Adverse stress, hippocampal networks, and Alzheimer's disease

Investigating Heterogeneity in the Relationship Between Marital Satisfaction and Cognitive Health by Gender and Across the Cognitive Function Distribution

Background and Objectives

Marital satisfaction has been established as an essential factor for promoting health and well-being in older adults. However, it is unclear whether marital satisfaction is also associated with cognitive health in this population. This study aimed to investigate the longitudinal association between marital satisfaction and cognitive function, while also exploring variations in this relationship by gender and across the cognitive function distribution.

Research Design and Methods

This study used 6 waves of the Korean Longitudinal Study of Ageing (KLoSA) and employed gender-stratified unconditional quantile regression (UQR) models with fixed effects (FE) to estimate the association between marital satisfaction and cognitive function across different quantiles of the cognitive function distribution. FE models controlled for unobserved individual-level confounders such as genetics, cognitive and noncognitive skills, and early childhood social and cultural background.

Results

The results of this study revealed that marital satisfaction was positively associated with cognitive function (b = 0.305), and this association was stronger in older men than in older women (b = 0.392 for older men vs b = 0.181 for older women). The UQR-FE models suggested that stronger association between marital satisfaction and cognitive function was observed among older men with lower cognitive function (b = 0.817 for 10th percentile vs b = 0.118 for 90th percentile). Among older women, no clear patterns of heterogeneity were found across the cognitive function distribution.

Discussion and Implications

The findings of this study highlight a significant degree of heterogeneity in the relationship between marital satisfaction and cognitive function among older men, with stronger associations observed in the lower percentiles of the cognitive function distribution. Interventions aimed at improving marital quality could be an effective strategy for promoting cognitive health in older adults, with an approach tailored to the individual's characteristics.

A proton-inhibited DEG/ENaC ion channel maintains neuronal ionstasis and promotes neuronal survival under stress

The nervous system participates in the initiation and modulation of systemic stress. Ionstasis is of utmost importance for neuronal function. Imbalance in neuronal sodium homeostasis is associated with pathologies of the nervous system. However, the effects of stress on neuronal Na⁺ homeostasis, excitability, and survival remain unclear. We report that the DEG/ENaC family member DEL-4 assembles into a proton-inactivated sodium channel. DEL-4 operates at the neuronal membrane and synapse to modulate Caenorhabditis elegans locomotion. Heat stress and starvation alter DEL-4 expression, which in turn alters the expression and activity of key stress-response transcription factors and triggers appropriate motor adaptations. Similar to heat stress and starvation, DEL-4 deficiency causes hyperpolarization of dopaminergic neurons and affects neurotransmission. Using humanized models of neurodegenerative diseases in C. elegans, we showed that DEL-4 promotes neuronal survival. Our findings provide insights into the molecular mechanisms by which sodium channels promote neuronal function and adaptation under stress.

Shared alterations in hippocampal structural covariance in subjective cognitive decline and migraine

Introduction

Subjective cognitive decline (SCD) and migraine are often comorbid. Hippocampal structural abnormalities have been observed in individuals with both SCD and migraine. Given the known structural and functional heterogeneity along the long axis (anterior to posterior) of the hippocampus, we aimed to identify altered patterns of structural covariance within hippocampal subdivisions associated with SCD and migraine comorbidities.

Methods

A seed-based structural covariance network analysis was applied to examine large-scale anatomical network changes of the anterior and posterior hippocampus in individuals with SCD, migraine and healthy controls. Conjunction analyses were used to identify shared network-level alterations in the hippocampal subdivisions in individuals with both SCD and migraine.

Results

Altered structural covariance integrity of the anterior and posterior hippocampus was observed in the temporal, frontal, occipital, cingulate, precentral, and postcentral areas in individuals with SCD and migraine compared with healthy controls. Conjunction analysis revealed that, in both SCD and migraine, altered structural covariance integrity was shared between the anterior hippocampus and inferior temporal gyri and between the posterior hippocampus and precentral gyrus. Additionally, the structural covariance integrity of the posterior hippocampus-cerebellum axis was associated with the duration of SCD.

Conclusion

This study highlighted the specific role of hippocampal subdivisions and specific structural covariance alterations within these subdivisions in the pathophysiology of SCD and migraine. These network-level changes in structural covariance may serve as potential imaging signatures for individuals who have both SCD and migraine.

Social participation and risk of developing dementia

The increasing number of people with dementia globally illustrates the urgent need to reduce dementia's scale and impact. Lifetime social participation may affect dementia risk by increasing cognitive reserve, and through brain maintenance by reducing stress and improving cerebrovascular health. It may therefore have important implications for individual behavior and public health policy aimed at reducing dementia burden. Observational study evidence indicates that greater social participation in midlife and late life is associated with 30-50% lower subsequent dementia risk, although some of this may not be causal. Social participation interventions have led to improved cognition but, partly due to short follow-up and small numbers of participants, no reduction in risk of dementia. We summarize the evidence linking social participation with dementia, discuss potential mechanisms by which social participation is likely to reduce and mitigate the impact of neuropathology in the brain, and consider the implications for future clinical and policy dementia prevention interventions.

Childhood Social Isolation as a Predictor of Retinal Neuronal Thickness in Middle Age: A Lifecourse Birth Cohort Study

OBJECTIVE

We investigated whether childhood social isolation was associated with retinal neural layer changes in adulthood, and whether this association was independent of other childhood or adulthood risk factors, including adult social isolation.

METHODS

Participants were members of the Dunedin Multidisciplinary Health and Development Study, a longitudinal population-based birth cohort from Aotearoa New Zealand ( n = 1037), born 1972 to 1973 and followed until age 45 years, with 94% of the living cohort still participating. Social isolation was recorded prospectively at ages 5, 7, 9, and 11 years, from teacher and parent report. Retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer thicknesses were measured via optical coherence tomography at age 45 years.

RESULTS

Childhood social isolation was associated with thinner average RNFL ( B = -0.739, p = .02), nasal RNFL ( B = -1.118, p = .005), and inferior RNFL ( B = -1.524, p = .007), although only nasal RNFL remained significant after adjustment. These associations were not fully explained by other psychosocial or physical health risk factors in childhood or adulthood, nor were they mediated by adult loneliness or social support.

CONCLUSIONS

Childhood social isolation was an independent predictor of RNFL thickness in middle age. Highlighting prospective links between childhood psychosocial adversity and retinal neuronal measures will help to inform future research into the utility of retinal neuronal thickness as a biomarker for neurodegeneration.

Amygdalo-nigral circuit mediates stress-induced vulnerability to the parkinsonian toxin MPTP

AIMS

The aim was to investigate the effect of mood disorders on parkinsonian toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced motor disability, substantia nigra pars compacta (SNc) dopaminergic (DA) neurons loss. Also, the neural circuit mechanism was elucidated.

METHODS

The depression-like (physical stress, PS) and anxiety-like (emotional stress, ES) mouse models were established by the three-chamber social defeat stress (SDS). The features of Parkinson's disease were reproduced by MPTP injection. Viral-based whole-brain mapping was utilized to resolve the stress-induced global changes in direct inputs onto SNc DA neurons. Calcium imaging and chemogenetic techniques were applied to verify the function of the related neural pathway.

RESULTS

We found that PS mice, but not ES mice, showed worse movement performance and more SNc DA neuronal loss than control mice after MPTP administration. The projection from the central amygdala (CeA) to the SNc^DA was significantly increased in PS mice. The activity of SNc-projected CeA neurons was enhanced in PS mice. Activating or inhibiting the CeA-SNc^DA pathway could mimic or block PS-induced vulnerability to MPTP.

CONCLUSIONS

These results indicated that projections from CeA to SNc DA neurons contribute to SDS-induced vulnerability to MPTP in mice.

Gender differences in the association between parity and cognitive function: Evidence from the UK biobank

While much previous work linking fertility history with late-life cognition has focused on a narrow set of cognitive measures and/or has used modest sample sizes in the analysis, our paper expands the size and scope of these linkages by analyzing cognitive function across five domains and precisely estimating gendered patterns between men and women. Results point to important gendered associations between parity and cognition: having children is likely associated with better cognitive function for fathers in all five domains. However, mothers show worse cognitive function in some domains (i.e., numeric memory, prospective memory, and fluid intelligence) than childless women. We explore the possibility of confounding in these associations and rule out the effects of genetic cognitive ability on fertility. We also find that adding controls for educational attainment differ by gender-strengthening associations between parity and cognition for men and largely eliminating them for women. The findings support previous work done on how life course contexts may link to the risk of dementia or cognitive impairment, highlighting parity as potential protective or risk factors to parents' cognitive health. The use of five cognitive domains yields variations in results, giving implications on measure selection of cognitive function and calling for replicated work covering more cognitive domains.

