Military-related risk factors in female veterans and risk of dementia

Specification curve analysis to identify heterogeneity in risk factors for dementia: findings from the UK Biobank

BACKGROUND

In 2020, the Lancet Commission identified 12 risk factors as priorities for prevention of dementia, and other studies identified APOE e4/e4 genotype and family history of Alzheimer's disease strongly associated with dementia outcomes; however, it is unclear how robust these relationships are across dementia subtypes and analytic scenarios. Specification curve analysis (SCA) is a new tool to probe how plausible analytical scenarios influence outcomes.

METHODS

We evaluated the heterogeneity of odds ratios for 12 risk factors reported from the Lancet 2020 report and two additional strong associated non-modifiable factors (APOE e4/e4 genotype and family history of Alzheimer's disease) with dementia outcomes across 450,707 UK Biobank participants using SCA with 5357 specifications across dementia subtypes (outcomes) and analytic models (e.g., standard demographic covariates such as age or sex and/or 14 correlated risk factors).

RESULTS

SCA revealed variable dementia risks by subtype and age, with associations for TBI and APOE e4/e4 robust to model specification; in contrast, diabetes showed fluctuating links with dementia subtypes. We found that unattributed dementia participants had similar risk factor profiles to participants with defined subtypes.

CONCLUSIONS

We observed heterogeneity in the risk of dementia, and estimates of risk were influenced by the inclusion of a combination of other modifiable risk factors; non-modifiable demographic factors had a minimal role in analytic heterogeneity. Future studies should report multiple plausible analytic scenarios to test the robustness of their association. Considering these combinations of risk factors could be advantageous for the clinical development and evaluation of novel screening models for different types of dementia.

Comparison of different definitions of traumatic brain injury: implications for cohort characteristics and survival in women, Philadelphia, USA

BACKGROUND

Traumatic brain injury (TBI) is an acute injury that is understudied in civilian cohorts, especially among women, as TBI has historically been considered to be largely a condition of athletes and military service people. Both the Centres for Disease Control and Prevention (CDC) and Department of Defense (DOD)/Veterans Affairs (VA) have developed case definitions to identify patients with TBI from medical records; however, their definitions differ. We sought to re-examine these definitions to construct an expansive and more inclusive definition among a cohort of women with TBI.

METHODS

In this study, we use electronic health records (EHR) from a single healthcare system to study the impact of using different case definitions to identify patients with TBI. Specifically, we identified adult female patients with TBI using the CDC definition, DOD/VA definition and a combined and expanded definition herein called the Penn definition.

RESULTS

We identified 4446 adult-female TBI patients meeting the CDC definition, 3619 meeting the DOD/VA definition, and together, 6432 meeting our expanded Penn definition that includes the CDC ad DOD/VA definitions.

CONCLUSIONS

Using the expanded definition identified almost two times as many patients, enabling investigations to more fully characterise these patients and related outcomes. Our expanded TBI case definition is available to other researchers interested in employing EHRs to investigate TBI.

To Calm and to Commend: Veterans' Musical Preferences Anticipating End of Life

INTRODUCTION

Since World War 1, physicians have noted the calming effects of music for military personnel experiencing "shell shock," Post Traumatic Stress Disorder (PTSD), or stress. Researchers have documented that stress or PTSD-like symptoms re-emerge for veterans at the end of life, triggered by hospital-like settings, co-occurring conditions, and debilitation. Dying veterans also face integration of their service and combat experiences into summations of their lives. In response, there has been a national movement for bedside ceremonies, often with music, to honor veterans.

MATERIALS AND METHODS

The project elicited veterans' musical preferences for calming and for music for honor services, using non-hospitalized veterans as surrogates for veterans in hospice. Respondent-driven sampling protected confidentiality and likely resulted in participants being representative of US veterans in terms of ethnicity, gender, and military branch. Recruitment materials contained all elements of informed consent, with consent collected in the introduction to the online survey. The survey had embedded links to musical performances, as well as write-in musical choices, and allowed US veterans from the Army, Air Force, Marines, and Navy to note their preferences both for music that was calming and music to be used in honor ceremonies. Online queries also asked about stress during service, usual coping strategies for stress, and current or past symptoms of PTSD. Links to hot lines were provided. The study was approved by the University of Arizona Institutional Review Board.

RESULTS

Listening to music was the most prevalent of the 20 coping mechanisms for stress in this sample of 30 veterans. Musical preferences were stable across age groups. For calming, music at resting heartbeat rhythms was chosen. Music from early adulthood or from the timelessness of the classics was selected most often. Modern music with lyrics has themes of duty, affirmation, gratitude, and relief. The nearly universal soothing effects of lullabies were recognized. For music for honor ceremonies, desires were often independent of the military branch. Patriotic songs, or songs recognizing multiple service branches, or with themes of peace and affirmation were more often chosen than music from a particular service branch.

CONCLUSION

Listening to music is a frequent coping strategy for veterans. While themes representing classical music choices are readily available in anthologies, other music chosen by this sample is not; the veterans' preferred music is rarely found in compilations of popular, movie, and TV music. Hospice and hospital intakes that document and communicate veterans' musical preferences to music therapists and therapeutic musicians may better support service men and women. Further research may examine veterans' preference for live or recorded music at end of life given the importance of meaning-making and the presence of others documented in the literature.

INviting Veterans InTo Enrollment in Alzheimer's Disease Research Centers (INVITE-ADRC): An NIA and VA-sponsored initiative to increase veteran participation in aging and dementia research

INTRODUCTION

Older military veterans often present with unique and complex risk factors for Alzheimer's disease (AD) and related dementias. Increasing veteran participation in research studies offers one avenue to advance the field and improve health outcomes.

METHODS

To this end, the National Institute on Aging (NIA) and Department of Veterans Affairs (VA) partnered to build infrastructure, improve collaboration, and intensify targeted recruitment of veterans. This initiative, INviting Veterans InTo Enrollment in Alzheimer's Disease Research Centers (INVITE-ADRC), provided funding for five sites and cross-site organizing structure. Diverse and innovative recruitment strategies were used.

RESULTS

Across five sites, 172 veterans entered registries, and 99 were enrolled into ADRC studies. Of the enrolled, 39 were veterans from historically underrepresented racial and ethnic groups.

CONCLUSIONS

This initiative laid the groundwork to establish sustainable relationships between the VA and ADRCs. The partnership between both federal agencies demonstrates how mutual interests can accelerate progress. In turn, efforts can help our aging veterans.

An EWAS of dementia biomarkers and their associations with age, African ancestry, and PTSD

BACKGROUND

Large-scale cohort and epidemiological studies suggest that PTSD confers risk for dementia in later life but the biological mechanisms underlying this association remain unknown. This study examined this question by assessing the influences of PTSD, APOE ε4 genotypes, DNA methylation, and other variables on the age- and dementia-associated biomarkers Aβ40, Aβ42, GFAP, NfL, and pTau-181 measured in plasma. Our primary hypothesis was that PTSD would be associated with elevated levels of these markers.

