challenge. In this study, we investigated the integrity levels of brain white matter in 34 patients with mild cognitive impairment (MCI) who later converted to AD and 53 stable MCI patients. We used diffusion tensor imaging (DTI) and automated fiber quantification to obtain the diffusion properties of 20 major white matter tracts. To identify which tracts and diffusion measures are most relevant to AD conversion, we used support vector machines (SVMs) to classify the AD conversion and non-conversion MCI patients based on the diffusion properties of each tract individually. We found that diffusivity measures from seven white matter tracts were predictive of AD conversion with axial diffusivity being the most predictive diffusion measure. Additional analyses revealed that white matter changes in the central and parahippocampal terminal regions of the right cingulate hippocampal bundle, central regions of the right inferior frontal occipital fasciculus, and posterior and anterior regions of the left inferior longitudinal fasciculus were the best predictors of conversion from MCI to AD. An SVM based on these white matter tract regions achieved an accuracy of 0.75. These findings provide additional potential biomarkers of AD risk in MCI patients.

Gender Differences of Dementia in Response to Intensive Self-Administered Transcranial and Intraocular Near-Infrared Stimulation

Background

Transcranial near-infrared (tNIR) stimulation was proven to be a safe, reliable, and effective treatment for cognitive and behavioral symptoms of dementia. Dementia patients of different genders differ in terms of gross anatomy, biochemistry, genetic profile, clinical presentations, and socio-psychological status. Studies of the tNIR effect on dementia have thus far been gender-neutral, with dementia subjects being grouped based on diagnoses or dementia severity. This trial hereby investigated how dementia subjects of different sex respond to tNIR treatment.

Methods

A total of 60 patient-caregiver dyads were enrolled and randomized to this double-blind, sham-controlled clinical trial. The tNIR light has a wavelength of 1,060 nm to 1,080 nm and was delivered via a photobiomodulation (PBM) unit. The active PBM unit emits near-infrared (NIR) light while the sham unit does not. The treatment consists of a six-minute tNIR light stimulation session twice daily for eight weeks. Neuropsychological assessments conducted at baseline (week 0) and endline (week 8) were compared within the female and male group and between different sex, respectively.

Results

Over the course of treatment, active-arm female subjects had a 20.2% improvement in Mini‐Mental State Exam (MMSE) (mean 4.8 points increase, p < 0.001) and active-arm male cohort had 19.3% improvement (p < 0.001). Control-arm female subjects had a 6.5% improvement in MMSE (mean 1.5 points increase, p < 0.03) and control-arm male subjects had 5.9% improvement (p = 0.35) with no significant differences in the mean MMSE between female and male subjects in both arms respectively. Other comparison of assessments including Clock Copying and Drawing Test, Logical Memory Test - immediate and delayed recall yielded nominal but not statistically significant differences. No significant differences were observed in the mean MMSE between female and male subjects in both arms respectively before treatment implementation (active arm, p = 0.12; control arm, p = 0.50) at week 0, or after treatment completion (active arm, p = 0.11; control arm, p = 0.74) at week 8.

Conclusion

Despite differences between female and male dementia subjects, the response to tNIR light stimulation does not demonstrate gender-based differences. Further studies are warranted to refine the tNIR treatment protocol for subjects suffering from dementia or dementia-related symptoms.

Sex differences in a murine model of Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy (CAA) is one of the common causes of lobar intracerebral hemorrhage and vascular cognitive impairment (VCI) in the aging population. Increased amyloid plaque deposition within cerebral blood vessels, specifically the smooth muscle layer, is linked to increased cerebral microbleeds (CMBs) and impaired cognition in CAA. Studies in Alzheimer's disease (AD) have shown that amyloid plaque pathology is more prevalent in the brains of elderly women (2/3rd of the dementia population) compared with men, however, there is a paucity of studies on sex differences in CAA. The objective of this study was to discern the sexual dichotomies in CAA. We utilized male and female Tg-SwDI mice (mouse model of CAA) at 12-14 months of age for this study. We evaluated sex differences in CMBs, cognitive function and inflammation. Cognition was assessed using Y-maze (spatial working memory) and Fear Conditioning (contextual memory). CMBs were quantified by ex vivo brain MRI scans. Inflammatory cytokines in brain were quantified using ELISA. Our results demonstrated that aging Tg-SwDI female mice had a significantly higher burden of CMBs on MRI as compared to males. Interestingly, these aging Tg-SwDI female mice also had significantly impaired spatial and contextual memory on Y maze and Fear Conditioning respectively. Furthermore, female mice had significantly lower circulating inflammatory cytokines, IL-1α, IL-2, IL-9, and IFN-γ, as compared to males. Our results demonstrate that aging female Tg-SwDI mice are more cognitively impaired and have higher number of CMBs, as compared to males at 12-14 months of age. This may be secondary to reduced levels of neural repair cytokines (IL-1α, IL-2, IL-9 and IFN-γ) involved in sex specific inflammatory signaling in CAA.

Gender differences in geriatric syndromes as mental illness and nervous system diseases in hospitalized Thai older patients

BACKGROUND

Older persons are affected by mental and neurological disorders differently, and gender plays a significant role influencing geriatric disorder differentiation. Accordingly this study characterized gender differences in geriatric syndromes among hospitalized elderly Thai patients.

METHODS

Probabilities of disease occurrence reflecting gender differences were calculated using historical data obtained from the Ministry of Public Health website, Thailand. We selected older patients aged 60 years and above admitted to inpatient departments in public hospitals with mental disorders and nervous system diseases from 2014 to 2018, counting over 160 000 cases each year. Descriptive statistics and odds ratios (ORs) were used to analyse and demonstrate gender differences.

RESULTS

Compared to older females, older males had higher occurrences of four mental disorders revealed by OR and 95% confidence interval (CI) values: substance abuse (5.74, 5.08-6.49), alcohol use (5.66, 5.44-5.89), behavioural problems (1.34, 1.31-1.37), and schizophrenia (1.10, 1.06-1.14). Lower incidences for older males were seen in the same values for three mental disorders: neurotic issues (0.46, 0.44-0.49), mood disorders (0.58, 0.56-0.60), and dementia (0.91, 0.88-0.94). For neurological disorders, men had similar higher incidences for epilepsy (1.67, 1.63-1.72), cerebral palsy (1.61, 1.57-1.65), nervous system inflammatory diseases (1.53, 1.46-1.60), ischaemic attacks (1.42, 1.36-1.48), miscellaneous other nervous disorders (1.20; 1.18-1.22), and Parkinson's disease (1.15, 1.12-1.19). By contrast, older men had lower incidences of multiple sclerosis (0.55, 0.35-0.86), migraines (0.66, 0.62-0.70), and Alzheimer's disease (0.75, 0.71-0.78).

CONCLUSION

Accurate characterization of gender differences in geriatric syndromes can better inform policies for appropriate early detection and prevention, and contribute to the development of treatment and intervention for various issues affecting elderly men and women's health.

Sex differences in in vivo tau neuropathology in a multiethnic sample of late middle-aged adults

It is unclear whether women have higher brain tau pathology. The objective of this study was to examine whether women have higher tau burden than men, and whether tau differences are independent of amyloid β (Aβ) burden. We conducted a cross-sectional analysis of a multiethnic sample of 252 nondemented late middle-aged (mean age: 64.1 years) adults with tau and amyloid Positron Emission Tomography (PET) data. Tau burden was measured as global standardized uptake value ratio (SUVR) in the middle/inferior temporal gyri and medial temporal cortex with 18F-MK-6240 PET. Aβ was measured as global SUVR with 18F-Florbetaben PET. Women had higher middle/inferior temporal gyri tau SUVR compared to men. However, no sex differences in the medial temporal cortex were observed. Women had higher brain Aβ SUVR compared to men. Continuous Aβ SUVR was positively correlated with medial temporal cortex and middle/inferior temporal gyri tau SUVR. However, there was no evidence of effect modification by Aβ SUVR on sex and tau. Compared with men, women in late middle age show higher tau burden, independent of Aβ.

Treating the most vulnerable: A discursive review of experimental pain in Alzheimer's disease

AIM

The purpose of this manuscript is to summarize research on how experimental pain is experienced by adults with Alzheimer's disease (AD) and to translate results into implications for nurses.

DESIGN

This discursive review synthesizes the results of three previous research studies exploring experimental pain in adults with AD.

