Brain Aging Research Articles

Anatomic Interpretability in Neuroimage Deep Learning: Saliency Approaches for Typical Aging and Traumatic Brain Injury.

The black box nature of deep neural networks (DNNs) makes researchers and clinicians hesitant to rely on their findings. Saliency maps can enhance DNN explainability by suggesting the anatomic localization of relevant brain features. This study compares seven popular attribution-based saliency approaches to assign neuroanatomic interpretability to DNNs that estimate biological brain age (BA) from magnetic resonance imaging (MRI). Cognitively normal (CN) adults (N = 13,394, 5,900 males; mean age: 65.82 ± 8.89years) are included for DNN training, testing, validation, and saliency map generation to estimate BA. To study saliency robustness to the presence of anatomic deviations from normality, saliency maps are also generated for adults with mild traumatic brain injury (mTBI, = 214, 135 males; mean age: 55.3 ± 9.9years). We assess saliency methods' capacities to capture known anatomic features of brain aging and compare them to a surrogate ground truth whose anatomic saliency is known a priori. Anatomic aging features are identified most reliably by the integrated gradients method, which outperforms all others through its ability to localize relevant anatomic features. Gradient Shapley additive explanations, input × gradient, and masked gradient perform less consistently but still highlight ubiquitous neuroanatomic features of aging (ventricle dilation, hippocampal atrophy, sulcal widening). Saliency methods involving gradient saliency, guided backpropagation, and guided gradient-weight class attribution mapping localize saliency outside the brain, which is undesirable. Our research suggests the relative tradeoffs of saliency methods to interpret DNN findings during BA estimation in typical aging and after mTBI.

Multiomic profiling reveals timing of menopause predicts prefrontal cortex aging and cognitive function.

A new case of dementia is diagnosed every 3 s. Beyond age, risk prediction of dementia is challenging. There is growing evidence of underlying processes that connect aging across organ systems and may provide insight for early detection, and there is a need to identify early biomarkers at an age when action can be taken to mitigate cognitive decline. We hypothesized that timing of menopause, a marker of ovarian aging, predicts brain age decades later. We used 2086 subjects with multiple "omics" measurements from post-mortem brain samples. Age at menopause (AAM) is positively correlated with cognitive function and negatively correlated with pre-frontal cortex aging acceleration (calculated as estimated biological age from DNA methylation minus chronological age). Genetic correlations showed that at least part of these associations is derived from shared heritability. To dissect the mechanism linking AAM to cognitive decline, we turned to transcriptomic data which confirmed that later AAM was associated with gene expression in pre-frontal cortex consistent with better cognition, and among those who reached menopause naturally, decreased gene expression of pathways implicated in aging. Those with surgical menopause displayed different molecular changes, including perturbed nicotinamide adenine dinucleotide (NAD+) activity, validated by metabolomics. Bile acid metabolism was perturbed in both groups, although different bile acid ratios were associated with AAM in each. Together, our data suggest that AAM is predictive of brain aging and cognition, with potential mediation by the gut, although through different mechanisms depending on the type of menopause.

Associations of Cognitive Function with Serum Magnesium and Phosphate in Hemodialysis Patients: A Cross-Sectional Analysis of the Osaka Dialysis Complication Study (ODCS)

Cognitive impairment and dementia are common in patients with chronic kidney disease, including those undergoing hemodialysis. Since magnesium and phosphate play important roles in brain function and aging, alterations in these and other factors related to bone mineral disorder (MBD) may contribute to low cognitive performance in patients on hemodialysis. This cross-sectional study examined the associations between cognitive function and MBD-related factors among 1207 patients on maintenance hemodialysis. Cognitive function was assessed by the Modified Mini-Mental State examination (3MS). The exposure variables of interest were serum magnesium, phosphate, calcium, calcium–phosphate product, intact parathyroid hormone, fetuin-A, T50 calciprotein crystallization test, use of phosphate binders, use of cinacalcet, and use of vitamin D receptor activators. Multivariable-adjusted linear regression models were used to examine the associations between 3MS and each of the exposure variables independent of 13 potential non-mineral confounders. We found that lower 3MS was associated with lower serum magnesium, lower phosphate, lower calcium–phosphate product, and nonuse of phosphate binders. These results suggest that magnesium and phosphate play potentially protective roles against cognitive impairment in this population.

