BACKGROUND:Mechanisms underlying the association between age-related arterial stiffening and poor brain health remain elusive. Cerebral blood flow (CBF) homeostasis may be implicated. This study ...evaluates how aortic stiffening relates to resting CBF and cerebrovascular reactivity (CVR) in older adults.
METHODS:Vanderbilt Memory & Aging Project participants free of clinical dementia, stroke, and heart failure were studied, including older adults with normal cognition (n=155; age, 72±7 years; 59% male) or mild cognitive impairment (n=115; age, 73±7 years; 57% male). Aortic pulse wave velocity (PWV; meters per second) was quantified from cardiac magnetic resonance. Resting CBF (milliliters per 100 g per minute) and CVR (CBF response to hypercapnic normoxia stimulus) were quantified from pseudocontinuous arterial spin labeling magnetic resonance imaging. Linear regression models related aortic PWV to regional CBF, adjusting for age, race/ethnicity, education, Framingham Stroke Risk Profile (diabetes mellitus, smoking, left ventricular hypertrophy, prevalent cardiovascular disease, atrial fibrillation), hypertension, body mass index, apolipoprotein E4 (APOE ε4) status, and regional tissue volume. Models were repeated testing PWV×APOE ε4 interactions. Sensitivity analyses excluded participants with prevalent cardiovascular disease and atrial fibrillation.
RESULTS:Among participants with normal cognition, higher aortic PWV related to lower frontal lobe CBF (β=−0.43; P=0.04) and higher CVR in the whole brain (β=0.11; P=0.02), frontal lobes (β=0.12; P<0.05), temporal lobes (β=0.11; P=0.02), and occipital lobes (β=0.14; P=0.01). Among APOE ε4 carriers with normal cognition, findings were more pronounced with higher PWV relating to lower whole-brain CBF (β=−1.16; P=0.047), lower temporal lobe CBF (β=−1.81; P=0.004), and higher temporal lobe CVR (β=0.26; P=0.08), although the last result did not meet the a priori significance threshold. Results were similar in sensitivity models. Among participants with mild cognitive impairment, higher aortic PWV related to lower CBF in the occipital lobe (β=−0.70; P=0.02), but this finding was attenuated when participants with prevalent cardiovascular disease and atrial fibrillation were excluded. Among APOE ε4 carriers with mild cognitive impairment, findings were more pronounced with higher PWV relating to lower temporal lobe CBF (β=−1.20; P=0.02).
CONCLUSIONS:Greater aortic stiffening relates to lower regional CBF and higher CVR in cognitively normal older adults, especially among individuals with increased genetic predisposition for Alzheimer’s disease. Central arterial stiffening may contribute to reductions in regional CBF despite preserved cerebrovascular reserve capacity.
Cerebrospinal fluid (CSF) neurofilament light (NFL) is a protein biomarker of axonal injury. To study whether NFL is associated with diffusion tensor imaging (DTI) measurements of white matter (WM) ...microstructure, Vanderbilt Memory & Aging Project participants with normal cognition (n = 77), early mild cognitive impairment (n = 15), and MCI (n = 55) underwent lumbar puncture to obtain CSF and 3T brain MRI. Voxel-wise analyses cross-sectionally related NFL to DTI metrics, adjusting for demographic and vascular risk factors. Increased NFL correlated with multiple DTI metrics (p-values < 0.05). An NFL × diagnosis interaction (excluding early mild cognitive impairment) on WM microstructure (p-values < 0.05) was detected, with associations strongest among MCI. Multiple NFL × CSF biomarker interactions were detected. Associations between NFL and worse WM metrics were strongest among amyloid-β42–negative, tau-positive, and suspected nonamyloid pathology participants. Findings suggest increased NFL, a biomarker of axonal injury, is correlated with compromised WM microstructure. Results highlight the role of elevated NFL in predicting WM damage in cognitively impaired older adults who are amyloid-negative, tau-positive, or meet suspected nonamyloid pathology criteria.
Although hippocampal volume has served as a long-standing predictor of cognitive decline, diffusion magnetic resonance imaging studies of white matter have shown similar relationships. Still, it ...remains unclear if gray matter and white matter interact to predict cognitive impairment and longitudinal decline. Here, we investigate whether free-water (FW) and FW-corrected fractional anisotropy (FAT) within medial temporal lobe white matter tracts provides meaningful contribution to cognition and cognitive decline beyond hippocampal volume. Using data from the Vanderbilt Memory & Aging Project (n = 319), we found that FW was associated with baseline memory and executive function beyond that of hippocampal volume and other comorbidities. Longitudinal analyses demonstrated significant interactions of hippocampal volume and inferior longitudinal fasciculus (p = 0.043) and cingulum bundle (p = 0.025) FAT on memory decline and with fornix FAT (p = 0.025) on decline in executive function. Results suggest that FW metrics of white matter have a unique role in cognitive decline and should be included in theoretical models of aging, cerebrovascular disease, and Alzheimer’s disease.
