Agent Orange Exposure and Dementia Diagnosis in US Veterans of the Vietnam Era

Microorganism-Driven 2,4-D Biodegradation: Current Status and Emerging Opportunities

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has been widely used around the world in both agricultural and non-agricultural fields due to its high activity. However, the heavy use of 2,4-D has resulted in serious environmental contamination, posing a significant risk to non-target organisms, including human beings. This has raised substantial concerns regarding its impact. In addition to agricultural use, accidental spills of 2,4-D can pose serious threats to human health and the ecosystem, emphasizing the importance of prompt pollution remediation. A variety of technologies have been developed to remove 2,4-D residues from the environment, such as incineration, adsorption, ozonation, photodegradation, the photo-Fenton process, and microbial degradation. Compared with traditional physical and chemical remediation methods, microorganisms are the most effective way to remediate 2,4-D pollution because of their rich species, wide distribution, and diverse metabolic pathways. Numerous studies demonstrate that the degradation of 2,4-D in the environment is primarily driven by enzymatic processes carried out by soil microorganisms. To date, a number of bacterial and fungal strains associated with 2,4-D biodegradation have been isolated, such as Sphingomonas, Pseudomonas, Cupriavidus, Achromobacter, Ochrobactrum, Mortierella, and Umbelopsis. Moreover, several key enzymes and genes responsible for 2,4-D biodegradation are also being identified. However, further in-depth research based on multi-omics is needed to elaborate their role in the evolution of novel catabolic pathways and the microbial degradation of 2,4-D. Here, this review provides a comprehensive analysis of recent progress on elucidating the degradation mechanisms of the herbicide 2,4-D, including the microbial strains responsible for its degradation, the enzymes participating in its degradation, and the associated genetic components. Furthermore, it explores the complex biochemical pathways and molecular mechanisms involved in the biodegradation of 2,4-D. In addition, molecular docking techniques are employed to identify crucial amino acids within an alpha-ketoglutarate-dependent 2,4-D dioxygenase that interacts with 2,4-D, thereby offering valuable insights that can inform the development of effective strategies for the biological remediation of this herbicide.

Assessing Risk Factors for Cognitive Decline Using Electronic Health Record Data: A Scoping Review

Background

The data and information contained within electronic health records (EHR) provide a rich, diverse, longitudinal view of real-world patient histories, offering valuable opportunities to study antecedent risk factors for cognitive decline. However, the extent to which such records' data have been utilized to elucidate the risk factors of cognitive decline remains unclear.

Methods

A scoping review was conducted following the PRISMA guideline, examining articles published between January 2010 and April 2023, from PubMed, Web of Science, and CINAHL. Inclusion criteria focused on studies using EHR to investigate risk factors for cognitive decline. Each article was screened by at least two reviewers. Data elements were manually extracted based on a predefined schema. The studied risk factors were classified into categories, and a research gap was identified.

Results

From 1,593 articles identified, 80 were selected. The majority (87.5%) were retrospective cohort studies, with 66.3% using datasets of over 10,000 patients, predominantly from the US or UK. Analysis showed that 48.8% of studies addressed medical conditions, 31.3% focused on medical interventions, and 17.5% on lifestyle, socioeconomic status, and environmental factors. Most studies on medical conditions were linked to an increased risk of cognitive decline, whereas medical interventions addressing these conditions often reduced the risk.

Conclusions

EHR data significantly enhanced our understanding of medical conditions, interventions, lifestyle, socioeconomic status, and environmental factors related to the risk of cognitive decline.