Association of depression with longitudinal changes in brain structure across the lifespan: A mendelian randomization study.

Understanding the impact of depression on brain aging benefits the prognosis of this disease and of the risk that other age-related brain disorders will develop in the same population. The aim of the present study was to explore the genetic effect of depression on longitudinal changes in brain structure throughout the lifespan using a Mendelian randomization approach. Summary data from a genome-wide association study of 195,321 to 377,277 participants in the FinnGen consortium were used to predict depression, anxiety disorders, mood disorders, and antidepressant use genetically. Data from 15,640 participants in the ENIGMA consortium were included to predict changes in 15 brain structures throughout the lifespan. The causal relationship between these depressive traits and the brain structure parameters was assessed by two-sample Mendelian randomization (including inverse-variance weighted). Sensitivity analyses were conducted for quality control. Depression slowed the decrease of cortical gray matter volume significantly throughout the lifespan (p = 0.001). Depression, anxiety, and mood disorders nominally decreased the rates of change of volume in the cerebellum gray matter, lateral ventricles, and cortical gray matter throughout the lifespan (p = 0.048, p = 0.021, p = 0.038, respectively). Antidepressants did not affect these rates of change significantly (p > 0.05). Sensitivity analyses confirmed the reliability of this study. Depression and its main symptoms have a slight effect on longitudinal changes in a few brain structures throughout the lifespan at the genetic level. These findings do not support the notion that depression affects macro-aging in the brain crucially.

Relationship between MRI brain-age heterogeneity, cognition, genetics and Alzheimer’s disease neuropathology

Brain ageing is highly heterogeneous, as it is driven by a variety of normal and neuropathological processes. These processes may differentially affect structural and functional brain ageing across individuals, with more pronounced ageing (older brain age) during midlife being indicative of later development of dementia. Here, we examined whether brain-ageing heterogeneity in unimpaired older adults related to neurodegeneration, different cognitive trajectories, genetic and amyloid-beta (Aβ) profiles, and to predicted progression to Alzheimer's disease (AD). Functional and structural brain age measures were obtained for resting-state functional MRI and structural MRI, respectively, in 3460 cognitively normal individuals across an age range spanning 42-85 years. Participants were categorised into four groups based on the difference between their chronological and predicted age in each modality: advanced age in both (n=291), resilient in both (n=260) or advanced in one/resilient in the other (n=163/153). With the resilient group as the reference, brain-age groups were compared across neuroimaging features of neuropathology (white matter hyperintensity volume, neuronal loss measured with Neurite Orientation Dispersion and Density Imaging, AD-specific atrophy patterns measured with the Spatial Patterns of Abnormality for Recognition of Early Alzheimer's Disease index, amyloid burden using amyloid positron emission tomography (PET), progression to mild cognitive impairment and baseline and longitudinal cognitive measures (trail making task, mini mental state examination, digit symbol substitution task). Individuals with advanced structural and functional brain-ages had more features indicative of neurodegeneration and they had poor cognition. Individuals with a resilient brain-age in both modalities had a genetic variant that has been shown to be associated with age of onset of AD. Mixed brain-age was associated with selective cognitive deficits. The advanced group displayed evidence of increased atrophy across all neuroimaging features that was not found in either of the mixed groups. This is in line with biomarkers of preclinical AD and cerebrovascular disease. These findings suggest that the variation in structural and functional brain ageing across individuals reflects the degree of underlying neuropathological processes and may indicate the propensity to develop dementia in later life. The National Institute on Aging, the National Institutes of Health, the Swiss National Science Foundation, the Kaiser Foundation Research Institute and the National Heart, Lung, and Blood Institute.