METHODS

Using a series of fictional clinical vignettes, the authors discuss how the results from three previous papers using acute experimental pain can potentially be translated into clinical practice. The authors also introduce the reader to the concept of research-related psychophysics using introductory definitions and concepts with the impetus to encourage other nurses to consider this research methodology.

RESULTS

Pain characteristics in AD that differ from cognitively intact controls must be explored to properly address pain in this population. Nurses are well positioned to address these issues in order to provide a high quality of care to adults with AD.

Fractal motor activity regulation and sex differences in preclinical Alzheimer's disease pathology

INTRODUCTION

Degradation in fractal motor activity regulation (FMAR), a measure of multiscale self-similarity of motor control, occurs in aging and accelerates with clinical progression to Alzheimer's disease (AD). Whether FMAR changes occur during the pre-symptomatic phase of the disease in women and men remains unknown.

METHODS

FMAR was assessed in cognitively normal participants (n = 178) who underwent 7 to 14 days of home actigraphy. Preclinical AD pathology was determined by amyloid imaging-Pittsburgh compound B (PiB) and cerebrospinal fluid (CSF) phosphorylated-tau181 (p-tau) to amyloid beta 42 (Aβ42) ratio.

RESULTS

Degradation in daytime FMAR was overall significantly associated with preclinical amyloid plaque pathology via PiB+ imaging (beta coefficient β = 0.217, standard error [SE] = 0.101, P = .034) and increasing CSF tau181-Aβ42 ratio (β = 0.220, SE = 0.084, P = .009). In subset analysis by sex, the effect sizes were significant in women for PiB+ (β = 0.279, SE = 0.112, P = .015) and CSF (β = 0.245, SE = 0.094, P = .011) but not in men (both Ps > .05). These associations remained after inclusion of daily activity level, apolipoprotein E ε4 carrier status, and rest/activity patterns.

DISCUSSION

Changes in daytime FMAR from actigraphy appear to be present in women early in preclinical AD. This may be a combination of earlier pathology changes in females reflected in daytime FMAR, and a relatively underpowered male group. Further studies are warranted to test FMAR as an early noncognitive physiological biomarker that precedes the onset of cognitive symptoms.

Genotype Load Modulates Amyloid Burden and Anxiety-Like Patterns in Male 3xTg-AD Survivors despite Similar Neuro-Immunoendocrine, Synaptic and Cognitive Impairments

The wide heterogeneity and complexity of Alzheimer’s disease (AD) patients’ clinical profiles and increased mortality highlight the relevance of personalized-based interventions and the need for end-of-life/survival predictors. At the translational level, studying genetic and age interactions in a context of different levels of expression of AD-genetic-load can help to understand this heterogeneity better. In the present report, a singular cohort of long-lived (19-month-old survivors) heterozygous and homozygous male 3xTg-AD mice were studied to determine whether their AD-genotype load can modulate the brain and peripheral pathological burden, behavioral phenotypes, and neuro-immunoendocrine status, compared to age-matched non-transgenic controls. The results indicated increased amyloid precursor protein (APP) levels in a genetic-load-dependent manner but convergent synaptophysin and choline acetyltransferase brain levels. Cognitive impairment and HPA-axis hyperactivation were salient traits in both 3xTg-AD survivor groups. In contrast, genetic load elicited different anxiety-like profiles, with hypoactive homozygous, while heterozygous resembled controls in some traits and risk assessment. Complex neuro-immunoendocrine crosstalk was also observed. Bodyweight loss and splenic, renal, and hepatic histopathological injury scores provided evidence of the systemic features of AD, despite similar peripheral organs’ oxidative stress. The present study provides an interesting translational scenario to study further genetic-load and age-dependent vulnerability/compensatory mechanisms in Alzheimer’s disease.

Interactive rather than independent effect of APOE and sex potentiates tau deposition in women

The apolipoprotein E gene (APOE) is the most important genetic risk factor for sporadic Alzheimer disease, with the ε4 allele being associated with increased cerebral amyloid-β and tau pathologies. Although APOE has been suggested to have a stronger effect in women as compared to men, there is a lack of comprehensive assessment on how the interactive effect of APOE and sex modulates regional vulnerability to tau accumulation. We previously have shown the regional vulnerability to the interactive effect of tau and APOE, yet the sex difference was not specifically addressed. In this study, we leveraged PET imaging data from the Translational Biomarkers in Aging and Dementia cohort at McGill University Research Centre for Studies in Aging to elucidate the APOE-by-sex interactive effect on tau burden. We hypothesized sex-dependent regional vulnerability to tau deposition. PET radiopharmaceuticals [18F]AZD4694 and [18F]MK6240 were used to assess amyloid-β and tau level respectively in 277 subjects from the Translational Biomarkers in Aging and Dementia cohort. We found that the interaction between APOE and sex, rather than their independent main effects, was associated with abnormal tau accumulation in medial temporal regions. Specifically, we found that female APOEε4 carriers showed significantly higher tau burden in early tau deposition regions including the hippocampus, entorhinal and parahippocampal cortices, after accounting for age, educational attainment, clinical diagnosis and neocortical amyloid load. We replicated these findings in 221 subjects from the Alzheimer's Disease Neuroimaging Initiative cohort, in which a different tau-PET radioligand, [18F]flortaucipir, was used to assess tau burden. In conclusion, this study provides evidence from two cohort studies that interactive rather than independent effect of APOE and sex potentiates early tau deposition in women. Our results have important implications for clinical trials and practice, which should take into consideration both APOEε4 carriage status and sex for identifying individuals with the highest probability of developing tau accumulation and clinical progression.

Sex Difference in Network Topology and Education Correlated With Sex Difference in Cognition During the Disease Process of Alzheimer

Background: Alzheimer's disease (AD) manifests differently in males and females. However, the neuro-mechanism and influence factors are still unknown. Objective: To explore sex differences in brain network topology during AD disease progression and its association with cognition and possible influencing factors. Methods: Resting-state functional magnetic resonance imaging (MRI) data and cognitive scores were collected from 82 AD patients (50 females), 56 amnestic mildly cognitive impaired patients (29 females), and 63 healthy controls (38 females). Global and regional topological network metrics and modular architecture were calculated. Two-way ANOVA was performed to explore group and sex interactions and their main effects. Mediation analysis was used to explore the relationship among education, inter/intra-network connectivity, and the Mini-Mental State Examination (MMSE) score. Results: Lower levels of education, lower MMSE scores, and a positive correlation between the level of education and MMSE scores were found in female AD patients (p = 0.024, r = 0.319). Significantly lower connectivity strength within the sensorimotor network, dorsal attention network, ventral attention network (VAN), and between the sensorimotor and VAN were observed in male AD patients (p = 0.006, 0.028, 0.046, and 0.013, respectively). Group and sex interactions were also found in nodal properties, mainly in the frontal lobe, temporal lobe, middle cingulum, precuneus, and postcentral gyrus. Several of the altered brain network properties were associated with cognitive behavior in male AD patients. Education regulated the MMSE score through the mediation of connection strength between the default mode and limbic networks (LN) in the patient group (aMCI and AD combined). Conclusion: Our results demonstrate that sex differences exist at the brain network level in AD. Sex differences in network topology and education are correlated with sex differences in cognition during AD progression.

Survival Bias and Crosstalk between Chronological and Behavioral Age: Age- and Genotype-Sensitivity Tests Define Behavioral Signatures in Middle-Aged, Old, and Long-Lived Mice with Normal and AD-Associated Aging

New evidence refers to a high degree of heterogeneity in normal but also Alzheimer's disease (AD) clinical and temporal patterns, increased mortality, and the need to find specific end-of-life prognosticators. This heterogeneity is scarcely explored in very old male AD mice models due to their reduced survival. In the present work, using 915 (432 APP23 and 483 C57BL/6 littermates) mice, we confirmed the better survival curves in male than female APP23 mice and respective wildtypes, providing the chance to characterize behavioral signatures in middle-aged, old, and long-lived male animals. The sensitivity of a battery of seven paradigms for comprehensive screening of motor (activity and gait analysis), neuropsychiatric and cognitive symptoms was analyzed using a cohort of 56 animals, composed of 12-, 18- and 24-month-old male APP23 mice and wildtype littermates. Most variables analyzed detected age-related differences. However, variables related to coping with stress, thigmotaxis, frailty, gait, and poor cognition better discriminated the behavioral phenotype of male APP23 mice through the three old ages compared with controls. Most importantly, non-linear age- and genotype-dependent behavioral signatures were found in long-lived animals, suggesting crosstalk between chronological and biological/behavioral ages useful to study underlying mechanisms and distinct compensations through physiological and AD-associated aging.