Epigenetic link between Agent Orange exposure and type 2 diabetes in Korean veterans

Conflicting findings have been reported regarding the association between Agent Orange (AO) exposure and type 2 diabetes. This study aimed to examine whether AO exposure is associated with the development of type 2 diabetes and to verify the causal relationship between AO exposure and type 2 diabetes by combining DNA methylation with DNA genotype analyses. An epigenome-wide association study and DNA genotype analyses of the blood of AO-exposed and AO-unexposed individuals with type 2 diabetes and that of healthy controls were performed. Methylation quantitative trait locus and Mendelian randomisation analyses were performed to evaluate the causal effect of AO-exposure-identified CpGs on type 2 diabetes. AO-exposed individuals with type 2 diabetes were associated with six hypermethylated CpG sites (cg20075319, cg21757266, cg05203217, cg20102280, cg26081717, and cg21878650) and one hypo-methylated CpG site (cg07553761). Methylation quantitative trait locus analysis showed the methylation levels of some CpG sites (cg20075319, cg20102280, and cg26081717) to be significantly different. Mendelian randomisation analysis showed that CpG sites that were differentially methylated in AO-exposed individuals were causally associated with type 2 diabetes; the reverse causal effect was not significant. These findings reflect the need for further epigenetic studies on the causal relationship between AO exposure and type 2 diabetes.

Airborne Exposure to Pollutants and Mental Health: A Review with Implications for United States Veterans

PURPOSE OF REVIEW

Inhalation of airborne pollutants in the natural and built environment is ubiquitous; yet, exposures are different across a lifespan and unique to individuals. Here, we reviewed the connections between mental health outcomes from airborne pollutant exposures, the biological inflammatory mechanisms, and provide future directions for researchers and policy makers. The current state of knowledge is discussed on associations between mental health outcomes and Clean Air Act criteria pollutants, traffic-related air pollutants, pesticides, heavy metals, jet fuel, and burn pits.

RECENT FINDINGS

Although associations between airborne pollutants and negative physical health outcomes have been a topic of previous investigations, work highlighting associations between exposures and psychological health is only starting to emerge. Research on criteria pollutants and mental health outcomes has the most robust results to date, followed by traffic-related air pollutants, and then pesticides. In contrast, scarce mental health research has been conducted on exposure to heavy metals, jet fuel, and burn pits. Specific cohorts of individuals, such as United States military members and in-turn, Veterans, often have unique histories of exposures, including service-related exposures to aircraft (e.g. jet fuels) and burn pits. Research focused on Veterans and other individuals with an increased likelihood of exposure and higher vulnerability to negative mental health outcomes is needed. Future research will facilitate knowledge aimed at both prevention and intervention to improve physical and mental health among military personnel, Veterans, and other at-risk individuals.

Implementation of STAR-VA for behavioral symptoms of dementia in acute care: Lessons learned

As the population grows, the incidence of dementia will increase. A common occurrence in people with dementia is behavioral and psychological symptoms of dementia (BPSD). BPSD can include apathy, aggression, resistance to care, and agitation. BPSD can start or worsen during an acute hospitalization, but these units are not well-equipped to handle BPSD, often relying on pharmacological interventions to address distress behaviors. One known behavioral intervention for BPSD is STAR-VA, an interdisciplinary approach to managing these behaviors. However, this intervention has not been utilized in acute care. Our team implemented STAR-VA in acute care at a Veterans Affairs hospital in the northeastern United States. Using the VA's Quality Enhancement Research Initiative (QUERI) implementation roadmap to guide our work, we first outlined the problem, completed a needs assessment with staff, and began implementation. Results from this quality improvement project demonstrated the feasibility and efficacy of STAR-VA in an acute care setting.

Impacts of dioxin exposure on brain connectivity estimated by DTI analysis of MRI images in men residing in contaminated areas of Vietnam

Introduction

Effects of dioxin exposure on gray matter volume have been reported in previous studies, but a few studies reported effects of dioxin exposure on white matter structure. Therefore, this study was undertaken to investigate the impact of dioxin exposure on white matter microstructure in men living in the most severely dioxin-contaminated areas in Vietnam.