METHODS

Analyses were based on data from a PTSD-enriched cohort of 849 individuals. We began by performing factor analyses of the biomarkers, the results of which identified a two-factor solution. Drawing from the ATN research framework, we termed the first factor, defined by Aβ40 and Aβ42, "Factor A" and the second factor, defined by GFAP, NfL and pTau-181, "Factor TN." Next, we performed epigenome-wide association analyses (EWAS) of the two-factor scores. Finally, using structural equation modeling (SEM), we evaluated (a) the influence of PTSD, age, APOE ε4 genotype and other covariates on levels of the ATN factors, and (b) tested the mediating influence of the EWAS-significant DNAm loci on these associations.

RESULTS

The Factor A EWAS identified one significant locus, cg13053408, in FANCD2OS. The Factor TN analysis identified 3 EWAS-significant associations: cg26033520 near ASCC1, cg23156469 in FAM20B, and cg15356923 in FAM19A4. The SEM showed age to be related to both factors, more so with Factor TN (β = 0.581, p < 0.001) than Factor A (β = 0.330, p < 0.001). Genotype-determined African ancestry was associated with lower Factor A (β = 0.196, p < 0.001). Contrary to our primary hypothesis, we found a modest negative bivariate correlation between PTSD and the TN factor scores (r = - 0.133, p < 0.001) attributable primarily to reduced levels of GFAP (r = - 0.128, p < 0.001).

CONCLUSIONS

This study identified novel epigenetic associations with ATN biomarkers and demonstrated robust age and ancestral associations that will be essential to consider in future efforts to develop the clinical applications of these tests. The association between PTSD and reduced GFAP, which has been reported previously, warrants further investigation.

Longitudinal study of traumatic-stress related cellular and cognitive aging

Traumatic stress is associated with both accelerated epigenetic age and increased risk for dementia. Accelerated epigenetic age might link symptoms of traumatic stress to dementia-associated biomarkers, such as amyloid-beta (Aβ) proteins, neurofilament light (NFL), and inflammatory molecules. We tested this hypothesis using longitudinal data obtained from 214 trauma-exposed military veterans (85 % male, mean age at baseline: 53 years, 75 % White) who were assessed twice over the course of an average of 5.6 years. Cross-lagged panel mediation models evaluated measures of lifetime posttraumatic stress disorder and internalizing and externalizing comorbidity (assessed at Time 1; T1) in association with T1 epigenetic age (per the GrimAge algorithm) and T1 plasma markers of neuropathology along with bidirectional temporal paths between T1 and T2 epigenetic age and the plasma markers. Results revealed that a measure of externalizing comorbidity was associated with accelerated epigenetic age (β = 0.30, p <.01), which in turn, was associated with subsequent increases in Aβ-40 (β = 0.20, p <.001), Aβ-42 (β = 0.18, p <.001), and interleukin-6 (β = 0.18, p <.01). T1 advanced epigenetic age and the T1 neuropathology biomarkers NFL and glial fibrillary acidic protein predicted worse performance on T2 neurocognitive tasks assessing working memory, executive/attentional control, and/or verbal memory (ps = 0.03 to 0.009). Results suggest that advanced GrimAge is predictive of subsequent increases in neuropathology and inflammatory biomarkers as well as worse cognitive function, highlighting the clinical significance of this biomarker with respect to cognitive aging and brain health over time. The finding that advanced GrimAge mediated the association between psychiatric comorbidity and future neuropathology is important for understanding potential pathways to neurodegeneration and early identification of those at greatest risk.

Association between stress-related disorders and the risk of dementia using the Korean National Sample Cohort: a matched cohort study

Post-traumatic stress disorder (PTSD) is associated with the development of dementia; however, the association of dementia risk with overall stress-related disorders is less known. This study investigated the association between stress-related disorders and the risk of dementia in a Korean nationwide sample cohort. The data analyzed in this study were acquired from the Korean National Health Insurance Service National Sample Cohort between 2002 and 2013. Using a 1:3 propensity score matching, 8906 patients with stress-related disorders and 26,718 control participants were included in the analysis. Patients with stress-related disorders had a higher risk of developing dementia after adjusting for covariates (hazard ratio [HR] = 1.15; 95% confidence interval [CI] 1.01-1.30) than control participants. Patients with PTSD showed the highest risk of increase (HR = 1.78) than those with other types of stress-related disorders. Patients with stress-related disorders showed the highest and significantly increased risk for Alzheimer's dementia (HR = 1.22, 95% CI 1.04-1.56). These results indicated an association between a history of stress-related disorders and the risk of dementia in the South Korean population. Further research investigating the causal mechanisms is needed.

Weaving Evidence into Action for Veterans with Dementia (WEAVE): Evaluation of implementation into long-term care practice

RATIONALE

Veterans living with dementia in long-term care have complex needs, with variable manifestation of symptoms of dementia that interact with their lived experience. Best practice dementia care prioritises nonpharmacological interventions; of which few have strong evidence. Implementation of evidence is complex, with evaluation of outcomes and processes necessary.

AIMS AND OBJECTIVES

This paper details the evaluation of implementation, at veteran and organisational level, of the Weaving Evidence into Action for Veterans with Dementia (WEAVE) programme.

METHODS

A Type 2 hybrid effectiveness-implementation design was used, underpinned by the Implementation Framework for Aged Care (IFAC). Programme intervention incorporated music therapy, exercise, reminiscence therapy and/or sensory modulation, offered over a 24-week period. Evaluation components included: (1) programme effectiveness for veterans with dementia for responsive behaviour, physical wellbeing, cognitive status, emotional state, medications and falls (at baseline, 8-week, 16-week and 24-week); and (2) implementation outcomes of reach and adoption, feasibility and acceptability, fidelity (via interviews) and a preliminary cost analysis.

RESULTS

Thirty-eight veterans participated in the 24-week programme, with high levels of engagement in interventions of their choice. Statistically significant improvements were seen across all veteran-level outcome measures, for functional capacity and reduced neuro-psychiatric and depressive symptoms. Ten staff members were interviewed, highlighting co-designed core elements were feasible and acceptable, and the momentum generated by resident and staff enthusiasm. Cost analysis included costs of programme set-up and running the 24-week intervention.

CONCLUSION

Key components of programme success were the therapeutic leaders, adherence to core elements of programme design, and veterans' choice in meaningful activity. Cost analysis supports deliberations for upscale across further care homes.

Weaving Evidence into Action for Veterans with dementia (WEAVE): Codesigning the implementation of nonpharmacological interventions for programme fidelity and sustainability

RATIONALE

Challenges associated with translating evidence into practice are well recognised and calls for effective strategies to reduce the time lag and successfully embed evidence-based practices into usual care are loud and clear. While a plethora of nonpharmacological interventions for people with dementia exist; few are based on strong evidence and there is little consideration for programme operationalisation in the complex environment of long-term care.

AIMS AND OBJECTIVES

This paper describes the preparation for the implementation of the Weaving Evidence into Action for Veterans with dementia project, incorporating the codesign of delivery of four evidence-based, nonpharmacological interventions.

METHOD

Implementation preparation for this type 2 hybrid effectiveness-implementation project was underpinned by the Implementation Framework for Aged Care (IFAC). A sociocultural-political contextual scan was undertaken, and reflection on the IFAC question 'why change?' with key stakeholders. Delivery of the four interventions of music therapy, exercise, reminiscence therapy and sensory modulation was explored using codesign methodology. Preparation of both intervention delivery personnel and recipients was via training, establishment of a change team and promotional/awareness-raising strategies.