Extra virgin olive oil beneficial effects on memory, synaptic function, and neuroinflammation in a mouse model of Down syndrome.

Clinical and preclinical studies have shown that extra virgin olive oil (EVOO), a major component of the Mediterranean diet, has beneficial effects on brain aging and cognition. Individuals with Down syndrome develop age-dependent cognitive decline and synaptic dysfunction. However, whether EVOO intake is beneficial in Down syndrome is not known. In this study, by implementing a mouse model of Down syndrome, we aimed to investigate the effect that chronic administration of EVOO has on memory, synaptic function, and neuroinflammation. Starting at 4 months of age Ts65dn mice were randomized to receive EVOO for 5 months in their diet, after which they were tested for learning and memory impairment. After euthanasia, synaptic function was measured in freshly obtained hippocampal slices, whereas brain tissues were assessed for inflammatory biomarkers. Compared with controls, mice receiving EVOO had a significant improvement in learning and spatial memory. Additionally, field potential recordings showed that treated mice had an improvement in synaptic function. Finally, array analysis showed that EVOO modulated the expression levels of several inflammatory biomarkers. Chronic administration of EVOO to a mouse model of Down syndrome has beneficial effects on memory impairments, synaptic function deficits and neuroinflammation. Our findings provide additional support for the potential therapeutic effects of EVOO also in individuals with Down syndrome.

Astrocytes and Memory: Implications for the Treatment of Memory-related Disorders.

Memory refers to the imprint accumulated in the brain by life experiences and represents the basis for humans to engage in advanced psychological activities such as thinking and imagination. Previously, research activities focused on memory have always targeted neurons. However, in addition to neurons, astrocytes are also involved in the encoding, consolidation, and extinction of memory. In particular, astrocytes are known to affect the recruitment and function of neurons at the level of local synapses and brain networks. Moreover, the involvement of astrocytes in memory and memory-related disorders, especially in Alzheimer's disease (AD) and post-traumatic stress disorder (PTSD), has been investigated extensively. In this review, we describe the unique contributions of astrocytes to synaptic plasticity and neuronal networks and discuss the role of astrocytes in different types of memory processing. In addition, we also explore the roles of astrocytes in the pathogenesis of memory-related disorders, such as AD, brain aging, PTSD and addiction, thus suggesting that targeting astrocytes may represent a potential strategy to treat memory-related neurological diseases. In conclusion, this review emphasizes that thinking from the perspective of astrocytes will provide new ideas for the diagnosis and therapy of memory-related neurological disorders.

Ablation of NAMPT in dopaminergic neurons leads to neurodegeneration and induces Parkinson's disease in mouse.

Nicotinamide phosphoribosyltransferase (NAMPT) is the key enzyme in the salvaging synthesize pathway of nicotinamide adenine dinucleotide (NAD). The neuroprotective roles of NAMPT on neurodegeneration have been explored in aging brain and Alzheimer's Disease. However, its roles in Parkinson's Disease (PD) remain to be elucidated. We found that the dopaminergic neurons in substantia nigra expressed higher levels of NAMPT than the other types of neurons. Using conditional knockout of the Nampt gene in dopaminergic neurons and utilizing a NAMPT inhibitor in the substantia nigra of mice, we found that the NAMPT deficiency triggered the time-dependent loss of dopaminergic neurons, the impairment of the dopamine nigrostriatal pathway, and the development of PD-like motor dysfunction. In the rotenone-induced PD mouse model, nicotinamide ribose (NR), a precursor of NAD, rescued the loss of dopaminergic neurons, the impairment of dopamine nigrostriatal pathway, and mitigated PD-like motor dysfunction. In SH-SY5Y cells, NAD suppression induced the accumulation of reactive oxygen species (ROS), mitochondrial impairment, and cell death, which was reversed by N-acetyl cysteine, an antioxidant and ROS scavenger. Rotenone decreased NAD level, induced the accumulation of ROS and the impairment of mitochondria, which was reversed by NR. In summary, our findings show that the ablation of NAMPT in dopaminergic neurons leads to neurodegeneration and contributes to the development of PD. The NAD precursors have the potential to protect the degeneration of dopaminergic neurons, and offering a therapeutic approach for the treatment of PD.