Methods

In 2019 brain MRI scans from 28 men living near Bien Hoa airbase were obtained at Dong Nai General Hospital, Vietnam, on a 3 T scanner using a conventional diffusion tensor imaging sequence. Two exposure markers were indicated by perinatal exposure estimated by assessment of maternal residency in a dioxin-contaminated area during pregnancy and by measurement of blood dioxin levels. A general linear model was used to compare fractional anisotropy (FA) values in 11 white matter tracts in both hemispheres between groups with and without perinatal dioxin exposure and groups with high and low blood dioxin levels after adjusting for covariates.

Results

The adjusted mean FA value in the left cingulum hippocampal part (CGH) was significantly lower in the perinatal dioxin exposure group compared with the group without perinatal dioxin exposure. The high blood TCDD group showed significantly reduced FA values in the left and right CGH and right uncinate fasciculus (UNC). Moreover, the high blood TEQ-PCDDs group showed significantly lower FA values in the left and right CGH and the left UNC. There were no significant differences in FA values between the groups with high and low TEQ-PCDFs levels or between the groups with high and low TEQ-PCDD/Fs levels.

Discussion

It was concluded that dioxin exposure during the perinatal period and adulthood may alter the microstructure of white matter tracts in individuals with neurodevelopmental disorders.

Improving care for veterans' environmental exposure concerns: applications of the consolidated framework for implementation research in program evaluation

BACKGROUND

Healthcare systems, like the US Department of Veterans Affairs (VA), need policies and procedures for delivering care to special populations including those with environmental exposure concerns. Despite being common and pervasive, especially among Veterans, environmental exposures are largely overlooked by healthcare providers. To successfully implement care for Veterans with military environmental exposure concerns, an understanding of contextual factors impeding care on the provider (e.g., knowledge and beliefs) and organizational (e.g., leadership's priorities) level is needed. Our goal was to conduct an operational needs assessment of providers to examine provider educational needs regarding Veterans' military environmental exposure concerns.

METHODS

In 2020, we surveyed 2,775 VA medical and behavioral health providers. Our cross-sectional assessment was informed by the Consolidated Framework for Implementation Research (CFIR) and assessed barriers and facilitators to the uptake and application of knowledge regarding interdisciplinary care for environmental exposure concerns. The web-based survey was emailed to providers across the United States representing a variety of disciplines and practice settings to reflect the interdisciplinary approach to care for environmental exposures. We used bivariate statistics to investigate the intervention setting, inner setting, and individual characteristics of providers regarding care for environmental exposure concerns.

RESULTS

Approximately one-third of VA medical and behavioral health clinicians report low to no knowledge of environmental exposure concerns. We find 88% of medical and 91% of behavioral health providers report they are ready to learn more about environmental exposures. Half of medical and behavioral health providers report they have access to information on environmental exposures and less than half report care for environmental exposures is a priority where they practice.

CONCLUSIONS

Our findings suggest interdisciplinary providers' knowledge of and discussion with Veterans about environmental exposures may be influenced by contextual factors at the organizational level. Considering individual-level factors and organizational culture is important to consider when supporting care for environmental exposures. Since this needs assessment, VA established targeted programs to improve care related to military environmental exposures in response to legislation; future exploration of these same variables or contextual factors is warranted.

Frontotemporal disorders: the expansive panoply of syndromes and spectrum of etiologies

Background

Frontotemporal lobe disorders (FTD) are amongst the most common brain neurodegenerative disorders. Their relatively covert, frequently subtle presentations and diverse etiologies, pose major challenges in diagnosis and treatments. Recent studies have yielded insights that the etiology in the majority are due to environmental and sporadic causes, rather than genetic in origin.

Aims

To retrospectively examine the cognitive and behavioral impairments in the veteran population to garner the range of differing syndrome presentations and etiological subcategories with a specific focus on frontotemporal lobe disorders.