RESULTS

The contextual scan revealed Australian government reforms and organisational imperatives facing long-term care services, while reflections on 'why change' flagged best practice dementia care at the local care home level. Several codesign sessions involved veterans with dementia, family members, care home staff members and volunteers to ensure programme alignment with needs and preferences, accounting for existing activities. Training was designed and delivered before programme commencement. A change team was established and strategies to support behaviour change instigated. Implementation evaluation is reported elsewhere.

CONCLUSION

The extended preparatory period for implementation, afforded by the COVID-19 pandemic on programme commencement, enabled time for widespread understanding of the programme and necessary upskill of staff. Comprehensive codesign with all stakeholders of programme components identified core and flexible elements necessary for fidelity of implementation.

The impact of Alzheimer's disease risk factors on the pupillary light response

Alzheimer's disease (AD) is the leading cause of dementia, and its prevalence is increasing and is expected to continue to increase over the next few decades. Because of this, there is an urgent requirement to determine a way to diagnose the disease, and to target interventions to delay and ideally stop the onset of symptoms, specifically those impacting cognition and daily livelihood. The pupillary light response (PLR) is controlled by the sympathetic and parasympathetic branches of the autonomic nervous system, and impairments to the pupillary light response (PLR) have been related to AD. However, most of these studies that assess the PLR occur in patients who have already been diagnosed with AD, rather than those who are at a higher risk for the disease but without a diagnosis. Determining whether the PLR is similarly impaired in subjects before an AD diagnosis is made and before cognitive symptoms of the disease begin, is an important step before using the PLR as a diagnostic tool. Specifically, identifying whether the PLR is impaired in specific at-risk groups, considering both genetic and non-genetic risk factors, is imperative. It is possible that the PLR may be impaired in association with some risk factors but not others, potentially indicating different pathways to neurodegeneration that could be distinguished using PLR. In this work, we review the most common genetic and lifestyle-based risk factors for AD and identify established relationships between these risk factors and the PLR. The evidence here shows that many AD risk factors, including traumatic brain injury, ocular and intracranial hypertension, alcohol consumption, depression, and diabetes, are directly related to changes in the PLR. Other risk factors currently lack sufficient literature to make any conclusions relating directly to the PLR but have shown links to impairments in the parasympathetic nervous system; further research should be conducted in these risk factors and their relation to the PLR.

Alzheimer's disease and related dementias among aging veterans: Examining gene-by-environment interactions with post-traumatic stress disorder and traumatic brain injury

INTRODUCTION

Post-traumatic stress disorder (PTSD) and traumatic brain injury (TBI) confer risk for Alzheimer's disease and related dementias (ADRD).

METHODS

This study from the Million Veteran Program (MVP) evaluated the impact of apolipoprotein E (APOE) ε4, PTSD, and TBI on ADRD prevalence in veteran cohorts of European ancestry (EA; n = 11,112 ADRD cases, 170,361 controls) and African ancestry (AA; n = 1443 ADRD cases, 16,191 controls). Additive-scale interactions were estimated using the relative excess risk due to interaction (RERI) statistic.

RESULTS

PTSD, TBI, and APOE ε4 showed strong main-effect associations with ADRD. RERI analysis revealed significant additive APOE ε4 interactions with PTSD and TBI in the EA cohort and TBI in the AA cohort. These additive interactions indicate that ADRD prevalence associated with PTSD and TBI increased with the number of inherited APOE ε4 alleles.

DISCUSSION

PTSD and TBI history will be an important part of interpreting the results of ADRD genetic testing and doing accurate ADRD risk assessment.

Does ADT Influence the Risk of Suicidal Ideation among US Veteran Prostate Cancer Patients Pre-Exposed to PTSD?

Post-traumatic stress disorder (PTSD) is defined as a mental health disease that has a high probability of developing among individuals who have experienced traumatic events [...].

Association of Traumatic Brain Injury with Late Life Neuropathological Outcomes in a Community-Based Cohort

BACKGROUND

Prior studies into the association of head trauma with neuropathology have been limited by incomplete lifetime neurotrauma exposure characterization.

OBJECTIVE

To investigate the neuropathological sequelae of traumatic brain injury (TBI) in an autopsy sample using three sources of TBI ascertainment, weighting findings to reflect associations in the larger, community-based cohort.

METHODS

Self-reported head trauma with loss of consciousness (LOC) exposure was collected in biennial clinic visits from 780 older adults from the Adult Changes in Thought study who later died and donated their brain for research. Self-report data were supplemented with medical record abstraction, and, for 244 people, structured interviews on lifetime head trauma. Neuropathology outcomes included Braak stage, CERAD neuritic plaque density, Lewy body distribution, vascular pathology, hippocampal sclerosis, and cerebral/cortical atrophy. Exposures were TBI with or without LOC. Modified Poisson regressions adjusting for age, sex, education, and APOE ɛ4 genotype were weighted back to the full cohort of 5,546 participants.

RESULTS

TBI with LOC was associated with the presence of cerebral cortical atrophy (Relative Risk 1.22, 95% CI 1.02, 1.42). None of the other outcomes was associated with TBI with or without LOC.

CONCLUSION

TBI with LOC was associated with increased risk of cerebral cortical atrophy. Despite our enhanced TBI ascertainment, we found no association with the Alzheimer's disease-related neuropathologic outcomes among people who survived to at least age 65 without dementia. This suggests the pathophysiological processes underlying post-traumatic neurodegeneration are distinct from the hallmark pathologies of Alzheimer's disease.

How Traumatic Brain Injury History Relates to Brain Health MRI Markers and Dementia Risk: Findings from the 3C Dijon Cohort

BACKGROUND

The long-term effects of traumatic brain injury (TBI) with loss of consciousness (LOC) on magnetic resonance imaging (MRI) markers of brain health and on dementia risk are still debated.

OBJECTIVE

To investigate the associations of history of TBI with LOC with incident dementia and neuroimaging markers of brain structure and small vessel disease lesions.

METHODS

The analytical sample consisted in 4,144 participants aged 65 and older who were dementia-free at baseline from the Three City -Dijon study. History of TBI with LOC was self-reported at baseline. Clinical Dementia was assessed every two to three years, up to 12 years of follow-up. A subsample of 1,675 participants <80 years old underwent a brain MRI at baseline. We investigated the associations between history of TBI with LOC and 1) incident all cause and Alzheimer's disease (AD) dementia using illness-death models, and 2) neuroimaging markers at baseline.

RESULTS

At baseline, 8.3% of the participants reported a history of TBI with LOC. In fully-adjusted models, participants with a history of TBI with LOC had no statistically significant differences in dementia risk (HR = 0.90, 95% CI = 0.60-1.36) or AD risk (HR = 1.03, 95% CI = 0.69-1.52), compared to participants without TBI history. History of TBI with LOC was associated with lower white matter volume (β= -4.58, p = 0.048), but not with other brain volumes, white matter hyperintensities volume, nor covert brain infarct.

CONCLUSION

This study did not find evidence of an association between history of TBI with LOC and dementia or AD dementia risks over 12-year follow-up, brain atrophy, or markers of small vessel disease.

