Sex differences in cognitive impairment and Alzheimer's disease

Factors associated with cognitive impairment in patients with atrial fibrillation: A systematic review and meta-analysis

BACKGROUND

Atrial fibrillation (AF) is associated with an increased risk of cognitive impairment. Therefore, exploring factors which may be associated with cognitive impairment is important. Correspondingly, this study aimed to systematically evaluate factors associated with cognitive impairment in AF patients by synthesizing relevant evidence.

METHODS

A database search of the PubMed, Embase, Cochrane Library, Web of Science, CBM, CNKI, Wanfang, and VIP databases was conducted from inception until December 21, 2023. The effect size was expressed as a combined odds ratio (OR) and 95 % confidence interval (95 % CI). The heterogeneity was qualitatively analyzed by Cochran's Q test and quantified by the I2 statistic.

RESULTS

A total of 7,128 studies were identified from the 8 databases, and 39 studies of 3,491,423 participants were included. A meta-analysis was performed on 19 influencing factors. Advanced age (OR=1.38, 95 % CI: 1.11-1.71), female sex (OR=2.19, 95 % CI: 1.18-4.06), smoking (OR=2.44, 95 % CI: 1.24-4.80), hypertension (OR=1.61, 95 % CI: 1.27-2.03), diabetes (OR=1.42, 95 % CI: 1.20-1.67), and hearing impairment (OR=1.37, 95 % CI: 1.05-1.81) were risk factors for cognitive impairment. A higher education level (OR=0.57, 95 % CI: 0.46-0.72), oral anticoagulants (OR=0.61, 95 % CI: 0.48-0.78), novel oral anticoagulants (OR=0.63, 95 % CI: 0.54-0.73), warfarin (OR=0.55, 95 % CI: 0.39-0.79), novel oral anticoagulants relative to warfarin (OR=0.88, 95 % CI: 0.81-0.97), catheter ablation (OR=0.74, 95 % CI: 0.58-0.94) and exercise (OR=0.66, 95 % CI: 0.61-0.72) were protective factors for cognitive impairment.

CONCLUSIONS

Age, sex, education level, smoking, exercise, hypertension, diabetes, hearing impairment, anticoagulation therapy, and catheter ablation were associated with cognitive impairment in AF patients.

Effect of heatwaves on mortality of Alzheimer's disease and other dementias among elderly aged 60 years and above in China, 2013-2020: a population-based study

Background

China has the largest number of dementia patients in the world, posing a significant health and economic burden. Alzheimer's disease (AD) and other dementia patients face a higher risk of mortality during heatwaves, but relevant studies on this topic have been limited so far.

Methods

The study extracted data from the China Cause of Death Reporting System (CDRS) on deaths of AD and other dementia patients aged 60 years and above between 2013 and 2020. Using an individual-level, time-stratified, and case-crossover study design, the effects of heatwaves across nine scenarios on dementia mortality were quantified by conditional logistic regression combined with distributed lag non-linear model (DLNM). Additionally, the attributable fractions (AFs) of deaths due to heatwaves were calculated.

Findings

A total of 399,036 death cases were reported caused by AD and other dementias during the study period. It was found that heatwaves significantly increased the risk of death among people with AD and other dementias. As the intensities and durations of the heatwaves increased, the lag0-7 cumulative odds ratios (CORs) of mortality increased progressively from 1.140 (95% CI: 1.118, 1.163) under the mildest heatwave to 1.459 (95% CI: 1.403, 1.518) under the most severe one, across nine heatwave scenarios examined. Additionally, under specific heatwave scenarios, sex and regions modified the mortality risk, but no significant age differences were observed. The AFs of AD and other dementia mortality due to milder heatwaves were lower compared to more severe heatwaves, ranging from 12.281% (95% CI: 10.555%, 14.015%) to 31.460% (95% CI: 28.724%, 34.124%).

Interpretation

The study provided critical insights into the substantial increase in heatwave-related mortality among AD and other dementia patients during and after heatwave events. The results from our quantitative analyses will provide needed scientific evidence for policymakers and practitioners to develop relevant policies and guidelines to protect the health and well-beings of vulnerable populations in future in the context of both seasonal changes and long-term climate change.

Funding

This work was supported by the Project of Prevention and Intervention on Major Diseases for Elderly in China, NCNCD [00240201307], the National Key Research and Development Program of China [2022YFC2602301, 2023YFC2308703] and the Science and Technology Fundamental Resources Investigation Program of China [2017FY101201].

Lifespan of male and female APP/PS1 and APP NL-F/NL-F mouse models of Alzheimer's disease

Alzheimer's disease (AD) disproportionately affects women, yet most preclinical research studies are male-centric. We performed lifespan analyses of male and female AD mouse models (APP/PS1 and APP NL-F/NL-F ) and their shared genetic background control (C57BL/6). Survival curves support significant sex differences between within genotypes. Minimal longevity revealed increased age in male APP/PS1, and decreased age in APP NL-F/NL-F mice. Maximal longevity revealed an increased average age in males. Furthermore, median lifespan differed between sex and genotype. This study supports sexual dimorphic survival in two mouse models of AD, emphasizing the need to examine mechanisms and treatments in both sexes.

Five-year changes in retinal nerve fibre layer thickness in the adult population: a population-based cohort study

CLINICAL RELEVANCE

Distinguishing between the pathological thinning of the retinal nerve fibre layer (RNFL) and age-related reduction requires a comprehensive understanding of the longitudinal changes in RNFL thickness within a healthy population.

BACKGROUND

To determine five-year changes in RNFL thickness and associated factors in people aged 45-69 years.

METHODS

This report pertains to the second and third phases of the Shahroud Eye Cohort Study. Participants were recruited by a multi-stage cluster sampling in Shahroud, Iran. Data on demographic details, visual acuity, non-cycloplegic refraction, and slit-lamp biomicroscopy were collected. High-definition optical coherence tomography was employed for retinal imaging.

RESULTS

A total of 1,524 eyes from 908 participants were examined. The average RNFL thickness was 92.2 ± 8.5 (95% CI: 91.6 to 92.8) and 93.1 ± 8.7 μm (95% CI: 92.5 to 93.7) in the first and second phases with a five-year mean change of 0.95 ± 4.15 μm (95% CI: 0.70 to 1.20). The RNFL thickness mean changes in the superior, inferior, nasal, and temporal quadrants were 2.51 ± 7.86 (95% CI: 2.01 to 3.02), 2.93 ± 7.39 (95% CI: 2.56 to 3.29), -0.53 ± 6.15 (95% CI: -0.84 to -0.21), and -1.01 ± 4.67 μm (95% CI: -1.27 to -0.75), respectively. The five-year changes in average RNFL thickness were inversely correlated with axial length (β = -0.69, p < 0.001), mean keratometry (β = -0.37, p = 0.017), and baseline RNFL thickness (β = -0.617, p < 0.001). In hyperopic individuals, the increase in average RNFL thickness (β = 0.65, p = 0.012) was significantly greater than in those with emmetropia. Macular volume (β = 1.65, p < 0.001) showed a direct association with five-year changes in average RNFL thickness.

CONCLUSION

Over 5 years, RNFL thickness changes were clinically insignificant in the normal population. The mean RNFL thickness seems to remain stable unless there is ocular disease. However, increased axial length and steeper keratometric readings were linked to RNFL thinning. Those with thicker RNFL measurements were at higher risk of thinning over time.

Investigating the Impact of Intracerebroventricular Streptozotocin on Female Rats with and without Ovaries: Implications for Alzheimer's Disease

To contribute to research on female models of Alzheimer's disease (AD), our aim was to study the effect of intracerebroventricular (ICV) injection of streptozotocin (STZ) in female rats, and to evaluate a potential neuroprotective action of ovarian steroids against STZ. Female rats were either ovariectomized (OVX) or kept with ovaries (Sham) two weeks before ICV injections. Animals were injected with either vehicle (artificial cerebrospinal fluid, aCSF) or STZ (3 mg/kg) and separated into four experimental groups: Sham + aCSF, Sham + STZ, OVX + aCSF and OVX + STZ. Nineteen days post-injection, we assessed different behavioral aspects: burying, anxiety and exploration, object recognition memory, spatial memory, and depressive-like behavior. Immunohistochemistry and Immunoblot analyses were performed in the hippocampus to examine changes in AD-related proteins and neuronal and microglial populations. STZ affected burying and exploratory behavior depending on ovarian status, and impaired recognition but not spatial memory. STZ and ovariectomy increased depressive-like behavior. Interestingly, STZ did not alter the expression of β-amyloid peptide or Tau phosphorylated forms. STZ affected the neuronal population from the Dentate Gyrus, where immature neurons were more vulnerable to STZ in OVX rats. Regarding microglia, STZ increased reactive cells, and the OVX + STZ group showed an increase in the total cell number. In sum, STZ partially affected female rats, compared to what was previously reported for males. Although AD is more frequent in women, reports about the effect of ICV-STZ in female rats are scarce. Our work highlights the need to deepen into the effects of STZ in the female brain and study possible sex differences.

iPLA2β loss leads to age-related cognitive decline and neuroinflammation by disrupting neuronal mitophagy

BACKGROUND

During brain aging, disturbances in neuronal phospholipid metabolism result in impaired cognitive function and dysregulation of neurological processes. Mutations in iPLA2β are associated with neurodegenerative conditions that significantly impact brain phospholipids. iPLA2β deficiency exacerbates mitochondrial dysfunction and abnormal mitochondrial accumulation. We hypothesized that iPLA2β contributes to age-related cognitive decline by disrupting neuronal mitophagy.