Methodology

The design is a retrospective, observational registry, case series with the collection of epidemiological, clinical, cognitive, laboratory and radiological data on people with cognitive and behavioral disorders. Inclusion criteria for entry were veterans evaluated exclusively at Orlando VA Healthcare System, neurology section, receiving a diagnosis of FTD by standard criteria, during the observation period dated from July 2016 to March 2021. Frontotemporal disorders (FTD) were delineated into five clinical 5 subtypes. Demographic, cardiovascular risk factors, cognitive, behavioral neurological, neuroimaging data and presumed etiological categories, were collected for those with a diagnosis of frontotemporal disorder.

Results

Of the 200 patients with FTD, further cognitive, behavioral neurological evaluation with standardized, metric testing was possible in 105 patients. Analysis of the etiological groups revealed significantly different younger age of the traumatic brain injury (TBI) and Gulf War Illness (GWI) veterans who also had higher Montreal Cognitive Assessment (MOCA) scores. The TBI group also had significantly more abnormalities of hypometabolism, noted on the PET brain scans. Behavioral neurological testing was notable for the findings that once a frontotemporal disorder had been diagnosed, the four different etiological groups consistently had abnormal FRSBE scores for the 3 principal frontal presentations of (i) abulia/apathy, (ii) disinhibition, and (iii) executive dysfunction as well as abnormal Frontal Behavioral Inventory (FBI) scores with no significant difference amongst the etiological groups. The most common sub-syndromes associated with frontotemporal syndromes were the Geschwind-Gastaut syndrome (GGS), Klüver-Bucy syndrome (KBS), involuntary emotional expression disorder (IEED), cerebellar cognitive affective syndrome (CCA), traumatic encephalopathy syndrome (TES) and prosopagnosia. Comparisons with the three principal frontal lobe syndrome clusters (abulia, disinhibition, executive dysfunction) revealed a significant association with abnormal disinhibition FRSBE T-scores with the GGS. The regression analysis supported the potential contribution of disinhibition behavior that related to this complex, relatively common behavioral syndrome in this series. The less common subsyndromes in particular, were notable, as they constituted the initial overriding, presenting symptoms and syndromes characterized into 16 separate conditions.

Conclusion

By deconstructing FTD into the multiple sub-syndromes and differing etiologies, this study may provide foundational insights, enabling a more targeted precision medicine approach for future studies, both in treating the sub-syndromes as well as the underlying etiological process.

Cognition and Amyloid-β in Older Veterans: Characterization and Longitudinal Outcomes of Data-Derived Phenotypes

Background

Within older Veterans, multiple factors may contribute to cognitive difficulties. Beyond Alzheimer's disease (AD), psychiatric (e.g., PTSD) and health comorbidities (e.g., TBI) may also impact cognition.

Objective

This study aimed to derive subgroups based on objective cognition, subjective cognitive decline (SCD), and amyloid burden, and then compare subgroups on clinical characteristics, biomarkers, and longitudinal change in functioning and global cognition.

Methods

Cluster analysis of neuropsychological measures, SCD, and amyloid PET was conducted on 228 predominately male Vietnam-Era Veterans from the Department of Defense-Alzheimer's Disease Neuroimaging Initiative. Cluster-derived subgroups were compared on baseline characteristics as well as 1-year changes in everyday functioning and global cognition.

Results

The cluster analysis identified 3 groups. Group 1 (n = 128) had average-to-above average cognition with low amyloid burden. Group 2 (n = 72) had the lowest memory and language, highest SCD, and average amyloid burden; they also had the most severe PTSD, pain, and worst sleep quality. Group 3 (n = 28) had the lowest attention/executive functioning, slightly low memory and language, elevated amyloid and the worst AD biomarkers, and the fastest rate of everyday functioning and cognitive decline.

CONCLUSIONS

Psychiatric and health factors likely contributed to Group 2's low memory and language performance. Group 3 was most consistent with biological AD, yet attention/executive function was the lowest score. The complexity of older Veterans' co-morbid conditions may interact with AD pathology to show attention/executive dysfunction (rather than memory) as a prominent early symptom. These results could have important implications for the implementation of AD-modifying drugs in older Veterans.