Consideration of sex and gender in Alzheimer's disease and related disorders from a global perspective

Sex or gender differences in the risk of Alzheimer's disease and related dementias (ADRD) differ by world region, suggesting that there are potentially modifiable risk factors for intervention. However, few epidemiological or clinical ADRD studies examine sex differences; even fewer evaluate gender in the context of ADRD risk. The goals of this perspective are to: (1) provide definitions of gender, biologic sex, and sexual orientation. and the limitations of examining these as binary variables; (2) provide an overview of what is known with regard to sex and gender differences in the risk, prevention, and diagnosis of ADRD; and (3) discuss these sex and gender differences from a global, worldwide perspective. Identifying drivers of sex and gender differences in ADRD throughout the world is a first step in developing interventions unique to each geographical and sociocultural area to reduce these inequities and to ultimately reduce global ADRD risk. HIGHLIGHTS: The burden of dementia is unevenly distributed geographically and by sex and gender. Scientific advances in genetics and biomarkers challenge beliefs that sex is binary. Discrimination against women and sex and gender minority (SGM) populations contributes to cognitive decline. Sociocultural factors lead to gender inequities in Alzheimer's disease and related dementias (ADRD) worldwide.

Sex and gender differences in mild traumatic brain injury/concussion

The high incidence of concussions/mild traumatic brain injury and the significant number of people with persisting concussion symptoms as well as the concern for delayed, neurodegenerative effects of concussions makes them a major public health concern. There is much to learn on concussions with respect to pathophysiology as well as vulnerability and resiliency factors. The heterogeneity in outcome after a concussion warrants a more personalized approach to better understand the biological and psychosocial factors that may affect outcome. In this chapter we address biological sex and gender as they impact different aspects of concussion including incidence, risk factors and outcome. As well, this chapter will provide a more fulsome overview of intimate partner violence, an often-overlooked cause of concussion in women. Applying the sex and gender lens to concussion/mild traumatic brain injury is imperative for discovery of its pathophysiology and moving closer to treatments.

A first insight into the clinical manifestation of posttraumatic stress disorder in dementia: a systematic literature review

Posttraumatic stress disorder (PTSD) is a prevalent disorder worldwide and often co-occurs in dementia. Both have a major impact on disease burden and quality of life. PTSD may be difficult to recognize in dementia and a structured diagnostic method is lacking. In order to get insight into the clinical diagnostics of PTSD in dementia, this systematic literature review evaluates the clinical presentation of PTSD and other relevant symptoms in people with dementia. PubMed, PsycINFO, Embase, and CINAHL were searched for all publications through 30 December 2021. Articles were included which met the following criteria: (i) description of at least one case with a current diagnosis of dementia and co-morbid PTSD; (ii) clinical presentation of symptoms being adequately described; (iii) no difference being made between chronic PTSD, PTSD with re-activation, and delayed onset PTSD. Of the 947 identified abstracts, 13 papers met the inclusion criteria and were included (describing 30 cases). Based on our rating, only one case completely fulfilled the DSM-5 criteria of PTSD. Avoidance was only described in three cases. Most commonly described symptoms were irritability and anger (E1, 9%), persistent negative emotional state (D4, 9%), and sleep disturbances (E6, 8%). In 93% of the case reports, other symptoms were also described, i.e. memory problems (58%), screaming (33.3%), and wandering (22.2%). People with dementia who have experienced a traumatic event seem to present, based on our rating method, with insufficient symptoms to meet all criteria for a PTSD DSM-5 diagnosis. The DSM-5 core symptom of avoidance was absent in most of the cases. Clinical presentation consists mainly of symptoms of irritability, anger, persistent negative emotional state, and sleep disturbances, often accompanied by other symptoms. These findings suggest that older people with dementia may have other symptom presentations than people without dementia.

An Integrative Review of Behavioral Disturbances in Veterans With Dementia and PTSD

OBJECTIVE

Both posttraumatic stress disorder (PTSD) and dementia have been associated with a variety of behavioral changes; however, little is known about the behavioral consequences of comorbid PTSD and dementia. An integrative review was conducted to identify and examine studies reporting on behavioral disturbances in Veterans with PTSD and dementia.

METHODS

PubMed and PsychINFO databases were searched for articles on behavioral disturbances in Veterans with comorbid PTSD and dementia.

RESULTS

Seven studies met inclusion for this review, sampling a total of 822 Veterans. Preliminary findings suggest that though Veterans with dementia and comorbid PTSD may present with more difficult behavioral symptoms, they do not typically display increased levels of aggression.

CONCLUSION

Given the limited study inventory, the key finding from this review highlights the lack of methodologically rigorous empirical studies on this topic. A research agenda is proposed to encourage future studies to address gaps in the literature.

Association of Race and Ethnicity With Incidence of Dementia Among Older Adults

IMPORTANCE

The racial and ethnic diversity of the US, including among patients receiving their care at the Veterans Health Administration (VHA), is increasing. Dementia is a significant public health challenge and may have greater incidence among older adults from underrepresented racial and ethnic minority groups.

OBJECTIVE

To determine dementia incidence across 5 racial and ethnic groups and by US geographical region within a large, diverse, national cohort of older veterans who received care in the largest integrated health care system in the US.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective cohort study within the VHA of a random sample (5% sample selected for each fiscal year) of 1 869 090 participants aged 55 years or older evaluated from October 1, 1999, to September 30, 2019 (the date of final follow-up).

EXPOSURES

Self-reported racial and ethnic data were obtained from the National Patient Care Database. US region was determined using Centers for Disease Control and Prevention (CDC) regions from residential zip codes.

MAIN OUTCOMES AND MEASURES

Incident diagnosis of dementia (9th and 10th editions of the International Classification of Diseases). Fine-Gray proportional hazards models were used to examine time to diagnosis, with age as the time scale and accounting for competing risk of death.

RESULTS

Among the 1 869 090 study participants (mean age, 69.4 [SD, 7.9] years; 42 870 women [2%]; 6865 American Indian or Alaska Native [0.4%], 9391 Asian [0.5%], 176 795 Black [9.5%], 20 663 Hispanic [1.0%], and 1 655 376 White [88.6%]), 13% received a diagnosis of dementia over a mean follow-up of 10.1 years. Age-adjusted incidence of dementia per 1000 person-years was 14.2 (95% CI, 13.3-15.1) for American Indian or Alaska Native participants, 12.4 (95% CI, 11.7-13.1) for Asian participants, 19.4 (95% CI, 19.2-19.6) for Black participants, 20.7 (95% CI, 20.1-21.3) for Hispanic participants, and 11.5 (95% CI, 11.4-11.6) for White participants. Compared with White participants, the fully adjusted hazard ratios were 1.05 (95% CI, 0.98-1.13) for American Indian or Alaska Native participants, 1.20 (95% CI, 1.13-1.28) for Asian participants, 1.54 (95% CI, 1.51-1.57) for Black participants, and 1.92 (95% CI, 1.82-2.02) for Hispanic participants. Across most US regions, age-adjusted dementia incidence rates were highest for Black and Hispanic participants, with rates similar among American Indian or Alaska Native, Asian, and White participants.

CONCLUSIONS AND RELEVANCE

Among older adults who received care at VHA medical centers, there were significant differences in dementia incidence based on race and ethnicity. Further research is needed to understand the mechanisms responsible for these differences.