Is KIBRA polymorphism associated with memory performance and cognitive impairment in Alzheimer's disease?

Genetic variations in a common single nucleotide polymorphism in the ninth intron of the KIBRA gene have been linked to memory performance and risk of Alzheimer's disease (AD). We examined the risk of AD related to presence of KIBRA T allele (versus CC homozygote) and to memory performance. The role of established genetic risk factors APOE ε4 and BDNF Met was also considered. Participants were cognitively healthy individuals (n = 19), participants with amnestic mild cognitive impairment (aMCI) due to AD (n = 99) and AD dementia (n = 37) from the Czech Brain Aging Study. Binary and multinomial logistic regressions compared odds of belonging to a certain diagnostic category and multivariate linear regressions assessed associations with memory. KIBRA T allele was associated with increased AD dementia risk (odds ratio [OR] = 5.98, p = 0.012) compared to KIBRA CC genotype. In APOE ε4 negative individuals, KIBRA T allele was associated with a greater risk of both aMCI due to AD (OR = 6.68, p = 0.038) and AD dementia (OR = 15.75, p = 0.009). In BDNF Met positive individuals, the KIBRA T allele was associated with a greater risk of AD dementia (OR = 10.98, p = 0.050). In AD dementia, the association between KIBRA T allele and better memory performance approached significance (β = 0.42; p = 0.062). The link between possessing the KIBRA T allele and better memory reached statistical significance only among BDNF Met carriers (β = 1.21, p = 0.027). Findings suggest that KIBRA T allele may not fully protect against AD dementia but could potentially delay progression of post-diagnosis cognitive deficits.

Neurofilament light and cognition in community-dwelling non-Hispanic Blacks.

No large-scale characterizations of neurofilament light chain (NfL) and cognitive outcomes have been conducted in community-dwelling non-Hispanic Blacks. This study aims to enhance the application of blood biomarkers, in particular NfL, to ethno-racially diverse communities. We assess the association of NfL with cognitive outcomes, hypothesizing that NfL can identify cognitive changes regardless of diagnostic category. Baseline data were analyzed among n = 283 non-Hispanic Blacks (NHB) from the multi-ethnic Health and Aging Brain Study- Health Disparities (HABS-HD). Plasma NfL was measured on the Simoa platform. Linear regression models were conducted, covarying for age, gender, and education. The majority of study participants (72%) were cognitively unimpaired (CU), with 21% having mild cognitive impairment (MCI), and 6.7% with Alzheimer's disease (AD). In adjusted models among the entire sample, significant associations existed between NfL and Trails A (p < 0.0001), Trails B (p < 0.0001), phonemic (FAS) and semantic (Animals) fluency (p = 0.03), and Symbol Digit Substitution (p < 0.001). When separated by diagnostic classification, significant associations were removed for functions involving executive functions for all diagnostic groups. Higher levels of NfL were positively associated with cognitive diagnosis, older age, and less education. Plasma NfL levels are significantly associated with measures of executive functioning, which elucidate NfL as a non-specific marker of neurodegeneration associated with efficiency of brain functions involving attention, processing, and generativity. NfL may be a sensitive measure for the detection of alterations in cognitive processing before the onset of phenotypic functional changes of neurodegeneration.