METHODOLOGY

We used aged wild-type (WT) mice and iPLA2β-/- mice as natural aging models to assess cognitive performance, iPLA2β expression in the cortex, levels of chemokines and inflammatory cytokines, and mitochondrial dysfunction, with a specific focus on mitophagy and the mitochondrial phospholipid profile. To further elucidate the role of iPLA2β, we employed adeno-associated virus (AAV)-mediated iPLA2β overexpression in aged mice and re-evaluated these parameters.

RESULTS

Our findings revealed a significant reduction in iPLA2β levels in the prefrontal cortex of aged brains. Notably, iPLA2β-deficient mice exhibited impaired learning and memory. Loss of iPLA2β in the PFC of aged mice led to increased levels of chemokines and inflammatory cytokines. This damage was associated with altered mitochondrial morphology, reduced ATP levels due to dysregulation of the parkin-independent mitophagy pathway, and changes in the mitochondrial phospholipid profile. AAV-mediated overexpression of iPLA2β alleviated age-related parkin-independent mitophagy pathway dysregulation in primary neurons and the PFC of aged mice, reduced inflammation, and improved cognitive function.

CONCLUSIONS

Our study suggests that age-related iPLA2β loss in the PFC leads to cognitive decline through the disruption of mitophagy. These findings highlight the potential of targeting iPLA2β to ameliorate age-related neurocognitive disorders.

Sex-based differences in neuropsychiatric symptoms are due to estradiol/ERα-dependent transcriptional regulation via the modulation of steroid levels by sirolimus

The sex of the patient often affects the prevalence, progression, and severity of many psychiatric disorders. The incidence, progression, and severity of Parkinson's disease and Alzheimer's disease, the most common neurodegenerative diseases, also differ between the sexes. Sex differences in autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), and anxiety are also observed in tuberous sclerosis complex (TSC). Neuropsychiatric symptoms are one of the most important manifestations of TSC, and the multiple neuropsychiatric symptoms are collectively referred to as TSC-associated neuropsychiatric disorders (TAND). We created TSC model mice (Tsc2 conditional knockout [cKO] mice) that developed epilepsy and TAND. Sex-based differences were observed for hyperactivity and cognitive dysfunctions in Tsc2 cKO mice with TAND, indicating more severe symptoms in female mice than in male mice. TSC is thought to be caused by the hyperactivation of mechanistic target of rapamycin complex 1 (mTORC1), and mTORC1 inhibitors improve almost all TSC symptoms. Treatment with sirolimus, an mTORC1 inhibitor, improved TAND in Tsc2 cKO mice. We aimed to elucidate the mechanism underlying sex-based differences in TAND using Tsc2 cKO mice and sirolimus. We found that estradiol (E2) and estrogen receptor (ER)α are involved in sex differences in neuropsychiatric symptoms, and discovered a novel function of sirolimus. We showed that sirolimus ameliorated TAND by modulating brain steroid levels and regulating E2/ERα-dependent transcriptional activation. This indicates sirolimus may be beneficial for the treatment of TAND as well as diseases caused by sex-based differences and steroid levels.

Chronic maternal exposure to low-dose PM2.5 impacts cognitive outcomes in a sex-dependent manner

There is no safe level of air pollution for human health. Traffic-related particulate matter (PM2.5) is a major in-utero toxin, mechanisms of action of which are not fully understood. BALB/c dams were exposed to an Australian level of traffic PM2.5 (5 µg/mouse/day, intranasal, 6 weeks before mating, during gestation and lactation). Male offspring had reduced memory in adulthood, whereas memory was normal in female littermates, similar to human responses. Maternal PM2.5 exposure resulted in oxidative stress and abnormal mitochondria in male, but not female, brains. RNA-sequencing analysis showed unique sex-related changes in newborn brains. Two X-chromosome-linked histone lysine demethylases, Kdm6a and Kdm5c, demonstrated higher expression in female compared to male littermates, in addition to upregulated genes with known functions to support mitochondrial function, synapse growth and maturation, cognitive function, and neuroprotection. No significant changes in Kdm6a and Kdm5c were found in male littermates, nor other genes, albeit significantly impaired memory function after birth. In primary foetal cortical neurons, PM2.5 exposure suppressed neuron and synaptic numbers and induced oxidative stress, which was prevented by upregulation of Kdm6a or Kdm5c. Therefore, timely epigenetic adaptation by histone demethylation to open DNA for translation before birth may be the key to protecting females against prenatal PM2.5 exposure-induced neurological disorders, which fail to occur in males associated with their poor cognitive outcomes.

An integrated approach to identifying sex-specific genes, transcription factors, and pathways relevant to Alzheimer's disease

BACKGROUND

Age represents a significant risk factor for the development of Alzheimer's disease (AD); however, recent research has documented an influencing role of sex in several features of AD. Understanding the impact of sex on specific molecular mechanisms associated with AD remains a critical challenge to creating tailored therapeutic interventions.

METHODS

The exploration of the sex-based differential impact on disease (SDID) in AD used a systematic review to first select transcriptomic studies of AD with data regarding sex in the period covering 2002 to 2021 with a focus on the primary brain regions affected by AD - the cortex (CT) and the hippocampus (HP). A differential expression analysis for each study and two tissue-specific meta-analyses were then performed. Focusing on the CT due to the presence of significant SDID-related alterations, a comprehensive functional characterization was conducted: protein-protein network interaction and over-representation analyses to explore biological processes and pathways and a VIPER analysis to estimate transcription factor activity.

RESULTS

We selected 8 CT and 5 HP studies from the Gene Expression Omnibus (GEO) repository for tissue-specific meta-analyses. We detected 389 significantly altered genes in the SDID comparison in the CT. Generally, female AD patients displayed more affected genes than males; we grouped said genes into six subsets according to their expression profile in female and male AD patients. Only subset I (repressed genes in female AD patients) displayed significant results during functional profiling. Female AD patients demonstrated more significant impairments in biological processes related to the regulation and organization of synapsis and pathways linked to neurotransmitters (glutamate and GABA) and protein folding, Aβ aggregation, and accumulation compared to male AD patients. These findings could partly explain why we observe more pronounced cognitive decline in female AD patients. Finally, we detected 23 transcription factors with different activation patterns according to sex, with some associated with AD for the first time. All results generated during this study are readily available through an open web resource Metafun-AD (https://bioinfo.cipf.es/metafun-ad/).

CONCLUSION

Our meta-analyses indicate the existence of differences in AD-related mechanisms in female and male patients. These sex-based differences will represent the basis for new hypotheses and could significantly impact precision medicine and improve diagnosis and clinical outcomes in AD patients.

IGF1R and FLT1 in female endothelial cells and CHD2 in male microglia play important roles in Alzheimer's disease based on gender difference analysis

OBJECTIVE

This study investigated sex-specific pathogenesis mechanisms in Alzheimer's disease (AD) using single-nucleus RNA sequencing (snRNA-seq) data.

METHODS

Data from the Gene Expression Omnibus (GEO) were searched using terms "Alzheimer's Disease", "single cell", and "Homo sapiens". Studies excluding APOE E4 and including comprehensive gender information with 10× sequencing methods were selected, resulting in GSE157827 and GSE174367 datasets from human prefrontal cortex samples. Sex-stratified analyses were conducted on these datasets, and the outcomes of the analysis for GSE157827 were compared with those of GSE174367. The findings were validated using expression profiling from the mouse dataset GSE85162. Furthermore, real-time PCR experiments in mice further confirmed these findings. The Seurat R package was used to identify cell types, and batch effects were mitigated using the Harmony R package. Cell proportions by sex were compared using the Mann-Whitney-Wilcoxon test, and gene expression variability was displayed with an empirical cumulative distribution plot. Differentially expressed genes were identified using the FindMarkers function with the MAST test. Transcription factors were analyzed using the RcisTarget R package.

RESULTS

Seven cell types were identified: astrocytes, endothelial cells, excitatory neurons, inhibitory neurons, microglia, oligodendrocytes, and oligodendrocyte progenitor cells. Additionally, five distinct subpopulations of both endothelial and microglial cells were also identified, respectively. Key findings included: (1) In endothelial cells, genes involved in synapse organization, such as Insulin Like Growth Factor 1 Receptor (IGF1R) and Fms Related Receptor Tyrosine Kinase 1(FLT1), showed higher expression in females with AD. (2) In microglial cells, genes in the ribosome pathway exhibited higher expression in males without AD compared to females (with or without AD) and males with AD. (3) Chromodomain Helicase DNA Binding Protein 2 (CHD2) negatively regulated gene expression in the ribosome pathway in male microglia, suppressing AD, this finding was further validated in mice. (4) Differences between Asians and Caucasians were observed based on sex and disease status stratification.

CONCLUSIONS

IGF1R and FLT1 in endothelial cells contribute to AD in females, while CHD2 negatively regulates ribosome pathway gene expression in male microglia, suppressing AD in humans and mice.

Age and Gender Differences in the Relationship Between Chronic Pain and Dementia Among Older Australians

OBJECTIVES

Chronic pain is a highly debilitating condition that affects older adults and has the potential to increase their odds of experiencing cognitive impairment. The primary objective of this study was to examine the correlation between chronic pain and dementia. Additionally, this research endeavors to ascertain whether the association between chronic pain and dementia differs by age and gender.

METHODS

Cross-sectional data were derived from the Survey of Disability, Ageing, and Carers. A total of 20 671 and 20 081 participants aged 65 years and older in 2015 and 2018, respectively, were included in this study. The pooled association between chronic pain and dementia was assessed using a multivariable logistic regression model. Furthermore, the study also examined the multiplicative interaction effects between chronic pain and age, as well as chronic pain and gender, with dementia.