Sex differences in biological aging with a focus on human studies

Aging is a complex biological process characterized by hallmark features accumulating over the life course, shaping the individual's aging trajectory and subsequent disease risks. There is substantial individual variability in the aging process between men and women. In general, women live longer than men, consistent with lower biological ages as assessed by molecular biomarkers, but there is a paradox. Women are frailer and have worse health at the end of life, while men still perform better in physical function examinations. Moreover, many age-related diseases show sex-specific patterns. In this review, we aim to summarize the current knowledge on sexual dimorphism in human studies, with support from animal research, on biological aging and illnesses. We also attempt to place it in the context of the theories of aging, as well as discuss the explanations for the sex differences, for example, the sex-chromosome linked mechanisms and hormonally driven differences.

The role of sex and gender in the selection of Alzheimer patients for clinical trial pre-screening

BACKGROUND

Alzheimer disease (AD) is a progressive neurodegenerative disorder affecting the elderly with a prevalence of 7.1% in women and 3.3% in men. Sex-related patterns have been reported in prognosis, biomarker status, and risk factors. Despite this, the interaction of sex has received limited attention, with AD trials persistently recruiting lower numbers of women than the population distribution and a lack of information on the sex-disaggregated effects of anti-dementia therapies. This is the first study aiming to identify the role of sex in the selection for screening in AD clinical trials.

METHODS

This cross-sectional study provides a comprehensive analysis of screening eligibility according to a set of pre-selection criteria currently applied at Fundació ACE memory clinic for a more efficient trial screening process. A cohort of 6667 women and 2926 men diagnosed with AD dementia (55%) or mild cognitive impairment (45%) was analyzed. We also assessed the frequencies of men and women effectively screened for trial enrolment over a period of 10 years. Additionally, data from AddNeuroMed study was used to explore trends in eligibility based on the education criteria.

RESULTS

Women showed a significantly lower chance of being eligible for screening than men (OR = 1.26; p < 0.01). This imbalance was confirmed by a lower frequency of women screened for enrolment compared to the study population (63.0% vs. 69.5%). Education was revealed as the key criterion contributing to this unbalance, with men showing over twice the chance of being screened compared with women (OR = 2.25, p < 0.01). Education-based differences were greater in earlier born patients, but the gap narrowed and achieved balance with increasing year of birth. This observation was replicated using data from other European populations included in AddNeuroMed study. Comorbidity was the most limiting criterion with sex differences in frequencies and significant discrimination against the selection of men (OR = 0.86, p < 0.01).

CONCLUSIONS

The large number of low-educated elderly women with AD demands for a sex-focused approach in clinical research. New assessment tools insensitive to education level should be developed to enable a proportional representation of women. Although this gender education gap is mostly inexistent in developed countries, economic or cultural factors may lead to different scenarios in other regions. Overlooking the impact of sex may lead to a handicap in AD research with a direct adverse impact on women's health.

Longitudinal quantification of metabolites and macromolecules reveals age- and sex-related changes in the healthy Fischer 344 rat brain

Normal aging is associated with numerous biological changes, including altered brain metabolism and tissue chemistry. In vivo characterization of the neurochemical profile during aging is possible using magnetic resonance spectroscopy, a powerful noninvasive technique capable of quantifying brain metabolites involved in physiological processes that become impaired with age. A prominent macromolecular signal underlies those of brain metabolites and is particularly visible at high fields; parameterization of this signal into components improves quantification and expands the number of biomarkers comprising the neurochemical profile. The present study reports, for the first time, the simultaneous absolute quantification of brain metabolites and individual macromolecules in aging male and female Fischer 344 rats, measured longitudinally using proton magnetic resonance spectroscopy at 7 T. We identified age- and sex-related changes in neurochemistry, with prominent differences in metabolites implicated in anaerobic energy metabolism, antioxidant defenses, and neuroprotection, as well as numerous macromolecule changes. These findings contribute to our understanding of the neurobiological processes associated with healthy aging, critical for the proper identification and management of pathologic aging trajectories. This article is part of the Virtual Special Issue titled COGNITIVE NEUROSCIENCE OF HEALTHY AND PATHOLOGICAL AGING. The full issue can be found on ScienceDirect athttps://www.sciencedirect.com/journal/neurobiology-of-aging/special-issue/105379XPWJP.

Amyloid toxicity in a Drosophila Alzheimer's model is ameliorated by autophagy activation

Alzheimer's disease (AD) is the prevailing form of dementia. Protein degradation and antioxidant pathways have a critical role in preventing the accumulation of protein aggregation; thus, failure of proteostasis in neurons along with redox imbalance mark AD. Herein, we exploited an AD Drosophila model expressing human amyloid precursor (hAPP) and beta-secretase 1 (hBACE1) proteins, to better understand the role of proteostatic or antioxidant pathways in AD. Ubiquitous expression of hAPP, hBACE1 in flies caused more severe degenerative phenotypes versus neuronal targeted expression; it also, suppressed proteasome activity, increased oxidative stress and significantly enhanced stress-sensitivity. Overexpression of Prosβ5 proteasomal subunit or Nrf2 transcription factor in AD Drosophila flies partially restored proteasomal activity but did not rescue hAPP, hBACE1 induced neurodegeneration. On the other hand, expression of autophagy-related Atg8a in AD flies decelerated neurodegeneration, increased stress-resistance, and improved flies' health-/lifespan. Overall, our data suggest that the noxious effects of amyloid-beta aggregates can be alleviated by enhanced autophagy, thus dietary or pharmacological interventions that target autophagy should be considered in AD therapeutic approaches.

A regional and cellular analysis of the early intracellular and extracellular accumulation of Aβ in the brain of 5XFAD mice

Intracellular Aβ (iAβ) expression, extracellular Aβ (eAβ) plaque formation and microglial reactivity are characteristic neuropathological events of Alzheimer's disease (AD) and have been detected in several transgenic mouse models of this disease. In this work we decided to investigate the early (2-7 months of age) development of these phenomena at both regional and cellular levels in 5XFAD mice, a severe transgenic mouse model of AD. We demonstrated that 1) Aβ pathology develops in many but not all brain regions, 2) iAβ is transient and almost always followed by eAβ in grey matter regions, and the respective levels are roughly proportional, and 3) in about 1/3 of the grey matter regions with Aβ pathology and in several white matter regions, eAβ plaques can appear where no iAβ-positive structures were detected. We also showed that male and female mice share a similar regional and cellular pattern of Aβ pathology development that is more prominent in females. Early iAβ is associated to the activation of microglia, while subsequent formation of eAβ plaques is associated with markedly increased density of microglial cells that acquire a characteristic clustered phenotype. Present analysis is relevant to set a reference for pathophysiological studies and to define specific targets for the test of therapeutic interventions in this widely used AD transgenic model.

Generalization of memory-related brain function in asymptomatic older women with a family history of late onset Alzheimer's Disease: Results from the PREVENT-AD Cohort

Late-onset Alzheimer's disease (AD) disproportionately affects women compared to men. Episodic memory decline is one of the earliest and most pronounced deficits observed in AD. However, it remains unclear whether sex influences episodic memory-related brain function in cognitively intact older adults at risk of developing AD. Here we used task-based multivariate partial least squares analysis to examine sex differences in episodic memory-related brain activity and brain activity-behavior correlations in a matched sample of cognitively intact older women and men with a family history of AD from the PREVENT-AD cohort study in Montreal, Canada (M_age=63.03±3.78; M_education=15.41±3.40). We observed sex differences in task-related brain activity and brain activity-behavior correlations during the encoding of object-location associative memories and object-only item memory, and the retrieval of object only item memories. Our findings suggest a generalization of episodic memory-related brain activation and performance in women compared to men. Follow up analyses should test for sex differences in the relationship between brain activity patterns and performance longitudinally, in association with risk factors for AD development. This article is part of the Virtual Special Issue titled COGNITIVE NEUROSCIENCE OF HEALTHY AND PATHOLOGICAL AGING. The full issue can be found on ScienceDirect at https://www.sciencedirect.com/journal/neurobiology-of-aging/special-issue/105379XPWJP.