Type 2 Diabetes Moderates the Association Between Amyloid and 1-Year Change in Everyday Functioning in Older Veterans

BACKGROUND

Type 2 diabetes mellitus (T2DM) affects ∼25% of Veterans, a prevalence rate double that of the general population. T2DM is associated with greater dementia risk and has been shown to exacerbate the impact of Alzheimer's disease (AD) risk factors on declines in daily functioning; however, there are few studies that investigate these patterns in older Veterans.

OBJECTIVE

This study sought to determine whether T2DM moderates the association between amyloid-β (Aβ) positron emission tomography (PET) and 1-year change in everyday functioning in older Veterans.

METHODS

One-hundred-ninety-eight predominately male Vietnam-Era Veterans without dementia from the Department of Defense-Alzheimer's Disease Neuroimaging Initiative (DoD-ADNI) with (n = 74) and without (n = 124) T2DM completed Aβ PET imaging and everyday functioning measures, including the Clinical Dementia Rating-Sum of Boxes (CDR-SB) and Everyday Cognition (ECog). Linear mixed effects models tested the moderating role of T2DM on the association between Aβ PET and 1-year change in everyday functioning.

RESULTS

The 3-way T2DM×Aβ PET×time interaction was significant for CDR-SB (p < 0.001) as well as the Memory (p = 0.007) and Language (p = 0.011) subscales from the ECog. Greater amyloid burden was associated with greater increases in functional difficulties, but only in Veterans with T2DM.

CONCLUSIONS

Higher Aβ was only associated with declines in everyday functioning over 1 year in Veterans with T2DM. Given that people with T2DM are more likely to have co-occurring cerebrovascular disease, the combination of multiple neuropathologies may result in faster declines. Future studies should examine how diabetes duration, severity, and medications impact these associations.

Agent Orange Herbicidal Toxin-Initiation of Alzheimer-Type Neurodegeneration

Background

Agent Orange (AO) is a Vietnam War-era herbicide that contains a 1 : 1 ratio of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). Emerging evidence suggests that AO exposures cause toxic and degenerative pathologies that may increase the risk for Alzheimer's disease (AD).

Objective

This study investigates the effects of the two main AO constituents on key molecular and biochemical indices of AD-type neurodegeneration.

Methods

Long Evans rat frontal lobe slice cultures treated with 250μg/ml of 2,4-D, 2,4,5-T, or both (D + T) were evaluated for cytotoxicity, oxidative injury, mitochondrial function, and AD biomarker expression.

Results

Treatment with the AO constituents caused histopathological changes corresponding to neuronal, white matter, and endothelial cell degeneration, and molecular/biochemical abnormalities indicative of cytotoxic injury, lipid peroxidation, DNA damage, and increased immunoreactivity to activated Caspase 3, glial fibrillary acidic protein, ubiquitin, tau, paired-helical filament phosphorylated tau, AβPP, Aβ, and choline acetyltransferase. Nearly all indices of cellular injury and degeneration were more pronounced in the D + T compared with 2,4-D or 2,4,5-T treated cultures.

Conclusions

Exposures to AO herbicidal chemicals damage frontal lobe brain tissue with molecular and biochemical abnormalities that mimic pathologies associated with early-stage AD-type neurodegeneration. Additional research is needed to evaluate the long-term effects of AO exposures in relation to aging and progressive neurodegeneration in Vietnam War Veterans.

Effect of TCDD exposure in adult female and male mice on the expression of miRNA in the ovaries and testes and associated reproductive functions