RESULTS

The pooled analysis demonstrated that chronic pain was associated with a heightened odds of dementia (adjusted odds ratio 1.95; 95% CI 1.85-2.05) among older Australians compared with their counterparts without chronic pain. The interaction effect indicated that individuals with chronic pain across all age groups exhibited increased odds of living with dementia. Additionally, women with chronic pain had higher odds of dementia compared with their counterparts without chronic pain and being male.

CONCLUSIONS

A continuous, coordinated, and tailored healthcare strategy is necessary to determine the pain management goals and explore early treatment options for chronic pain in older adults, particularly in groups with the greatest need.

Sex and Gender Differences in Alzheimer's Disease: Genetic, Hormonal, and Inflammation Impacts

Two-thirds of Americans with Alzheimer's disease are women, indicating a profound variance between the sexes. Variances exist between the sexes in the age and intensity of the presentation, cognitive deficits, neuroinflammatory factors, structural and functional brain changes, as well as psychosocial and cultural circumstances. Herein, we summarize the existing evidence for sexual dimorphism and present the available evidence for these distinctions. Understanding these complexities is critical to developing personalized interventions for the prevention, care, and treatment of Alzheimer's disease.

Integrative Multi-omics Analysis to Characterize Herpes Virus Infection Increases the Risk of Alzheimer's Disease

Evidence suggests that herpes virus infection is associated with an increased risk of Alzheimer's disease (AD), and innate and adaptive immunity plays an important role in the association. Although there have been many studies, the mechanism of the association is still unclear. This study aims to reveal the underlying molecular and immune regulatory network through multi-omics data and provide support for the study of the mechanism of infection and AD in the future. Here, we found that the herpes virus infection significantly increased the risk of AD. Genes associated with the occurrence and development of AD and genetically regulated by herpes virus infection are mainly enrichment in immune-related pathways. The 22 key regulatory genes identified by machine learning are mainly immune genes. They are also significantly related to the infiltration changes of 3 immune cell in AD. Furthermore, many of these genes have previously been reported to be linked, or potentially linked, to the pathological mechanisms of both herpes virus infection and AD. In conclusion, this study contributes to the study of the mechanisms related to herpes virus infection and AD, and indicates that the regulation of innate and adaptive immunity may be an effective strategy for preventing and treating herpes virus infection and AD. Additionally, the identified key regulatory genes, whether previously studied or newly discovered, may serve as valuable targets for prevention and treatment strategies.

Fatty acid sensing in the brain: The role of glial-neuronal metabolic crosstalk and horizontal lipid flux

The central control of energy homeostasis is a regulatory axis that involves the sensing of nutrients, signaling molecules, adipokines, and neuropeptides by neurons in the metabolic centers of the hypothalamus. However, non-neuronal glial cells are also abundant in the hypothalamus and recent findings have underscored the importance of the metabolic crosstalk and horizontal lipid flux between glia and neurons to the downstream regulation of systemic metabolism. New transgenic models and high-resolution analyses of glial phenotype and function have revealed that glia sit at the nexus between lipid metabolism and neural function, and may markedly impact the brain's response to dietary lipids or the supply of brain-derived lipids. Glia comprise the main cellular compartment involved in lipid synthesis, lipoprotein production, and lipid processing in the brain. In brief, tanycytes provide an interface between peripheral lipids and neurons, astrocytes produce lipoproteins that transport lipids to neurons and other glia, oligodendrocytes use brain-derived and dietary lipids to myelinate axons and influence neuronal function, while microglia can remove unwanted lipids in the brain and contribute to lipid re-utilization through cholesterol efflux. Here, we review recent findings regarding glial-lipid transport and highlight the specific molecular factors necessary for lipid processing in the brain, and how dysregulation of glial-neuronal metabolic crosstalk contributes to imbalanced energy homeostasis. Furthering our understanding of glial lipid metabolism will guide the design of future studies that target horizontal lipid processing in the brain to ameliorate the risk of developing obesity and metabolic disease.

Change in cognitive performance during seven-year follow-up in midlife is associated with sex, age, and education - The Cardiovascular Risk in Young Finns Study

OBJECTIVE

Sex, age, and education are associated with the level of cognitive performance. We investigated whether these factors modulate the change in cognitive performance in midlife by leveraging the longitudinal data from the Cardiovascular Risk in Young Finns Study (YFS).

METHODS

Participants of the YFS cohort performed a computer-based Cambridge Neuropsychological Test Automated Battery (CANTAB) in 2011 and 2018 (n = 1671, age 41-56 years in 2018). Overall cognitive performance and domains representing learning and memory, working memory, reaction time, and information processing were extracted by common principal component analysis from the longitudinal cognitive data. Linear models adjusted for baseline cognitive performance were used to study the association of sex, age, and education with changes in overall cognitive performance and in the cognitive domains.

RESULTS

Cognitive performance decreased in all domains (overall cognition -0.56 SD, p < 0.001; working memory -0.81 SD, p < 0.001; learning and memory -0.70 SD, p < 0.001; reaction time -0.06 SD, p = 0.019; information processing -0.03 SD, p = 0.016). The decrease in working memory and information processing was greater in females compared to males. Cognitive performance decreased more in older participants in all domains. Education alleviated the decrease in cognitive performance in all domains except reaction time. The beneficial effect of education was greater for males.

CONCLUSIONS

This study describes the natural course of aging-related changes in cognitive performance in midlife, the critical time window for early prevention of clinical cognitive decline. These findings provide a reference for studies focusing on determinants of pathological cognitive decline deviating from normal changes in cognitive performance.

Memory enhancing and neuroprotective effects of apomorphine in a rat model of dementia

Oxidative stress from generation of increased reactive oxygen species or has been reported to play an important role in dementia. Oxidative stress due to free radicals of oxygen or reactive oxygen species could be precipitating factors in the etiology of dementia. Apomorphine has been reported to have neuroprotective effects. To monitor memory enhancing and neuroprotective effects of apomorphine, we determined the antioxidant enzymes activities, lipid peroxidation, acetylcholine esterase (AChE) activity in brain and plasma, following repetitive administration of apomorphine in rat model of dementia. Biogenic amine levels were also monitored in hippocampus. Repeated administration of scopolamine was taken as an animal model of dementia. Decreased glutathione peroxidase, superoxide dismutase and catalase activities were observed in these animal models of dementia. While increased lipid peroxidation was also observed in the brain and plasma samples. The results showed significant effects of apomorphine. The activities of antioxidant enzymes displayed increased activities in both brain and plasma. Glutathione peroxidase and catalase activities were found to be significantly higher in brain and plasma of apomorphine treated rats. Superoxide dismutase (SOD) was significantly decreased in plasma of scopolamine injected rats; and a decreased tendency (non-significant) of SOD in brain was also observed. AChE activity in brain and plasma was significantly decreased in scopolamine treated rats. Learning and memory of rats in the present study was assessed by Morris Water Maze (MWM). Short-term memory and long-term memory was impaired significantly in scopolamine treated rats, which was prevented by apomorphine. Moreover, a marked decrease in biogenic amines was also found in the brain of scopolamine treated rats and was reverted in apomorphine treated rats. Results showed that scopolamine-treatment induced memory impairment and induced oxidative stress in rats as compared to saline-treated controls. These impairments were significantly restored by apomorphine administration. In conclusion, our data suggests that apomorphine at the dose of 1 mg/kg could be a potential therapeutic agent to treat dementia and related disorders.

Mechanisms of Neuronal Reactivation in Memory Consolidation: A Perspective from Pathological Conditions

Memory consolidation refers to a process by which labile newly formed memory traces are progressively strengthened into long term memories and become more resistant to interference. Recent work has revealed that spontaneous hippocampal activity during rest, commonly referred to as "offline" activity, plays a critical role in the process of memory consolidation. Hippocampal reactivation occurs during sharp-wave ripples (SWRs), which are events associated with highly synchronous neural firing in the hippocampus and modulation of neural activity in distributed brain regions. Memory consolidation occurs primarily through a coordinated communication between hippocampus and neocortex. Cortical slow oscillations drive the repeated reactivation of hippocampal memory representations together with SWRs and thalamo-cortical spindles, inducing long-lasting cellular and network modifications responsible for memory stabilization.In this review, we aim to comprehensively cover the field of "reactivation and memory consolidation" research by detailing the physiological mechanisms of neuronal reactivation and firing patterns during SWRs and providing a discussion of more recent key findings. Several mechanistic explanations of neuropsychiatric diseases propose that impaired neural replay may underlie some of the symptoms of the disorders. Abnormalities in neuronal reactivation are a common phenomenon and cause pathological impairment in several diseases, such as Alzheimer's disease (AD), epilepsy and schizophrenia. However, the specific pathological changes and mechanisms of reactivation in each disease are different. Recent work has also enlightened some of the underlying pathological mechanisms of neuronal reactivation in these diseases. In this review, we further describe how SWRs, ripples and slow oscillations are affected in Alzheimer's disease, epilepsy, and schizophrenia. We then compare the differences of neuronal reactivation and discuss how different reactivation abnormalities cause pathological changes in these diseases. Aberrant neural reactivation provides insights into disease pathogenesis and may even serve as biomarkers for early disease progression and treatment response.

Impact of sex and hypoxia on brain region-specific expression of membrane androgen receptor AR45 in rats

Background

Sex differences in oxidative stress-associated cognitive decline are influenced by sex hormone levels. Notably, oxidative stress-associated neuronal cell death can be exacerbated through testosterone signaling via membrane androgen receptor AR45, which is complexed with G protein Gαq within plasma membrane-associated lipid rafts. The objective of this study was to elucidate the impact of sex on the expression of AR45 and Gαq in brain regions associated with cognitive function, specifically hippocampus subregions and entorhinal cortex. Additionally, we investigated whether chronic intermittent hypoxia (CIH), an oxidative stressor with sex-specific effects, would modulate AR45 and Gαq expression in these brain regions.

