Medicine (RMH) - Research Publications
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ItemNo Preview AvailableAssociations between dual‐decline in cognition and gait speed with risk of dementia – results from the ASPREE trial cohort(Wiley, 2022-12)Background Dual decline in gait speed and cognition is associated with an increased risk of dementia. However, it is unclear if risks are conferred by decline in domain‐specific cognition and gait. We aimed to examine associations between dual decline in gait speed and cognition (global cognition, memory, processing speed and verbal fluency) with risk of dementia. Methods Prospective cohort study. Participants were from the ASPREE (ASPirin in Reducing Events in the Elderly) study, a double‐blind, randomized, placebo‐controlled trial of low dose aspirin in older adults (≥70 years; ≥65 if US minority). Of 19,114 randomized participants, 16,855 (88%) had longitudinal gait and cognitive data. Gait speed was measured at 0, 2, 4, 6 years and close‐out. Cognitive measures included Modified Mini‐Mental State examination (3MS, global cognition), Hopkins Verbal Learning Test‐Revised (HVLT‐R, memory), Symbol Digit Modalities (SDMT, processing speed) and Controlled Oral Word Association Test (COWAT‐F, verbal fluency), assessed at years 0, 1, 3, 5, and close‐out. Participants were classified into four groups: 1) dual decline in gait and cognition; 2) gait decline only; 3) cognitive decline only and 4) non‐decliners. Cognitive decline was defined as membership of the lowest tertile of annual change. Gait decline was defined as decline in gait speed ≥0.05 m/s per year across the study. Dementia (DSM‐IV criteria) was adjudicated by an expert panel using cognitive tests, functional status and clinical records. Cox proportional hazard models were used to estimate risk of dementia adjusting for covariates with death as competing risk. Results The mean age of participants was 75.0 (SD4.4) years. Compared with non‐decliners, risk of dementia was highest in the gait+HVLT‐R decliners (HR 24.7; 95% CI 16.3‐37.3), followed by the gait+3MS (HR 22.2; 95% CI 15.0‐32.9), gait+COWAT‐F (HR 4.66 95%; CI 3.5‐6.3) and gait+SDMT (HR 4.3 95% CI 3.2‐5.8) groups. Dual decliners also had higher risk of dementia than those with either gait or cognitive decline alone for 3MS and HVLT‐R. Conclusion The combination of decline in gait speed and memory may be the best suited to predict future dementia risk.
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ItemNo Preview AvailableContribution of modifiable dementia risk factors to cognitive performance and subjective cognition in middle‐aged adults(Wiley, 2022-12)Background Characterization of the contribution of modifiable risk factors (MRF) to dementia generally consider MRFs individually, despite strong evidence that MRFs co‐occur. In a large group of middle‐aged adults, the prevalence and co‐occurrence of MRFs for dementia was determined, spanning five broad domains (mood, lifestyle behaviours (e.g., physical inactivity), cardiovascular health, cognitive/social engagement, and sleep). We then investigated relationships between MRFs, both individually and combined, to cognitive performance and subjective cognition. Method Middle‐aged adults (n = 1610), most (70%) with a family history of dementia, enrolled in the Healthy Brain Project, completed an extensive set of questionnaires about their physical and psychological health and lifestyle. Participants also completed the Cogstate Brief Battery (CBB), and the Cognitive Function Instrument (CFI), a measure of subjective cognition. Participants were classified according to the number of domains (mood, lifestyle behaviours, cardiovascular health, cognitive/social engagement, and sleep, ranging from 0‐5) in which they reported at least one MRF. Age, sex, education and ethnicity were adjusted for in analyses. Result Most participants (65%) reported at least one MRF in two or more domains (Fig 1A). Compared to participants reporting no MRFs, participants who reported at least one MRF in 3‐5 domains showed worse memory performance and reported greater subjective cognitive concerns, with magnitudes of differences moderate to large (d = 0.30‐0.93; Fig 1B). Participants who reported at least one MRF in five domains also showed worse attention than those reporting no MRFs (d = 0.58). When individual MRFs were considered simultaneously, MRFs in the mood (e.g., anxiety symptomatology) and cognitive/social engagement domains (e.g., leisure activities) were associated with worse attention and memory performance. Individual MRFs reflecting mood and sleep symptomatology were associated with greater subjective cognitive concerns. Conclusion In middle‐aged community dwelling adults, multidomain MRFs for dementia are highly prevalent and co‐occur, and are associated with poorer cognitive outcomes. This suggests that the presence of multiple MRFs as early as midlife may have negative neurological outcomes, however, this will need to be explored in future neuroimaging studies. These findings indicate that multidomain lifestyle prevention trials in middle‐aged adults may be useful to delay or prevent future cognitive impairment or dementia.