Chronic Stress, Depression, and Alzheimer's Disease: The Triangle of Oblivion

Chronic stress and high levels of the main stress hormones, and glucocorticoids (GC), are implicated in susceptibility to brain pathologies such as depression and Alzheimer's disease (AD), as they promote neural plasticity damage and glial reactivity, which can lead to dendritic/synaptic loss, reduced neurogenesis, mood deficits, and impaired cognition. Moreover, depression is implicated in the development of AD with chronic stress being a potential link between both disorders via common neurobiological underpinnings. Hereby, we summarize and discuss the clinical and preclinical evidence related to the detrimental effect of chronic stress as a precipitator of AD through the activation of pathological mechanisms leading to the accumulation of amyloid β (Aβ) and Tau protein. Given that the modern lifestyle increasingly exposes individuals to high stress loads, it is clear that understanding the mechanistic link(s) between chronic stress, depression, and AD pathogenesis may facilitate the treatment of AD and other stress-related disorders.

Common Neuropsychiatric S ymptoms in Alzheimer's Disease, Mild Cognitive Impairment, and Subjective Memory Complaints: A Unified Framework

The Alzheimer's disease (AD) continuum is a unique spectrum of cognitive impairment that typically involves the stages of subjective memory complaints (SMC), mild cognitive impairment (MCI), and AD dementia. Neuropsychiatric symptoms (NPS), such as apathy, anxiety, stress, and depression, are highly common throughout the AD continuum. However, there is a dearth of research on how these NPS vary across the AD continuum, especially SMC. There is also disagreement on the effects of specific NPS on each stage of the AD continuum due to their collinearity with other NPS, cognitive decline, and environmental factors (e.g., stress). In this article, we conduct a novel perspective review of the scientific literature to understand the presence of NPS across the AD continuum. Specifically, we review the effects of apathy, depression, anxiety, and stress in AD, MCI, and SMC. We then build on this knowledge by proposing two theories of NPS' occurrence across the AD continuum. Consequently, we highlight the current landscape, limitations (e.g., differing operationalization), and contentions surrounding the NPS literature. We also outline theories that could clear up contention and inspire future NPS research.

Fertility History and Risk of Cognitive Impairment Among Older Parents in the United States

OBJECTIVES

I work from a gendered life-course perspective to examine the association between older parents' fertility history (i.e., timing and parity) and their risk of cognitive impairment in the United States.

METHODS

I analyze nationally representative data from 9 waves over 16 years of the Health and Retirement Study (2000-2016). The sample includes 14,543 respondents (6,108 men and 8,435 women) aged 50 and older at the baseline survey. I examine the relationship between parity, age at first birth, and age at last birth with risk of cognitive impairment using nonlinear discrete-time hazard models.

RESULTS

Adjusting for the effects of full covariates, there are U-shaped relationships between women's age at last birth and risk of cognitive impairment and between women's parity and risk of cognitive impairment. In the sensitivity tests, the relationships remain robust when sampling weights are applied, or mortality selection is corrected.

DISCUSSION

Fertility timing and parity are likely factors associated with the risk of cognitive impairment for older women. Understanding fertility history and its impact on cognition can help identify the most vulnerable subpopulations, so that more effective interventions can be made to improve cognitive functioning among older adults.

Ameliorating Effect of Morin Hydrate on Chronic Restraint Stress-induced Biochemical Disruption, Neuronal, and Behavioral Dysfunctions in BALB/c Mice

INTRODUCTION

Morin hydrate (MH) is a bioflavonoid component of many fruits and vegetables. Our previous research demonstrated that MH provides neuroprotection in mouse models of acute restraint stress and sleep deprivation by attenuating hippocampal neuronal damage and enhancing memory. Based on these findings, our study investigated the role of MH in chronic stress-induced neuronal and biochemical perturbations in BALB/c mice.

METHODS

Male BALB/c mice were divided into 6 groups (n=6). Groups 1 and 2 received vehicle (10 mL/kg normal saline), groups 3-5 received MH (5, 10, 20 mg/kg IP), while group 6 received ginseng (25 mg/kg) daily and 30 minutes afterward were restrained in a plastic cylindrical restrainer for 14 days.

RESULTS

Immobility time in the forced swim test increased in the MH-treated group, indicating an antidepressant-like effect. Also, a reduction in frequency and duration of open arms exploration was observed in the elevated plus-maze (EPM) test in stressed mice, and administration of MH (5, 10, 20 mg/kg, IP) reversed these effects. An increase in blood levels of glucose, triglycerides, total cholesterol, and brain malondialdehyde and nitrite levels was observed in the stressed groups, which was reversed by MH. Furthermore, MH reversed the stress-induced reduction in HDL cholesterol and glutathione (GSH) levels and attenuated stress-induced alterations in the prefrontal cortex and hippocampus.

CONCLUSION

Our findings suggest that MH attenuated chronic restraint stress-behavioral and biochemical perturbations, probably due to its capability to decrease oxidative stress and brain neuronal damage.

HIGHLIGHTS

Chronic stress perturbs physiological and psychological homeostasis;Morin hydrate normalized chronic stress-induced biochemical disruptions;Morin hydrate attenuated structural changes in prefrontal cortex and hippocampus.

PLAIN LANGUAGE SUMMARY

Stress is a state of being overwhelmed by demands exceeding the personal and social means of coping. Exposure to excessive stress has resulted in disruption of neurochemical and physiological processes, which sometimes manifest as behavioural abnormalities. Therefore to cope with the stressful life style, there is need to develop a therapeutic agent of plant origin. Morin hydrate is a flavonoid with known antioxidant and neuroprotective properties; however, its effect in a stressful condition has not been studies. The study thus evaluated ameliorating effect of Morin hydrate on chronic restraint stress-induced biochemical disruption, neuronal and behavioral dysfunctions in BALB/c mice. To achieve this, mice were exposed to chronic restraint stress protocol for fourteen days. Behavioural changes were examined using various techniques. The vital parameters like antioxidant, glucose and nitrite levels were also taken. Our findings show that Morin hydrate prevented behavioral abnormalities and damage to the brain cells. It also inhibited stress-induced biochemical disturbance.

Feasibility of Hair Cortisol as a Biomarker of Chronic Stress in People With Dementia

Hair cortisol concentrations (HCC) are an innovative way to measure chronic stress relying on a small sample of hair. To date, there are no studies that have studied HCC as a biomarker of chronic stress in individuals with dementia. Given the vulnerability to chronic stress in people with dementia, using HCC as an objective measure of physiological stress in those with dementia has potential to enhance our understanding of this population. The goal of this exploratory, multidisciplinary, pilot study was to establish feasibility of HCC testing in people with dementia as a biomarker of chronic stress. HCC was examined over a 6-month period to assess physiological stress response during a transition to memory care. Newly admitted memory care residents ( n = 13, mean age = 82) were followed over 6 months. Residents’ hair samples and health information were collected at 3-month intervals. HCC levels significantly changed during the transition to memory care, which may reflect chronic physiological stress. Participants with frequent behavioral and psychological symptoms of dementia (BPSD) had significantly lower HCC at baseline and exhibited a blunted cortisol reactivity at follow-up. Based on detected changes in HCC, participants likely experienced stress reactions during the transition to memory care, providing preliminary evidence that HCC may be a useful, non-invasive measure of physiological stress in this population. This approach may also be applied to understanding the significance of person-centered care environments on minimizing chronic stress for people with dementia.

Chronic Stress Induces Hippocampal Mitochondrial Damage in APPPS1 Model Mice and Wildtype Littermates

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disorder and the most common cause of dementia worldwide. Despite decades of investigation, the etiology of AD is not fully understood, although emerging evidence suggest that chronic environmental and psychological stress plays a role in the mechanisms and contributes to the risk of developing AD. Thus, dissecting the impact of stress on the brain could improve our understanding of the pathological mechanisms.