Methods

Adult male and female Sprague-Dawley rats were exposed to CIH or normoxia (room air) during their sleep phase for 14 days. We quantified AR45 and Gαq protein expression in various cognition-associated brain regions [dorsal hippocampal CA1, CA3, dentate gyrus (DG), and entorhinal cortex (ETC)] via western blotting. For comparisons, AR45 and Gαq protein expression were also assessed in brain regions outside the hippocampal-ETC circuit [thalamus (TH) and striatum (STR)].

Results

The highest AR45 levels were expressed in the hippocampal CA1 and DG while the lowest expression was observed in the extrahippocampal STR. The highest Gαq levels were expressed in the hippocampal-associated ETC while the lowest expression was observed in the extrahippocampal TH. Females expressed higher levels of AR45 in the hippocampal DG compared to males, while no sex differences in Gαq expression were observed regardless of brain region assessed. Moreover, there was no effect of CIH on AR45 or Gαq expression in any of the brain regions examined. AR45 expression was positively correlated with Gαq expression in the CA1, DG, ETC, TH, and STR in a sex-dependent manner.

Conclusion

Our findings reveal enrichment of AR45 and Gαq protein expression within the hippocampal-ETC circuit, which is vulnerable to oxidative stress and neurodegeneration during cognitive decline. Nonetheless, CIH does not modulate the expression of AR45 or Gαq. Importantly, there are sex differences in AR45 expression and its association with Gαq expression in various brain regions, which may underlie sex-specific differences in cognitive and motor function-associated declines with aging.

Relationship between frailty and executive function by age and sex in the Canadian Longitudinal Study on Aging

Frailty reflects age-related damage to multiple physiological systems. Executive dysfunction is often a presenting symptom of diseases characterized by cognitive impairment. A decline in cardiovascular health is associated with worse executive function. We tested the hypothesis that higher frailty would be associated with executive dysfunction and that cardiovascular health would mediate this relationship. Middle- and older-aged adults at baseline (n = 29,591 [51% female]) and 3-year follow-up (n = 25,488 [49% females]) from the Canadian Longitudinal Study on Aging (comprehensive cohort) were included. Frailty was determined at baseline from a 61-item index, a cumulative cardiovascular health score was calculated from 30 variables at baseline, and participants completed a word-color Stroop task as an assessment of executive function. Multiple linear regressions and mediation analyses of cardiovascular health were conducted between frailty, Stroop interference-condition reaction time, and cardiovascular health in groups stratified by both age and sex (middle-aged males [MM], middle-aged females [MF], older-aged males [OM], older-aged females [OF]). Frailty (MM, 0.15 ± 0.05; MF, 0.16 ± 0.06; OM, 0.21 ± 0.06; OF, 0.23 ± 0.06) was negatively associated with cardiovascular health (MM, 0.12 ± 0.08; MF, 0.11 ± 0.07; OM, 0.20 ± 0.10; OF, 0.18 ± 0.09; β > 0.037, p < 0.001), as well as the Stroop reaction time at 3-year follow-up (MM, 23.7 ± 7.9; MF, 23.1 ± 7.3; OM, 32.9 ± 13.1; OF, 30.9 ± 12.0; β > 2.57, p < 0.001) across all groups when adjusted for covariates. Cardiovascular health was a partial (~ 10%) mediator between frailty and reaction time, aside from MFs. In conclusion, higher frailty levels are associated with executive dysfunction, which was partially mediated by cardiovascular health. Strategies to improve frailty and better cardiovascular health may be useful for combatting the age-related decline in executive function.

Dysglycemia, gender, and cognitive performance in older persons living with mild cognitive impairment: findings from a cross-sectional, population-based study

OBJECTIVE

This study aims to examine the relationship between dysglycemia - also known as pre-diabetes or impaired glucose tolerance- and cognitive abilities in an older population living Mild Cognitive Impairment (MCI) and stratified by gender.

STUDY DESIGN

This is a retrospective study with data gathered from a large Italian clinical-based database.

MAIN OUTCOME MEASURES

The evaluation of cognitive performances by the Mini-Mental State Examination and the Addenbrooke's Cognitive Examination Revised rating scale as tests of screening and a comprehensive neuropsychological evaluation of several cognitive areas.

RESULTS

The study comprised 682 subjects (445 F/237 M) with a mean age of 76.08 ± 9.03 (range: 66-93) years. In all population, subjects with dysglycemia 193 (28.3%) had significantly poorer performance in memory (p = 0.006) and logic reasoning (p = 0.007) when compared with subjects without dysglycemia. The linear regression analyses revealed significant differences in the correlates of cognitive domains between gender groups. Independent of multiple covariates, women with dysglycemia showed worse performances in attention and short-term memory domains as compared with men. Even in the absence of dysglycemia women were more likely to show lower score in screening test of general cognition and attention.

CONCLUSIONS

Our findings suggest that dysglycemia in older individuals with MCI is associated with declines in specific cognitive domains, potentially influenced by gender. Implementing a comprehensive approach involving risk stratification and preventive strategies may be more effective in averting further cognitive decline in this high-risk population.

Androgen effects on mesoprefrontal dopamine systems in the adult male brain

Epidemiological data show that males are more often and/or more severely affected by symptoms of prefrontal cortical dysfunction in schizophrenia, Parkinson's disease and other disorders in which dopamine circuits associated with the prefrontal cortex are dysregulated. This review focuses on research showing that these dopamine circuits are powerfully regulated by androgens. It begins with a brief overview of the sex differences that distinguish prefrontal function in health and prefrontal dysfunction or decline in aging and/or neuropsychiatric disease. This review article then spotlights data from human subjects and animal models that specifically identify androgens as potent modulators of prefrontal cortical operations and of closely related, functionally critical measures of prefrontal dopamine level or tone. Candidate mechanisms by which androgens dynamically control mesoprefrontal dopamine systems and impact prefrontal states of hypo- and hyper-dopaminergia in aging and disease are then considered. This is followed by discussion of a working model that identifies a key locus for androgen modulation of mesoprefrontal dopamine systems as residing within the prefrontal cortex itself. The last sections of this review critically consider the ways in which the organization and regulation of mesoprefrontal dopamine circuits differ in the adult male and female brain, and highlights gaps where more research is needed.

The Drug Burden Index Is Associated With Measures of Cognitive Function Among Older Adults in the Health, Aging, and Body Composition Study

BACKGROUND

Anticholinergic and sedative medications affect cognition among older adults. The Drug Burden Index (DBI) is a validated measure of exposure to these medications, with higher DBI scores indicating higher drug burden. This ancillary analysis investigated the association between DBI and cognition assessed by the Modified Mini-Mental State Examination (3MS) and the Digit Symbol Substitution Test (DSST).

METHODS

The Health, Aging, and Body Composition Study was a prospective study of community-dwelling adults aged 70-79 years at enrollment. Using data from years 1, 5, and 10, DBI was calculated using medication data per participant. Linear mixed modeling was used to assess cross-sectional and longitudinal effects of DBI on 3MS and DSST. Adjusted models included biological sex, race, education level, APOE status, and death. Sensitivity analyses included testing the strength of the associations for each year and testing attrition due to death as a possible confounding factor via Cox-Proportional Hazard models.

RESULTS

After adjustment, DBI was inversely associated with 3MS and DSST scores. These associations became stronger in each subsequent year. Neither DBI at year 1 nor within-person change in DBI were predictive of longitudinal declines in either cognitive measure. Sensitivity analyses indicated that DBI, 3MS, and DSST were associated with a greater risk of attrition due to death.

CONCLUSIONS

Results suggest that in years when older adults had a higher DBI scores, they had significantly lower global cognition and slower processing speed. These findings further substantiate the DBI as a useful pharmacological tool for assessing the effect of medication exposure.

Sex Differences in the Association Between Vascular Risk Factors and Cognitive Decline: A UK Biobank Study

Background

Age-related cognitive decline is accelerated by vascular risk factors for cerebral small vessel disease. However, the association of vascular risk factors with cerebral small vessel disease contributing to the sex differences in cognitive decline remains unclear.

Objectives

The purpose of this study was to evaluate sex differences in cognitive decline and the association between vascular risk factors and cognitive decline by sex.

Methods

We used data from the UK Biobank (>55 years of age; n = 19,067) to assess cognitive tests (executive function, processing speed, and memory) while adjusting for baseline measurements to examine how vascular risk factors affect cognition. A univariate regression analysis was used to assess sex differences at the first time point (2014). A repeated measure analysis with a mixed effect model was used to determine cognitive decline (between 2014 and 2019). Any significant interaction between vascular risk factors and sex was investigated.

Results

Females had lower scores in all 3 domains at the first cognitive tests (2014). We found a significant sex-by-time interaction over a 5-year period in matrix pattern completion (P = 0.03). After adjusting for vascular risk factors, this interaction was reduced (P = 0.08). High low-density lipoprotein, low education, and high blood pressure had a greater effect on the rate of cognitive decline in the executive function for females compared to males for the sex∗vascular risk factor interaction (P < 0.05).

Conclusions

The rate of cognitive decline did not differ significantly between males and females. However, the impact of several vascular risk factors on cognitive decline was greater in females than in males.