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ItemNo Preview AvailableCerebrospinal fluid neurofilament light chain differentiates behavioural variant frontotemporal dementia progressors from ‘phenocopy’ non‐progressors(Wiley, 2022-12)Background Distinguishing behavioural variant frontotemporal dementia (bvFTD) from non‐neurodegenerative ‘non‐progressor’, ‘phenocopy’ mimics of frontal lobe dysfunction, can be one of the most challenging clinical dilemmas. A biomarker of neuronal injury, neurofilament light chain (NfL), could reduce misdiagnosis and delay. Method Cerebrospinal fluid (CSF) NfL, amyloid beta 1‐42 (AB42), total and phosphorylated tau (T‐tau, P‐tau) levels were examined in patients with an initial diagnosis of bvFTD. Based on follow up information, patients were categorised as Progressors. Non‐Progressors were subtyped in to Phenocopy Non‐Progressors (non‐neurological/neurodegenerative final diagnosis), and Static Non‐Progressors (static deficits, not fully explained by non‐neurological/neurodegenerative causes). Result Forty‐three patients were included: 20 Progressors, 23 Non‐Progressors (15 Phenocopy, 8 Static), 20 controls. NfL concentrations were lower in Non‐Progressors (Non‐Progressors Mean, M=554pg/mL, 95%CI:[461, 675], Phenocopy Non‐Progressors M=459pg/mL, 95%CI:[385, 539], Static Non‐Progressors M=730pg/mL, 95%CI:[516, 940]), compared to bvFTD Progressors (M=2397pg/mL, 95%CI:[1607, 3332]). NfL distinguished Progressors from Non‐Progressors with the highest accuracy (area under the curve 0.92, 90%/87% sensitivity/specificity, 86%/91% positive/negative predictive value, 88% accuracy). Static Non‐Progressors tended to have higher T‐tau and P‐tau levels compared to Phenocopy Non‐Progressors. Conclusion This study demonstrated strong diagnostic utility of CSF NfL in distinguishing bvFTD from phenocopy non‐progressor variants, at baseline, with high accuracy, in a real‐world clinical setting. This has important clinical implications to improve outcomes for patients and clinicians facing this challenging clinical dilemma, as well as for healthcare services, and clinical trials. Further research is required to investigate heterogeneity within the non‐progressor group and potential diagnostic algorithms, and prospective studies are underway assessing plasma NfL.