OBJECTIVE

We aimed to study the effect of chronic stress on the hippocampal proteome in male APPPS1 transgenic mice and wildtype (WT) littermates.

METHODS

APPPS1 and WT mice were subjected to 4 weeks of chronic stress followed by 3 weeks of continued diurnal disruption. Hippocampal tissue was used for proteomics analysis using label-free quantitative DIA based LC-MS/MS analysis.

RESULTS

We identified significantly up- and downregulated proteins in both APPPS1 and WT mice exposed to chronic stress compared to the control groups. Via interaction network mapping, significant proteins could be annotated to specific pathways of mitochondrial function (oxidative phosphorylation and TCA cycle), metabolic pathways, AD pathway and synaptic functions (long term potentiation). In WT mice, chronic stress showed the highest impact on complex I of the oxidative phosphorylation pathway, while in APPPS1 mice this pathway was compromised broadly by chronic stress.

CONCLUSION

Our data shows that chronic stress and amyloidosis additively contribute to mitochondrial damage in hippocampus. Although these results do not explain all effects of chronic stress in AD, they add to the scientific knowledge on the topic.

Naturally Occurring Antioxidant Therapy in Alzheimer’s Disease

It is estimated that the prevalence rate of Alzheimer’s disease (AD) will double by the year 2040. Although currently available treatments help with symptom management, they do not prevent, delay the progression of, or cure the disease. Interestingly, a shared characteristic of AD and other neurodegenerative diseases and disorders is oxidative stress. Despite profound evidence supporting the role of oxidative stress in the pathogenesis and progression of AD, none of the currently available treatment options address oxidative stress. Recently, attention has been placed on the use of antioxidants to mitigate the effects of oxidative stress in the central nervous system. In preclinical studies utilizing cellular and animal models, natural antioxidants showed therapeutic promise when administered alone or in combination with other compounds. More recently, the concept of combination antioxidant therapy has been explored as a novel approach to preventing and treating neurodegenerative conditions that present with oxidative stress as a contributing factor. In this review, the relationship between oxidative stress and AD pathology and the neuroprotective role of natural antioxidants from natural sources are discussed. Additionally, the therapeutic potential of natural antioxidants as preventatives and/or treatment for AD is examined, with special attention paid to natural antioxidant combinations and conjugates that are currently being investigated in human clinical trials.

Parental status in later life and parents' risk of cognitive impairment

Parental status can influence parents’ well-being in significant ways, but little research has examined its impact on older adults’ cognitive health in the U.S. Using data from the National Health and Aging Trends Study (NHATS) 2011–2019, this study examines whether parental status is related to the risk of cognitive impairment among older adults in the U.S. We found that the presence of adult children (i.e., having at least one living adult child) was associated with a lower risk of cognitive impairment for older parents. Moreover, compared to childless older adults, older parents who had three and more children, who had adult daughter(s), and who had biological/adopted adult children displayed a significantly lower risk of cognitive impairment. This study highlights the importance of adult children as resources of support and caring that may benefit older parents’ cognitive health. The findings can help to identify the most vulnerable subpopulations among aging adults so that medical workers and policy makers can design effective strategies to protect cognitive function for those “at risk” older adults.

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Parental status is an important factor related to older adults’ cognitive health.

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Presence of adult children was associated with a lower risk of cognitive impairment than being childlessness.

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Having 3+ children, adult daughter(s), or biological children was associated with lower risk of cognitive impairment.

Enduring glucocorticoid-evoked exacerbation of synaptic plasticity disruption in male rats modelling early Alzheimer's disease amyloidosis

Synaptic dysfunction is a likely proximate cause of subtle cognitive impairment in early Alzheimer's disease. Soluble oligomers are the most synaptotoxic forms of amyloid ß-protein (Aß) and mediate synaptic plasticity disruption in Alzheimer's disease amyloidosis. Because the presence and extent of cortisol excess in prodromal Alzheimer's disease predicts the onset of cognitive symptoms we hypothesised that corticosteroids would exacerbate the inhibition of hippocampal synaptic long-term potentiation in a rat model of Alzheimer's disease amyloidosis. In a longitudinal experimental design using freely behaving pre-plaque McGill-R-Thy1-APP male rats, three injections of corticosterone or the glucocorticoid methylprednisolone profoundly disrupted long-term potentiation induced by strong conditioning stimulation for at least 2 months. The same treatments had a transient or no detectible detrimental effect on synaptic plasticity in wild-type littermates. Moreover, corticosterone-mediated cognitive dysfunction, as assessed in a novel object recognition test, was more persistent in the transgenic animals. Evidence for the involvement of pro-inflammatory mechanisms was provided by the ability of the selective the NOD-leucine rich repeat and pyrin containing protein 3 (NLRP3) inflammasome inhibitor Mcc950 to reverse the synaptic plasticity deficit in corticosterone-treated transgenic animals. The marked prolongation of the synaptic plasticity disrupting effects of brief corticosteroid excess substantiates a causal role for hypothalamic-pituitary-adrenal axis dysregulation in early Alzheimer's disease.

Highlighting Immune System and Stress in Major Depressive Disorder, Parkinson's, and Alzheimer's Diseases, with a Connection with Serotonin

There is recognition that both stress and immune responses are important factors in a variety of neurological disorders. Moreover, there is an important role of several neurotransmitters that connect these factors to several neurological diseases, with a special focus in this paper on serotonin. Accordingly, it is known that imbalances in stressors can promote a variety of neuropsychiatric or neurodegenerative pathologies. Here, we discuss some facts that link major depressive disorder, Alzheimer’s, and Parkinson’s to the stress and immune responses, as well as the connection between these responses and serotonergic signaling. These are important topics of investigation which may lead to new or better treatments, improving the life quality of patients that suffer from these conditions.

The Association between Widowhood and Cognitive Function among Chinese Elderly People: Do Gender and Widowhood Duration Make a Difference?

Few studies have examined the effects of widowhood on cognitive function in Chinese elderly individuals. We conducted a longitudinal study to assess the association between widowhood and cognitive function and further explored gender differences in this association and the impact of widowhood duration. The analytical sample consisted of 5872 Chinese elderly people who participated in the Chinese Longitudinal Healthy Longevity Survey (CLHLS) and were followed up from 2005 to 2014. We used the Chinese version of the Mini-Mental State Examination (MMSE) to assess cognitive function. Widowhood duration was calculated from the self-reported year at which the spouse passed away. Multilevel growth models were employed to estimate the association between widowhood and cognitive function while adjusting for many demographic and socioeconomic characteristics. Widowhood status was associated with cognitive decline among Chinese elderly individuals after adjusting for covariates (B = −0.440, 95% CI −0.727 to −0.152), and this association was only statistically significant among men (B = −0.722, 95% CI −1.104 to −0.339). Being widowed for 5 years or less (B = −0.606, 95% CI −1.112 to −0.100), 16–20 years (B = −0.937, 95% CI −1.685 to −0.190), and 21+ years (B = −1.401, 95% CI −1.967 to −0.834) predicted worse cognitive function in men, while being widowed for more than 21+ years (B = −0.655, 95% CI −1.186 to −0.124) was associated with cognitive decline in women. More attention should be directed towards widowed men and long-term widowed elderly individuals.

Parental Death and Cognitive Impairment: An Examination by Gender and Race-ethnicity

OBJECTIVES

We provide the first nationally representative longitudinal study of cognitive impairment in relation to parental death from childhood through early adulthood, midlife, and later adulthood, with attention to heterogeneity in the experience of parental death.

METHOD

We analyzed data from the Health and Retirement Study (2000-2016). The sample included 13,392 respondents, contributing 72,860 person-periods. Cognitive impairment was assessed using the modified version of the Telephone Interview for Cognitive Status (TICS). Discrete-time hazard regression models were estimated to predict the odds of cognitive impairment.

RESULTS

Both exposure and timing of parental death were related to risk of cognitive impairment in late life and associations vary by gender. The detrimental effect of a father's death was comparable for daughters and sons although exposure to mother's death had stronger effects on daughter's than son's risk of cognitive impairment. Father's death at younger ages had the strongest effect on sons' late-life risk of cognitive impairment whereas mother's death in middle adulthood had the strongest effect on daughters' risk. We found no significant racial-ethnic variation in the association between parental death and cognitive impairment.