Sex as a Determinant of Age-Related Changes in the Brain

The notion of notable anatomical, biochemical, and behavioral distinctions within male and female brains has been a contentious topic of interest within the scientific community over several decades. Advancements in neuroimaging and molecular biological techniques have increasingly elucidated common mechanisms characterizing brain aging while also revealing disparities between sexes in these processes. Variations in cognitive functions; susceptibility to and progression of neurodegenerative conditions, notably Alzheimer's and Parkinson's diseases; and notable disparities in life expectancy between sexes, underscore the significance of evaluating aging within the framework of gender differences. This comprehensive review surveys contemporary literature on the restructuring of brain structures and fundamental processes unfolding in the aging brain at cellular and molecular levels, with a focus on gender distinctions. Additionally, the review delves into age-related cognitive alterations, exploring factors influencing the acceleration or deceleration of aging, with particular attention to estrogen's hormonal support of the central nervous system.

Successful ageing is associated with falls among older adults in India: a large population based across-sectional study based on LASI

BACKGROUND

Falls are common in the elderly and can lead to adverse consequences, like injuries, hospitalization, disability even mortality. Successful ageing emerged in sight to assess physical, psychological and social status of older adults. This study is conducted to explore the association between them in a large Indian community-dwelling population.

METHODS

Data were based on the wave 1 survey of the Longitudinal Ageing Study in India (LASI). People aged 60 and above with complete information were included. The elderly met five standards including absence of chronic diseases, freedom from disability, high cognitive ability, free from depressive symptoms and active social engagement, were classified into successful agers. The assessment of falls, fall-related injuries and multiple falls depended on interview. Multivariate logistic regression was conducted to find the associations between falls, fall-injury, multiple falls and successful ageing after adjusting both socio-demographic and biological covariates. The log-likelihood ratio test was calculated interactions in subgroups.

RESULTS

31,345 participants in LASI were finally included in our study. Of them, 20.25% reported fall, and 25% were classified into successful agers. After full adjustment, successful ageing was negatively associated with falls (OR 0.70; 95%CI 0.65-0.76) and multiple falls (OR 0.70; 95%CI 0.63-0.78). And the association did not show the significance in older adults with fall-related injuries (OR 0.86; 95%CI 0.72-1.04).

CONCLUSIONS

Successful ageing was negatively associated with falls and multiple falls, but not fall-related injuries in older people in India. Future studies are demanded to explore the causal relationship and to reveal the underlying mechanism.

Cognitive performance trends among European older adults: exploring variations across cohorts, gender, and educational levels (2007-2017)

BACKGROUND

This study explores recent cohort trends in cognitive performance among older Europeans from 2007 to 2017, addressing three key questions: (1) Did cognitive performance improve universally and across the performance distribution during this period? (2) Did these improvements occur across educational levels and for both men and women? (3) Can established risk factors explain these performance gains?

METHODS

Using data from the Survey of Health, Ageing and Retirement in Europe (SHARE) across 12 European countries, we assessed immediate recall, delayed recall, and verbal fluency in individuals aged 60 to 94 in both 2007 and 2017 (n = 32 773). Differences between the two time points were estimated with linear mixed effects regression models and quantile regression.

RESULTS

Cognitive performance improved in all age groups, across educational levels, and for both men and women between 2007 and 2017. Notably, improvements were more pronounced at the upper end of the performance distribution for delayed recall and verbal fluency. Education explained approximately 20% of the observed improvements. Risk factors did not explain the observed improvements.

CONCLUSIONS

European cohorts of both younger-old and older adults continue to exhibit improvements in cognitive performance. Variation in the size of the cohort improvements across the performance distributions in delayed recall and in verbal fluency may contribute to growing inequalities in cognitive outcomes. Future research should further investigate the potential heterogeneity in cognitive performance gains.

TRIAL REGISTRATION

Not applicable.

Sex and aging signatures of proteomics in human cerebrospinal fluid identify distinct clusters linked to neurodegeneration

Sex and age are major risk factors for chronic diseases. Recent studies examining age-related molecular changes in plasma provided insights into age-related disease biology. Cerebrospinal fluid (CSF) proteomics can provide additional insights into brain aging and neurodegeneration. By comprehensively examining 7,006 aptamers targeting 6,139 proteins in CSF obtained from 660 healthy individuals aged from 43 to 91 years old, we subsequently identified significant sex and aging effects on 5,097 aptamers in CSF. Many of these effects on CSF proteins had different magnitude or even opposite direction as those on plasma proteins, indicating distinctive CSF-specific signatures. Network analysis of these CSF proteins revealed not only modules associated with healthy aging but also modules showing sex differences. Through subsequent analyses, several modules were highlighted for their proteins implicated in specific diseases. Module 2 and 6 were enriched for many aging diseases including those in the circulatory systems, immune mechanisms, and neurodegeneration. Together, our findings fill a gap of current aging research and provide mechanistic understanding of proteomic changes in CSF during a healthy lifespan and insights for brain aging and diseases.

Thermoneutral temperature exposure enhances slow-wave sleep with a correlated improvement in amyloid pathology in a triple-transgenic mouse model of Alzheimer's disease

Accumulation of amyloid-β (Aβ) plays an important role in Alzheimer's disease (AD) pathology. There is growing evidence that disordered sleep may accelerate AD pathology by impeding the physiological clearance of Aβ from the brain that occurs in normal sleep. Therapeutic strategies for improving sleep quality may therefore help slow disease progression. It is well documented that the composition and dynamics of sleep are sensitive to ambient temperature. We therefore compared Aβ pathology and sleep metrics derived from polysomnography in 12-month-old female 3xTg-AD mice (n = 8) exposed to thermoneutral temperatures during the light period over 4 weeks to those of age- and sex-matched controls (n = 8) that remained at normal housing temperature (22°C) during the same period. The treated group experienced greater proportions of slow wave sleep (SWS)-i.e. epochs of elevated 0.5-2 Hz EEG slow wave activity during non-rapid eye movement (NREM) sleep-compared to controls. Assays performed on mouse brain tissue harvested at the end of the experiment showed that exposure to thermoneutral temperatures significantly reduced levels of DEA-soluble (but not RIPA- or formic acid-soluble) Aβ40 and Aβ42 in the hippocampus, though not in the cortex. With both groups pooled together and without regard to treatment condition, NREM sleep continuity and any measure of SWS within NREM at the end of the treatment period were inversely correlated with DEA-soluble Aβ40 and Aβ42 levels, again in the hippocampus but not in the cortex. These findings suggest that experimental manipulation of SWS could offer useful clues into the mechanisms and treatment of AD.

Sex-Specific Entorhinal Cortex Functional Connectivity in Cognitively Normal Older Adults with Amyloid-β Pathology

Sex and apolipoprotein E (APOE) genotype have been shown to influence the risk and progression of Alzheimer's disease (AD). However, the impact of these factors on the functional connectivity of the entorhinal cortex (ERC) in clinically unpaired older adults (CUOA) with amyloid-β (Aβ +) pathology remains unclear. A total of 1022 cognitively normal older adults with Aβ + (603 females and 586 APOE ε4 +) from the Anti-Amyloid Treatment in Asymptomatic Alzheimer's (A4) study were included in this study. The 2 × 2 (gender, 2 APOE genotypes) analysis of covariance was performed to compare the demographic information, cognitive performance, and volumetric MRI data among these groups. Voxel-wise comparisons of bilateral ERC functional connectivity (FC) were conducted, and partial correlation analyses were used to explore the associations between cognitive performance and ERC-FC strength. We found that the APOE genotype influenced ERC functional connectivity mainly in the sensorimotor network (SMN). Males exhibited higher ERC-FC in the salience network (SN), while females displayed higher ERC-FC in the default mode network (DMN), executive control network (ECN), and reward network. The interplay of sex and APOE genotype on ERC-FC was observed in the SMN and cerebellar lobe. The ERC-FC was associated with executive function and memory performance in individuals with CUOA-Aβ + . Our findings provide evidence of sex-specific ERC functional connectivity compensation mechanism in cognitively normal older adults with Aβ + pathology. This study may contribute to a better understanding of the mechanisms underlying the early stages of AD and may help develop personalized interventions in preclinical AD.

Low testosterone levels relate to poorer cognitive function in women in an APOE-ε4-dependant manner

BACKGROUND

Past research suggests that low testosterone levels relate to poorer cognitive function and higher Alzheimer's disease (AD) risk; however, these findings are inconsistent and are mostly derived from male samples, despite similar age-related testosterone decline in females. Both animal and human studies demonstrate that testosterone's effects on brain health may be moderated by apolipoprotein E ε4 allele (APOE-ε4) carrier status, which may explain some previous inconsistencies. We examined how testosterone relates to cognitive function in older women versus men across healthy aging and the AD continuum and the moderating role of APOE-ε4 genotype.

METHODS

Five hundred and sixty one participants aged 55-90 (155 cognitively normal (CN), 294 mild cognitive impairment (MCI), 112 AD dementia) from the Alzheimer's Disease Neuroimaging Initiative (ADNI), who had baseline cognitive and plasma testosterone data, as measured by the Rules Based Medicine Human DiscoveryMAP Panel were included. There were 213 females and 348 males (self-reported sex assigned at birth), and 52% of the overall sample were APOE-ε4 carriers. We tested the relationship of plasma testosterone levels and its interaction with APOE-ε4 status on clinical diagnostic group (CN vs. MCI vs. AD), global, and domain-specific cognitive performance using ANOVAs and linear regression models in sex-stratified samples. Cognitive domains included verbal memory, executive function, processing speed, and language.

RESULTS

We did not observe a significant difference in testosterone levels between clinical diagnostic groups in either sex, regrardless of APOE-ε4 status. Across clinical diagnostic group, we found a significant testosterone by APOE-ε4 interaction in females, such that lower testosterone levels related to worse global cognition, processing speed, and verbal memory in APOE-ε4 carriers only. We did not find that testosterone, nor its interaction with APOE-ε4, related to cognitive outcomes in males.