Mitochondria-Targeted Therapeutics for Alzheimer's Disease: The Good, the Bad, the Potential

Significance: Alzheimer's disease (AD) is the leading cause of dementia. Thus far, 99.6% of clinical trials, including those targeting energy metabolism, have failed to exert disease-modifying efficacy. Altered mitochondrial function and disruption to the brain bioenergetic system have long-been documented as early events during the pathological progression of AD. Recent Advances: While therapeutic approaches that directly promote mitochondrial bioenergetic machinery or eliminate reactive oxygen species have exhibited limited translatability, emerging strategies targeting nonenergetic aspects of mitochondria provide novel therapeutic targets with the potential to modify AD risk and progression. Growing evidence also reveals a critical link between mitochondrial phenotype and neuroinflammation via metabolic reprogramming of glial cells. Critical Issues: Herein, we summarize major classes of mitochondrion-centered AD therapeutic strategies. In addition, the discrepancy in their efficacy when translated from preclinical models to clinical trials is addressed. Key factors that differentiate the responsiveness to bioenergetic interventions, including sex, apolipoprotein E genotype, and cellular diversity in the brain, are discussed. Future Directions: We propose that the future development of mitochondria-targeted AD therapeutics should consider the interactions between bioenergetics and other disease mechanisms, which may require cell-type-specific targeting to distinguish neurons and non-neuronal cells. Moreover, a successful strategy will likely include stratification by metabolic phenotype, which varies by sex and genetic risk profile and dynamically changes throughout the course of disease. As the network of mitochondrial integration expands across intracellular and systems level biology, assessment of intended, the good, versus unintended consequences, the bad, will be required to reach the potential of mitochondrial therapeutics.

Sexual Dimorphism in the 3xTg-AD Mouse Model and Its Impact on Pre-Clinical Research

Female sex is a leading risk factor for developing Alzheimer’s disease (AD). Sexual dimorphism in AD is gaining attention as clinical data show that women are not only more likely to develop AD but also to experience worse pathology and faster cognitive decline. Pre-clinical AD research in animal models often neglects to address sexual dimorphism in evaluation of behavioral or molecular characteristics and outcomes. This can compromise its translation to a clinical setting. The triple-transgenic AD mouse model (3xTg-AD) is a commonly used but unique AD model because it exhibits both amyloid and tau pathology, essential features of the human AD phenotype. Mounting evidence has revealed important sexually dimorphic characteristics of this animal model that have yet to be reviewed and thus, are often overlooked in studies using the 3xTg-AD model. In this review we conduct a thorough analysis of reports of sexual dimorphism in the 3xTg-AD model including findings of molecular, behavioral, and longevity-related sex differences in original research articles through August 2020. Importantly, we find results to be inconsistent, and that strain source and differing methodologies are major contributors to lack of consensus regarding traits of each sex. We first touch on the nature of sexual dimorphism in clinical AD, followed by a brief summary of sexual dimorphism in other major AD murine models before discussing the 3xTg-AD model in depth. We conclude by offering four suggestions to help unify pre-clinical mouse model AD research inspired by the NIH expectations for considering sex as a biological variable.

Association between exenatide use and incidence of Alzheimer's disease

INTRODUCTION

Recent developments suggest that insulin-sensitizing agents used to treat type II diabetes (T2DM) may also prove useful in reducing the risk of Alzheimer's disease (AD). The objective of this study is to analyze the association between exenatide use among Medicare beneficiaries with T2DM and the incidence of AD.

METHODS

We performed a retrospective cohort analysis on claims data from a 20% random sample of Medicare beneficiaries with T2DM from 2007 to 2013 (n = 342,608). We compared rates of incident AD between 2009 and 2013 according to exenatide use in 2007-2008, measured by the number of 30-day-equivalent fills. We adjusted for demographics, comorbidities, and use of other drugs. Unmeasured confounding was assessed with an instrumental variables approach.

RESULTS

The sample was mostly female (65%), White (76%), and 74 years old on average. Exenatide users were more likely to be male (38% vs. 35%), White (87% vs. 76%), and younger (by 4.2 years) than non-users. Each additional 30-day-equivalent claim was associated with a 2.4% relative reduction in incidence (odds ratio 0.976; 95% confidence interval 0.963-0.989; P < .001). There was no evidence of unmeasured confounding.

DISCUSSION

Exenatide use is associated with a reduced incidence of AD among Medicare beneficiaries aged 65 years or older with T2DM. The association shown in this study warrants consideration by clinicians prescribing insulin sensitizing agents to patients.

Potential of Caffeine in Alzheimer's Disease-A Review of Experimental Studies

Alzheimer's disease (AD) is the most common type of dementia leading to progressive memory loss and cognitive impairment. Considering that pharmacological treatment options for AD are few and not satisfactory, increasing attention is being paid to dietary components that may affect the development of the disease. Such a dietary component may be caffeine contained in coffee, tea or energy drinks. Although epidemiological data suggest that caffeine intake may counteract the development of cognitive impairment, results of those studies are not conclusive. The aim of the present study is to review the existing experimental studies on the efficacy of caffeine against AD and AD-related cognitive impairment, focusing on the proposed protective mechanisms of action. In conclusion, the reports of studies on experimental AD models generally supported the notion that caffeine may exert some beneficial effects in AD. However, further studies are necessary to elucidate the role of caffeine in the effects of its sources on cognition and possibly AD risk.

Estrogen receptor involvement in vascular cognitive impairment and vascular dementia pathogenesis and treatment

Vascular cognitive impairment (VCI) is a term that encompasses a continuum of cognitive disorders with cerebrovascular pathology contribution, ranging from mild cognitive impairment to vascular dementia (VaD). VCI and VaD, thus, represent an interesting intersection between cardiovascular disease and neurodegenerative disorders such as Alzheimer's disease (AD) and a rising area of research in recent years. Although VCI and VaD research has identified various causes and explanations for disease development, many aspects remain unclear, particularly sex differences in VCI (e.g., epidemiology), unlike those available for cardiovascular disease and AD. Despite limited information in the literature, several studies have observed an association of estrogen receptor (ER) polymorphisms and VaD. If further explored, this association could provide valuable insights for novel therapeutic approaches. This review aims to provide a brief epidemiological overview and subsequent discussion exploring concepts of brain aging and involvement of estrogen receptors in potential mechanisms of VCI/VaD pathogenesis and treatment development.

Deep learning encodes robust discriminative neuroimaging representations to outperform standard machine learning

Recent critical commentaries unfavorably compare deep learning (DL) with standard machine learning (SML) approaches for brain imaging data analysis. However, their conclusions are often based on pre-engineered features depriving DL of its main advantage — representation learning. We conduct a large-scale systematic comparison profiled in multiple classification and regression tasks on structural MRI images and show the importance of representation learning for DL. Results show that if trained following prevalent DL practices, DL methods have the potential to scale particularly well and substantially improve compared to SML methods, while also presenting a lower asymptotic complexity in relative computational time, despite being more complex. We also demonstrate that DL embeddings span comprehensible task-specific projection spectra and that DL consistently localizes task-discriminative brain biomarkers. Our findings highlight the presence of nonlinearities in neuroimaging data that DL can exploit to generate superior task-discriminative representations for characterizing the human brain.

Recent critical commentaries unfavorably compare deep learning (DL) with standard machine learning (SML) for brain imaging data analysis. Here, the authors show that if trained following prevalent DL practices, DL methods substantially improve compared to SML methods by encoding robust discriminative brain representations.

Decomposition of gender differences in cognitive functioning: National Survey of the Japanese elderly

Background

It is well known that females generally live longer than males, but women tend to suffer from more illnesses and limitations than men do, also for dementia. However, limited empirical evidence is available why this ‘male-female health-survival paradox’ is observed. This study aimed to investigate factors which account for gender differences in health, particularly cognitive functioning and decline among older adults.

Methods

Data were retrieved from the National Survey of the Japanese Elderly, which is a longitudinal survey of a nationwide representative sample of Japanese adults aged 60 or over. Gender differences in cognitive functioning and decline in three-year follow-ups were decomposed using Blinder–Oaxaca decomposition analysis, regarding demographic, socioeconomic, and health-related factors into the ‘explained’ component, by differences in individual attributes listed above, and the ‘unexplained’ component.

Results

Empirical analyses showed that women’s lower cognitive functioning was partly explained by the endowment effect. Moreover, a shorter duration of formal education and a larger proportion with their longest occupation being domestic worker accounted for steeper cognitive decline and more prevalent mild cognitive impairment in women than in men.

Conclusion

This empirical study suggested that gender differences in cognitive functioning and decline account for different individual attributes of social determinants among men and women. Particularly, men seem to be more engaged in activities which accumulate intellectual experiences through education and occupation, as suggested by the cognitive reserve hypothesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-020-01990-1.