DISCUSSION

It is important to explore the gender-specific pathways through which parental death leads to increased risk of cognitive impairment so that effective interventions can be implemented to reduce risk.

A national longitudinal study of marital quality and cognitive decline among older men and women

We provide one of the first national longitudinal studies of the association between trajectories of marital quality and cognitive functioning among older adults, with close attention paid to gender differences. Data were drawn from the Health and Retirement Study (HRS) 2006-2016. Marital quality trajectories were assessed at three waves: 2006/2008, 2010/2012, and 2014/2016. Cognitive trajectories were assessed at five waves: 2008, 2010, 2012, 2014, and 2016. The final analytic sample included 7901 respondents age 50 and older (4334 men and 3567 women) who were either married or cohabiting during the study period. Results from parallel linear growth curve models suggest that among older adults, initial positive marital quality was associated with better initial cognition, and initial negative marital quality was associated with worse initial cognition. Results from multiple group analysis further suggest that marital quality was significantly associated with men's cognitive trajectories but not women's. Among men, an increase in positive marital quality was associated with a slower rate of cognitive decline, whereas an increase in negative marital quality was associated with a faster rate of cognitive decline. These findings suggest that older men who experience a decline in marital quality may be vulnerable to cognitive decline and that reducing marital strain and improving marital quality may protect men's cognitive health in later life.

Gender Differences in the Link Between Marital Status and the Risk of Cognitive Impairment: Results From the Korean Longitudinal Study of Aging

In the context of South Korea, characterized by increasing population aging and a changing family structure, this study examined differences in the risk of cognitive impairment by marital status and investigated whether this association differs by gender. The data were derived from the 2006-2018 Korean Longitudinal Study of Aging. The sample comprised 7,568 respondents aged 45 years or older, who contributed 30,414 person-year observations. Event history analysis was used to predict the odds of cognitive impairment by marital status and gender. Relative to their married counterparts, never-married and divorced people were the most disadvantaged in terms of cognitive health. In addition, the association between marital status and cognitive impairment was much stronger for men than for women. Further, gender-stratified analyses showed that, compared with married men, never-married men had a higher risk of cognitive impairment, but there were no significant effects of marital status for women.

Methyl Jasmonate: Behavioral and Molecular Implications in Neurological Disorders

Methyl jasmonate (MJ) is a derivative of the jasmonate family which is found in most tropical regions of the world and present in many fruits and vegetables such as grapevines, tomato, rice, and sugarcane. MJ is a cyclopentanone phytohormone that plays a vital role in defense against stress and pathogens in plants. This has led to its isolation from plants for studies in animals. Many of these studies have been carried out to evaluate its therapeutic effects on behavioral and neurochemical functions. It has however been proposed to have beneficial potential over a wide range of neurological disorders. Hence, this review aims to provide an overview of the neuroprotective properties of MJ and its probable mechanisms of ameliorating neurological disorders. The information used for this review was sourced from research articles and scientific databases using 'methyl jasmonate', 'behavior', 'neuroprotection', 'neurodegenerative diseases', and 'mechanisms' as search words. The review highlights its influences on behavioral patterns of anxiety, aggression, depression, memory, psychotic, and stress. The molecular mechanisms such as modulation of the antioxidant defense, inflammatory biomarkers, neurotransmitter regulation, and neuronal regeneration, underlying its actions in managing neurodegenerative diseases like Alzheimer's and Parkinson's diseases are also discussed. This review, therefore, provides a detailed evaluation of methyl jasmonate as a potential neuroprotective compound with the ability to modify behavioral and molecular biomarkers underlying neurological disorders. Hence, MJ could be modeled as a guided treatment for the management of brain diseases.

Grape seed extract effects on hippocampal neurogenesis, synaptogenesis and dark neurons production in old mice. Can this extract improve learning and memory in aged animals?

BACKGROUND

During the elderly, hippocampal neurogenesis and synaptogenesis reduce and dark neurons (DNs) increase, leading to cognitive impairment. It is believed that natural products can protect the neural cells and system by protecting from damages or promoting regeneration. Therefore, the effects of grape seed extract (GSE) on the hippocampus of aged mice were investigated in this study.

METHODS

twelve old mice were divided into two groups of control and GSE. Animals in the GSE group received 300 mg/kg of GSE for eight weeks via gavage. At the end of treatment, cognition performance was evaluated by Morris water maze (MWM) and passive avoidance tests. Hippocampal neurogenesis, synaptogenesis and DNs production were evaluated with immunohistochemistry and histological evaluations on 5-micron coronal tissue sections.

RESULTS

The hippocampal mean number of double cortin positive cells (DCX⁺) per unit area, as well as synaptophysin expression in the GSE group, were significantly higher than the control group (p < 0.01). The frequency of DNs in the GSE group was lower than the control group (p < 0.05). Behavioral tests showed that GSE improves memory and learning performance.

CONCLUSION

Consuming GSE in the elderly can potentially alleviate the age-related reduction of hippocampal neurogenesis and synaptogenesis. It is also able to decrease hippocampal DNs production and increase memory and learning.

Dysbiosis and Alzheimer's Disease: A Role for Chronic Stress?

Alzheimer’s disease (AD) is an incurable, neuropsychiatric, pathological condition that deteriorates the worth of geriatric lives. AD is characterized by aggregated senile amyloid plaques, neurofibrillary tangles, neuronal loss, gliosis, oxidative stress, neurotransmitter dysfunction, and bioenergetic deficits. The changes in GIT composition and harmony have been recognized as a decisive and interesting player in neuronal pathologies including AD. Microbiota control and influence the oxidoreductase status, inflammation, immune system, and the endocrine system through which it may have an impact on the cognitive domain. The altered and malfunctioned state of microbiota is associated with minor infections to complicated illnesses that include psychosis and neurodegeneration, and several studies show that microbiota regulates neuronal plasticity and neuronal development. The altered state of microbiota (dysbiosis) may affect behavior, stress response, and cognitive functions. Chronic stress-mediated pathological progression also has a well-defined role that intermingles at various physiological levels and directly impacts the pathological advancement of AD. Chronic stress-modulated alterations affect the well-established pathological markers of AD but also affect the gut–brain axis through the mediation of various downstream signaling mechanisms that modulate the microbial commensals of GIT. The extensive literature reports that chronic stressors affect the composition, metabolic activities, and physiological role of microbiota in various capacities. The present manuscript aims to elucidate mechanistic pathways through which stress induces dysbiosis, which in turn escalates the neuropathological cascade of AD. The stress–dysbiosis axis appears a feasible zone of work in the direction of treatment of AD.

Navigating Alzheimer's Disease via Chronic Stress: The Role of Glucocorticoids

Alzheimer's disease (AD) is a chronic intensifying incurable progressive disease leading to neurological deterioration manifested as impairment of memory and executive brain functioning affecting the physical ability like intellectual brilliance, common sense in patients. The recent therapeutic approach in Alzheimer's disease is only the symptomatic relief further emerging the need for therapeutic strategies to be targeted in managing the underlying silent killing progression of dreaded pathology. Therefore, the current research direction is focused on identifying the molecular mechanisms leading to the evolution of the understanding of the neuropathology of Alzheimer's disease. The resultant saturation in the area of current targets (amyloid β, τ Protein, oxidative stress etc.) has led the scientific community to rethink of the mechanistic neurodegenerative pathways and reprogram the current research directions. Although, the role of stress has been recognized for many years and contributing to the development of cognitive impairment, the area of stress has got the much-needed impetus recently and is being recognized as a modifiable menace for AD. Stress is an unavoidable human experience that can be resolved and normalized but chronic activation of stress pathways unsettle the physiological status. Chronic stress mediated activation of neuroendocrine stimulation is generally linked to a high risk of developing AD. Chronic stress-driven physiological dysregulation and hypercortisolemia intermingle at the neuronal level and leads to functional (hypometabolism, excitotoxicity, inflammation) and anatomical remodeling of the brain architecture (senile plaques, τ tangles, hippocampal atrophy, retraction of spines) ending with severe cognitive deterioration. The present review is an effort to collect the most pertinent evidence that support chronic stress as a realistic and modifiable therapeutic earmark for AD and to advocate glucocorticoid receptors as therapeutic interventions.