BrainSim: AI-Driven Brain MRI Simulation for Alzheimer’s Disease Diagnosis

Alzheimer's Disease, a progressive neurodegenerative disorder with no cure, presents a formidable challenge to global healthcare. The simulation of brain states, encompassing both rejuvenation and aging, aids clinicians in understanding disease progression and early detection. Recent advances in deep adversarial neural networks, effective in generating age-varied facial images, are now applied to brain MRI simulations across different time states. However, existing methods for brain MRI synthesis predominantly focus on aging simulation, lacking rejuvenation capabilities, and relying heavily on longitudinal data. Access to rejuvenated brain scans is essential as it can help researchers track the structural changes and biomarkers in the early stage of AD, facilitating AD research and personalized treatments. Additionally, previous methods are often 2D-based, failing to capture complex 3D spatial information obtained by 3D scans. To overcome these limitations, I propose BrainSim, a novel longitudinal brain MRI synthesis framework. Specifically, BrainSim leverages a bidirectional cycle-consistent generative neural network to generate rejuvenated and aged MRI scans simultaneously using cross-sectional scans only. BrainSim incorporates a 3D conditional U-Net as its fundamental model, facilitating the direct generation of 3D MRI scans conditioned on the subject's health state and sex. BrainSim was evaluated against benchmark models using longitudinal data and a pre-trained age predictor to assess the quality of generated images. Experiments using the ADNI dataset show BrainSim's state-of-the-art performance in brain aging and rejuvenation tasks, marking significant advancements in MRI synthesis for Alzheimer's research and drug development.

Plasma proteomics-based organ-specific aging for all-cause mortality and cause-specific mortality: a prospective cohort study.

Individual's aging rates vary across organs. However, there are few methods for assessing aging at organ levels and whether they contribute differently to mortalities remains unknown. We analyzed data from 45,821 adults in the UK Biobank, using plasma proteomics and machine learning to estimate biological ages for 12 major organs. The differences between biological age and chronological age, referred to as "age gaps," were calculated for each organ. Partial correlation analyses were used to assess the association between age gaps and modifiable factors. Adjusted multivariable Cox regression models were applied to examine the association of age gaps with all-cause mortality, cause-specific mortalities, and cancer-specific mortalities. We reveal a complex network of varied associations between multi-organ aging and modifiable factors. All age gaps increase the risk of all-cause mortality by 6-60%. The risk of death varied from 5.54 to 29.18 times depending on the number of aging organs. Cause-specific mortalities are associated with certain organs' aging. For mental diseases mortality, and nervous system mortality, only brain aging exhibited a significant increased risk of HR 2.38 (per SD, 95% CI: 2.06-2.74) and 1.99 (per SD, 95% CI: 1.84-2.16), respectively. Age gaps of stomach were also a specific indicator for gastric cancer. Eventually, we find that an organ's biological age selectively influences the aging of other organ systems. Our study demonstrates that accelerated aging in specific organs increases the risk of mortality from various causes. This provides a potential tool for early identification of at-risk populations, offering a relatively objective method for precision medicine.

Brain aging and Alzheimer's disease, a perspective from non-human primates.

Brain aging is compared between Cercopithecinae (macaques and baboons), non-human Hominidae (chimpanzees, orangutans, and gorillas), and their close relative, humans. β-amyloid deposition in the form of senile plaques (SPs) and cerebral β-amyloid angiopathy (CAA) is a frequent neuropathological change in non-human primate brain aging. SPs are usually diffuse, whereas SPs with dystrophic neurites are rare. Tau pathology, if present, appears later, and it is generally mild or moderate, with rare exceptions in rhesus macaques and chimpanzees. Behavior and cognitive impairment are usually mild or moderate in aged non-human primates. In contrast, human brain aging is characterized by early tau pathology manifested as neurofibrillary tangles (NFTs), composed of paired helical filaments (PHFs), progressing from the entorhinal cortex, hippocampus, temporal cortex, and limbic system to other brain regions. β-amyloid pathology appears decades later, involves the neocortex, and progresses to the paleocortex, diencephalon, brain stem, and cerebellum. SPs with dystrophic neurites containing PHFs and CAA are common. Cognitive impairment and dementia of Alzheimer's type occur in about 1-5% of humans aged 65 and about 25% aged 85. In addition, other proteinopathies, such as limbic-predominant TDP-43 encephalopathy, amygdala-predominant Lewy body disease, and argyrophilic grain disease, primarily affecting the archicortex, paleocortex, and amygdala, are common in aged humans but non-existent in non-human primates. These observations show that human brain aging differs from brain aging in non-human primates, and humans constitute the exception among primates in terms of severity and extent of brain aging damage.