Spinal muscular atrophy: Broad disease spectrum and sex-specific phenotypes

Spinal muscular atrophy (SMA) is one of the major genetic disorders associated with infant mortality. More than 90% of cases of SMA result from deletions of or mutations in the Survival Motor Neuron 1 (SMN1) gene. SMN2, a nearly identical copy of SMN1, does not compensate for the loss of SMN1 due to predominant skipping of exon 7. The spectrum of SMA is broad, ranging from prenatal death to infant mortality to survival into adulthood. All tissues, including brain, spinal cord, bone, skeletal muscle, heart, lung, liver, pancreas, gastrointestinal tract, kidney, spleen, ovary and testis, are directly and/or indirectly affected in SMA. Accumulating evidence on impaired mitochondrial biogenesis and defects in X chromosome-linked modifying factors, coupled with the sexual dimorphic nature of many tissues, point to sex-specific vulnerabilities in SMA. Here we review the role of sex in the pathogenesis of SMA.

Matching of the postmortem hypothalamus from patients and controls

The quality of postmortem hypothalamus research depends strongly on a thorough clinical investigation and documentation of the patient's disorder and therapies. In addition, a systematic and professional neuropathological investigation of the entire brain of both the cases and the controls is absolutely crucial. In the experience of the Netherlands Brain Bank (NBB), about 20% of the clinical neurological diagnoses, despite being made in first rate clinics, have to be revised or require extra diagnoses after a complete and thorough neuropathologic review by the NBB. The neuropathology examination may reveal for instance that the elderly "controls" already have preclinical neurodegenerative alterations. In postmortem studies, the patient and control groups must be matched for as many as possible of the known confounding factors. This is necessary to make the groups as similar as possible, except for the topic being investigated. Confounding factors are present (i) before, (ii) during, and (iii) after death. They are, respectively: (i) genetic background, systemic diseases, duration and gravity of illness, medicines and addictive compounds used, age, sex, gender identity, sexual orientation, clock- and seasonal time of death, and lateralization; (ii) agonal state, stress of dying; and (iii) postmortem delay, freezing procedures, fixation, and storage time. Agonal state is generally estimated by measuring the pH of the brain. However, there are disorders in which pH is lower as a part of the disease process. Because of the large number of potentially confounding factors that differ according to, for instance, brain area and disease, a brain bank should have a large number of controls at its disposal for appropriate matching. If matching fails for some confounders, the influence of the confounders may be determined by statistical methods, such as analysis of variance or the regression models.

Trends in Mortality Rates for Alzheimer's Disease and Other Dementias Over 30 Years in China

OBJECTIVE

This study examines trends in the mortality of Alzheimer's disease and other dementias in China from 1990 to 2019.

METHODS

The data were drawn from the Global Burden of Disease Study 2019 (GBD 2019), and an age-period-cohort model was used for analysis.

RESULTS

The net drift was .152% (95% confidence interval [CI]: .069%, .235%) per year for men (P < .05) and .024% (95% CI: -.078%, .126%) per year for women. The local drift values were below 0 in both genders for people aged 45-54 years (P < .05), and above 0 for males aged 60-94 years and females aged 60-79 years (P < .05). In the same birth cohort, the risk of mortality of Alzheimer's disease and other dementias exponentially increases with age for both genders.

CONCLUSION

More rapid and effective efforts are needed to mitigate the substantial impact of Alzheimer's and other dementias on the health of China's elderly.

Social Isolation and Cognitive Functioning: A Quasi-Experimental Approach

OBJECTIVES

This study aimed to assess the relationship between social isolation and cognitive functioning.

METHODS

Data were retrieved from the National Survey of the Japanese Elderly, a nationally representative sample of Japanese adults, aged 60 years or older. We estimated a social isolation index to incorporate variables, such as social interactions, social engagement, and social support, with perceived social isolation, for a comprehensive measurement. The association of social isolation with cognitive functioning was assessed using a panel data fixed-effects model, controlling for age, socioeconomic status, health-related variables, and time-invariant heterogeneity. Moreover, we conducted analyses using the System Generalised Method of Moments (GMM) to address the dynamic relationship of cognitive functioning and potential endogeneity.

RESULTS

For both men and women, the association between social isolation and cognitive functioning was significant, particularly among those aged 75 or older, as a 1% increase in social isolation was associated with decreased cognitive functioning (24% decrease for men, and 20% decrease for women). However, this association was not confirmed by the System GMM, after addressing endogeneity.

DISCUSSION

Our findings potentially suggest that the association between social relationship and cognitive functioning reported in previous studies was biased, due to endogeneity. Although we did not observe causal impacts, this does not necessarily mean that social isolation does not have a negative impact on health, as both positive and negative consequences of social relationships may exist. Further research is needed to reveal the causal relationship, as well as the detailed mechanisms of health effects of social relationships.

Association Between Plasma Metabolites and Psychometric Scores Among Children With Developmental Disabilities: Investigating Sex-Differences

Background: Developmental disabilities are defined by delays in learning, language, and behavior, yet growing evidence has revealed disturbances in metabolic systems that may also be present. Little is known about whether these metabolic issues contribute to the symptoms or severity of these disabilities, or whether sex plays a role in these associations, given that boys are disproportionately affected by some developmental disabilities. Here we sought to investigate the correlation between psychometric scores, sex, and the plasma metabolome. Methods: The plasma metabolomes of children with autism spectrum disorder (ASD; n = 167), idiopathic developmental delay (i-DD; n = 51), Down syndrome (DS; n = 31), and typically developing controls (TD; n = 193) were investigated using NMR spectroscopy. Spearman rank correlations and multiple linear regression models (adjusted for child's neurodevelopmental diagnosis, child's sex, child's age, child's race/ethnicity, maternal age at child's birth, and parental homeownership) were used to examine the association between plasma metabolites and sex in relation to psychometric measures of cognitive skills, adaptive behavior, and maladaptive behavior in our study population. Results: Higher levels of metabolites involved in cellular energy and mitochondrial function among children with ASD (fumarate and cis-aconitate), DS (lactate), and TD (pyruvate) are associated with poorer cognitive and adaptive subscales. Similarly, higher o-acetylcarnitine associated with deficits in cognitive subscales among all DS cases and TD boys, and carnitine correlated with increased maladaptive behavior among girls with ASD and girls with DS. Among children with DS, elevated myo-inositol, ornithine, and creatine correlated with poorer scores across several subscales. Even among TD cases, elevated 3-hydroxybutyrate correlated with decreased receptive language. In contrast, higher levels of glutamate were associated with better socialization skills among ASD cases. Even after adjusting for the child's neurodevelopmental diagnosis, sex, and other possible confounders, key metabolites including glycolysis metabolites (lactate and pyruvate), ketone bodies (3-hydroxybutyrate and acetoacetate), TCA cycle metabolites (cis-aconitate and fumarate), as well as ornithine were associated with deficits in multiple domains of cognitive function, adaptive skills, and aberrant behaviors. Conclusions: Our results highlight that some plasma metabolites may relate to specific functional subdomains within cognitive, adaptive, and behavioral development with some variation by diagnosis and sex.

Socioeconomic Disparities and Gender Inequalities in Dementia: a Community-Dwelling Population Study from a Middle-Income Country

The proportion of the world's older adults and of its dementia cases is increasing in low and middle-income countries. This is particularly true in Colombia. There, the number of individuals with dementia may increase five-fold by 2050. Yet research is lacking on dementia in such settings. This work estimates the prevalence of dementia in a community-dwelling population in Colombia. It also assesses how gender-based differences in cardiovascular conditions and socioeconomic disparities affect dementia. This work analyzes data on 2000 respondents at least 60 years of age in the Health, Well-Being, And Aging (SABE) study in Bogota. Respondents with dementia are those who have cognitive impairment and at least two limitations in instrumental activities of daily living. The SABE study finds 8.4% of respondents have dementia. Age, cardiovascular risks, and socioeconomic disparities contributed to higher odds of dementia. The contributors to dementia can differ for men and women. For example, socioeconomic disparities were a larger contributor to dementia for women than men. The findings support the cognitive reserve hypothesis on dementia. This holds that pre-existing cognitive processes and compensatory mechanisms influence dementia. Women in Latin America are more likely to suffer from socioeconomic disparities that limit their cognitive reserve. This research points to several policy implications that can help offset these disparities and reduce the prevalence of dementia.