Late-onset epilepsy and subsequent increased risk of dementia

Inflammation is considered as a key pathogenesis factor of dementia and epilepsy. However, epilepsy's association with dementia, particularly its role in the development of dementia, remains unclear. To evaluate the association between epilepsy and the risk of dementia, in Taiwan, we have now conducted a retrospective cohort study comprising 675 individuals (age, ≥50 years) with epilepsy and 2,025 matched control subjects without epilepsy. In order to match individuals diagnosed with epilepsy with those with no diagnosis of epilepsy (comparison cohort), we utilized exact matching at a ratio of 1:3. Compared with those in the comparison cohort, individuals in the epilepsy cohort had a significantly increased risk of developing dementia (adjusted hazard ratio = 2.87, p < 0.001). A similar result has been observed after stratifying for sex (adjusted hazard ratio in males = 2.95, p < 0.001; adjusted hazard ratio in females = 2.66, p < 0.001). To conclude, based on these data, epileptic individuals ≥50 years were at a greater risk of developing dementia than people who do not have epilepsy, which indicates that a diagnosis of epilepsy presents a greater risk for the development of dementia.

Chronic Stress in Cognitive Processes: Cortisol Dynamic Range of Secretion Is Associated with Perception of Unsafety Environment in a Venezuelan Population

BACKGROUND

Understanding diurnal secretion of cortisol in association with behavioral attitudes as a result of perception of unsafety environment is a main interest in prospective studies establishing the impact of chronic stress in cognitive processes. Adaptive secretion of cortisol, a biomarker of the hypothalamic-hypophysis-adrenal (HPA) axis, has been correlated with perception of uncertainty in surroundings as a consequence of perseverative cognition and unconscious thoughts.

OBJECTIVE

To determine whether diurnal secretion pattern of cortisol was associated with behavioral attitudes indexes generated from answers to standardized questionnaires from Panamerican Health Organization/World Health Organization (PAHO/WHO) agencies.

METHODS

Saliva cortisol dynamic range was evaluated by immuno-essay. Cortisol awakening response (CAR) and total secreted cortisol was established in a cross-sectional study of four saliva samples per day from volunteers (n = 135) between 19 and 65 years old.

RESULTS

Saliva cortisol dynamic range followed a significant decay along the day. Reduction of social interaction and increase of defensive behavioral attitude was associated with older groups of age. In this study, two subgroups of subjects with a steeper cortisol secretion (slope significant non-zero), and flatter cortisol secretion (slope no significant non-zero) were detected. Noticeable, we determined an association between measurements of cortisol secretion from subjects with a flatter cortisol dynamic range and behavioral defensive and inhibition of social interaction indexes.

CONCLUSION

These findings suggested chronical dysregulation of HPA axis as a result of perseverative cognitive perception of unsafety environment which may be precedent to cognitive impairment in the population.

Environmental Risk Factors for Early-Onset Alzheimer's Dementia and Frontotemporal Dementia: A Case-Control Study in Northern Italy

Background: Early-onset dementia (EOD) is defined as dementia with symptom onset before 65 years. The role of environmental risk factors in the etiology of EOD is still undefined. We aimed at assessing the role of environmental risk factors in EOD etiology, taking into account its different clinical types. Methods: Using a case-control study, we recruited all EOD cases referred to Modena hospitals from 2016 to 2019, while the referent population was drawn from cases' caregivers. We investigated residential history, occupational and environmental exposures to chemicals and lifestyle behaviors through a self-administered questionnaire. We computed the odds ratios of EOD risk (overall and restricting to the Alzheimer's dementia (AD) or frontotemporal dementia (FTD) diagnoses) and the corresponding 95% confidence intervals using an unconditional logistic regression model. Results: Fifty-eight EOD patients (19 FTD and 32 AD) and 54 controls agreed to participate. Most of the investigated exposures, such as occupational exposure to aluminum, pesticides, dyes, paints or thinners, were associated with an increased odds ratio (OR) for FTD but not for AD. Long-term use of selenium-containing dietary supplements was associated with increased OR for EOD and, particularly, for FTD. For both EOD forms, smoking and playing football showed an increased odds ratio, while cycling was associated with increased risk only in FTD. Overall sports practice appeared to be a protective factor for both types. Conclusions: Our results suggest a role of environmental and behavioral risk factors such as some chemical exposures and professional sports in EOD etiology, in particular with reference to FTD. Overall sports practice may be associated with a reduced EOD risk.

Heat stress induced oxidative damage and perturbation in BDNF/ERK1/2/CREB axis in hippocampus impairs spatial memory

Heat exposure is an environmental stress that causes diverse heat related pathophysiological changes under extreme conditions. The brain including hippocampal region which is associated with learning and memory is significantly affected by heat stress resulting in memory impairment. However, the effect of heat on the spatial memory remains unclear. The present study aimed to explore the effect of heat stress on hippocampus and spatial memory in rats. Rat model of acute heat stress was used which was divided into two groups, viz. moderate heat stress (MHS) and severe heat stress (SHS). Redox parameters evaluation revealed that MHS and SHS exposure markedly increase the production of malondialdehyde (MDA), oxidised glutathione (GSSG), reactive oxidative species (ROS), protein oxidation level and decrease the reduced glutathione (GSH) levels in the hippocampal tissue. Furthermore, Cresyl Violet (CV) staining of hippocampal region showed higher pyknosis in rats exposed to SHS. Pronounced increase of caspase3 expression and Fluoro Jade-C (FJ-C) positive cells were observed in SHS resulting in neuronal injury and apoptosis in CA3 region of hippocampus culminating in spatial memory deficit. Our data also suggest that heat stress induces phospho Extracellular signal-regulated kinases (pERK)1/2 activation induced by Brain-derived neurotrophic factor (BDNF) leading to further activation of phospho cAMP-response element binding protein (pCREB) under MHS. However, during SHS, BDNF and pCREB expression were completely dysregulated and not sufficient to rescue cognitive decline in rats. In conclusion, SHS induces pathological alterations that include oxidative damage and apoptosis of hippocampal neurons, disturbing BDNF/ERK1/2/CREB axis that may affect spatial memory.

Sex differences in exercise efficacy: Is midlife a critical window for promoting healthy cognitive aging?

Dementia is one of the most pressing health care issues of this century. As no curative treatment for dementia exists, research efforts are growing to identify effective lifestyle interventions to prevent or delay onset. One such promising strategy that promotes cognitive and brain health is engaging in physical exercise. However, current exercise recommendations are imprecise. To advance the potential of exercise as a preventative and treatment strategy, important questions regarding moderators (ie, biological sex and age) are being addressed in the literature. Biological sex is recognized as an important variable to consider in exercise efficacy on brain health, with females showing greater cognitive gains. This may be related to sex differences in underlying mechanisms. Here, we argue to better understand the sex differences in exercise efficacy, the timing of exercise intervention should also be considered. Specifically, we present the hypothesis that midlife in females is a critical window for the implementation of exercise as an early intervention to promote brain health and prevent dementia. Further, we speculate that exercise interventions targeting midlife will be of critical importance for the female brain, as females exit this period of the lifespan at greater risk for cognitive impairment. Given the potential sex differences in dementia risk and prevalence, it is imperative to assess potential sex differences in exercise efficacy as an early intervention during midlife.

Dietary Inflammatory Potential and the Risk of Neurodegenerative Diseases in Adults

Nutrition and diet have been suggested to enhance or inhibit cognitive performance and the risk of several neurodegenerative diseases. We conducted a systematic review to elucidate the relationship between the inflammatory capacity of a person's diet and the risk of incident neurodegenerative diseases. We searched major medical databases for articles published through June 30, 2018. Original, full-text, English-language articles on studies with human participants which investigated the link between dietary inflammatory potential and risk of developing neurodegenerative diseases were included. Duplicate and irrelevant studies were removed, and data were compiled through critical analysis. Initially, 457 articles were collected via the searching method, of which 196 studies remained after removal of duplicates. Fourteen articles were screened and found to be relevant to the scope of the review. After critical analysis, 10 were included in the final review. In all studies but one, a higher dietary inflammatory index (DII) was related to higher risk of developing neurodegenerative disease symptoms, including memory and cognition decline and multiple sclerosis. Of 3 studies that assessed the association of DII with levels of circulating inflammation markers, 2 indicated that DII was positively correlated with inflammatory marker levels. Low literacy, an unhealthy lifestyle, and individual nutritional status were the factors involved in a diet with inflammatory potential. These findings enhance confidence that DII is an appropriate tool for measurement of dietary inflammatory potential and validate the role of diets with inflammatory potential in the pathophysiology of neurodegenerative diseases. DII may be correlated with levels of circulating inflammatory markers.