Methylation of the AIM2 gene: An epigenetic mediator of PTSD-related inflammation and neuropathology plasma biomarkers

BACKGROUND

Posttraumatic stress disorder (PTSD) is associated with inflammation and various forms of chronic disease. The Absent in Melanoma 2 (AIM2) gene has been implicated in mechanisms of inflammation and anxiety, and methylation at a particular locus in this gene (cg10636246) has previously been shown to influence the association between PTSD and elevated C-reactive protein levels in blood.

METHOD

We tested if this association might extend to other indicators of inflammation and to plasma-based measures of neuropathology in a cohort of post-9/11 US military veterans. Using a Bayesian approach, mediation models were tested cross-sectionally (n = 478) and longitudinally (n = 298). Peripheral markers of inflammation and neuropathology were measured with ultra-sensitive Single Molecule Array (Simoa®) technology.

RESULTS

Analyses revealed indirect effects of PTSD symptom severity on peripheral indices of both inflammation (interleukin [IL]6, IL-10, tumor necrosis factor-α; indirect standardized [std.] ß range = 0.018-0.023, all p-values adjusted for multiple testing [p_adj ] < 0.05) and neuropathology (neurofilament light [NFL]; indirect std. ß = -0.018, p_adj  = 0.02) via AIM2 methylation. This indirect effect was also evident when predicting IL-10 at a follow-up assessment (indirect std. ß = -0.018, p_adj  = 0.04) controlling for baseline IL-10.

CONCLUSIONS

Given that AIM2 methylation mediated the association between PTSD symptoms and multiple inflammatory and neuropathology markers, our results suggest that AIM2 methylation may offer clinical utility for indexing risk for adverse health outcomes associated with these peripheral indices of inflammation and neuropathology. Results also suggest a possible shared etiology underlying the frequent co-occurrence of inflammation and neuropathology.

Sex Differences in the Risk of Dementia in Older Veterans

BACKGROUND

Studies have demonstrated women to have a higher prevalence of dementia compared to men. However, sex differences in dementia incidence are controversial with conflicting reports showing women with higher, lower, or similar incidence. Source of difference may be due to clinical setting and lack of consideration of competing risk of death. We examined dementia incidence in a sample of the national Veteran population to determine differences by sex.

METHODS

We examined data from the Veterans Health Administration (VHA), the largest integrated health care system in the United States. We studied 947 797 Veterans aged ≥55 years (mean age: 69.9 ± 8.4, 3% female) evaluated in the VHA from October 1, 1999 to September 30, 2019. We estimated age-adjusted incidence rates of dementia (International Classification of Diseases, 9th and 10th Edition codes) by sex, and used Fine-Gray proportional hazards models with age as time scale to examine time to diagnosis, accounting for competing risk of death.

RESULTS

During the follow-up (mean 8.4 years), 11.3% (n = 106 977, 11.4% men and 8.0% women) of Veterans developed dementia. Age-adjusted incidence was 12.6/1 000 person-years for men and 12.7/1 000 person-years for women. Compared to male Veterans, risk dementia was slightly higher among females (hazard ratio = 1.15; 95% confidence interval: 1.10-1.20), and on average, female Veterans developed dementia 0.2 years earlier than male Veterans. After additional adjustment for race, education, medical, and psychiatric conditions, results were similar.

CONCLUSIONS

Among older Veterans in a national cohort, women had a slightly increased risk for developing dementia compared to men after accounting for competing risk of death.

Traumatic brain injuries among veterans and the risk of incident dementia: A systematic review & meta-analysis

BACKGROUND

Traumatic brain injuries (TBI) among military veterans are increasingly recognized as important causes of both short and long-term neuropsychological dysfunction. However, the association between TBI and the development of dementia is controversial. This systematic review and meta-analysis sought to quantify the risks of all-cause dementia including Alzheimer's diseases and related dementias (ADRD), and to explore whether the relationships are influenced by the severity and recurrence of head injuries.

METHODS

Database searches of Medline, Embase, Ovid Healthstar, PubMed and PROSPERO were undertaken from inception to December 2020 and supplemented with grey literature searches without language restrictions. Observational cohort studies examining TBI and incident dementia among veterans were analysed using Dersimonian-Laird random-effects models.

RESULTS

Thirteen cohort studies totalling over 7.1 million observations with veterans were included. TBI was associated with an increased risk of all-cause dementia (hazard ratio [HR] = 1.95, 95% confidence interval [CI]: 1.55-2.45), vascular dementia (HR = 2.02, 95% CI: 1.46-2.80), but not Alzheimer's disease (HR = 1.30, 95% CI: 0.88-1.91). Severe and penetrating injuries were associated with a higher risk of all-cause dementia (HR = 3.35, 95% CI: 2.47-4.55) than moderate injuries (HR = 2.82, 95% CI: 1.44-5.52) and mild injuries (HR = 1.91, 95% CI: 1.30-2.80). However, the dose-response relationship was attenuated when additional studies with sufficient data to classify trauma severity were included.

CONCLUSION

TBI is a significant risk factor for incident all-cause dementia and vascular dementia. These results need to be interpreted cautiously in the presence of significant heterogeneity.

The effect of the 2018 Japan Floods on cognitive decline among long-term care insurance users in Japan: a retrospective cohort study

BACKGROUND

The July 2018 Japan Floods caused enormous damage to western Japan. Such disasters can especially impact elderly persons. Research has shown that natural disasters exacerbated a decline in cognitive function, but to date, there have been no studies examining the effects of this disaster on the elderly. The object of this study was to reveal the effect of this disaster in terms of cognitive decline among the elderly.

METHODS

Study participants were certified users of the long-term care insurance (LTCI) system in Hiroshima, Okayama, and Ehime prefectures from May 2018 to June 2018. The observation period was from July 2018 to December 2018. Our primary outcome was cognitive decline after the disaster using a dementia symptomatology assessment. In addition to a crude model, a multivariate Cox proportional hazards model was used to assess the cognitive decline of victims, adjusting for age classification, gender, the level of dementia scale before the disaster occurred, residential environment, whether a participant used facilities shut down after the disaster, and population density. After we confirmed that the interaction term between victims and residential environment was statistically significant, we stratified them for the analysis.

RESULTS

The total number of participants was 264,614. Victims accounted for 1.10% of the total participants (n = 2,908). For the Cox proportional hazards model, the hazard ratio of the victims was 1.18 (95% confidential interval (CI): 1.05-1.32) in the crude model and 1.12 (95% CI: 1.00-1.26) in the adjusted model. After being stratified by residential environment, the hazard ratio of home victims was 1.20 (95% CI: 1.06-1.36) and the hazard ratio of facility victims was 0.89 (95% CI: 0.67-1.17).

CONCLUSIONS

This study showed that elderly living at home during the 2018 Japan Floods were at risk for cognitive decline. Medical providers, care providers, and local governments should establish a system to check on the cognitive function of elderly victims and provide necessary care support.