Latent change-on-change between amyloid accumulation and cognitive decline.

While the influence of cross-sectional β-amyloid (Aβ) on longitudinal changes in cognition is well established, longitudinal change-on-change between Aβ and cognition is less explored. A series of bivariate latent change score models (LCSM) examined the relationship between changes in 11C-Pittsburgh Compound-B (PiB) positron emission tomography (PET) and the Preclinical Alzheimer's Cognitive Composite-5 (PACC-5) while adjusting for covariates, including cross-sectional medial temporal lobe (MTL) tau-PET burden. We selected 352 clinically normal older participants with up to 9 years of PiB-PET and PACC-5 data from the Harvard Aging Brain Study (HABS). Aβ accumulation was associated with subsequent cognitive decline beyond the effects of cross-sectional Aβ burden. Within this model including covariates such as age, sex, and apolipoprotein ε4 (APOEε4) status, we found no evidence supporting previously published associations between cross-sectional tau-PET and cognitive intercept/slope. Short-term Aβ changes are significantly associated with cognitive decline in clinically normal older adults and may eclipse the effect of cross-sectional Aβ and MTL tau. Aβ accumulation is associated with subsequent cognitive decline. High Aβ burden is not the sole metric signaling impending cognitive decline. Contrary to prior work, MTL tau-PET and cognition were not associated in our models. Models of bivariate latent Aβ and cognitive change may eclipse theeffects of MTL tau.

Association between SMOFlipid and impaired brain development on term-equivalent age brain magnetic resonance imaging in very preterm infants

Soybean oil, medium-chain triglycerides, olive oil, and fish oil (SMOFlipid) is used without evidence of benefits. We investigated the relationship between lipid emulsions and brain injury in term-equivalent age magnetic resonance imaging (MRI) in 148 very preterm infants with a birth weight of < 1500 g at ≤ 32 gestational weeks in a neonatal intensive care unit. Infants who received soybean-based lipid emulsions between January 2015 and December 2018 were compared with those who received SMOFlipids between January 2019 and December 2022. A negative binomial generalized linear model was applied for bivariate analysis. Modified log-Poisson regression with generalized linear models and a robust variance estimator (Huber–White) were applied to adjust for potential confounders. The Kidokoro score was used to determine if lipid emulsion type would affect brain morphology and growth at term-equivalent age. Eighty-six (58.9%) received SMOFlipid. SMOFlipid was associated with lower focal signal abnormality, myelination delay, increased extracerebral space, and cerebellar volume reduction (P = 0.02, P = 0.007, P = 0.01, P = 0.02, respectively). SMOFlipidis are associated with brain insult, especially in white matter, cortical gray matter, and the cerebellum. Well-designed studies are needed to investigate the effect of lipid emulsions on the central nervous system.

Phosphorylated tau protein serum levels increase over time in patients with chronic heart failure