Impact of Alzheimer's disease and related dementia diagnosis following treatment for bladder cancer

OBJECTIVES

Our objective was to assess the incidence of Alzheimer's Disease and related dementia diagnosis following treatment for muscle-invasive bladder cancer and impact on survival outcomes.

MATERIALS AND METHODS

A total of 4814 patients diagnosed with clinical stage T2-T4a, N0, M0 bladder cancer between January 1, 2002 to December 31, 2011 using the Surveillance, Epidemiology, and End Results (SEER)-Medicare database were identified. Alzheimer's disease and related dementia diagnosis was identified using International Statistical Classification of Disease-Ninth Edition outpatient and inpatient codes. Incidence of dementia following treatment were calculated and reported as dementia cases per 10,000 person-years. Cox proportional hazards models were used to assess the impact of dementia on survival outcomes.

RESULTS

Of the 4814 patients, 2403 (49.9%) underwent radical cystectomy (RC) and 2411 (50.1%) underwent radiotherapy (RTX) and/or chemotherapy (CTX). Overall, 837 (17.4%) patients developed Alzheimer's disease and related dementia following bladder cancer treatment. There was no significant difference in the incidence of Alzheimer's disease and related dementia following either treatment. Patients diagnosed with Alzheimer's disease and related dementia had worse overall (Hazard Ratio (HR), 2.64; 95% Confidence Interval (CI), 2.41-2.89) and cancer-specific (HR, 2.45; 95% CI, 2.18-2.76) survival than those without a dementia diagnosis following treatment.

CONCLUSION

While we observed no difference in new-onset Alzheimer's disease and related dementia diagnosis following RC or RTX and/or CTX, patients with a Alzheimer's and related dementia diagnosis was associated with worse overall and cancer-specific survival. These findings have important implications for screening and the development of targeted interventions for improving outcomes in older adults following complex cancer treatments, as observed in this bladder cancer population.

The effects of stress on cardiovascular disease and Alzheimer's disease: Physical exercise as a counteract measure

AD is a complicated multi-systemic neurological disorder that involves different biological pathways. Several risk factors have been identified, including chronic stress. Chronic stress produces an alteration in the activity of the hypothalamic pituitary adrenal (HPA) system, and the autonomic nervous system (ANS), which over time increase the risk of AD and also the incidence of cardiovascular disease (CVD) and risk factors, such as hypertension, obesity and type 2 diabetes, associated with cognitive impairment and AD. Considering the multi-factorial etiology of AD, understanding the complex interrelationships between different risk factors is of potential interest for designing adequate strategies for preventing, delaying the onset or slowing down the progression of this devastating disease. Thus, in this review we will explore the general mechanisms and evidence linking stress, cardiovascular disease and AD, and discuss the potential benefits of physical activity for AD by counteracting the negative effects of chronic stress, CVD and risk factors.

Sex and Gender Driven Modifiers of Alzheimer's: The Role for Estrogenic Control Across Age, Race, Medical, and Lifestyle Risks

Research indicates that after advanced age, the major risk factor for late-onset Alzheimer’s disease (AD) is female sex. Out of every three AD patients, two are females with postmenopausal women contributing to over 60% of all those affected. Sex- and gender-related differences in AD have been widely researched and several emerging lines of evidence point to different vulnerabilities that contribute to dementia risk. Among those being considered, it is becoming widely accepted that gonadal steroids contribute to the gender disparity in AD, as evidenced by the “estrogen hypothesis.” This posits that sex hormones, 17β-estradiol in particular, exert a neuroprotective effect by shielding females’ brains from disease development. This theory is further supported by recent findings that the onset of menopause is associated with the emergence of AD-related brain changes in women in contrast to men of the same age. In this review, we discuss genetic, medical, societal, and lifestyle risk factors known to increase AD risk differently between the genders, with a focus on the role of hormonal changes, particularly declines in 17β-estradiol during the menopause transition (MT) as key underlying mechanisms.

Stress and verbal memory in patients with Alzheimer's disease: different role of cortisol and anxiety

Objectives: Chronic stress has shown to have marked effects on learning and memory. A broader understanding of these effects has special interest in the context of Alzheimer's disease (AD). This study aims to analyze the moderating effect of cognitive impairment in the relationships between stress and verbal memory performance by considering biological and psychological measures of stress. Method: The sample consisted of 80 AD patients and 104 healthy controls. Salivary cortisol and state anxiety was measured as stress markers. Memory Alteration test (M@T) and Hopkins verbal learning test (HVLT-R) were used to measure verbal memory. Results: In controls, cortisol level was negatively associated with HVLT-R total, learning and delayed recall scores as well as M@T free recall scores, while in patients, such associations were not significant. In this group, cortisol negative effects were limited to HVLT-R learning and M@T semantic memory scores. In both groups, anxiety was associated with better M@T encoding and free recall scores. Besides, inverted U-shaped relationships were observed between anxiety and HVLT-R total recall and learning scores as well as M@T orientation scores. Conclusion: Cortisol levels and anxiety are differentially associated with memory performance in older adults. In general, the negative relationship between cortisol levels and memory observed in healthy elderly weakens in AD. However, moderate state anxiety levels seem to be associated with a better memory performance in AD patients and in healthy elderly.

The Effects of Hand Massage on Stress and Agitation Among People with Dementia in a Hospital Setting: A Pilot Study

Agitation in people with dementia is a growing concern as it causes distress for both patients and their nurses and may contribute to relational disorders. Previous studies involving patients with dementia living in long-term care facilities have reported decreased agitation following massage. The objective of this pilot study was to investigate the effect of hand massage on agitation and biological markers of stress in patients with dementia hospitalized in an acute geriatric psychiatry service. In this randomized controlled trial we included 40 agitated patients with dementia with an intervention group and a control group. The study is designed to test the effect of seven hand massages over three continuous weeks on agitation and levels of salivary cortisol (sC) and alpha-amylase (sAA). Compared to the control group, the intervention group exhibited larger increases in sC and sAA at week 1 from before to after the massage, but larger decreases at week 2 and 3, with a significant group effect for sAA at week 2. Agitation scores were not significantly different between the groups but tended to decrease more in the intervention group than the control group. This study provides first encouraging results suggesting that hand massage might have beneficial effects on stress and agitation in hospitalized patients with dementia. It also highlights the challenges associated with conducting such studies with this complex patient population. Further studies are needed to confirm these findings and the benefits of hand massage as part of routine care for patients with dementia.

Alzheimer's Disease and Its Potential Alternative Therapeutics

Alzheimer’s Disease (AD) is a chronic neurodegenerative disease that affects over 5 million individuals in the United States alone. Currently, there are only two kinds of pharmacological interventions available for symptomatic relief of AD; Acetyl Cholinesterase Inhibitors (AChEI) and N-methyl-D-aspartic Acid (NMDA) receptor antagonists and these drugs do not slow down or stop the progression of the disease. Several molecular targets have been implicated in the pathophysiology of AD, such as the tau (τ) protein, Amyloid-beta (Aβ), the Amyloid Precursor Protein (APP) and more and several responses have also been observed in the advancement of the disease, such as reduced neurogenesis, neuroinflammation, oxidative stress and iron overload. In this review, we discuss general features of AD and several small molecules across different experimental AD drug classes that have been studied for their effects in the context of the molecular targets and responses associated with the AD progression. These drugs include: Paroxetine, Desferrioxamine (DFO), N-acetylcysteine (NAC), Posiphen/-(−)Phenserine, JTR-009, Carvedilol, LY450139, Intravenous immunoglobulin G 10%, Indomethacin and Lithium Carbonate (Li₂CO₃).