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental contaminant found widely across the world. While animal and human studies have shown that exposure to TCDD may cause significant alterations in the reproductive tract, the effect of TCDD on the expression of miRNA in the reproductive organs has not been previously tested. In the current study, we exposed adult female or male mice to TCDD or vehicle and bred them to study the impact on reproduction. The data showed that while TCDD treatment of females caused no significant change in litter size, it did alter the survival of the pups. Also, TCDD exposure of either the male or female mice led to an increase in the gestational period. While TCDD did not alter the gross morphology of the ovaries and testes, it induced significant alterations in the miRNA expression. The ovaries showed the differential expression of 426 miRNAs, of which 315 miRNAs were upregulated and 111 miRNA that were downregulated after TCDD exposure when compared to the vehicle controls. In the testes, TCDD caused the differential expression of 433 miRNAs, with 247 miRNAs upregulated and 186 miRNAs downregulated. Pathway analysis showed that several of these dysregulated miRNAs targeted reproductive functions. The current study suggests that the reproductive toxicity of TCDD may result from alterations in the miRNA expression in the reproductive organs. Because miRNAs also represent one of the epigenetic pathways of gene expression, our studies suggest that the transgenerational toxicity of TCDD may also result from dysregulation in the miRNAs.

Effects of defoliant exposure and medication use on the development of Parkinson's disease in veterans

BACKGROUND

Vietnam-era veterans were exposed to Agent Orange (AO), which is associated with a high prevalence of Parkinson's disease (PD). However, little is known about the development of PD-like symptoms caused by drug-induced parkinsonism (DIP) in such populations. This study aimed to investigate PD incidence and PD risk following exposure to AO or DIP-risk drugs in veterans.

METHODS

A retrospective cohort study was conducted using 12 years (2009-2020) of electronic medical records of the Veterans Health Service Medical Center, the largest Veterans Affairs hospital in South Korea (n = 37,246; 100% male; age, 65.57 ± 8.12 years). Exposure to AO or DIP-risk drugs, including antipsychotic, prokinetic, anti-epileptic, dopamine-depleting and anti-anginal agents, was assessed in veterans with PD, operationally defined as having a PD diagnosis and one or more prescriptions for PD treatment. The PD risk was calculated using multiple logistic regression analysis adjusted for age and comorbidities.

RESULTS

The rates of DIP-risk drug use and AO exposure were 37.92% and 62.62%, respectively. The PD incidence from 2010 to 2020 was 3.08%; 1.30% with neither exposure, 1.63% with AO exposure, 4.38% with DIP-risk drug use, and 6.33% with both. Combined exposure to AO and DIP-risk drugs increased the PD risk (adjusted odds ratio = 1.68, 95% confidence interval, 1.36-2.08, P < 0.001).

CONCLUSIONS

The PD incidence was 1.31 times higher with AO exposure alone and 1.68 times higher with AO exposure and DIP-risk drug use. The results suggest the necessity for careful monitoring and DIP-risk drug prescription in patients with AO exposure.

[The exposome in the context of preventive measures for Alzheimer's and Parkinson's diseases]

BACKGROUND

Preventive measures addressing the exposome can counteract neurodegenerative diseases.

OBJECTIVE

This article gives an overview on the influence of general and individual exogenous factors (environmental influences and lifestyle changes) as well as endogenous factors (e.g. metabolic alterations) on the development and progression of Alzheimer's disease (AD) and Parkinson's disease (PD).

METHODS

Summary and evaluation of current scientific studies and evidence regarding the exposome and prevention of AD and PD.

RESULTS

Numerous studies could demonstrate a potential influence of environmental influences associated with industrialization (general exogenous factors), such as pesticides, solvents or air pollution on the development of AD and PD. Additionally, individually addressable changes of lifestyle (individual exogenous factors, e.g. physical activity, cognitive stimulation, nutrition and sleep) contribute to disease protection and modification and are becoming increasingly more important in light of still limited therapeutic interventions. Moreover, other exogenous factors (medication, noise pollution, head trauma and heavy metals) are discussed as risk factors for AD and/or PD. Endogenous factors (e.g., changes of the enteral microbiome, systemic inflammation and neuroinflammation, metabolic changes) can contribute to disease development by a higher potential for interacting with exogenous factors.

