Proteomic analysis of Alzheimer's disease cerebrospinal fluid reveals alterations associated with APOE ε4 and atomoxetine treatment.

Alzheimer's disease (AD) is currently defined by the aggregation of amyloid-ß (Aß) and tau proteins in the brain. Although biofluid biomarkers are available to measure Aß and tau pathology, few markers are available to measure the complex pathophysiology that is associated with these two cardinal neuropathologies. Here, we characterized the proteomic landscape of cerebrospinal fluid (CSF) changes associated with Aß and tau pathology in 300 individuals using two different proteomic technologies-tandem mass tag mass spectrometry and SomaScan. Integration of both data types allowed for generation of a robust protein coexpression network consisting of 34 modules derived from 5242 protein measurements, including disease-relevant modules associated with autophagy, ubiquitination, endocytosis, and glycolysis. Three modules strongly associated with the apolipoprotein E ε4 (APOE ε4) AD risk genotype mapped to oxidant detoxification, mitogen-associated protein kinase signaling, neddylation, and mitochondrial biology and overlapped with a previously described lipoprotein module in serum. Alterations of all three modules in blood were associated with dementia more than 20 years before diagnosis. Analysis of CSF samples from an AD phase 2 clinical trial of atomoxetine (ATX) demonstrated that abnormal elevations in the glycolysis CSF module-the network module most strongly correlated to cognitive function-were reduced by ATX treatment. Clustering of individuals based on their CSF proteomic profiles revealed heterogeneity of pathological changes not fully reflected by Aß and tau.

Patterns of cognitive domain abnormalities enhance discrimination of dementia risk prediction: The ARIC study.

INTRODUCTION: The contribution of neuropsychological assessments to risk assessment for incident dementia is underappreciated. METHODS: We analyzed neuropsychological testing results in dementia-free participants in the Atherosclerosis Risk in Communities (ARIC) study. We examined associations of index domain-specific neuropsychological test performance with incident dementia using cumulative incidence curves and Cox proportional hazards models. RESULTS: Among 5296 initially dementia-free participants (mean [standard deviation] age of 75.8 [5.1] years; 60.1% women, 22.2% Black) over a median follow-up of 7.9 years, the covariate-adjusted hazard ratio varied substantially depending on the pattern of domain-specific performance and age, in an orderly manner from single domain language abnormalities (lowest risk) to single domain executive or memory abnormalities, to multidomain abnormalities including memory (highest risk). DISCUSSION: By identifying normatively defined cognitive abnormalities by domains based on neuropsychological test performance, there is a conceptually orderly and age-sensitive spectrum of risk for incident dementia that provides valuable information about the likelihood of progression. HIGHLIGHTS: Domain-specific cognitive profiles carry enhanced prognostic value compared to mild cognitive impairment. Single-domain non-amnestic cognitive abnormalities have the most favorable prognosis. Multidomain amnestic abnormalities have the greatest risk for incident dementia. Patterns of domain-specific risks are similar by sex and race.

Associations of mid-to-late-life inflammation with late-life mobility and the influences of chronic comorbidities, race, and social determinants of health: The Atherosclerosis Risk in Communities Study.

BACKGROUND: Relationships of midlife inflammation with late-life mobility and influences of chronic health conditions, race, and social determinants of health (SDoH) on these relationships are poorly understood. METHODS: Among 4758 community-dwelling participants (41% men, 20% Black), high-sensitivity C-reactive protein (hsCRP) was measured over 20+ years: in midlife at study visit 2 (V2: 1990-1992, 47-68 years); at V4 (1996-1998, 53-74 years); and with concurrent late-life 4-m gait speed at V5 (2011-2013, 67-88 years, mean 75 years). SDoH measures included race, the national-rank area deprivation index, education, and income. We examined associations of late-life gait speed with midlife hsCRP (V2 continuous and clinically high ≥3 mg/L), with 20-year hsCRP history from midlife (V2-V5 average continuous hsCRP and clinically high ≥3 mg/L) and with inflammation accumulation (visits and years with high hsCRP). Regression models adjusted for demographic, cardiovascular, and SDoH measures; effect modification by the presence of other common chronic conditions (obesity, diabetes, hypertension) and race were examined, with and without accounting for SDoH. RESULTS: High midlife hsCRP was associated with slower late-life gait speed, even among those without chronic conditions in midlife: -4.6 cm/s (95% CI: -6.4, -2.8). Importantly, sustained high hsCRP was associated with a 20-year slowing of -10.0 cm/s (-14.9, -5.1) among those who never experienced obesity, diabetes, or hypertension over the 20-year period. Associations were similar between Black participants, -3.8 cm/s (-6.9, -0.7) and White participants -3.3 (-4.5, -2.2) per interquartile range of midlife hsCRP; effect modifications by chronic conditions and race were unsupported throughout. Results were robust to accounting for SDoH or otherwise; however, worse SDoH was associated with higher inflammation and slower gait speed in both Black and White participants. CONCLUSIONS: Inflammation in midlife may contribute to clinically meaningful late-life slowing of gait speed, even among otherwise healthy-appearing adults and regardless of race and socioeconomic disadvantage. Regular monitoring and interventions for inflammation may be warranted from midlife.

Mid-life plasma proteins associated with late-life prefrailty and frailty: a proteomic analysis.