CONCLUSIONS

Findings suggest that low testosterone levels in older female APOE-ε4 carriers across the aging-MCI-AD continuum may have deleterious, domain-specific effects on cognitive performance. Although future studies including additional sex hormones and longitudinal cognitive trajectories are needed, our results highlight the importance of including both sexes and considering APOE-ε4 carrier status when examining testosterone's role in cognitive health.

Age-Related Aspects of Sex Differences in Event-Related Brain Oscillatory Responses: A Turkish Study

Earlier research has suggested gender differences in event-related potentials/oscillations (ERPs/EROs). Yet, the alteration in event-related oscillations (EROs) in the delta and theta frequency bands have not been explored between genders across the three age groups of adulthood, i.e., 18-50, 51-65, and >65 years. Data from 155 healthy elderly participants who underwent a neurological examination, comprehensive neuropsychological assessment (including attention, memory, executive function, language, and visuospatial skills), and magnetic resonance imaging (MRI) from past studies were used. The delta and theta ERO powers across the age groups and between genders were compared and correlational analyses among the ERO power, age, and neuropsychological tests were performed. The results indicated that females displayed higher theta ERO responses than males in the frontal, central, and parietal regions but not in the occipital location between 18 and 50 years of adulthood. The declining theta power of EROs in women reached that of men after the age of 50 while the theta ERO power was more stable across the age groups in men. Our results imply that the cohorts must be recruited at specified age ranges across genders, and clinical trials using neurophysiological biomarkers as an intervention endpoint should take gender into account in the future.

Alzheimer's disease as a women's health challenge: a call for action on integrative precision medicine approaches

Alzheimer's Disease (AD) is marked by pronounced sex differences in pathophysiology and progression. However, the field has yet to fully recognize AD as a women's health issue, delaying the development of targeted preventative strategies and treatments. This perspective explores the elements impacting AD in women, identifying sex specificity in risk factors, highlighting new diagnostic approaches with electronic health records, and reviewing key molecular studies to underscore the need for integrative precision medicine approaches. Established AD risk factors such as advancing age, the apolipoprotein E4 allele, and poorer cardiovascular health affect women differently. We also shed light on sociocultural risk factors, focusing on the gender disparities that may play a role in AD development. From a biological perspective, sex differences in AD are apparent in biomarkers and transcriptomics, further emphasizing the need for targeted diagnostics and treatments. The convergence of novel multiomics data and cutting-edge computational tools provides a unique opportunity to study the molecular underpinnings behind sex dimorphism in AD. Thus, precision medicine emerges as a promising framework for understanding AD pathogenesis through the integration of genetics, sex, environment, and lifestyle. By characterizing AD as a women's health challenge, we can catalyze a transformative shift in AD research and care, marked by improved diagnostic accuracy, targeted interventions, and ultimately, enhanced clinical outcomes.

Gut-Brain Axis: Focus on Sex Differences in Neuroinflammation

In recent years, there has been a growing interest in the concept of the "gut-brain axis". In addition to well-studied diseases associated with an imbalance in gut microbiota, such as cancer, chronic inflammation, and cardiovascular diseases, research is now exploring the potential role of gut microbial dysbiosis in the onset and development of brain-related diseases. When the function of the intestinal barrier is altered by dysbiosis, the aberrant immune system response interacts with the nervous system, leading to a state of "neuroinflammation". The gut microbiota-brain axis is mediated by inflammatory and immunological mechanisms, neurotransmitters, and neuroendocrine pathways. This narrative review aims to illustrate the molecular basis of neuroinflammation and elaborate on the concept of the gut-brain axis by virtue of analyzing the various metabolites produced by the gut microbiome and how they might impact the nervous system. Additionally, the current review will highlight how sex influences these molecular mechanisms. In fact, sex hormones impact the brain-gut microbiota axis at different levels, such as the central nervous system, the enteric nervous one, and enteroendocrine cells. A deeper understanding of the gut-brain axis in human health and disease is crucial to guide diagnoses, treatments, and preventive interventions.

My Parent, Myself, or My Child: Whose Education Matters Most for Trajectories of Cognitive Aging in Middle Age?

The growing body of evidence linking intergenerational education and late-life cognitive decline is almost exclusively from high-income countries, despite rapid intergenerational changes in education in low- and middle-income countries (LMICs). We used data from the Mexican Health and Aging Study (n = 8,822), a cohort study of Mexican adults aged ≥50 years (2001-2018), to evaluate whether parental education (none vs. any formal schooling), one's own education (less than primary school vs. completion of primary school), or an adult child's education (less than high school vs. completion of high school) was associated with verbal memory z scores. We used linear mixed models with inverse probability of attrition weights. Educational attainment in all 3 generations was associated with baseline verbal memory scores, independent of the prior generation's education. Lower parental (β = -0.005, 95% confidence interval: -0.009, -0.002) and respondent (β = -0.013, 95% confidence interval: -0.017, -0.010) educational level were associated with faster decline in delayed (but not immediate) verbal memory z scores. Associations between adult child's education and respondent's verbal memory decline varied by exposure specification. The educational attainment of parents and adult children may influence the cognitive aging of middle-aged and older adults in LMICs. These results have important implications given recent structural shifts in educational attainment in many LMICs.

Association of physical activity and vitamin D deficiency with cognitive impairment in older adults: a population based cross-sectional analysis

Objectives

The global aging situation is becoming increasingly critical and cognitive impairment in the elderly has become a public health burden of concern. Physical activity (PA) and vitamin D may play a key role in improving cognitive impairment. However, little studies have examined the interaction between these two. The purpose of this study was to assess the association of PA and vitamin D with cognitive impairment in older adults, as well as the interactions of PA and vitamin D.

Materials and methods

This study was conducted by multi-stage random sampling of elderly people ≥60 years old, and a total sample of 2,492 (1,207 male and 1,285 female, mean age of 69.41 ± 6.75 years) with complete data was included in the analysis. PA was assessed by the Global Physical Activity Questionnaire, and < 600 MET-min/week was used as the division criteria. Serum vitamin D was measured by high-performance liquid chromatography tandem mass spectrometry, and 25-hydroxyvitamin D2/D3 concentration < 20 ng/mL was used as a vitamin D deficiency criterion. Cognitive function was assessed by three subtests: the Consortium to Establish a Registry for Alzheimer's disease word learning test (CERAD-WL) for immediate and delayed learning, the Animal Fluency Test (AFT) for verbal fluency; and the Digit Symbol Substitution Test (DSST) for information processing speed and switching attention. All three subtests were scored at less than the lowest quartile of the score as a criterion for cognitive impairment. Statistical analysis was performed using SPSS for chi-square test, rank sum test, interaction analysis, subgroup analysis, and regression analysis.

Results

Lower level of PA is associated with higher odds of cognitive impairment (CERAD W-L: OR = 1.596, 95% CI: 1.338-1.905, p < 0.001; AFT: OR = 1.833, 95% CI: 1.534-2.190, p < 0.001; DSST: OR = 1.936, 95% CI: 1.609-2.329, p < 0.001). Vitamin D deficiency has significant effects in AFT (OR = 1.322, 95% CI: 1.103-1.584, p = 0.003) and DSST (OR = 1.619, 95% CI: 1.345-1.948, p < 0.001). After adjusted for covariates, PA and vitamin D have multiplicative interaction on AFT (OR = 0.662, 95% CI: 0.448-0.977, p = 0.038) and DSST (OR = 0.775, 95% CI: 0.363-0.868, p = 0.009). The interaction between PA and vitamin D was not significant in the CERAD W-L (OR = 0.757, 95% CI: 0.508-1.128, p = 0.172).

Conclusion

The results showed that lower level of PA and vitamin D deficiency were associated with higher odds of cognitive impairment in the elderly population and that there was a multiplicative interaction between PA and vitamin D on cognitive function, with a significant effect of vitamin D on cognitive impairment in high PA conditions.

Mediterranean diet related to 3-year incidence of cognitive decline: results from a cohort study in Chinese rural elders

OBJECTIVE

This study aims to examine the effect of the Mediterranean diet (MeDi) on cognitive decline among the Chinese elderly with a 3-year follow-up.

METHODS

This study is divided into two waves: wave-1 January 2019 to June 2019 (n = 2313); wave-2 January 2022 to March 2022 (n = 1648). MeDi scores were calculated from the Mediterranean Diet Adherence Screener (MEDAS), with the scoring of low compliance (0-6 points) and high compliance (7-14 points). The Mini-Mental State Examination (MMSE) was used to assess cognitive function. An MMSE score dropping ≥ 2 points from baseline was defined as cognitive decline. The relationships between MeDi score and cognitive decline were analyzed by linear regression models or Binary logistic regression.

RESULTS

During the 3-year follow-up, 23.8% of patients exhibited cognitive decline. The study revealed a significant difference in MMSE score changes between low and high MeDi adherence groups (p < 0.001). MeDi score was negatively correlated with cognitive deterioration (β = -0.020, p = 0.026). MeDi score was only negatively associated with cognitive decline in the female subgroup aged ≥65 years (β = -0.034, p = 0.033). The food beans (OR = 0.65, 95%CI:0.51, 0.84), fish (OR = 0.72, 95%CI:0.54, 0.97), and cooked vegetables (OR = 0.68, 95%CI:0.53, 0.84) were protective factors for cognitive decline.

CONCLUSIONS

This study suggests that greater adherence to the MeDi is linked to a reduced risk of cognitive decline in elderly people. However, this is found only in women who are 65 years old or older. It also found long-term adherence to beans, fish, and vegetables are more effective in improving cognitive function.