Symptomatic Herpes Simplex Virus Infection and Risk of Dementia in US Veterans: a Cohort Study

A Taiwanese cohort study found that symptomatic herpes simplex virus (HSV) infection was associated with a threefold increased risk of developing dementia; however, antiherpetic medication reduced the risk by 90%. Our aim was to verify and further investigate this finding in the US Veteran population using comprehensive electronic medical records from the Veterans Health Administration (VHA). Eighty-seven thousand six hundred eighty-seven Veterans aged 50 or older with symptomatic HSV-1/HSV-2 infection and 217,895 matched controls were identified in VHA data between January 1, 2001, and December 31, 2014, and followed until December 31, 2019. International Classification of Diseases (ICD) codes, ninth and tenth revisions, were used to define dementia. To define HSV infection, we utilized VHA data on antiherpetic medications and laboratory tests in addition to ICD codes. Cox proportional hazards models were used to analyze the effects of HSV infection and antiherpetic medication on the risk of developing dementia. The analysis revealed an adjusted HR of 0.80 (95% CI, 0.78-0.83) for the development of dementia among those with symptomatic HSV relative to those without. Among the 61,776 HSV-1/HSV-2 patients who were treated with antiherpetic medication, 4836 patients (7.8%) developed dementia (adjusted HR = 0.75; 95% CI, 0.72-0.78); this translated to a population average of one additional year of being dementia free in those who were taking antiherpetic medication. In contrast to Tzeng et al. we did not find that HSV infection was associated with an increased risk of dementia. Like their findings, we found that antiherpetic medication was associated with a protective effect against dementia. Future prospective studies are needed to further investigate this effect.

Cerebrospinal Fluid MicroRNA Changes in Cognitively Normal Veterans With a History of Deployment-Associated Mild Traumatic Brain Injury

A history of traumatic brain injury (TBI) increases the odds of developing Alzheimer's disease (AD). The long latent period between injury and dementia makes it difficult to study molecular changes initiated by TBI that may increase the risk of developing AD. MicroRNA (miRNA) levels are altered in TBI at acute times post-injury (<4 weeks), and in AD. We hypothesized that miRNA levels in cerebrospinal fluid (CSF) following TBI in veterans may be indicative of increased risk for developing AD. Our population of interest is cognitively normal veterans with a history of one or more mild TBI (mTBI) at a chronic time following TBI. We measured miRNA levels in CSF from three groups of participants: (1) community controls with no lifetime history of TBI (ComC); (2) deployed Iraq/Afghanistan veterans with no lifetime history of TBI (DepC), and (3) deployed Iraq/Afghanistan veterans with a history of repetitive blast mTBI (DepTBI). CSF samples were collected at the baseline visit in a longitudinal, multimodal assessment of Gulf War veterans, and represent a heterogenous group of male veterans and community controls. The average time since the last blast mTBI experienced was 4.7 ± 2.2 years [1.5 - 11.5]. Statistical analysis of TaqMan^TM miRNA array data revealed 18 miRNAs with significant differential expression in the group comparisons: 10 between DepTBI and ComC, 7 between DepC and ComC, and 8 between DepTBI and DepC. We also identified 8 miRNAs with significant differential detection in the group comparisons: 5 in DepTBI vs. ComC, 3 in DepC vs. ComC, and 2 in DepTBI vs. DepC. When we applied our previously developed multivariable dependence analysis, we found 13 miRNAs (6 of which are altered in levels or detection) that show dependencies with participant phenotypes, e.g., ApoE. Target prediction and pathway analysis with miRNAs differentially expressed in DepTBI vs. either DepC or ComC identified canonical pathways highly relevant to TBI including senescence and ephrin receptor signaling, respectively. This study shows that both TBI and deployment result in persistent changes in CSF miRNA levels that are relevant to known miRNA-mediated AD pathology, and which may reflect early events in AD.

Women's Mental Health in the U.S. Military - Where Are We Now? A Review of Recent Research

PURPOSE OF REVIEW

The field of women's mental health has grown in the military healthcare system, which has begun to acknowledge and address the sex-specific differences in mental health for service women. The purpose of this review is to examine recent research in active duty populations addressing perinatal mental health, post-traumatic stress disorder (PTSD), depression, and gender isolation.

RECENT FINDINGS

Within the examined literature focused on active duty populations, analyses by sex and gender continue to exist as notable gaps, and a majority of studies reviewed either do not aim to examine sex or gender-based differences, and/or do not analyze data with an eye towards these paradigms. Within perinatal mental health, the lack of studies led to an inability to make any notable conclusions. PTSD was the area with the most robust publications focused on active duty women, studies of major depression showed significant occupational impact, and the area of gender isolation continues to grow as a promising field with practical implications. We discuss current promising research and advance ideas for future research trajectories that will provide clinicians, policy makers, and scientists with more data to support improved mental healthcare for both military women and men.

Head injury and 25-year risk of dementia

INTRODUCTION

Head injury is associated with significant morbidity and mortality. Long-term associations of head injury with dementia in community-based populations are less clear.

METHODS

Prospective cohort study of 14,376 participants (mean age 54 years at baseline, 56% female, 27% Black, 24% with head injury) enrolled in the Atherosclerosis Risk in Communities (ARIC) Study. Head injury was defined using self-report and International Classification of Diseases, Ninth/Tenth Revision (ICD-9/10) codes. Dementia was defined using cognitive assessments, informant interviews, and ICD-9/10 and death certificate codes.

RESULTS

Head injury was associated with risk of dementia (hazard ratio [HR] = 1.44, 95% confidence interval [CI] = 1.3-1.57), with evidence of dose-response (1 head injury: HR = 1.25, 95% CI = 1.13-1.39, 2+ head injuries: HR = 2.14, 95% CI = 1.86-2.46). There was evidence for stronger associations among female participants (HR = 1.69, 95% CI = 1.51-1.90) versus male participants (HR = 1.15, 95% CI = 1.00-1.32), P-for-interaction < .001, and among White participants (HR = 1.55, 95% CI = 1.40-1.72) versus Black participants (HR = 1.22, 95% CI = 1.02-1.45), P-for-interaction = .008.

DISCUSSION

In this community-based cohort with 25-year follow-up, head injury was associated with increased dementia risk in a dose-dependent manner, with stronger associations among female participants and White participants.

Epidemiology of Chronic Effects of Traumatic Brain Injury

Although many patients diagnosed with traumatic brain injury (TBI), particularly mild TBI, recover from their symptoms within a few weeks, a small but meaningful subset experience symptoms that persist for months or years after injury and significantly impact quality of life for the person and their family. Factors associated with an increased likelihood of negative TBI outcomes include not only characteristics of the injury and injury mechanism, but also the person’s age, pre-injury status, comorbid conditions, environment, and propensity for resilience. In this article, as part of the Brain Trauma Blueprint: TBI State of the Science framework, we examine the epidemiology of long-term outcomes of TBI, including incidence, prevalence, and risk factors. We identify the need for increased longitudinal, global, standardized, and validated assessments on incidence, recovery, and treatments, as well as standardized assessments of the influence of genetics, race, ethnicity, sex, and environment on TBI outcomes. By identifying how epidemiological factors contribute to TBI outcomes in different groups of persons and potentially impact differential disease progression, we can guide investigators and clinicians toward more-precise patient diagnosis, along with tailored management, and improve clinical trial designs, data evaluation, and patient selection criteria.

Increased risk of dementia in older female US veterans with alcohol use disorder

AIM

To determine whether alcohol use disorder (AUD) is associated with increased dementia risk among older women veterans.