CONCLUSION

Despite the comprehensive scientific evidence confirming the significance of the exposome for the pathogenesis of AD and PD, the great potential of preventive measures has not yet been exploited. A clarification of the high potential of lifestyle changes should be a therapeutic standard not only for individuals with manifest PD/AD but also for individuals with a risk profile or with suspected prodromal disease. Further investigations on the influence of environmental factors and the implementation of preventive strategies to avoid exposure should be the focus of international efforts.

Agent Orange Causes Metabolic Dysfunction and Molecular Pathology Reminiscent of Alzheimer's Disease

Background

Agent Orange, an herbicide used during the Vietnam War, contains 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). Agent Orange has teratogenic and carcinogenic effects, and population-based studies suggest Agent Orange exposures lead to higher rates of toxic and degenerative pathologies in the peripheral and central nervous system (CNS).

Objective

This study examines the potential contribution of Agent Orange exposures to neurodegeneration.

Methods

Human CNS-derived neuroepithelial cells (PNET2) treated with 2,4-D and 2,4,5-T were evaluated for viability, mitochondrial function, and Alzheimer's disease (AD)-related proteins.

Results

Treatment with 250μg/ml 2,4-D or 2,4,5-T significantly impaired mitochondrial function, caused degenerative morphological changes, and reduced viability in PNET2 cells. Correspondingly, glyceraldehyde-3-phosphate dehydrogenase expression which is insulin-regulated and marks the integrity of carbohydrate metabolism, was significantly inhibited while 4-hydroxy-2-nonenal, a marker of lipid peroxidation, was increased. Tau neuronal cytoskeletal protein was significantly reduced by 2,4,5-T, and relative tau phosphorylation was progressively elevated by 2,4,5-T followed by 2,4-D treatment relative to control. Amyloid-β protein precursor (AβPP) was increased by 2,4,5-T and 2,4-D, and 2,4,5-T caused a statistical trend (0.05 < p<0.10) increase in Aβ. Finally, altered cholinergic function due to 2,4,5-T and 2,4-D exposures was marked by significantly increased choline acetyltransferase and decreased acetylcholinesterase expression, corresponding with responses in early-stage AD.

Conclusion

Exposures to Agent Orange herbicidal chemicals rapidly damage CNS neurons, initiating a path toward AD-type neurodegeneration. Additional research is needed to understand the permanency of these neuropathologic processes and the added risks of developing AD in Agent Orange-exposed aging Vietnam Veterans.

Long-term effects of defoliant exposure on brain atrophy progression in humans

As the most toxic dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin is classified as a group 1 human carcinogen. We investigated the long-term effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure on the progression of brain atrophy in humans. We retrospectively selected 546 patients exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (exposed group) and 1353 patients not exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (control group). The patients in both groups underwent brain T1-weighted magnetic resonance imaging (MRI) twice. We divided the patients into two propensity score-matched groups, analyzed voxel-wise whole brain atrophy in the MRI images of each patient, and compared the progression of brain atrophy between the two groups. The exposed group showed significant brain atrophy progression in the bilateral frontal and temporal lobes, compared with the control group. The ventrolateral prefrontal area in the frontal lobe and whole temporal lobe were the main atrophic regions in the exposed group, compared with the control group. The neurotoxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin can damage the brain, even in patients exposed to it over 40 years ago. Humans exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin should thus be evaluated for progression of brain atrophy.

Agent Orange Reviewed: Potential Role in Peripheral Neuropathy and Neurodegeneration