Abstract Background/Introduction Amongst various potential biomarkers associated with cognitive deficits, phosphorylated Tau (pTau) appears to link brain and cardiac abnormalities through a systemic tauopathy pathway. Purpose A recent report on the potential importance of myocardial pTau in chronic heart failure (HF) prompted the here described longitudinal quantification of circulating pTau serum levels in patients with HF. We hypothesized that serum pTau accumulates in HF and is associated with markers of myocardial dysfunction. Methods Eligible patients within the prospective, investigator-initiated, monocentric follow-up study Cognition.Matters-HF were older than 18 years, suffered from stable chronic HF and were free from major neurological or psychiatric disorders. Beyond the cardiological assessment including transthoracic echocardiography and six minute walking distance (6-MWD), investigations at baseline, 1 year and 3 years comprised extensive, domain-specific psychological testing and volumetric brain magnetic resonance imaging. Serum pTau was measured using the pTau181 advantage kit. Results Serum samples were available from 78 patients. Mean age was 63±10 years and 87% were men. Serum pTau longitudinally increased from a median of 1.05 (quartiles 0.26, 1.21) pg/ml at baseline to 1.84 (1.36, 3.60) pg/ml after 3 years (p&amp;lt;0.001). During that time period, LVEF, NT-proBNP, 6-MWD and the hippocampal volume remained unaltered, whereas global brain volume and cortical thickness shrank age-appropriately. Cognitive testing revealed that domain-specific T-scores within 36 months remained stable for attentional intensity and executive functioning, and even improved for memory. When we entered baseline values of age and above-mentioned cardiac, brain-volumetric, and cognitive parameters into a multivariable regression model predicting log-transformed pTau, only age (β=0.34), NT-proBNP (β=0.24) and GBV (β=0.26) were independently associated with pTau serum levels (R2=0.18). Consistently, at 36 months, the same predictors were selected by the model (R2=0.29): age (β=0.41), NT-proBNP (β=0.43), and global brain volume (β=0.26). Moreover, higher baseline pTau (β=0.23) and lower 6-MWD (β=-0.39) independently predicted ΔpTau with an explained variance (R2) of 0.24. Conclusions We observed a prominent increase of serum pTau over time, which was predicted by prevalent myocardial dysfunction. Moreover, absolute NT-proBNP levels were independently associated with absolute pTau serum levels, along with age and global brain volume. Mechanistically, phosphorylation of cardiac tau is thought to destabilize its interaction with microtubules causing microtubule detyronisation and increased myocardial stiffness through enhancing the mechanical resistance of contracting cardiomyocytes. The etiological role of pTau in the development of HF and the potential of serum pTau as a novel biomarker of chronic HF warrants further studies.

The Adult Changes in Thought (ACT) Medical Records Abstraction Project: A Resource for Research on Biological, Psychosocial and Behavioral Factors on the Aging Brain and Alzheimer’s Disease and Related Dementias

Background: Adult Changes in Thought (ACT), a prospective cohort study, enrolls older adult members of Kaiser Permanente Washington. We describe an ambitious project to abstract medical records facilitating epidemiological investigation. Methods: Abstracted data include medications; laboratory results; women’s health; blood pressure; physical injuries; cardiovascular, neurological, psychiatric and other medical conditions. Results: Of 1419 of 5763 participants with completed abstractions, 1387 (97.7%) were deceased; 602 (42.4%) were diagnosed with Alzheimer’s Disease and Related Dementias; 985 (69.4%) had a brain autopsy. Each participant had an average of 34.3 (SD = 13.4) years of data abstracted. Over 64% had pharmacy data preceding 1977; 87.5% had laboratory data preceding 1988. Stroke, anxiety, depression and confusion during hospitalization were common among participants diagnosed with dementia. Conclusions: Medical records are transformed into data for analyses with outcomes derived from other ACT data. We provide detailed, unparalleled longitudinal clinical data to support a variety of epidemiological research on clinical-pathological correlations.

New Insights on the Effects of Krill Oil Supplementation, a High-Fat Diet, and Aging on Hippocampal-Dependent Memory, Neuroinflammation, Synaptic Density, and Neurogenesis