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ItemNo Preview AvailableModifiable dementia risk factors associated with higher CSF tau and poorer cognition in middle‐aged adults(Wiley, 2022-12)Background Modifiable factors in domains such as mood, lifestyle behaviours, cardiovascular health, cognitive/social engagement, and sleep are associated with increased risk for dementia. These modifiable risk factors could promote Alzheimer’s disease (AD) related biological processes, such as beta‐amyloid (Aβ) or tau accumulation, but these associations remain poorly understood. This study aimed to determine associations between modifiable dementia risk factors with Aβ, tau, and cognition in cognitively unimpaired middle‐aged adults. Method Middle‐aged adults (n = 82) (age range 40‐70) enrolled in a biomarker sub‐study of the Healthy Brain Project completed self‐report questionnaires about their physical and psychological health and lifestyle. Cerebrospinal fluid (CSF) levels of Aβ42, total tau (t‐tau), and phosphorylated tau (p‐tau) (Roche Elecsys) were obtained. A comprehensive neuropsychological battery was administered to measure cognition, and composite scores were derived for memory, executive function, and the Preclinical Alzheimer’s Cognitive Composite (PACC). Participants were classified according to reporting normal modifiable risk (NMR) (risk in ≤1 domains; n = 34) or high modifiable risk (HMR) (risk in ≥2 domains; n = 48) across five domains (mood, lifestyle behaviours, cardiovascular health, cognitive and social engagement, and sleep). Result Compared to those with NMR, those with HMR had increased t‐tau (d = 0.54, p = .021) and p‐tau (d = 0.47, p = .044) levels but did not differ on Aβ42 (d = 0.23, p = .319) after adjusting for age and sex. With age, sex, and education adjusted for, HMR participants showed worse performance on PACC (d = 0.69, p = .003), executive function (d = 0.55, p = .016), and episodic memory (d = 0.40, p = 0.076) compared to NMR participants. Differences in cognitive performance remained when levels of Aβ42, t‐tau and p‐tau levels were controlled in the models [PACC (d = 0.59, p = .011), memory (d = 0.64, p = .005) and executive function (d = 0.45, p = .049)]. Conclusion Modifiable dementia risk factors across multiple domains are related to higher total and phosphorylated tau levels and with subtle cognitive deficits, but not with Aβ, in middle‐aged adults. Together with the observation that differences in cognition across modifiable risk groups remained when Aβ and tau levels were controlled statistically, this suggests that modifiable dementia risk factors may increase risk through neurodegenerative processes non‐specific to AD, such as increased cerebrovascular burden, although this needs to be confirmed in future neuroimaging studies.
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ItemNo Preview AvailablePlasma pTau181/Aβ42 identifies cognitive change earlier than CSF pTau181/Ab42(Wiley Open Access, 2022-12)Background Plasma biomarkers now show an accuracy in detecting Amyloid Beta (Aβ) similar to AD biomarkers derived from cerebral spinal fluid (CSF). However, the ability of plasma AD biomarkers, alone or in combination, to predict cognitive decline has not yet been compared to that of CSF AD biomarkers. Method Plasma biomarker data from 233 participants’ first visit in the Australian Imaging, Biomarkers and Lifestyle study (AIBL) was submitted to linear mixed effects models (LME) to quantify the relationship with change in cognition (measured using the AIBL PACC) and in clinical disease stage (CDR SoB) in both PET Aβ‐ (Centiloid value <20CL) and Aβ+ (Centiloid value ≥20CL) participant subgroups. Separate models were used to assess CSF (Elecsys) and plasma (ADx NeuroSciences) data for Aβ42, pTau181 and the pTau181/Aβ42 ratio. Biomarker values were classified into low vs high levels based on ROC‐derived thresholds optimizing separation of PET Aβ status (low vs high at 20 CL). Changes in cognitive and clinical symptoms were then compared between the low/high plasma biomarker groups. Result In Aβ‐ participants, no significant interactions between binary biomarker classification and time were observed for AIBL PACC or CDR SoB, for either CSF or plasma biomarkers. In the Aβ+ participants, interactions between the binary plasma biomarker classification and change in cognition were greater in magnitude that those detected for CSF biomarker classification. For plasma, abnormally high values of both pTau181 and the pTau181/Aβ42 ratio predicted a significant increase over time in CDR SoB (Figure 1H & 1L) and a significant decrease over time in the AIBL PACC score (Figure 1F & 1J), compared the group with low values on the same biomarkers. In cognitively unimpaired Aβ‐ participants, the AIBL PACC score declined in those with abnormally high values of the pTau181 and the pTau181/Aβ42 ratio (Figure 1F & 1J). Conclusion Assays to measure pTau181 and Aβ42 in the plasma possess an accuracy equivalent to those derived from CSF. In particular, abnormally high levels of plasma pTau181 or the ratio of pTau181 to Aβ42 ratio provide a strong prediction of early cognitive changes, even in those with normal PET Aβ status.