Agent Orange, a dioxin-containing toxin, was used as an herbicide during the Vietnam War. Exposures to Agent Orange were initially linked to birth defects among Vietnamese civilians residing near aerially sprayed regions. Years later, returning South Korean and U.S. Veterans exposed to Agent Orange exhibited increased rates of malignancy, cardiovascular disease, diabetes and birth defects in their offspring. Growing evidence that herbicides and pesticides contribute to chronic diseases including neurodegeneration raises concern that Agent Orange exposures may have increased the risk for later development of peripheral or central nervous system (CNS) degeneration. This article reviews published data on the main systemic effects and the prevalence rates, relative risks, characteristics and correlates of Agent Orange-associated peripheral neuropathy and CNS dementia-associated diseases. The critical findings were that relatively high levels of Agent Orange exposure increased risk of developing peripheral neuropathy either alone or as a co-factor complication of diabetes mellitus and likely contributed to the pathogenesis of CNS degenerative diseases, including Alzheimer's, Parkinson's and vascular dementias. Given the protracted intervals between the Agent Orange exposures and disease emergence, additional research is needed to identify mechanistic correlates of the related neurological disorders, including lifestyle co-factors.

Dementia in military and veteran populations: a review of risk factors-traumatic brain injury, post-traumatic stress disorder, deployment, and sleep

The military population face a unique set of risk factors that may increase the risk of being diagnosed with dementia. Traumatic brain injury (TBI) and post-traumatic stress disorder (PTSD) have a higher prevalence in this group in comparison to the civilian population. By delving into the individual relationships between TBI and dementia, and PTSD and dementia, we are able to better explore dementia in the military and veteran populations. While there are some inconsistencies in results, the TBI-dementia association has become more widely accepted. Moderate-to-severe TBI has been found to increase the risk of being diagnosed with Alzheimer's disease. A correlation between PTSD and dementia has been established, however, whether or not it is a causal relationship remains unclear. Factors such as blast, combat and chemical exposure may occur during a deployment, along with TBI and/or PTSD diagnosis, and can impact the risk of dementia. However, there is a lack of literature exploring the direct effects of deployment on dementia risk. Sleep problems have been observed to occur in those following TBI, PTSD and deployment. Poor sleep has been associated with possible dementia risk. Although limited studies have focused on the link between sleep and dementia in military and veteran populations, sleep is a valuable factor to study due to its association and interconnection with other military/veteran factors. This review aims to inform of various risk factors to the cognitive health of military members and veterans: TBI, PTSD, deployment, and sleep.

Association of Military Employment With Late-Life Cognitive Decline and Dementia: A Population-Based Prospective Cohort Study

INTRODUCTION

As the number of U.S. veterans over age 65 has increased, interest in whether military service affects late-life health outcomes has grown. Whether military employment is associated with increased risk of cognitive decline and dementia remains unclear.

MATERIALS AND METHODS

We used data from 4,370 participants of the longitudinal Adult Changes in Thought (ACT) cohort study, enrolled at age 65 or older, to examine whether military employment was associated with greater cognitive decline or higher risk of incident dementia in late life. We classified persons as having military employment if their first or second-longest occupation was with the military. Cognitive status was assessed at each biennial Adult Changes in Thought study visit using the Cognitive Abilities Screening Instrument, scored using item response theory (CASI-IRT). Participants meeting screening criteria were referred for dementia ascertainment involving clinical examination and additional cognitive testing. Primary analyses were adjusted for sociodemographic characteristics and APOE genotype. Secondary analyses additionally adjusted for indicators of early-life socioeconomic status and considered effect modification by age, gender, and prior traumatic brain injury with loss of consciousness TBI with LOC.

RESULTS

Overall, 6% of participants had military employment; of these, 76% were males. Military employment was not significantly associated with cognitive change (difference in modeled 10-year cognitive change in CASI-IRT scores in SD units (95% confidence interval [CI]): -0.042 (-0.19, 0.11), risk of dementia (hazard ratio [HR] [95% CI]: 0.92 [0.71, 1.18]), or risk of Alzheimer's disease dementia (HR [95% CI]: 0.93 [0.70, 1.23]). These results were robust to additional adjustment and sensitivity analyses. There was no evidence of effect modification by age, gender, or traumatic brain injury with loss of consciousness.

CONCLUSIONS

Among members of the Adult Changes in Thought cohort, military employment was not associated with increased risk of cognitive decline or dementia. Nevertheless, military veterans face the same high risks for cognitive decline and dementia as other aging adults.