The Association among Hypothalamic Subnits, Gonadotropic and Sex Hormone Plasmas Levels in Alzheimer's Disease

This study investigates the sex-specific role of the Hypothalamic-Pituitary-Gonadal axis in Alzheimer's disease progression, utilizing ADNI1 data for 493 individuals, analyzing plasma levels of gonadotropic and sex hormones, and examining neurodegeneration-related brain structures. We assessed plasma levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), progesterone (P4), and testosterone (T), along with volumetric measures of the hippocampus, entorhinal cortex, and hypothalamic subunits, to explore their correlation with Alzheimer's disease markers across different cognitive statuses and sexes. Significant cognitive status effects were observed for all volumetric measures, with a distinct sex-by-cognitive status interaction for hypothalamic volume, indicating a decrease in males but not in females across cognitive impairment stages. Regression analyses showed specific hypothalamic subunit volume related to hormone levels, accounting for up to approximately 40% of the variance (p < 0.05). The findings highlight sex differences in neurodegeneration and hormonal regulation, suggesting potential for personalized treatments and advancing the understanding of Alzheimer's disease etiology.

Sex differences in cognitive function trajectories and their determinants in older adults: Evidence from the Chinese longitudinal healthy longevity survey

OBJECTIVES

To examine sex differences in the cognitive trajectories of a nationally representative sample of older people living in China and to explore potential determinants of these trajectories.

METHODS

The study included 2230 women and 2171 men who were cognitively healthy and aged over 60 at the first observation from the Chinese Longitudinal Healthy Longevity Survey based on the 2008-2018 cohort. Cognitive function was measured using the Chinese version of the Mini-Mental State Examination (MMSE). Group-based trajectory modeling was used to identify potential heterogeneity of longitudinal changes over the 10 years in each gender. Logistic regression was used to investigate associations between baseline characteristics (age, education, fertility history, sleep length, physical activity, and health status and behaviors) and trajectory classes.

RESULTS

Three trajectories (labeled stable, slow decline, and rapid decline) were identified according to the changes in MMSE scores for both women and men. For the women, both the slow and rapid decline groups accounted for a larger proportion (14.7% and 11.0%, respectively) than the male decline groups (8.1% and 6.6%, respectively), and the women had a lower baseline MMSE score with a faster decline. In the multivariable logistic regression analyses, older age, less education, older age at first birth, poorer functional abilities, hearing impairment, and lower baseline MMSE scores were significantly associated with cognitive decline in both the female and male groups compared to the stable group. For the women, sleeping over 9 h was also associated with a rapid cognitive decline trajectory, while current exercise and being overweight/obese were protective factors against cognitive decline.

CONCLUSIONS

The women had an overall more serious cognitive decline than men. The potential determinants of cognitive decline identified in this study could be considered for developing specific intervention strategies aimed at promoting a healthy brain and preventing cognitive decline in different sexes, especially in low-income and developing countries.

Dentate Gyrus Granule Cells Show Stability of BDNF Protein Expression in Mossy Fiber Axons with Age, and Resistance to Alzheimer's Disease Neuropathology in a Mouse Model

Brain-derived neurotrophic factor (BDNF) is important in the development and maintenance of neurons and their plasticity. Hippocampal BDNF has been implicated in Alzheimer's disease (AD) because hippocampal levels in AD patients and AD animal models are often downregulated, suggesting that reduced BDNF contributes to AD. However, the location where hippocampal BDNF protein is most highly expressed, the mossy fiber (MF) axons of dentate gyrus granule cells (GCs), has been understudied, and not in controlled conditions. Therefore, we evaluated MF BDNF protein in the Tg2576 mouse model of AD. Tg2576 and wild-type (WT) mice of both sexes were examined at 2-3 months of age, when amyloid-β (Aβ) is present in neurons but plaques are absent, and 11-20 months of age, after plaque accumulation. As shown previously, WT mice exhibited high levels of MF BDNF protein. Interestingly, there was no significant decline with age in either the genotype or sex. Notably, MF BDNF protein was correlated with GC ΔFosB, a transcription factor that increases after 1-2 weeks of elevated neuronal activity. We also report the novel finding that Aβ in GCs or the GC layer was minimal even at old ages. The results indicate that MF BDNF is stable in the Tg2576 mouse, and MF BDNF may remain unchanged due to increased GC neuronal activity, since BDNF expression is well known to be activity dependent. The resistance of GCs to long-term Aβ accumulation provides an opportunity to understand how to protect vulnerable neurons from increased Aβ levels and therefore has translational implications.

Predicting sojourn times across dementia disease stages, institutionalization, and mortality

INTRODUCTION

Inferring the timeline from mild cognitive impairment (MCI) to severe dementia is pivotal for patients, clinicians, and researchers. Literature is sparse and often contains few patients. We aim to determine the time spent in MCI, mild-, moderate-, severe dementia, and institutionalization until death.

METHODS

Multistate modeling with Cox regression was used to obtain the sojourn time. Covariates were age at baseline, sex, amyloid status, and Alzheimer's disease (AD) or other dementia diagnosis. The sample included a register (SveDem) and memory clinics (Amsterdam Dementia Cohort and Memento).

RESULTS

Using 80,543 patients, the sojourn time from clinically identified MCI to death across all patient groups ranged from 6.20 (95% confidence interval [CI]: 5.57-6.98) to 10.08 (8.94-12.18) years.

DISCUSSION

Generally, sojourn time was inversely associated with older age at baseline, males, and AD diagnosis. The results provide key estimates for researchers and clinicians to estimate prognosis.

Hyperbaric oxygen alleviates selective domains of cognitive and motor deficits in female 5xFAD mice

Treatment of Alzheimer's disease (AD) has been limited to managing of symptoms or anti-amyloid therapy with limited results and uncertainty. Seeking out new therapies that can reverse the effects of this devastating disease is important. Hyperbaric oxygen (HBO) therapy could be such a candidate as it has been shown to improve brain function in certain neurological conditions. Furthermore, the role sex plays in the vulnerability/resilience to AD remains equivocal. An understanding of what makes one sex more vulnerable to AD could unveil new pathways for therapy development. In this study, we investigated the effects of HBO on cognitive, motor, and affective function in a mouse model of AD (5xFAD) and assessed protein oxidation in peripheral tissues as a safety indicator. The motor and cognitive abilities of 5xFAD mice were significantly impaired. HBO therapy improved cognitive flexibility and associative learning of 5xFAD females but not males, but HBO had no effect other aspects of cognition. HBO also reversed AD-related declines in balance but had no impact on gait and anxiety-like behavior. HBO did not affect body weights or oxidative stress in peripheral tissues. Our study provides further support for HBO therapy as a potential treatment for AD and emphasizes the importance of considering sex as a biological variable in therapeutic development. Further investigations into the underlying mechanisms of HBO's sex-specific responses are warranted, as well as optimizing treatment protocols for maximum benefits.

Temporal Alterations in White Matter in An App Knock-In Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia and results in neurodegeneration and cognitive impairment. White matter (WM) is affected in AD and has implications for neural circuitry and cognitive function. The trajectory of these changes across age, however, is still not well understood, especially at earlier stages in life. To address this, we used the AppNL-G-F/NL-G-F knock-in (APPKI) mouse model that harbors a single copy knock-in of the human amyloid precursor protein (APP) gene with three familial AD mutations. We performed in vivo diffusion tensor imaging (DTI) to study how the structural properties of the brain change across age in the context of AD. In late age APPKI mice, we observed reduced fractional anisotropy (FA), a proxy of WM integrity, in multiple brain regions, including the hippocampus, anterior commissure (AC), neocortex, and hypothalamus. At the cellular level, we observed greater numbers of oligodendrocytes in middle age (prior to observations in DTI) in both the AC, a major interhemispheric WM tract, and the hippocampus, which is involved in memory and heavily affected in AD, prior to observations in DTI. Proteomics analysis of the hippocampus also revealed altered expression of oligodendrocyte-related proteins with age and in APPKI mice. Together, these results help to improve our understanding of the development of AD pathology with age, and imply that middle age may be an important temporal window for potential therapeutic intervention.

Maximizing utility of neuropsychological measures in sex-specific predictive models of incident Alzheimer's disease in the Framingham Heart Study

INTRODUCTION

Sex differences in neuropsychological (NP) test performance might have important implications for the diagnosis of Alzheimer's disease (AD). This study investigates sex differences in neuropsychological performance among individuals without dementia at baseline.

METHODS

Neuropsychological assessment data, both standard test scores and process coded responses, from Framingham Heart Study participants were analyzed for sex differences using regression model and Cox proportional hazards model. Optimal NP profiles were identified by machine learning methods for men and women.

RESULTS

Sex differences were observed in both summary scores and composite process scores of NP tests in terms of adjusted means and their associations with AD incidence. The optimal NP profiles for men and women have 10 and 8 measures, respectively, and achieve 0.76 mean area under the curve for AD prediction.

DISCUSSION

These results suggest that NP tests can be leveraged for developing more sensitive, sex-specific indices for the diagnosis of AD.

Factors affecting cognitive frailty improvement and progression in Taiwanese older adults

BACKGROUND

Knowledge of predictors of cognitive frailty (CF) trajectories is required to develop preventive strategies to delay or reverse the progression from CF to dementia and other adverse outcomes. This 2-year prospective study aimed to investigate factors affecting the progression and improvement of CF in older Taiwanese adults.