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ItemNitrous oxide-induced neurological disorders: an increasing public health concern.(Wiley, 2022-05)BACKGROUND: Neurological presentations resulting from nitrous oxide (N2 O) abuse are increasing in Australia and worldwide. Despite known neuropsychiatric sequelae, N2 O canisters remain readily available and its use unregulated. AIMS: To examine the demographics, clinical and electrophysiological findings of patients presenting with neurological complications of N2 O abuse, and thus inform clinicians and public health decision-makers of the significant public health concerns of this increasing practice. METHODS: Consecutive patients presenting to a tertiary referral metropolitan hospital were included in this series. Patients were identified by a search of discharge summaries of patients admitted with acute or subacute neuropathy or myelopathy and a history of N2 O abuse, and from the electrophysiology database. RESULTS: Thirteen patients were identified, most presenting with subacute paraesthesia, sensory ataxia and lower limb weakness. Eleven had low serum vitamin B12 . Spinal magnetic resonance imaging was consistent with subacute combined degeneration in eight. Nerve conduction studies revealed a motor or sensorimotor axonal neuropathy (three with motor predominance). There was a bimodal demographic distribution consisting of socially isolated, international university students and local residents with a history of mental illness and polydrug abuse. CONCLUSIONS: Recreational N2 O use is an emerging health problem in Australia. International university students and patients with pre-existing mental illness or polydrug use appear to be at increased risk. A severe motor neuropathy may emerge following vitamin B12 replacement. Public health measures are required to limit the availability of N2 O and to educate adolescents and young adults about the potential for significant harm.
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ItemNo Preview AvailableContinued white matter fibre degeneration over 3 years after ischemic stroke(Wiley, 2021-12)Abstract Background We aimed to chart white matter integrity over 3 years after stroke, to examine if post‐stroke loss of white matter continues to be accelerated compared to control participants. Method We applied a longitudinal “fixel”‐based analysis, sensitive to fibre tract‐specific differences within a voxel, to assess axonal loss in stroke (N=71, 22 women) compared to control participants (N=36, 13 women) across the whole brain. We studied microstructural differences in fibre density and macrostructural (morphological) changes in fibre cross‐section. Result In stroke participants, we observed significantly lower fibre density and cross‐section from 3 months to 3 years. The changes were widespread and affected the corpus callosum, bilateral inferior fronto‐occipital fasciculus, right superior longitudinal fasciculus. Conclusion We conclude that ischemic stroke is associated with extensive and continued neurodegeneration that significantly affects white matter micro and macrostructure across the whole brain. These findings confirm that the deleterious effects of stroke on white matter continue several years following the event.