Cognitive Impairment and Dementia in Primary Care: Current Knowledge and Future Directions Based on Findings From a Large Cross-Sectional Study in Crete, Greece

Introduction: Dementia severely affects the quality of life of patients and their caregivers; however, it is often not adequately addressed in the context of a primary care consultation, especially in patients with multi-morbidity. Study Population and Methods: A cross-sectional study was conducted between March-2013 and December-2014 among 3,140 consecutive patients aged >60 years visiting 14 primary health care practices in Crete, Greece. The Mini-Mental-State-Examination [MMSE] was used to measure cognitive status using the conventional 24-point cut-off. Participants who scored low on MMSE were matched with a group of elders scoring >24 points, according to age and education; both groups underwent comprehensive neuropsychiatric and neuropsychological assessment. For the diagnosis of dementia and Mild-Cognitive-Impairment (MCI), the Diagnostic and Statistical Manual-of-Mental-Disorders (DSM-IV) criteria and the International-Working-Group (IWG) criteria were used. Chronic conditions were categorized according to ICD-10 categories. Logistic regression was used to provide associations between chronic illnesses and cognitive impairment according to MMSE scores. Generalized Linear Model Lasso Regularization was used for feature selection in MMSE items. A two-layer artificial neural network model was used to classify participants as impaired (dementia/MCI) vs. non-impaired. Results: In the total sample of 3,140 participants (42.1% men; mean age 73.7 SD = 7.8 years), low MMSE scores were identified in 645 (20.5%) participants. Among participants with low MMSE scores 344 (54.1%) underwent comprehensive neuropsychiatric evaluation and 185 (53.8%) were diagnosed with Mild-Cognitive-Impairment (MCI) and 118 (34.3%) with dementia. Mental and behavioral disorders (F00-F99) and diseases of the nervous system (G00-G99) increased the odds of low MMSE scores in both genders. Generalized linear model lasso regularization indicated that 7/30 MMSE questions contributed the most to the classification of patients as impaired (dementia/MCI) vs. non-impaired with a combined accuracy of 82.0%. These MMSE items were questions 5, 13, 19, 20, 22, 23, and 26 of the Greek version of MMSE assessing orientation in time, repetition, calculation, registration, and visuo-constructive ability. Conclusions: Our study identified certain chronic illness-complexes that were associated with low MMSE scores within the context of primary care consultation. Also, our analysis indicated that seven MMSE items provide strong evidence for the presence of dementia or MCI.

Loss of DEK Expression Induces Alzheimer's Disease Phenotypes in Differentiated SH-SY5Y Cells

Alzheimer’s disease (AD) is the most common cause of dementia and is characterized by the buildup of β-amyloid plaques and neurofibrillary Tau tangles. This leads to decreased synaptic efficacy, cell death, and, consequently, brain atrophy in patients. Behaviorally, this manifests as memory loss and confusion. Using a gene ontology analysis, we recently identified AD and other age-related dementias as candidate diseases associated with the loss of DEK expression. DEK is a nuclear phosphoprotein with roles in DNA repair, cellular proliferation, and inhibiting apoptosis. Work from our laboratory determined that DEK is highly expressed in the brain, particularly in regions relevant to learning and memory, including the hippocampus. Moreover, we have also determined that DEK is highly expressed in neurons. Consistent with our gene ontology analysis, we recently reported that cortical DEK protein levels are inversely proportional to dementia severity scores in elderly female patients. However, the functional role of DEK in neurons is unknown. Thus, we knocked down DEK in an in vitro neuronal model, differentiated SH-SY5Y cells, hypothesizing that DEK loss would result in cellular and molecular phenotypes consistent with AD. We found that DEK loss resulted in increased neuronal death by apoptosis (i.e., cleaved caspases 3 and 8), decreased β-catenin levels, disrupted neurite development, higher levels of total and phosphorylated Tau at Ser262, and protein aggregates. We have demonstrated that DEK loss in vitro recapitulates cellular and molecular phenotypes of AD pathology.

APOEɛ4 Gene Dose and Sex Effects on Alzheimer's Disease MRI Biomarkers in Older Adults with Mild Cognitive Impairment

Background:

APOEɛ4 and sex have been linked to increased risk for conversion to Alzheimer’s disease (AD). However, the relationship between APOEɛ4 gene dose, sex, and AD biomarkers remains understudied.

Objective:

To investigate the effect of APOEɛ4 dose on AD biomarkers in a sample of older adults with mild cognitive impairment (MCI), and to examine whether APOEɛ4 dose modifies AD risk differently in MCI women and men.

Methods:

We examined cross-sectional AD biomarkers for participants with MCI (n = 930, 55–96 years old) from three large aging cohorts. Region of interest MRI volumes, global cognition, and episodic memory were analyzed by number of APOEɛ4 alleles and stratified by sex.

Results:

Across all participants, number of APOEɛ4 alleles was associated with smaller hippocampal and amygdala volumes and poorer cognition. When stratified by sex, women showed an APOEɛ4 dose effect for bilateral hippocampal and left amygdala volumes and cognition. In contrast, men showed an APOEɛ4 dose effect for hippocampal volumes with a trend in amygdala, but cognition did not differ between men with 1 and 2 APOEɛ4 alleles. Women with 2 APOEɛ4 alleles had poorer memory between 65–69 and poorer global cognition between 70–74 compared to men with 2 APOEɛ4 alleles.

Conclusion:

APOEɛ4 confers a dose effect on AD biomarkers in patients with MCI, and the number of APOEɛ4 alleles has a greater detrimental impact in women than men, which may be specific to a critical time window.

Evidence-based prevention of Alzheimer's disease: systematic review and meta-analysis of 243 observational prospective studies and 153 randomised controlled trials

BACKGROUND

Evidence on preventing Alzheimer's disease (AD) is challenging to interpret due to varying study designs with heterogeneous endpoints and credibility. We completed a systematic review and meta-analysis of current evidence with prospective designs to propose evidence-based suggestions on AD prevention.

METHODS

Electronic databases and relevant websites were searched from inception to 1 March 2019. Both observational prospective studies (OPSs) and randomised controlled trials (RCTs) were included. The multivariable-adjusted effect estimates were pooled by random-effects models, with credibility assessment according to its risk of bias, inconsistency and imprecision. Levels of evidence and classes of suggestions were summarised.

RESULTS

A total of 44 676 reports were identified, and 243 OPSs and 153 RCTs were eligible for analysis after exclusion based on pre-decided criteria, from which 104 modifiable factors and 11 interventions were included in the meta-analyses. Twenty-one suggestions are proposed based on the consolidated evidence, with Class I suggestions targeting 19 factors: 10 with Level A strong evidence (education, cognitive activity, high body mass index in latelife, hyperhomocysteinaemia, depression, stress, diabetes, head trauma, hypertension in midlife and orthostatic hypotension) and 9 with Level B weaker evidence (obesity in midlife, weight loss in late life, physical exercise, smoking, sleep, cerebrovascular disease, frailty, atrial fibrillation and vitamin C). In contrast, two interventions are not recommended: oestrogen replacement therapy (Level A2) and acetylcholinesterase inhibitors (Level B).

INTERPRETATION

Evidence-based suggestions are proposed, offering clinicians and stakeholders current guidance for the prevention of AD.

Parity and the risk of incident dementia: a COSMIC study

AIMS

To investigate the association between parity and the risk of incident dementia in women.

METHODS

We pooled baseline and follow-up data for community-dwelling women aged 60 or older from six population-based, prospective cohort studies from four European and two Asian countries. We investigated the association between parity and incident dementia using Cox proportional hazards regression models adjusted for age, educational level, hypertension, diabetes mellitus and cohort, with additional analysis by dementia subtype (Alzheimer dementia (AD) and non-Alzheimer dementia (NAD)).

RESULTS

Of 9756 women dementia-free at baseline, 7010 completed one or more follow-up assessments. The mean follow-up duration was 5.4 ± 3.1 years and dementia developed in 550 participants. The number of parities was associated with the risk of incident dementia (hazard ratio (HR) = 1.07, 95% confidence interval (CI) = 1.02-1.13). Grand multiparity (five or more parities) increased the risk of dementia by 30% compared to 1-4 parities (HR = 1.30, 95% CI = 1.02-1.67). The risk of NAD increased by 12% for every parity (HR = 1.12, 95% CI = 1.02-1.23) and by 60% for grand multiparity (HR = 1.60, 95% CI = 1.00-2.55), but the risk of AD was not significantly associated with parity.

CONCLUSIONS

Grand multiparity is a significant risk factor for dementia in women. This may have particularly important implications for women in low and middle-income countries where the fertility rate and prevalence of grand multiparity are high.