METHODS

In total, 832 community-dwelling people aged ≥ 65 years were eligible. Fried's five frailty criteria were used to measure prefrailty and frailty, while cognitive performance was assessed by the Clinical Dementia Rating and Mini-Mental State Examination. Each component of reversible CF and potentially reversible CF was assigned a score, with a total score ranging 0 to 5 points. Two annual follow-up CF assessments were conducted. The group-based trajectory model was applied to identify latent CF trajectory groups, and a multinomial logistic regression was used to examine relationships of explanatory variables with CF trajectories.

RESULTS

According to data on 482 subjects who completed the two annual follow-ups, three CF trajectories of robust, improvement, and progression were identified. After adjusting for the baseline CF state, CF progression was significantly associated with an older age (odds ratio [OR] = 1.08; 95% confidence interval [CI], 1.02 ~ 1.14), a lower Tinetti balance score (OR = 0.72; 95% CI, 0.54 ~ 0.96), a slower gait (OR = 0.98; 95% CI, 0.97 ~ 0.99), and four or more comorbidities (OR = 2.65; 95% CI, 1.19 ~ 5.90), while CF improvement was not significantly associated with any variable except the baseline CF state. In contrast, without adjusting for the baseline CF state, CF progression was significantly associated with an older age, female sex, balance scores, gait velocity, regular exercise, the number of comorbidities, and depression, while CF improvement was significantly associated with female sex, balance scores, and the number of comorbidities.

CONCLUSIONS

The baseline CF state, an older age, poorer balance, slower gait, and a high number of comorbidities may contribute to CF progression, while the baseline CF state may account for associations of engaging in regular exercise and depression with CF development.

Hormone Replacement Therapy and Alzheimer's Disease: Current State of Knowledge and Implications for Clinical Use

Alzheimer's disease (AD) is a progressive neurodegenerative disorder responsible for over half of dementia cases, with two-thirds being women. Growing evidence from preclinical and clinical studies underscores the significance of sex-specific biological mechanisms in shaping AD risk. While older age is the greatest risk factor for AD, other distinct biological mechanisms increase the risk and progression of AD in women including sex hormones, brain structural differences, genetic background, immunomodulation and vascular disorders. Research indicates a correlation between declining estrogen levels during menopause and an increased risk of developing AD, highlighting a possible link with AD pathogenesis. The neuroprotective effects of estrogen vary with the age of treatment initiation, menopause stage, and type. This review assesses clinical and observational studies conducted in women, examining the influence of estrogen on cognitive function or addressing the ongoing question regarding the potential use of hormone replacement therapy (HRT) as a preventive or therapeutic option for AD. This review covers recent literature and discusses the working hypothesis, current use, controversies and challenges regarding HRT in preventing and treating age-related cognitive decline and AD. The available evidence indicates that estrogen plays a significant role in influencing dementia risk, with studies demonstrating both beneficial and detrimental effects of HRT. Recommendations regarding HRT usage should carefully consider the age when the hormonal supplementation is initiated, baseline characteristics such as genotype and cardiovascular health, and treatment duration until this approach can be more thoroughly investigated or progress in the development of alternative treatments can be made.

Does education moderate gender disparities in later-life memory function? A cross-national comparison of harmonized cognitive assessment protocols in the United States and India

INTRODUCTION

We compared gender disparities in later-life memory, overall and by education, in India and the United States (US).

METHODS

Data (N = 7443) were from harmonized cognitive assessment protocols (HCAPs) in the Longitudinal Aging Study of India-Diagnostic Assessment of Dementia (LASI-DAD; N = 4096; 2017-19) and US Health and Retirement Study HCAP (HRS-HCAP; N = 3347; 2016-17). We derived harmonized memory factors from each study using confirmatory factor analysis. We used multivariable-adjusted linear regression to compare gender disparities in memory function between countries, overall and by education.

RESULTS

In the United States, older women had better memory than older men (0.28 SD-unit difference; 95% CI: 0.22, 0.35). In India, older women had worse memory than older men (-0.15 SD-unit difference; 95% CI: -0.20, -0.10), which attenuated with increasing education and literacy.

CONCLUSION

We observed gender disparities in memory in India that were not present in the United States, and which dissipated with education and literacy.

Oxidative damage in neurodegeneration: roles in the pathogenesis and progression of Alzheimer disease

Alzheimer disease (AD) is associated with multiple etiologies and pathological mechanisms, among which oxidative stress (OS) appears as a major determinant. Intriguingly, OS arises in various pathways regulating brain functions, and it seems to link different hypotheses and mechanisms of AD neuropathology with high fidelity. The brain is particularly vulnerable to oxidative damage, mainly because of its unique lipid composition, resulting in an amplified cascade of redox reactions that target several cellular components/functions ultimately leading to neurodegeneration. The present review highlights the "OS hypothesis of AD," including amyloid beta-peptide-associated mechanisms, the role of lipid and protein oxidation unraveled by redox proteomics, and the antioxidant strategies that have been investigated to modulate the progression of AD. Collected studies from our groups and others have contributed to unraveling the close relationships between perturbation of redox homeostasis in the brain and AD neuropathology by elucidating redox-regulated events potentially involved in both the pathogenesis and progression of AD. However, the complexity of AD pathological mechanisms requires an in-depth understanding of several major intracellular pathways affecting redox homeostasis and relevant for brain functions. This understanding is crucial to developing pharmacological strategies targeting OS-mediated toxicity that may potentially contribute to slow AD progression as well as improve the quality of life of persons with this severe dementing disorder.

Cognitive Performance and Incident Alzheimer's Dementia in Men Versus Women

BACKGROUND

The utility of neuropsychological measurements as forerunners of Alzheimer's Disease Dementia (AD) in individuals with normal cognition or mild cognitive impairment (MCI) is undeniable.

OBJECTIVES

To assess the differential prognostic value of cognitive performance in older men versus women.

DESIGN

Longitudinal analysis of data acquired from the National Alzheimer's Coordinating Center Uniform Data Set.

SETTINGS

Data on older adults (≥60 years) were derived from 43 National Institute on Aging - funded Alzheimer's Disease Research Centers.

PARTICIPANTS

10,073 cognitively unimpaired (CU) older adults followed for 5.5±3.8 years and 3,925 participants with amnestic MCI monitored for 3.5±2.8 years.

MEASUREMENTS

The domains of episodic memory, verbal fluency, naming, attention, processing speed and executive function were assessed. Cox proportional hazards models examined associations between individual cognitive domains and AD incidence separately for each participant set. CU and MCI. These predictive models featured individual neuropsychological measures, sex, neuropsychological measure by sex interactions, as well as a number of crucial covariates.

RESULTS

Episodic memory and verbal fluency were differentially related to future AD among CU individuals, explaining a larger proportion of risk variance in women compared to men. On the other hand, naming, attention and executive function were differentially related to future AD among participants with MCI, accounting for a greater fraction of risk variance in men than women.

CONCLUSION

Cognitive performance is differentially related to risk of progressing to AD in men versus women without dementia.

Cerebrovascular Dysfunction in Alzheimer's Disease and Transgenic Rodent Models

Alzheimer's Disease (AD) and Alzheimer's Disease-Related Dementia (ADRD) are the primary causes of dementia that has a devastating effect on the quality of life and is a tremendous economic burden on the healthcare system. The accumulation of extracellular beta-amyloid (Aβ) plaques and intracellular hyperphosphorylated tau-containing neurofibrillary tangles (NFTs) in the brain are the hallmarks of AD. They are also thought to be the underlying cause of inflammation, neurodegeneration, brain atrophy, and cognitive impairments that accompany AD. The discovery of APP, PS1, and PS2 mutations that increase Aβ production in families with early onset familial AD led to the development of numerous transgenic rodent models of AD. These models have provided new insight into the role of Aβ in AD; however, they do not fully replicate AD pathology in patients. Familial AD patients with mutations that elevate the production of Aβ represent only a small fraction of dementia patients. In contrast, those with late-onset sporadic AD constitute the majority of cases. This observation, along with the failure of previous clinical trials targeting Aβ or Tau and the modest success of recent trials using Aβ monoclonal antibodies, has led to a reappraisal of the view that Aβ accumulation is the sole factor in the pathogenesis of AD. More recent studies have established that cerebral vascular dysfunction is one of the earliest changes seen in AD, and 67% of the candidate genes linked to AD are expressed in the cerebral vasculature. Thus, there is an increasing appreciation of the vascular contribution to AD, and the National Institute on Aging (NIA) and the Alzheimer's Disease Foundation recently prioritized it as a focused research area. This review summarizes the strengths and limitations of the most commonly used transgenic AD animal models and current views about the contribution of Aβ accumulation versus cerebrovascular dysfunction in the pathogenesis of AD.

Sex modifies effects of imaging and CSF biomarkers on cognitive and functional outcomes: a study of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by memory and functional impairments. Two of 3 patients with AD are biologically female; therefore, the biological underpinnings of this diagnosis disparity may inform interventions slowing the AD progression. To bridge this gap, we conducted analyses of 1078 male and female participants from the Alzheimer's Disease Neuroimaging Initiative to examine associations between levels of cerebral spinal fluid (CSF)/neuroimaging biomarkers and cognitive/functional outcomes. The Chow test was used to quantify sex differences by determining if biological sex affects relationships between the studied biomarkers and outcomes. Multiple magnetic resonance imaging (whole brain, entorhinal cortex, middle temporal gyrus, fusiform gyrus, hippocampus), position emission tomography (AV45), and CSF (P-TAU, TAU) biomarkers were differentially associated with cognitive and functional outcomes. Post-hoc bootstrapped and association analyses confirmed these differential effects and emphasized the necessity of using separate, sex-stratified models. The studied imaging/CSF biomarkers may account for some of the sex-based variation in AD pathophysiology. The identified sex-varying relationships between CSF/imaging biomarkers and cognitive/functional outcomes warrant future biological investigation in independent cohorts.