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ItemNo Preview AvailableExamining the structural correlates of amyloid‐beta in people with DLB(Wiley, 2021-12)Background Dementia with Lewy bodies (DLB) is a neurodegenerative disorder characterized pathologically by the deposition of alpha synuclein. Many patients with DLB also have brain compatible with Alzheimer’s disease (namely Amyloid‐β and tau), which can lead to challenges with clinical diagnosis and management. In this study we aim to understand the influence of Aβ on brain atrophy in DLB patients. Method 19 participants with probable DLB underwent 3T MRI T1‐weighted (voxel size=0.8x0.8x0.8mm3, TR=2400ms, TE=2.31ms) and β‐amyloid (Aβ) PET (radiotracer 18F‐NAV4694) imaging. Participants were grouped into Aβ negative (n=10; age=71.6±5.8 years) and Aβ positive (n=9; age=75.1±4.3 years) with a threshold of 50 centiloid units to identify neuropathological change (Amadoru et al. 2020). Brain volume measures (regional subcortical grey matter and global white and grey matter) were segmented from T1‐weighted images with FreeSurfer (Fischl et al. 2002, Fischl 2012). Given previous literature suggesting prominence of thalamic structural changes in DLB, we also specifically analysed changes in the thalamus by segmenting the thalamus into 25 nuclei, which were then grouped into six regions (anterior, lateral, ventral, intralaminar, medial and posterior) (Watson et al. 2017, Iglesias et al. 2018). All brain volumes were expressed as fractions of intracranial volume to account for differences in head size. Group comparison analyses were not controlled for age and sex as both these covariates did not statistically differ between groups. Result Brain volume differed significantly between Aβ‐ and Aβ+ DLB patients in the left thalamus (Aβ‐:4.39±0.37x103, Aβ+:4.07±0.19x103, p=0.03) and right thalamus (Aβ‐:4.17±0.34x103, Aβ+:3.84±0.22 x103, p=0.03). Specifically, the ventral (LEFT; Aβ‐:1.78±0.15, Aβ+:1.63±0.14, p=0.03. RIGHT; Aβ‐:1.83±0.15, Aβ+:1.65±0.12, p=0.01) and posterior (LEFT; Aβ‐:1.30±0.12, Aβ+:1.17±0.10, p=0.04. RIGHT; Aβ‐:1.42±0.14, Aβ+:1.21±0.12, p=0.003) regions were significantly reduced in Aβ+ compared to Aβ‐ DLB patients. Conclusion We demonstrated significant thalamic atrophy in Aβ+ patients compared to Aβ‐ DLB patients. We did not observe significant differences in grey matter and hippocampal volume between patient groups. This study showed that AD‐related processes in DLB patients are associated with thalamic atrophy, specifically in the ventral and posterior regions. Future studies would benefit a larger DLB cohort to further understand the association between AD‐related pathology and the regional thalamic correlates of clinical function.
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ItemNo Preview AvailableThe effects of concurrent cognitive and meta-cognitive training on neuropsychiatric symptoms of people living with younger onset dementia: Protocol for a pilot trial(Wiley, 2021-12-01)BACKGROUND: Neuropsychiatric symptoms (NPS) are behavioural and psychological disturbances frequent in people with dementia that have been linked with lower quality of life, lower cognitive functioning and greater caregiver distress, especially for caregivers of people with younger-onset dementia (YOD) (1). Several drug and non-drug treatments targeting NPS have been investigated in recent years. However, to the best of our knowledge, no treatment has been developed that concurrently targets and trains cognitive and meta-cognitive processes which are implicated in the expression of NPS. The aim of this pilot trial is to investigate the effects on NPS of a mobile application-based intervention simultaneously training both processes by incorporating elements of cognitive training and cognitive-behavioural therapy. METHOD: Twenty participants with YOD will be randomised to the training group or to a control group. Participants in the experimental condition will train at home three times a week for four weeks with remote therapist support. NPS, cognitive, psychological and caregiver outcomes will be assessed before and immediately after the intervention. RESULT: The mobile application is in the design stage and further studies are underway to incorporate the views of people with YOD and their care-partners, as well as clinicians, to the design. Recruitment of participants is expected in the second half of 2021. CONCLUSION: Findings from this trial will further our understanding of the utility of concurrently targeting cognitive and meta-cognitive processes in people with YOD when treating NPS and will inform a revision of the application. We believe that results from this study will have important implications for the management and treatment of NPS in the ever-growing field of interventions utilising technology. 1 Baillon, S., Gasper, A., Wilson-Morkeh, F., Pritchard, M., Jesu, A. and Velayudhan, L., 2019. Prevalence and Severity of Neuropsychiatric Symptoms in Early- Versus Late-Onset Alzheimer's Disease. American Journal of Alzheimer's Disease & Other Dementias®, 34(7-8), pp.433-438.