DESIGN

Cohort study.

SETTING

United States.

PARTICIPANTS

Women veterans with AUD aged ≥ 55 years (n = 2207), receiving care from Veterans Health Administration medical centers from October 2004 to September 2015 with one or more follow-up visit and an age-matched sample of women veterans without AUD (n = 2207). Women at baseline with prevalent dementia or AUD in remission were excluded.

MEASUREMENTS

AUD, substance use disorder (SUD), smoking, psychiatric (depression, anxiety, post-traumatic stress disorder, anxiety) and medical comorbidities (diabetes, hypertension, stroke, chronic obstructive pulmonary disorder, traumatic brain disorder) and dementia determined by the International Classification of Diseases, 9th revision, Clinical Modification codes. Cox proportional hazards models were used to determine the association between AUD and dementia risk during follow-up. Sensitivity analyses were performed by excluding women (n = 349) with comorbid SUD and by excluding women (n = 1568) currently smoking.

FINDINGS

Veteran women had a mean [standard deviation (SD)] age of 65.0 (5.6) years at baseline. During follow-up (median 4 years, interquartile range: 2-6) 3.7% of women (n = 82) with AUD developed dementia compared with 1.1% (n = 24) without AUD (P < 0.001). After adjustment for demographics, medical and psychiatric conditions and accounting for different Veteran's Integrated Service Networks, the adjusted hazard ratio (aHR) for dementia was 3.12 (95% CI = 1.90-5.12) for women with AUD compared with women without AUD. After removing women with SUD (aHR = 3.53, 95% CI = 2.13-5.85) and women currently smoking (aHR = 3.80, 95% CI = 2.11-6.84), results were similar.

CONCLUSIONS

Alcohol use disorder among female US veterans aged more than 55 years appears to be associated with a more than threefold increase of dementia.

Traumatic brain injury and sight loss in military and veteran populations- a review

War and combat exposure pose great risks to the vision system. More recently, vision related deficiencies and impairments have become common with the increased use of powerful explosive devices and the subsequent rise in incidence of traumatic brain injury (TBI). Studies have looked at the effects of injury severity, aetiology of injury and the stage at which visual problems become apparent. There was little discrepancy found between the frequencies or types of visual dysfunctions across blast and non-blast related groups, however complete sight loss appeared to occur only in those who had a blast-related injury. Generally, the more severe the injury, the greater the likelihood of specific visual disturbances occurring, and a study found total sight loss to only occur in cases with greater severity. Diagnosis of mild TBI (mTBI) is challenging. Being able to identify a potential TBI via visual symptoms may offer a new avenue for diagnosis.

Brain Injury and Later-Life Cognitive Impairment and Neuropathology: The Honolulu-Asia Aging Study

BACKGROUND

Findings are inconsistent regarding the role of traumatic head injury in the subsequent development of neurologic outcomes.

OBJECTIVE

Examine the relationship between head injury and later cognitive impairment.

METHODS

A sample of 3,123 Japanese-American men was assessed for history of head injury and evaluated for cognitive impairment using the Cognitive Abilities Screening Instrument (CASI). For a subsample of 676 respondents, neuropathologic results from those with and without head injury were compared.

RESULTS

Although the crude model showed an association between history of head injury and later severe cognitive impairment, the relationship lost significance in the adjusted model (OR = 1.320, CI: 0.90-1.93), regardless of time between injury and impairment. Similar to cognitive impairment, hippocampal sclerosis was observed significantly more in the brains of respondents with a history of head injury in the crude model, but the relationship weakened in the adjusted model (OR = 1.462, CI: 0.68-3.12). After adjustment, decedents with a head injury demonstrated marginally higher brain weight (OR = 1.003, CI: 1.00-1.01).

CONCLUSION

We did not find a relationship between head injury and subsequent cognitive decline in this cohort. The neuropathology results also displayed no strong association between history of head injury and specific brain lesions and characteristics. These results support other findings in prospective cohorts. However, they could be influenced by the demographic make-up of the sample (male Japanese-Americans) or by the observation that the majority reported only a single head injury.

Demographic, Health, and Exposure Risks Associated With Cognitive Loss, Alzheimer's Disease and Other Dementias in US Military Veterans

The US military veteran population receiving care through the Veterans Health Administration (VHA) is particularly susceptible to cognitive impairment and dementias such as Alzheimer's disease and related dementias due to demographic, clinical, and economic factors. In this report we summarize the prevalence of dementia among US veterans and risks associated with AD and related dementias. We discuss the likelihood that these risks may be increasing in those about to enter the age in which dementias are common. We propose that VHA, the largest integrated health care system in the US, has shown promise in managing health risks that impact dementia prevention and propose further system wide approaches to be assessed for effective dementia prevention and care delivery.

The long-term consequences of trauma and posttraumatic stress disorder symptoms on later life cognitive function and dementia risk

Stress may be a risk factor for dementia, however it is unknown whether post-traumatic stress disorder (PTSD) symptoms are associated with incident dementia in community-dwelling older individuals. The aim was to determine whether lifetime major trauma with and without re-experiencing of PTSD symptoms is associated with later-life cognition and dementia risk. Participants were 1,700 community-dwelling older adults (65+) in the longitudinal ESPRIT study followed over 14 years. Lifetime major traumatic exposure and PTSD were assessed using Watson's PTSD Inventory. Cognitive tests assessed global cognition, visual memory, verbal fluency, psychomotor speed and executive function. Incident dementia was diagnosed according to DSM-IV criteria. Lifetime major trauma (versus no trauma) was associated with significantly increased executive function and increased global function in men, however women with lifetime trauma and re-experiencing symptoms had a significantly increased risk of low global cognition. Over 14 years, lifetime trauma without re-experiencing symptoms was associated with a significantly decreased risk of incident dementia, particularly for women. Lifetime major trauma without re-experiencing symptoms (but not with) may be protective for later life cognitive function. However, the mechanisms and moderating factors underlying these association requires further investigation.

Post-traumatic stress disorder as a risk factor for dementia: systematic review and meta-analysis

BACKGROUND

Post-traumatic stress disorder (PTSD) has been identified as a potential risk factor for developing dementia. There are currently, however, no meta-analyses quantifying this risk.

AIMS

To systematically review and quantify the risk of future dementia associated with PTSD across populations. PROSPERO registration number CRD42019130392.

METHOD

We searched nine electronic databases up to 25 October 2019 for longitudinal studies assessing PTSD and risk of dementia. We used random- and fixed-effects meta-analyses to pool estimates across studies.

RESULTS

PTSD was associated with a significant risk for all-cause dementia: pooled hazard ratio HR = 1.61 (95% CI 1.43-1.81, I2= 85.8%, P < 0.001; n = 1 693 678; 8 studies). Pooled HR was 1.61 (95% CI 1.46-1.78; I2= 80.9%, P < 0.001; n = 905 896; 5 studies) in veterans, and 2.11 (95% CI 1.03-4.33, I2= 91.2%, P < 0.001; n = 787 782; 3 studies) in the general population. The association between PTSD and dementia remained significant after excluding studies with high risk of bias (HR = 1.55, 95% CI 1.39-1.73, I2= 83.9%, P < 0.001; n = 1 684 928; 7 studies). Most studies included were retrospective and there was evidence of high heterogeneity.