•Evaluated free-water (FW) metrics in medial temporal lobe (MTL) white matter tracts•MTL FW is associated with hippocampal volume•MTL FW is associated with memory and executive function•MTL FW metrics have unique contribution to cognitive performance•MTL FW metrics interact with hippocampal volume to predict cognitive decline
Cognitive decline may prevent liver transplant (LT) recipients from staying healthy and independent. This study examined associations of objective and subjective, rated by LT recipients and ...caregivers, cognitive decline with patient-reported physical and psychological symptom distress, ability to perform household tasks, and workplace productivity among LT recipients. Sixty pairs of LT recipients and caregivers participated in this cross-sectional study. Subjective cognition was measured by the Everyday Cognition. Objective cognition was assessed with four cognitive tests, including the Repeatable Battery for the Assessment of Neuropsychological Status. Patient-reported outcomes were assessed with the Rotterdam Symptom Checklist-Modified, Profile of Mood States-Short Form, Creative Therapy Consultants Homemaking Assessment, and Work Limitations Questionnaire. Linear regression analyses related objective and subjective cognition to the patient-reported outcomes. While objective cognitive decline was not associated with any patient-reported outcomes, subjective cognitive decline was significantly associated with the outcomes. Higher LT recipient self-rated cognitive decline was associated with higher physical symptom distress (
= 0.30,
= 0.006) and workplace productivity loss (
= 14.85,
< 0.0001). Higher caregiver-rated cognitive decline was associated with lower household tasks performance (
= -18.55,
= 0.015). Findings suggest to consider subjective cognition when developing an individualized post-transplant care plan.
Objective cognitive assessments, a gold standard diagnostic tool for cognitive impairment, may not be feasible in busy liver transplantation (LT) practice because they are often time consuming. This ...study determined whether subjective cognition, patients’ self‐ratings and/or caregivers’ ratings of patients’ cognition, reflects objective cognition in LT recipients. A convenience sample of 60 adult LT recipients and their caregivers, recruited at a single transplant center, participated in this cross‐sectional descriptive study. Subjective cognition (ie, recipient self‐rated and caregiver rated) was measured using the Everyday Cognition (ECog; global and 6 domain scores). Objective global and domain‐specific cognition of recipients was measured using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), Trail Making Test parts A and B, Digit Span Backward, and Rey‐Osterrieth Complex Figure. Agreement between LT recipients’ ECog scores and those of their caregivers was fair to moderate (intraclass correlation coefficient = 0.48 for global score, 0.35‐0.56 for domain scores). Significant, albeit rather weak, correlations were found between subjective and objective scores. Recipients’ ECog visuospatial abilities scores were correlated with Rey‐Osterrieth Complex Figure scores (rs = −0.39; P = 0.007), whereas caregivers’ ECog global, attention, visuospatial abilities, and organization scores were, respectively, correlated with the scores of RBANS global (rs = −0.33; P = 0.04) and attention (rs = −0.46; P = 0.005), Rey‐Osterrieth Complex Figure (Copy; rs = −0.34; P = 0.03), and Trail Making Test part A (rs = 0.31; P = 0.049). The findings suggest that caregivers may estimate LT recipients’ cognition better than recipients themselves. Caregivers may provide supplemental information that could be useful for clinicians when considering the cognitive functioning of LT recipients.
Abstract Objective The objective of this study was to compare whether different sources of cognitive complaint (i.e., subjective and informant) predict diagnostic conversion in nondemented older ...adults. Methods Participants from the National Alzheimer's Coordinating Center had a baseline diagnosis of normal cognition (NC; n = 4414; mean age, 73 ± 8 years; 69% female) or mild cognitive impairment (MCI; n = 1843; mean age, 74 ± 8 years; 52% female). Multinomial logistic regression related baseline cognitive complaint (no complaint, self only, informant only, or both self and informant) to diagnostic outcome (reversion, stable, or conversion). Results At follow-up, 14% of NC participants converted to MCI/dementia (3.5 ± 1.8 years), and 41% of MCI participants converted to dementia (3.0 ± 1.6 years). Among NC participants, self complaint only (odds ratio OR, 2.1; 99% confidence interval (CI),1.5–2.9; P < .001), informant complaint only (OR, 2.2; 99% CI, 1.2–3.9; P < .001), and both self and informant complaint (OR, 4.2; 99% CI, 2.9–6.0; P < .001) were associated with diagnostic conversion compared with no complaint. Among participants with MCI—compared with no complaint, informant complaint only (OR, 2.2; 99% CI, 1.2–4.3, P = .002), and both self and informant complaint (OR, 2.9; 99% CI, 1.8–4.8; P < .001)—were associated with conversion. Conclusions Cognitive complaints are related to conversion among nondemented older adults. Complaint from both (i.e. mutual complaint) sources was most predictive of diagnostic outcome, followed by informant complaint, highlighting the need for obtaining informant corroboration to enhance prognosis and distinguish underlying pathological processes from normal cognitive aging. Self complaint was related inconsistently to diagnostic outcome.