Krill oil (KO) has been described as having the potential to ameliorate the detrimental consequences of a high-fat diet (HFD) on the aging brain, though the magnitude and mechanism of this benefit is unclear. We thus hypothesized that dietary KO supplementation could counteract the effects of cognitive aging and an HFD on spatial learning, neuroinflammation, neurogenesis, and synaptic density in the cortex and hippocampus of aged rats. Sixteen-month-old Sprague Dawley rats were fed for 12 weeks while being divided into four groups: control (CON); control with KO supplementation (CONKO); high-fat diet (HF); and high-fat diet with KO supplementation (HFKO). We measured food consumption, body mass, spatial memory (Morris water maze), microglia, neurogenesis, cytokine concentrations, and synaptic markers (post-synaptic density-95 and synaptophysin). Predictably, an HFD did induce significant differences in body weights, with the high-fat groups gaining more weight than the low-fat controls. However, KO supplementation did not produce significant changes in the other quantified parameters. Our results demonstrate that the dietary KO dose provided in the current study does not benefit hippocampal or cortical functions in an aging model. Our results provide a benchmark for future dosing protocols that may eventually prove to be beneficial.

Predictive power of the eTBI score for 30 day outcome in elderly patients with traumatic brain Injury

Traumatic brain injury (TBI) is a common problem in elderly individuals, with significant morbidity and mortality. The elderly Traumatic Brain Injury (eTBI) score, a novel tool for predicting outcomes in elderly patients with TBI, has shown promising results in previous studies. This study aimed to validate the eTBI score in a larger cohort of elderly patients with TBI in the Middle East. We conducted a retrospective study on 337 TBI patients with a mean age of 73.04 ± 8.73, admitted to a tertiary care hospital between March 2021 and November 2022. Within 30 days of admission, the patients’ conditions, including mortality and entering a vegetative state, were evaluated. The study population was split into three groups based on eTBI score: low, medium, and high risk; then patients were divided into two subgroups based on their Glasgow Outcome Scale (GOS ≤ 2, GOS > 2) in 30 days from hospital admission. Poor outcomes (mortality and entering a vegetative state) occurred in 24.3% of the study population. Within 30 days of hospital admission, 88% of low-risk patients experienced some degree of improvement, while 100% of high-risk patients died or fell into a vegetative state. In the medium-risk group, there was a significant correlation between unresponsive pupil (P = 0.006), initial GCS score (P = 0.003), need for a ventilator device (P = 0.015), need for surgical treatment (P = 0.031) and poor outcomes. Despite having a low sensitivity (21% vs. 57%), the eTBI score performed well in terms of accuracy (81% vs. 88%), specificity (100 vs. 98%), positive predictive value (100% vs. 90%), and negative predictive value (80% vs. 88%) for both eTBI ≤ 0 and eTBI ≤ 3 thresholds. The eTBI score is a reliable tool for predicting outcomes in elderly patients with TBI. This scoring system has a positive predictive value of 100% in the eTBI ≤ 0 group, which shows that 100% of the patients who are predicted by the eTBI score to have a poor outcome will indeed have a poor outcome. Patients in the high-risk group should be closely monitored and provided with intensive care, while those in the low-risk group can be reassured about their prognosis. The eTBI score can also be used in conjunction with other clinical factors to inform treatment decisions for patients in the medium-risk group.

Accumulation of F-actin drives brain aging and limits healthspan in Drosophila

The actin cytoskeleton is a key determinant of cell structure and homeostasis. However, possible tissue-specific changes to actin dynamics during aging, notably brain aging, are not understood. Here, we show that there is an age-related increase in filamentous actin (F-actin) in Drosophila brains, which is counteracted by prolongevity interventions. Critically, decreasing F-actin levels in aging neurons prevents age-onset cognitive decline and extends organismal healthspan. Mechanistically, we show that autophagy, a recycling process required for neuronal homeostasis, is disabled upon actin dysregulation in the aged brain. Remarkably, disrupting actin polymerization in aged animals with cytoskeletal drugs restores brain autophagy to youthful levels and reverses cellular hallmarks of brain aging. Finally, reducing F-actin levels in aging neurons slows brain aging and promotes healthspan in an autophagy-dependent manner. Our data identify excess actin polymerization as a hallmark of brain aging, which can be targeted to reverse brain aging phenotypes and prolong healthspan.