Mindfulness and psychoeducation to manage stress in amnestic mild cognitive impairment: A pilot study

Objectives: Amnestic mild cognitive impairment (aMCI) often corresponds to the prodromal stage of Alzheimer disease (AD). The aMCI stage represents a crucial time window to apply preventive interventions in an attempt to delay cognitive decline. Stress, one of AD's modifiable risk factors frequently co-occurring with aMCI, stands out as a key intervention target. The goal of this study was to assess the impacts of two non-pharmacological interventions, mindfulness and psychoeducation, on stress at the psychological and physiological levels among aMCI older adults. Methods: Forty-eight aMCI participants were randomized between a mindfulness-based intervention (MBI) and a psychoeducation-based intervention (PBI) for eight weekly sessions. Anxiety symptoms, perceived stress levels, cortisol awakening response (CAR), and coping strategies were assessed pre- and post-intervention. Mindfulness attitudes and time dedicated to at-home meditative practices were evaluated in the MBI group. Results: The main results revealed a slight reduction of the CAR among MBI participants who practiced meditation at home the most and a decrease in perceived stress levels in the PBI group. Both interventions enhanced problem-focused coping strategies. Conclusion: In sum, this pilot study supports the potential of MBI and PBI to reduce stress at the physiological and psychological level, respectively, and increase coping strategies in older adults at risk for AD.

Marital status and cognitive impairment in the United States: evidence from the National Health and Aging Trends Study

PURPOSE

We provide population-based longitudinal evidence of marital status differences in the risk of cognitive impairment and dementia in the United States.

METHODS

Data were from the longitudinal National Health and Aging Trends Study, 2011-2018. The sample included 7508 respondents aged 65 years and older who contributed 25,897 person-year records. We estimated discrete-time hazard models to predict the risk of dementia and cognitive impairment, not dementia (CIND), as well as impairment in three major cognitive domains: memory, orientation, and executive function.

RESULTS

Relative to their married counterparts, divorced and widowed elders had higher odds of dementia and CIND, as well as higher odds of impairment in each of the cognitive domains. Never-married elders had higher odds of impairment in memory and orientation than their married counterparts but did not differ significantly in the odds of impaired executive function, dementia, or CIND. Cohabiting elders did not differ significantly from married respondents on any measure of cognitive impairment. We found no gender differences in the associations between marital status and the measures of cognitive impairment.

CONCLUSIONS

Marital status is a potentially important but overlooked social risk/protective factor for cognitive impairment. Divorced and widowed older adults are particularly vulnerable to cognitive impairment.

Association of social contact with dementia and cognition: 28-year follow-up of the Whitehall II cohort study

BACKGROUND

There is need to identify targets for preventing or delaying dementia. Social contact is a potential target for clinical and public health studies, but previous observational studies had short follow-up, making findings susceptible to reverse causation bias. We therefore examined the association of social contact with subsequent incident dementia and cognition with 28 years' follow-up.

METHODS AND FINDINGS

We conducted a retrospective analysis of the Whitehall II longitudinal prospective cohort study of employees of London civil service departments, aged 35-55 at baseline assessment in 1985-1988 and followed to 2017. Social contact was measured six times through a self-report questionnaire about frequency of contact with non-cohabiting relatives and friends. Dementia status was ascertained from three linked clinical and mortality databases, and cognition was assessed five times using tests of verbal memory, verbal fluency, and reasoning. Cox regression models with inverse probability weighting to account for attrition and missingness examined the association between social contact at age 50, 60, and 70 years and subsequent incident dementia. Mixed linear models examined the association of midlife social contact between 45 and 55 years and cognitive trajectory during the subsequent 14 years. Analyses were adjusted for age, sex, ethnicity, socioeconomic status, education, health behaviours, employment status, and marital status. Of 10,308 Whitehall II study participants, 10,228 provided social contact data (mean age 44.9 years [standard deviation (SD) 6.1 years] at baseline; 33.1% female; 89.1% white ethnicity). More frequent social contact at age 60 years was associated with lower dementia risk (hazard ratio [HR] for each SD higher social contact frequency = 0.88 [95% CI 0.79, 0.98], p = 0.02); effect size of the association of social contact at 50 or 70 years with dementia was similar (0.92 [95% CI 0.83, 1.02], p = 0.13 and 0.91 [95% CI 0.78, 1.06], p = 0.23, respectively) but not statistically significant. The association between social contact and incident dementia was driven by contact with friends (HR = 0.90 [95% CI 0.81, 1.00], p = 0.05), but no association was found for contact with relatives. More frequent social contact during midlife was associated with better subsequent cognitive trajectory: global cognitive function was 0.07 (95% CI 0.03, 0.11), p = 0.002 SDs higher for those with the highest versus lowest tertile of social contact frequency, and this difference was maintained over 14 years follow-up. Results were consistent in a series of post hoc analyses, designed to assess potential biases. A limitation of our study is ascertainment of dementia status from electronic health records rather than in-person assessment of diagnostic status, with the possibility that milder dementia cases were more likely to be missed.

CONCLUSIONS

Findings from this study suggest a protective effect of social contact against dementia and that more frequent contact confers higher cognitive reserve, although it is possible that the ability to maintain more social contact may be a marker of cognitive reserve. Future intervention studies should seek to examine whether improving social contact frequency is feasible, acceptable, and efficacious in changing cognitive outcomes.

Chronic stress impairs the aquaporin-4-mediated glymphatic transport through glucocorticoid signaling

BACKGROUND

The glymphatic system has recently been proposed to function as a brain-wide macroscopic system for the clearance of potentially harmful molecules, such as amyloid beta (e.g., Aβ), from the brain parenchyma. Previous literatures have established that the glymphatic function is dramatically suppressed by aging, traumatic brain injury, and some diseases. However, the effect of chronic stress on the glymphatic function and its underlying mechanism remains largely unknown.

METHODS

Adult mice were randomly divided into four groups: chronic unpredictable mild stress (CUMS)-treated group, CUMS simultaneously treated with mifepristone (MFP) group, dexamethasone (DEX)-treated group, and control group. Stress response was observed by assessing the change of body weight, plasma corticosterone level, and behavior tests. The level of Aβ42 in cerebral tissue was assessed by ELISA. The glymphatic function was determined by using fluorescence tracer injection. The expression and localization of aquaporin-4 (AQP4) were evaluated by immunohistochemistry and western blot. The transcription level of AQP4 and anchoring molecules was evaluated by real-time PCR.

FINDINGS

Compared with control group, CUMS-treated mice exhibited the impairment of global glymphatic function especially in the anterior brain. This change was accompanied by the decreased expression and polarization of AQP4, reduced transcription of AQP4, agrin, laminin, and dystroglycan in the anterior cortex. Similarly, the glucocorticoid receptor (GR) agonist DEX exposure could reduce the glymphatic function and AQP4 expression. Moreover, the GR antagonist MFP treatment could significantly rescue the glymphatic function and reverse the expression and polarization of AQP4 impaired by CUMS.

CONCLUSION

Chronic stress could impair the AQP4-mediated glymphatic transport in the brain through glucocorticoid signaling. Our results also suggest that GR antagonist could be beneficial to rescue the glymphatic function suppressed by chronic stress.

High Cortisol and the Risk of Dementia and Alzheimer's Disease: A Review of the Literature

Introduction: Cortisol effects on the brain are exerted through two distinct receptors, inducing complex and even opposite effects on the cerebral structures implicated in the various cognitive functions. High cortisol may also have deleterious effects on the brain structures and contribute to neurodegeneration, in particular Alzheimer’s disease (AD), via different mechanisms.

Objective: To examine the interrelationships between cortisol, cognitive impairment and AD.

Methods: Review of the literature.

Results: Clinical studies found that elevated cortisol was associated with poorer overall cognitive functioning, as well as with poorer episodic memory, executive functioning, language, spatial memory, processing speed, and social cognition; while in animals, glucocorticoid administration resulted in cognitive impairment and abnormal behavior. In cognitively healthy subjects, higher cortisol levels have been associated with an increased risk of cognitive decline and AD. Subjects with dementia and Mild Cognitive Impairment (MCI) due to AD have been found to have higher CSF cortisol levels than cognitively healthy controls. Elevated CSF cortisol may also be associated with a more rapid cognitive decline in MCI due to AD. Elevated cortisol levels have been also found in delirium. High cortisol may mediate the impact of stressful life events, high neuroticism, depression, sleep disturbances, as well as cardiovascular risk factors on cognitive performance, neurodegeneration, and cognitive decline. High cortisol may also exert neurotoxic effects on the hippocampus, and promote oxidative stress and amyloid β peptide toxicity. Further possible underlying mechanisms include the interactions of cortisol with inflammatory mediators, neurotransmitters, and growth factors.

Conclusion: Elevated cortisol levels may exert detrimental effects on cognition and contribute to AD pathology. Further studies are needed to investigate cortisol-reducing and glucocorticoidreceptor modulating interventions to prevent cognitive decline.