Approximately 30% of older adults exhibit the neuropathological features of Alzheimer's disease without signs of cognitive impairment. Yet, little is known about the genetic factors that allow these ...potentially resilient individuals to remain cognitively unimpaired in the face of substantial neuropathology. We performed a large, genome-wide association study (GWAS) of two previously validated metrics of cognitive resilience quantified using a latent variable modelling approach and representing better-than-predicted cognitive performance for a given level of neuropathology. Data were harmonized across 5108 participants from a clinical trial of Alzheimer's disease and three longitudinal cohort studies of cognitive ageing. All analyses were run across all participants and repeated restricting the sample to individuals with unimpaired cognition to identify variants at the earliest stages of disease. As expected, all resilience metrics were genetically correlated with cognitive performance and education attainment traits (P-values < 2.5 × 10-20), and we observed novel correlations with neuropsychiatric conditions (P-values < 7.9 × 10-4). Notably, neither resilience metric was genetically correlated with clinical Alzheimer's disease (P-values > 0.42) nor associated with APOE (P-values > 0.13). In single variant analyses, we observed a genome-wide significant locus among participants with unimpaired cognition on chromosome 18 upstream of ATP8B1 (index single nucleotide polymorphism rs2571244, minor allele frequency = 0.08, P = 2.3 × 10-8). The top variant at this locus (rs2571244) was significantly associated with methylation in prefrontal cortex tissue at multiple CpG sites, including one just upstream of ATPB81 (cg19596477; P = 2 × 10-13). Overall, this comprehensive genetic analysis of resilience implicates a putative role of vascular risk, metabolism, and mental health in protection from the cognitive consequences of neuropathology, while also providing evidence for a novel resilience gene along the bile acid metabolism pathway. Furthermore, the genetic architecture of resilience appears to be distinct from that of clinical Alzheimer's disease, suggesting that a shift in focus to molecular contributors to resilience may identify novel pathways for therapeutic targets.
OBJECTIVETo cross-sectionally relate multiple small vessel disease (SVD) neuroimaging markers to cognition among older adults.
METHODSVanderbilt Memory & Aging Project participants free of clinical ...dementia and stroke (n = 327, age 73 ± 7 years, 59% male, 40% with mild cognitive impairment) completed neuropsychological assessment and 3T MRI to measure white matter hyperintensities (WMH), perivascular spaces (PVS), cerebral microbleeds (CMBs), and lacunes. Linear regressions related each SVD marker to neuropsychological performances and adjusted for age, sex, race/ethnicity, education, cognitive diagnosis, APOE ε4 presence, Framingham Stroke Risk Profile, and intracranial volume.
RESULTSWMH related to the most neuropsychological measures, including the Boston Naming Test, Animal Naming, Coding, Number Sequencing, Executive Function Composite, and Hooper Visual Organization Test performances (p ≤ 0.01). PVS related to multiple information processing and executive function performances (p ≤ 0.02). Lacunes and CMBs related to fewer measures than expected. Combined models simultaneously testing multiple statistically significant SVD predictors suggested that WMH, PVS, and CMBs each independently related to information processing and executive function performances; however, compared to other SVD markers, PVS remained statistically significant in models related to information processing and executive functioning performances.
CONCLUSIONSAs expected, increased WMH corresponded to poorer performances across multiple cognitive domains. PVS, previously considered a benign neuroimaging feature in older adults, may have important clinical implications because PVS was related to information processing and executive function performances even in combined models. On the basis of models with multiple SVD predictors, WMH, PVS, and CMBs may each reflect a separate pathway of small vessel injury.
Proteomics research has been transformed due to high-throughput liquid chromatography (LC-MS/MS) tandem mass spectrometry instruments combined with highly sophisticated automated sample preparation ...and multiplexing workflows. However, scaling proteomics experiments to large sample cohorts (hundreds to thousands) requires thoughtful quality control (QC) protocols. Robust QC protocols can help with reproducibility, quantitative accuracy, and provide opportunities for more decisive troubleshooting. Our laboratory conducted a plasma proteomics study of a cohort of N = 335 patient samples using tandem mass tag (TMTpro) 16-plex batches. Over the course of a 10-month data acquisition period for this cohort we collected 271 pooled QC LC-MS/MS result files obtained from MS/MS analysis of a patient-derived pooled plasma sample, representative of the entire cohort population. This sample was tagged with TMTzero or TMTpro reagents and used to inform the daily performance of the LC-MS/MS instruments and to allow within and across sample batch normalization. Analytical variability of a number of instrumental and data analysis metrics including protein and peptide identifications, peptide spectral matches (PSMs), number of obtained MS/MS spectra, average peptide abundance, percent of peptides with a Δ m/z between ±0.003 Da, percent of MS/MS spectra obtained at the maximum injection time, and the retention time of selected tracking peptides were evaluated to help inform the design of a robust LC-MS/MS QC workflow for use in future cohort studies. This study also led to general tips for using selected metrics to inform real-time troubleshooting of LC-MS/MS performance issues with daily QC checks.
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