Publications by authors named "JT O'Brien"

Functional brain changes such as altered cerebral blood flow occur long before the onset of clinical symptoms in Alzheimer's disease (AD) and other neurodegenerative disorders. While cerebral hypoperfusion occurs in established AD, middle-aged carriers of genetic risk factors for AD, including APOE ε4, display regional hyperperfusion due to hypothesised pleiotropic or compensatory effects, representing a possible early biomarker of AD and facilitating earlier AD diagnosis. However, it is not clear whether hyperperfusion already exists even earlier in life.

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Objectives: We assessed the modulation of allostatic load (AL) by engagement in healthy habits and life stressors, mediated through resilience and the perceived influence of the stressors. Sleep was included as third mediator given extensive evidence associating to all the analysed factors.

Methods: Structural equation models to assess the modulation of AL by either traumatic or psychosocial stressors and healthy habits were generated with data from 620 mid-life adults (age 51.

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Co-morbid Alzheimer's disease (AD) pathology (amyloid-beta and tau) is commonly observed in Lewy body dementia (LBD), and this may affect clinical outcomes. A systematic review of the effect of AD co-pathology on longitudinal clinical outcomes in LBD was conducted. A search of MEDLINE and EMBASE (October 2024) yielded n = 3558 records that were screened by two independent reviewers.

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Background: Genetic risk factors start to affect the brain and behavior in Alzheimer's disease (AD) before clinical symptoms occur. Although AD is mainly associated with memory deficits, attention and executive dysfunctions can present at the early presymptomatic stages in middle age for those with non-modifiable risks.

Objective: Here, we investigated whether known risk genes for AD already affected attention in young adulthood.

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Article Synopsis
  • The study aimed to assess changes in cardiac [123I]-metaiodobenzylguanidine uptake in individuals with mild cognitive impairment with Lewy bodies (MCI-LB) who initially had normal scans.
  • Eight participants underwent follow-up scans 2 to 4 years after their baseline assessments, with all repeat scans also returning normal results.
  • Despite normal scans, three participants showed a significant decrease in uptake (over 10%) and the overall mean change in uptake was a decline of 5.2%.
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Article Synopsis
  • - Brain Age Gap is related to dementia in older adults, but its link to dementia risk-factors and cognitive performance in middle-aged individuals is less explored.
  • - A study involving 552 cognitively healthy middle-aged participants showed that brain age gap correlates with factors like hypertension and alcohol intake, but not with genetic risk factors (like the APOE ε4 allele) or cognitive performance.
  • - Findings suggest that addressing modifiable risk factors may help in developing therapies to prevent dementia in middle-aged populations.
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Article Synopsis
  • Caregiver histories are valuable for diagnosing neurodegenerative diseases; the study analyzed 4952 caregiver questionnaires from 2481 participants.
  • Using advanced machine learning, researchers achieved high diagnostic accuracy (mean AUC 0.83) between different diseases, while observing changes in symptoms over time.
  • The findings stress the importance of structured caregiver reports for diagnosing dementia and suggest the Cambridge Behavioural Inventory can effectively track disease progression in clinical settings.
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Inflammation is an important risk factor, a potential therapeutic target for cognitive decline and dementia, and an inherent feature of autoimmune and immune-mediated rheumatic diseases. The risk of cognitive impairment and dementia is increased in individuals with immune-mediated rheumatic diseases, particularly in those with cardiovascular risk factors and cardiovascular disease. Immunomodulatory medications have been associated with a reduced risk of dementia, but whether this effect is mediated through their anti-inflammatory immunomodulating properties or other mechanisms, such as cardiovascular risk reduction, is unclear.

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The innate immune system plays an integral role in the progression of many neurodegenerative diseases. In addition to central innate immune cells (e.g.

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: The pathophysiology of Alzheimer's disease (AD) may begin developing years or even decades prior to the manifestation of its first symptoms. The APOE ε4 genotype is a prominent genetic risk for AD that has been found to be associated with brain changes across the lifespan since early adulthood. Thus, studying brain changes that may occur in young adults with an APOE ε4 status is highly relevant.

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Neuroinflammation is an important pathogenic mechanism in many neurodegenerative diseases, including those caused by frontotemporal lobar degeneration (FTLD). Postmortem and in vivo imaging studies have shown brain inflammation early in these conditions, proportionate to symptom severity and rate of progression. However, evidence for corresponding blood markers of inflammation and their relationship with central inflammation and clinical outcome are limited.

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Importance: Traumatic brain injuries (TBI) represent an important, potentially modifiable risk factor for dementia. Despite frequently observed vascular imaging changes in individuals with TBI, the relationships between TBI-associated changes in brain imaging and clinical outcomes have largely been overlooked in community cases of TBI.

Objective: To assess whether TBI are associated with and interact with midlife changes in neuroimaging and clinical features in otherwise healthy individuals.