A data-driven prospective study of dementia among older adults in the United States

Background

Studies examining risk factors for dementia have typically focused on testing a priori hypotheses within specific risk factor domains, leaving unanswered the question of what risk factors across broad and diverse research fields may be most important to predicting dementia. We examined the relative importance of 65 sociodemographic, early-life, economic, health and behavioral, social, and genetic risk factors across the life course in predicting incident dementia and how these rankings may vary across racial/ethnic (non-Hispanic white and black) and gender (men and women) groups.

Methods and findings

We conducted a prospective analysis of dementia and its association with 65 risk factors in a sample of 7,908 adults aged 51 years and older from the nationally representative US-based Health and Retirement Study. We used traditional survival analysis methods (Fine and Gray models) and a data-driven approach (random survival forests for competing risks) which allowed us to account for the semi-competing risk of death with up to 14 years of follow-up. Overall, the top five predictors across all groups were lower education, loneliness, lower wealth and income, and lower self-reported health. However, we observed variation in the leading predictors of dementia across racial/ethnic and gender groups such that at most four risk factors were consistently observed in the top ten predictors across the four demographic strata (non-Hispanic white men, non-Hispanic white women, non-Hispanic black men, non-Hispanic black women).

Conclusions

We identified leading risk factors across racial/ethnic and gender groups that predict incident dementia over a 14-year period among a nationally representative sample of US aged 51 years and older. Our ranked lists may be useful for guiding future observational and quasi-experimental research that investigates understudied domains of risk and emphasizes life course economic and health conditions as well as disparities therein.

Sex Differences in Antipsychotic and Benzodiazepine Prescribing Patterns: A Cohort Study of Newly Admitted Nursing Home Residents with Dementia in Ontario, Canada

BACKGROUND

In nursing homes, residents with dementia frequently receive potentially inappropriate medications that are associated with an increased risk of adverse events. Despite known sex differences in clinical presentation and sociodemographic characteristics among persons with dementia, few studies have examined sex differences in patterns and predictors of potentially inappropriate medication use.

OBJECTIVES

The objectives of this study were to examine sex differences in the patterns of antipsychotic and benzodiazepine use in the 180 days following admission to a nursing home, estimate clinical and sociodemographic predictors of antipsychotic and benzodiazepine use in male and female residents, and explore the effects of modification by sex on the predictors of using these drug therapies.

METHODS

We conducted a retrospective cohort study of 35,169 adults aged 66 years and older with dementia who were newly admitted to nursing homes in Ontario, Canada between 2011 and 2014. Health administrative databases were linked to detailed clinical assessment data collected using the Resident Assessment Instrument (RAI-MDS 2.0). Cox proportional hazards models were adjusted for clinical and sociodemographic covariates to estimate the rate of antipsychotic and benzodiazepine initiation and discontinuation in the 180 days following nursing home admission in the total sample and stratified by sex. Sex-covariate interaction terms were used to assess whether sex modified the association between covariates and the rate of drug therapy initiation or discontinuation following nursing home entry.

RESULTS

Across 638 nursing homes, our analytical sample included 22,847 females and 12,322 males. At admission, male residents were more likely to be prevalent antipsychotic users than female residents (33.8% vs 28.3%; p < 0.001), and female residents were more likely to be prevalent benzodiazepine users than male residents (17.2% vs 15.3%, p < 0.001). In adjusted models, female residents were less likely to initiate an antipsychotic after admission (hazard ratio [HR] 0.79, 95% confidence interval [CI] 0.73-0.86); however, no sex difference was observed in the rate of benzodiazepine initiation (HR 1.04, 95% CI 0.96-1.12). Female residents were less likely than males to discontinue antipsychotics (HR 0.89, 95% CI 0.81-0.98) and benzodiazepines (HR 0.82, 95% CI 0.75-0.89). Sex modified the association between some covariates and the rate of changes in drug use (e.g., widowed males exhibited an increased rate of antipsychotic discontinuation (p-interaction = 0.03) compared with married males), but these associations were not statistically significant among females. Sex did not modify the effect of frailty on the rates of initiation and discontinuation.

CONCLUSIONS

Males and females with dementia differed in their exposure to antipsychotics and benzodiazepines at nursing home admission and their patterns of use following admission. A greater understanding of factors driving sex differences in potentially inappropriate medication use may help tailor interventions to reduce exposure in this vulnerable population.

Sex differences in dementia: on the potentially mediating effects of educational attainment and experiences of psychological distress

BACKGROUND

Old-age dementias are known to disproportionally affect women as well as individuals with low educational attainment. The higher lifetime risk of dementia among women is usually attributed to their longer life expectancy. However, the impact of sex, and subsequent gender inequity, is likely to be more multifaceted than this explanation implies. Not least because of historical inequities in access to education between the sexes and the gender and socio-economic gradients in risk factors such as stress, depression and social isolation. Consequently, the present study sought to test whether differences in educational attainment and experiences of general psychological distress mediate the association between female sex and dementia.

METHODS

The study utilizes data obtained through the Gothenburg H70 Birth Cohort Study and the Prospective Populations Study on Women (n = 892). Data were analysed using Confirmatory Factor Analysis (CFA) and Structural Equation Modelling (SEM) with Weighted Least Squares Means and Variance adjusted (WLSMV) estimation. General psychological distress was indicated by a latent variable and constructed from five manifest items (previous depression, stress, self-esteem, chronic loneliness and satisfaction with social situation) that were all measured at baseline.

RESULTS

While the results could not corroborate that education directly mediates the effect of sex on dementia, level of distress was predicted by both female sex (0.607, p < .001) and education (- 0.166, p < .01) and, in turn, shown to be significantly associated with dementia (0.167, p < .05), also after controlling for confounders. When time from baseline to diagnosis was increased through sequential exclusion of dementia cases, the effect of distress on dementia was no longer significant.

CONCLUSION

The overall findings suggest that social (dis) advantage predicts general psychological distress, which thereby constitutes a potential, and rarely acknowledged, pathway between female sex, education, and dementia. They further underline the importance of attending to both education and distress as 'gendered' phenomena when considering the nature of their associations with dementia. However, the possibility of reverse causality bias must be acknowledged and the need for longitudinal studies with longer follow-up stressed.

Acute phase markers in CSF reveal inflammatory changes in Alzheimer's disease that intersect with pathology, APOE ε4, sex and age

It is unknown how neuroinflammation may feature in the etiology of Alzheimer's disease (AD). We profiled acute phase response (APR) proteins (α1-antitrypsin, α1-antichymotrypsin, ceruloplasmin, complement C3, ferritin, α-fibrinogen, β-fibrinogen, γ-fibrinogen, haptoglobin, hemopexin) in CSF of 1291 subjects along the clinical and biomarker spectrum of AD to investigate the association between inflammatory changes, disease outcomes, and demographic variables. Subjects were stratified by Aβ₄₂/t-tau as well as the following clinical diagnoses: cognitively normal (CN); subjective cognitive decline (SCD); mild cognitive impairment (MCI); and AD dementia. In separate multiple regressions (adjusting for diagnosis, age, sex, APOE-ε4) of each APR protein and a composite of all APR proteins, CSF Aβ₄₂/t-tau status was associated with elevated ferritin, but not any other APR protein in CN and SCD subjects. Rather, the APR was elevated along with symptomatic progression (CN < SCD < MCI < AD), and this was elevation was mediated by CSF p-tau181. APOE ε4 status did not affect levels of any APR proteins in CSF, while these were elevated in males and with increased age. The performance of the APR in predicting clinical diagnosis was influenced by APOE ε4 status, sex, and age. These data provide new insight into inflammatory changes in AD and how this intersects with pathology changes and patient demographics.