Mast Cells in Stress, Pain, Blood-Brain Barrier, Neuroinflammation and Alzheimer's Disease

Mast cell activation plays an important role in stress-mediated disease pathogenesis. Chronic stress cause or exacerbate aging and age-dependent neurodegenerative diseases. The severity of inflammatory diseases is worsened by the stress. Mast cell activation-dependent inflammatory mediators augment stress associated pain and neuroinflammation. Stress is the second most common trigger of headache due to mast cell activation. Alzheimer's disease (AD) is a progressive irreversible neurodegenerative disease that affects more women than men and woman's increased susceptibility to chronic stress could increase the risk for AD. Modern life-related stress, social stress, isolation stress, restraint stress, early life stress are associated with an increased level of neurotoxic beta amyloid (Aβ) peptide. Stress increases cognitive dysfunction, generates amyloid precursor protein (APP), hyperphosphorylated tau, neurofibrillary tangles (NFTs), and amyloid plaques (APs) in the brain. Stress-induced Aβ persists for years and generates APs even several years after the stress exposure. Stress activates hypothalamic-pituitary adrenal (HPA) axis and releases corticotropin-releasing hormone (CRH) from hypothalamus and in peripheral system, which increases the formation of Aβ, tau hyperphosphorylation, and blood-brain barrier (BBB) disruption in the brain. Mast cells are implicated in nociception and pain. Mast cells are the source and target of CRH and other neuropeptides that mediate neuroinflammation. Microglia express receptor for CRH that mediate neurodegeneration in AD. However, the exact mechanisms of how stress-mediated mast cell activation contribute to the pathogenesis of AD remains elusive. This mini-review highlights the possible role of stress and mast cell activation in neuroinflammation, BBB, and tight junction disruption and AD pathogenesis.

Distinct Stress Response and Altered Striatal Transcriptome in Alpha-Synuclein Overexpressing Mice

Parkinson's disease (PD) is a progressive neurodegenerative disorder with motor symptoms and a plethora of non-motor and neuropsychiatric features that accompany the disease from prodromal to advanced stages. While several genetic defects have been identified in familial forms of PD, the predominance of cases are sporadic and result from a complex interplay of genetic and non-genetic factors. Clinical evidence, moreover, indicates a role of environmental stress in PD, supported by analogies between stress-induced pathological consequences and neuronal deterioration observed in PD. From this perspective, we set out to investigate the effects of chronic stress exposure in the context of PD by using a genetic mouse model that overexpresses human wildtype SNCA. Mimicking chronic stress was achieved by adapting a chronic unpredictable mild stress protocol (CUMS) comprising eight different stressors that were applied randomly over a period of eight weeks starting at an age of four months. A distinctive stress response with an impact on anxiety-related behavior was observed upon SNCA overexpression and CUMS exposure. SNCA-overexpressing mice showed prolonged elevation of cortisol metabolites during CUMS exposure, altered anxiety-related traits, and declined motor skills surfacing with advanced age. To relate our phenotypic observations to molecular events, we profiled the striatal and hippocampal transcriptome and used a 2 × 2 factorial design opposing genotype and environment to determine differentially expressed genes. Disturbed striatal gene expression and minor hippocampal gene expression changes were observed in SNCA-overexpressing mice at six months of age. Irrespective of the CUMS-exposure, genes attributed to the terms neuroinflammation, Parkinson's signaling, and plasticity of synapses were altered in the striatum of SNCA-overexpressing mice.

The opioid system in stress-induced memory disorders: From basic mechanisms to clinical implications in post-traumatic stress disorder and Alzheimer's disease

Cognitive and emotional impairment are a serious consequence of stress exposure and are core features of neurological and psychiatric conditions that involve memory disorders. Indeed, acute and chronic stress are high-risk factors for the onset of post-traumatic stress disorder (PTSD) and Alzheimer's disease (AD), two devastating brain disorders associated with memory dysfunction. Besides the sympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis, stress response also involves the activation of the opioid system in brain regions associated with stress regulation and memory processing. In this context, it is possible that stress-induced memory disorders may be attributed to alterations in the interaction between the neuroendocrine stress system and the opioid system. In this review, we: (1) describe the effects of acute and chronic stress on memory, and the modulatory role of the opioid system, (2) discuss the contribution of the opioid system to the pathophysiology of PTSD and AD, and (3) present evidence of current and potential therapies that target the opioid receptors to treat PTSD- and AD-associated symptoms.

Stress and the Etiopathogenesis of Alzheimer's Disease and Depression

Alzheimer's disease (AD) is a multifactorial neurodegenerative disorder with a complex physiopathology whose initiators are poorly defined. Accumulating clinical and experimental evidence suggests a causal role of lifetime stress in AD. This chapter summarizes current knowledge about how chronic stress and its accompanying high levels of glucocorticoid (GC) secretion, trigger the two main pathomechanisms of AD: (i) misprocessing of amyloid precursor protein (APP) and the generation of amyloid beta (Aβ) and (ii) Tau hyperphosphorylation and aggregation. Given that depression is a well-known stress-related illness, and the evidence that depression may precede AD, this chapter also explores neurobiological mechanisms that may be common to depressive and AD pathologies. This review also discusses emerging insights into the role of Tau and its malfunction in disrupting neuronal cascades and neuroplasticity and, thus triggering brain pathology.

Lifetime affective problems and later-life cognitive state: Over 50 years of follow-up in a British birth cohort study

BACKGROUND

Affective problems increase the risk of dementia and cognitive impairment, yet the life course dimension of this association is not clearly understood. We aimed to investigate how affective problems across the life course relate to later-life cognitive state.

METHODS

Data from 1269 participants from the Medical Research Council National Survey of Health and Development (NSHD, the British 1946 birth cohort) were used. Prospectively-assessed measures of affective symptoms spanning ages 13-69 and categorised into case-level thresholds. Outcomes consisted of a comprehensive measure of cognitive state (Addenbrooke's Cognitive Examination (ACE-III)), verbal memory, and letter search speed and accuracy at age 69.

RESULTS

Complementary life course models demonstrated that having 2 or more case-level problems across the life course was most strongly associated with poorer cognitive outcomes, before and after adjusting for sex, childhood cognition, childhood and midlife occupational position and education.

LIMITATIONS

A disproportionate loss to follow-up of those who had lower childhood cognitive scores may have led to underestimation of the strength of associations.

DISCUSSION

Using a population-based prospective study we provide evidence that recurrent lifetime affective problems predicts poorer later-life cognitive state, and this risk can be already manifest in early old age (age 69). Our findings raise the possibility that effective management to minimise affective problems reoccurring across the life course may reduce the associated risk of cognitive impairment and decline.

Corticosterone is correlated to mediators of neural plasticity and epigenetic potential in the hippocampus of Senegalese house sparrows (Passer domesticus)

Our previous research on range-expanding house sparrows in Kenya revealed that (i) range-edge birds released more corticosterone (CORT) in response to a stressor than range-core birds, ii) that range-edge birds were more exploratory than range-core birds, and that (iii) all birds exhibited extensive variation in genome-wide DNA methylation among individuals, regardless of their position along the range expansion. Within the hippocampus, mediators of neural plasticity such as brain-derived neurotrophic factor (BDNF), can influence and be influenced by CORT, hippocampus-associated behaviors and regulatory epigenetic modification enzymes. Here, we investigated whether individuals and populations colonizing a new geographic range, Senegal, vary in the expression of BDNF and DNA methyltransferases (DNMTs) within the hippocampus and the release of CORT in response to a stressor. DNMT expression is an important mediator of epigenetic potential, the propensity of a genome to capacitate phenotypic variation via mechanisms such as DNA methylation. We surveyed three populations across Senegal, predicting that hippocampal BDNF and DNMT expression would be highest at the range-edge, and that BDNF and DNMT would be inversely related to one another, but would each positively covary with CORT within individuals. We found a nonlinear relationship between CORT and BDNF expression within individuals. Moreover, we found that CORT positively covaried with DNMT1 expression in a more recently established population, while the reverse was true in the oldest population (i.e. at the range-core). Our study is among the first to explore whether and how variation in CORT regulation contributes to variation in mediators of neural plasticity and epigenetic potential within the hippocampus of a range-expanding vertebrate.