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Introduction: We tested associations between two retinal measures (optic disc pallor, peripapillary retinal nerve fiber layer [pRNFL] thickness) and four magnetic resonance imaging markers of cerebral small vessel disease (SVD; lacunes, microbleeds, white matter hyperintensities, and enlarged perivascular spaces [ePVSs]).

Methods: We used PallorMetrics to quantify optic disc pallor from fundus photographs, and pRNFL thickness from optical coherence tomography scans. Linear and logistic regression assessed relationships between retinal measures and SVD markers.

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Brain atrophy and cortical thinning are typically observed in people with Alzheimer's disease (AD) and, to a lesser extent, in those with mild cognitive impairment. In asymptomatic middle-aged apolipoprotein ε4 (ΑPOE4) carriers, who are at higher risk of future AD, study reports are discordant with limited evidence of brain structural differences between carriers and non-carriers of the ε4 allele. Alternative imaging markers with higher sensitivity at the presymptomatic stage, ideally quantified using typically acquired structural MRI scans, would thus be of great benefit for the detection of early disease, disease monitoring and subject stratification.

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Background Impaired glucose metabolism is characteristic of several types of dementia, preceding cognitive symptoms and structural brain changes. Reduced glucose uptake in specific brain regions, detected using fluorine 18 (F) fluorodeoxyglucose (FDG) PET, is a valuable diagnostic marker in Alzheimer disease (AD). However, the use of F-FDG PET in clinical practice may be limited by equipment availability and high cost.

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Background And Objectives: Retrospective studies indicate that dementia with Lewy bodies (DLB) may be preceded by a mild cognitive impairment (MCI) prodrome. Research criteria for the prospective identification of MCI with Lewy bodies (MCI-LB) have been developed. We aimed to assess the prognosis of a prospectively identified MCI-LB cohort at 2 key milestones, 3- and 5 years after diagnosis, to examine classification stability over time and rates of adverse outcomes (dementia or death).

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PREVENT is a multi-centre prospective cohort study in the UK and Ireland that aims to examine midlife risk factors for dementia and identify and describe the earliest indices of disease development. The PREVENT dementia programme is one of the original epidemiological initiatives targeting midlife as a critical window for intervention in neurodegenerative conditions. This paper provides an overview of the study protocol and presents the first summary results from the initial baseline data to describe the cohort.

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Changes in the brain's physiology in Alzheimer's disease are thought to occur early in the disease's trajectory. In this study our aim was to investigate the brain's neurochemical profile in a midlife cohort in relation to risk factors for future dementia using single voxel proton magnetic resonance spectroscopy. Participants in the multi-site PREVENT-Dementia study (age range 40-59 year old) underwent 3T magnetic resonance spectroscopy with the spectroscopy voxel placed in the posterior cingulate/precuneus region.

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Drugs of abuse cause changes in the prefrontal cortex (PFC) and associated regions that impair inhibitory control over drug-seeking. Breaking the contingencies between drug-associated cues and the delivery of the reward during extinction learning reduces relapse. Vagus nerve stimulation (VNS) has previously been shown to enhance extinction learning and reduce drug-seeking.

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Background/objective: The corticobasal syndrome (CBS) is a complex asymmetric movement disorder, with cognitive impairment. Although commonly associated with the primary 4-repeat-tauopathy of corticobasal degeneration, clinicopathological correlation is poor, and a significant proportion is due to Alzheimer's disease (AD). Synaptic loss is a pathological feature of many clinical and preclinical tauopathies.

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Introduction: Cerebral small vessel disease (SVD) is a common cause of stroke/vascular dementia with few effective treatments. Neuroinflammation and increased blood-brain barrier (BBB) permeability may influence pathogenesis. In rodent models, minocycline reduced inflammation/BBB permeability.

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Dementia with Lewy bodies (DLB) is a neurodegenerative condition often co-occurring with Alzheimer's disease (AD) pathology. Characterizing white matter tissue microstructure using Neurite Orientation Dispersion and Density Imaging (NODDI) may help elucidate the biological underpinnings of white matter injury in individuals with DLB. In this study, diffusion tensor imaging (DTI) and NODDI metrics were compared in 45 patients within the dementia with Lewy bodies spectrum (mild cognitive impairment with Lewy bodies (n = 13) and probable dementia with Lewy bodies (n = 32)) against 45 matched controls using conditional logistic models.

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Background: Fatigue is a common symptom in cerebral small vessel disease (SVD), but its pathogenesis is poorly understood. It has been suggested that inflammation may play a role. We determined whether central (neuro) inflammation and peripheral inflammation were associated with fatigue in SVD.

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A reduction in the volume of the thalamus and its nuclei has been reported in Alzheimer's disease, mild cognitive impairment and asymptomatic individuals with risk factors for early-onset Alzheimer's disease. Some studies have reported thalamic atrophy to occur prior to hippocampal atrophy, suggesting thalamic pathology may be an early sign of cognitive decline. We aimed to investigate volumetric differences in thalamic nuclei in middle-aged, cognitively unimpaired people with respect to dementia family history and apolipoprotein ε4 allele carriership and the relationship with cognition.

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