Association of sex and APOE ε4 with brain tau deposition and atrophy in older adults with Alzheimer's disease

The objective of this study was to assess the association of sex and the apolipoprotein E (APOE) ε4 allele with brain tau deposition and atrophy in older adults with Alzheimer's disease (AD) using quantitative 18F-AV-1451 positron emission tomography (PET) and magnetic resonance imaging (MRI). Methods: Preprocessed 18F-AV-1451 tau PET, raw T1-weighted structural MR images, demographic information, cerebrospinal fluid (CSF) total tau (t-tau) and phosphorylated tau (p-tau) measurements from 57 elderly individuals with AD were downloaded from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database. An iteratively reblurred Van Cittert partial volume correction (PVC) method was applied to all preprocessed PET images. MRI images were used for PET spatial normalization and gray matter volume calculation. 18F-AV-1451 PET standardized uptake value ratio (SUVR) was calculated relative to the cerebellum gray matter. The effect of sex and APOE ε4 status on SUVR and gray matter volume were assessed at both region of interest (ROI) and voxelwise levels. Results: Female APOE ε4 carriers (FACs) had significant higher 18F-AV-1451 SUVRs in the lateral temporal, parietal, posterior cingulate, medial temporal, inferior temporal, entorhinal cortex, amygdala and parahippocampal gyrus regions, and exhibited smaller gray matter volumes in the posterior cingulate, medial temporal, inferior temporal and amygdala regions, as compared to the non-FACs (NFACs) comprised of female APOE ε4 non-carriers, male APOE ε4 carriers and male APOE ε4 non-carriers. Voxelwise analysis revealed forebrain and limbic clusters with greater 18F-AV-1451 SUVRs and lower gray matter volume between FACs compared to the NFACs. Negative correlations between ROI 18F-AV-1451 SUVRs and gray matter volumes were significant after adjusting for age and years of education. Conclusions: Among elderly individuals with AD, sex modified the effects of the APOE ε4 allele on region-specific tau deposition and gray matter volume. FACs had elevated brain region-specific tau PET SUVR and decreased gray matter volume in comparison to NFACs. The study provides a basis for the use of precision medicine in the diagnosis of AD and evaluation of therapeutics using 18F-AV-1451 PET and structural MRI.

Gender Dysphoria: A Review Investigating the Relationship Between Genetic Influences and Brain Development

Gender dysphoria (GD) is a facet of modern human biology which is believed to be derived from the sexual differentiation of the brain. GD “involves a conflict between a person’s physical or assigned gender and the gender with which he/she/they identify”, as defined in the DSM-5. Individuals report feeling uncomfortable and faced with prejudice from those around them, affecting their mental health. Elucidating the relationship between genetic influences on gonadal and brain development could give an insight into understanding this clinical condition. To explore this issue, a review of the literature database was carried out. Evidence suggests that abnormal biological processes, including mutations in certain genes, can lead to abnormal gonadal development, causing some fetuses to present with indifferent gonads and to be reassigned at birth to the default female sex. This disparity in genetic influences relates to an increased likelihood of a diagnosis of GD. An investigation into complete androgen insensitivity syndrome, involving androgen receptor (AR) gene mutation, suggests that such individuals also experience GD. It is known that the brains of males and females are different. Evidence further suggests that brain anatomy and neuronal signaling pathways are more closely aligned with a person’s perceived gender identity. Individuals who present with discordant gonadal and brain developments experience psychological challenges that may contribute to a state of unease or generalized dissatisfaction with their biological sex. These point to a possible biological and genetic underpinning of GD as stemming from a discordance between gonadal and brain development. However, not enough evidence has associated these differences with GD. Further research is required to elucidate the true mechanisms and possible inheritance pattern of GD for a better education and greater understanding by clinicians and the general public on perceptions regarding GD.

CHI3L2 Expression Levels Are Correlated with AIF1, PECAM1, and CALB1 in the Brains of Alzheimer's Disease Patients

Alzheimer's disease (AD) represents one of the main forms of dementia that afflicts our society. The expression of several genes has been associated with disease development. Despite this, the number of genes known to be capable of discriminating between AD patients according to sex remains deficient. In our study, we performed a transcriptomes meta-analysis on a large court of brains of healthy control subjects (n = 2139) (NDHC) and brains of AD patients (n = 1170). Our aim was to verify the brain expression levels of CHI3L2 and its correlation with genes associated with microglia-mediated neuroinflammation (IBA1), alteration of the blood-brain barrier (PECAM1), and neuronal damage (CALB1). We showed that the CHI3L2, IBA1, PECAM1, and CALB1 expression levels were modulated in the brains of patients with AD compared to NDHC subjects. Furthermore, both in NDHC and in AD patient's brains, the CHI3L2 expression levels were directly correlated with IBA1 and PECAM1 and inversely with CALB1. Additionally, the expression levels of CHI3L2, PECAM1, and CALB1 but not of IBA1 were sex-depended. By stratifying the samples according to age and sex, correlation differences emerged between the expression levels of CHI3L2, IBA1, PECAM1, and CALB1 and the age of NDHC subjects and AD patients. CHI3L2 represents a promising gene potentially involved in the key processes underlying Alzheimer's disease. Its expression in the brains of sex-conditioned AD patients opens up new possible sex therapeutic strategies aimed at controlling imbalance in disease progression.

Natriuretic Peptides, Cognitive Impairment and Dementia: An Intriguing Pathogenic Link with Implications in Hypertension

The natriuretic peptides (NPs) belong to a family of cardiac hormones that exert relevant protective functions within the cardiovascular system. An increase of both brain and atrial natriuretic peptide levels, particularly of the amino-terminal peptides (NT-proBNP and NT-proANP), represents a marker of cardiovascular damage. A link between increased NP levels and cognitive decline and dementia has been reported in several human studies performed both in general populations and in cohorts of patients affected by cardiovascular diseases (CVDs). In particular, it was reported that the elevation of NP levels in dementia can be both dependent and independent from CVD risk factors. In the first case, it may be expected that, by counteracting early on the cardiovascular risk factor load and the pathological processes leading to increased aminoterminal natriuretic peptide (NT-proNP) level, the risk of dementia could be significantly reduced. In case of a link independent from CVD risk factors, an increased NP level should be considered as a direct marker of neuronal damage. In the context of hypertension, elevated NT-proBNP and mid-regional (MR)-proANP levels behave as markers of brain microcirculatory damage and dysfunction. The available evidence suggests that they could help in identifying those subjects who would benefit most from a timely antihypertensive therapy.

Towards an understanding of women's brain aging: the immunology of pregnancy and menopause

Women are at significantly greater risk of developing Alzheimer's disease and show higher prevalence of autoimmune conditions relative to men. Women's brain health is historically understudied, and little is therefore known about the mechanisms underlying epidemiological sex differences in neurodegenerative diseases, and how female-specific factors may influence women's brain health across the lifespan. In this review, we summarize recent studies on the immunology of pregnancy and menopause, emphasizing that these major immunoendocrine transition phases may play a critical part in women's brain aging trajectories.

Sex-dependent autosomal effects on clinical progression of Alzheimer's disease

Sex differences in the manifestations of Alzheimer's disease are under intense investigation. Despite the emerging importance of polygenic predictions for Alzheimer's disease, sex-dependent polygenic effects have not been demonstrated. Here, using a sex crossover analysis, we show that sex-dependent autosomal genetic effects on Alzheimer's disease can be revealed by characterizing disease progress via the hazard function. We first performed sex-stratified genome-wide associations, and then applied derived sex-dependent weights to two independent cohorts. Relative to sex-mismatched scores, sex-matched polygenic hazard scores showed significantly stronger associations with age-at-disease-onset, clinical progression, amyloid deposition, neurofibrillary tangles, and composite neuropathological scores, independent of apolipoprotein E. Models without using hazard weights, i.e. polygenic risk scores, showed lower predictive power than polygenic hazard scores with no evidence for sex differences. Our results indicate that revealing sex-dependent genetic architecture requires the consideration of temporal processes of Alzheimer's disease. This has strong implications not only for the genetic underpinning of Alzheimer's disease but also for how we estimate sex-dependent polygenic effects for clinical use.

Tempe, Tofu, and Amyloid-β 1-40 Serum Levels in Ovariectomized Rats

BACKGROUND

Estrogens have been found to reduce amyloid-β (Aβ) levels, a risk factor associated with dementia. We hypothesized that phytoestrogenic soybean products such as tempe and tofu might show similar effects.

OBJECTIVE

The aim of this study were to analyze the effect of tempe and tofu flour on Aβ1-40 serum levels in ovariectomized rats.

METHODS

This research was conducted on female Sprague Dawley rats, aged 12 months. Before the intervention rats underwent ovariectomy (OVx) and were grouped into 5 intervention groups which were given tempe flour, tofu flour, estradiol, or casein as an active control. There was also a non-OVx control group which was fed a normal diet.

RESULTS

The intake of tempe and tofu flour decreased Aβ serum levels in all estrogen and phytoestrogenic treatment groups, offsetting effects of OVx (but not in the casein group, where Aβ levels rise).

CONCLUSION

The tempe flour group showed the strongest decrease in serum Aβ levels compared to the other groups. Future studies should investigate whether tempe can reduce Aβ levels in patients with dementia.