CONCLUSIONS

This is the first meta-analysis quantifying the association of PTSD and risk of dementia showing that PTSD is a strong and potentially modifiable risk factor for all-cause dementia. Future studies investigating potential causal mechanisms, and the protective value of treating PTSD are needed.

Sex as a Biological Variable in Preclinical Modeling of Blast-Related Traumatic Brain Injury

Approaches to furthering our understanding of the bioeffects, behavioral changes, and treatment options following exposure to blast are a worldwide priority. Of particular need is a more concerted effort to employ animal models to determine possible sex differences, which have been reported in the clinical literature. In this review, clinical and preclinical reports concerning blast injury effects are summarized in relation to sex as a biological variable (SABV). The review outlines approaches that explore the pertinent role of sex chromosomes and gonadal steroids for delineating sex as a biological independent variable. Next, underlying biological factors that need exploration for blast effects in light of SABV are outlined, including pituitary, autonomic, vascular, and inflammation factors that all have evidence as having important SABV relevance. A major second consideration for the study of SABV and preclinical blast effects is the notable lack of consistent model design—a wide range of devices have been employed with questionable relevance to real-life scenarios—as well as poor standardization for reporting of blast parameters. Hence, the review also provides current views regarding optimal design of shock tubes for approaching the problem of primary blast effects and sex differences and outlines a plan for the regularization of reporting. Standardization and clear description of blast parameters will provide greater comparability across models, as well as unify consensus for important sex difference bioeffects.

Agitation and impulsivity in mid and late life as possible risk markers for incident dementia

To identify knowledge gaps regarding new-onset agitation and impulsivity prior to onset of cognitive impairment or dementia the International Society to Advance Alzheimer's Research and Treatment Neuropsychiatric Syndromes (NPS) Professional Interest Area conducted a scoping review. Extending a series of reviews exploring the pre-dementia risk syndrome Mild Behavioral Impairment (MBI), we focused on late-onset agitation and impulsivity (the MBI impulse dyscontrol domain) and risk of incident cognitive decline and dementia. This scoping review of agitation and impulsivity pre-dementia syndromes summarizes the current biomedical literature in terms of epidemiology, diagnosis and measurement, neurobiology, neuroimaging, biomarkers, course and prognosis, treatment, and ongoing clinical trials. Validations for pre-dementia scales such as the MBI Checklist, and incorporation into longitudinal and intervention trials, are needed to better understand impulse dyscontrol as a risk factor for mild cognitive impairment and dementia.

Association of traumatic brain injury with dementia and memory decline in older adults in the United States

INTRODUCTION

To examine associations of history of traumatic brain injuries (TBIs) with loss of consciousness (LOC) with dementia incidence and memory decline.

METHODS

We studied 2718 participants from the 1992 enrollment cohort of the Health and Retirement Study (HRS) aged 65 years or older in 2000. History of TBI with LOC was self-reported in 1992. Dementia was assessed using four algorithms established in HRS. Participants were followed from 2000 to 2014 with repeated measures of dementia and memory performance. Cox models and linear mixed-effects models were used.

RESULTS

In 1992, 11.9% of the participants reported a history of TBI with LOC. In fully adjusted models for all four algorithms, participants with a history of TBI with LOC had no statistically significant difference in dementia incidence nor in memory decline, compared to participants without TBI history.

DISCUSSION

Our study did not find evidence of a long-term association between history of TBI with LOC (of unknown frequency and severity) and dementia incidence or memory decline.

A review of the use of time-varying covariates in the Fine-Gray subdistribution hazard competing risk regression model

In survival analysis, time‐varying covariates are covariates whose value can change during follow‐up. Outcomes in medical research are frequently subject to competing risks (events precluding the occurrence of the primary outcome). We review the types of time‐varying covariates and highlight the effect of their inclusion in the subdistribution hazard model. External time‐dependent covariates are external to the subject, can effect the failure process, but are not otherwise involved in the failure mechanism. Internal time‐varying covariates are measured on the subject, can effect the failure process directly, and may also be impacted by the failure mechanism. In the absence of competing risks, a consequence of including internal time‐dependent covariates in the Cox model is that one cannot estimate the survival function or the effect of covariates on the survival function. In the presence of competing risks, the inclusion of internal time‐varying covariates in a subdistribution hazard model results in the loss of the ability to estimate the cumulative incidence function (CIF) or the effect of covariates on the CIF. Furthermore, the definition of the risk set for the subdistribution hazard function can make defining internal time‐varying covariates difficult or impossible. We conducted a review of the use of time‐varying covariates in subdistribution hazard models in articles published in the medical literature in 2015 and in the first 5 months of 2019. Seven percent of articles published included a time‐varying covariate. Several inappropriately described a time‐varying covariate as having an association with the risk of the outcome.

Systemic Immune Dyshomeostasis Model and Pathways in Alzheimer's Disease

Alzheimer’s disease (AD) still remains an enigma for researchers and clinicians. The onset of AD is insidious, gradually progressive and multifactorial. The recent accumulated scientific evidences suggests that the pathological changes resemble the autoimmune-driven self-sustaining inflammatory process as a result of prolonged oxidative stress and immune dyshomeostasis. Apart from aging, during life span various other factors—mainly environmental, lifestyle, chronic stress, polymicrobial infections and neuroendocrine functions—affect the immune system. Here, we provide crosstalk among “trigger insults/inflammatory stimulus” i.e., polymicrobial infection, chronic stress, pro-inflammatory diet and cholinergic signaling to put forward a “Systemic Immune Dyshomeostasis” model as to connect the events leading to AD development and progression. Our model implicates altered cholinergic signaling and suggests pathological stages with various modifiable risk factors and triggers at different chronological age and stage of cognitive decline. The search of specific autoantibodies for AD which may serve as the suitable blood/CSF biomarkers should be actively pursued for the early diagnosis of AD. The preventive and therapeutic strategies should be directed towards maintaining the normal functioning of the immune system throughout the life span and specific modulation of the immune responses in the brain depending on the stage of changes in brain.

Gender Differences in Outcomes after Traumatic Brain Injury among Service Members and Veterans

This scoping study describes the range of outcomes in traumatic brain injury (TBI) studies of military service members and veterans addressing gender differences. A secondary purpose is to identify differences in outcomes between male and female participants in such studies. We searched PubMed, CiNAHL, and PsycInfo databases for relevant articles. Two reviewers independently screened results. Of 822 unique titles and abstracts screened for eligibility, 55 full articles were reviewed, with 29 studies meeting full inclusion criteria. Twenty of the 29 included studies used retrospective designs and all but two used data collected from Veterans Affairs or Department of Defense health care settings. TBI was diagnosed by self-report, screening, and evaluation procedures, and medical record documentation. Ten different outcome categories were identified among the included studies. In general, female service members and veterans have not been well represented in TBI outcomes research. Evidence suggests that female veterans with mild TBI (mTBI) report more neurobehavioral symptoms and use more outpatient services than male veterans. Studies also indicate that female veterans with TBI are more frequently diagnosed with depression. Additional research is essential to support precision treatment recommendations for female veterans with TBI, as women represent a growing proportion of the patients served by the Veterans Health Administration. LEVEL OF EVIDENCE: IV.