Physical frailty is a syndrome that typically manifests in later life, although the pathogenic process causing physical frailty likely begins decades earlier. To date, few studies have examined the biological signatures in mid-life associated with physical frailty later in life. Among 4,189 middle-aged participants (57.8 ± 5.0 years, 55.8% women) from the Atherosclerosis Risk in Community (ARIC) study, we evaluated the associations of 4,955 plasma proteins (log 2-transformed and standardized) measured using the SomaScan platform with their frailty status approximately 20 years later. Using multinomial logistic regression models adjusting for demographics, health behaviors, kidney function, total cholesterol, and comorbidities, 12 and 221 proteins were associated with prefrailty and frailty in later life, respectively (FDR p < 0.05). Top frailty-associated proteins included neurocan core protein (NCAN, OR = 0.66), fatty acid-binding protein heart (FABP3, OR = 1.62) and adipocyte (FABP4, OR = 1.65), as well proteins involved in the contactin-1 (CNTN1), toll-like receptor 5 (TLR5), and neurogenic locus notch homolog protein 1 (NOTCH1) signaling pathway relevant to skeletal muscle regeneration, myelination, and inflammation. Pathway analyses suggest midlife dysregulation of inflammation, metabolism, extracellular matrix, angiogenesis, and lysosomal autophagy among those at risk for late-life frailty. After further adjusting for midlife body mass index (BMI) - an established frailty risk factor - only CNTN1 (OR = 0.75) remained significantly associated with frailty. Post-hoc analyses demonstrated that the top 41 midlife frailty-associated proteins mediate 32% of the association between mid-life BMI and late-life frailty. Our findings provide new insights into frailty etiology earlier in the life course, enhancing the potential for prevention.

Proteomic analysis of cardiorespiratory fitness for prediction of mortality and multisystem disease risks.

Despite the wide effects of cardiorespiratory fitness (CRF) on metabolic, cardiovascular, pulmonary and neurological health, challenges in the feasibility and reproducibility of CRF measurements have impeded its use for clinical decision-making. Here we link proteomic profiles to CRF in 14,145 individuals across four international cohorts with diverse CRF ascertainment methods to establish, validate and characterize a proteomic CRF score. In a cohort of around 22,000 individuals in the UK Biobank, a proteomic CRF score was associated with a reduced risk of all-cause mortality (unadjusted hazard ratio 0.50 (95% confidence interval 0.48-0.52) per 1 s.d. increase). The proteomic CRF score was also associated with multisystem disease risk and provided risk reclassification and discrimination beyond clinical risk factors, as well as modulating high polygenic risk of certain diseases. Finally, we observed dynamicity of the proteomic CRF score in individuals who undertook a 20-week exercise training program and an association of the score with the degree of the effect of training on CRF, suggesting potential use of the score for personalization of exercise recommendations. These results indicate that population-based proteomics provides biologically relevant molecular readouts of CRF that are additive to genetic risk, potentially modifiable and clinically translatable.

Biomarkers of Neurodegeneration and Alzheimer's Disease Neuropathology in Adolescents and Young Adults with Youth-Onset Type 1 or Type 2 Diabetes: A Proof-of-Concept Study.

Adult-onset diabetes increases one's risk of neurodegenerative disease including Alzheimer's disease (AD); however, the risk associated with youth-onset diabetes (Y-DM) remains underexplored. We quantified plasma biomarkers of neurodegeneration and AD in participants with Y-DM from the SEARCH cohort at adolescence and young adulthood (Type 1, n = 25; Type 2, n = 25; 59% female; adolescence, age = 15 y/o [2.6]; adulthood, age = 27.4 y/o [2.2]), comparing them with controls (adolescence, n = 25, age = 14.8 y/o [2.7]; adulthood, n = 21, age = 24.9 y/o [2.8]). Plasma biomarkers, including glial fibrillary acidic protein (GFAP), neurofilament light chain protein (NfL), phosphorylated tau-181 (pTau181), and amyloid beta (Aß40, Aß42), were measured via Simoa. A subset of participants (n = 7; age = 27.5 y/o [5.7]) and six controls (age = 25.1 y/o [4.5]) underwent PET scans to quantify brain amyloid and tau densities in AD sensitive brain regions. Y-DM adolescents exhibited lower plasma levels of Aß40, Aß42, and GFAP, and higher pTau181 compared to controls (p < 0.05), a pattern persisting into adulthood (p < 0.001). All biomarkers showed significant increases from adolescence to adulthood in Y-DM (p < 0.01), though no significant differences in brain amyloid or tau were noted between Y-DM and controls in adulthood. Preliminary evidence suggests that preclinical AD neuropathology is present in young people with Y-DM, indicating a potential increased risk of neurodegenerative diseases.

Signatures and Discriminative Abilities of Multi-Omics between States of Cognitive Decline.

Dementia poses a substantial global health challenge, warranting an exploration of its intricate pathophysiological mechanisms and potential intervention targets. Leveraging multi-omic technology, this study utilizes data from 2251 participants to construct classification models using lipidomic, gut metabolomic, and cerebrospinal fluid (CSF) proteomic markers to distinguish between the states of cognitive decline, namely, the cognitively unimpaired state, mild cognitive impairment, and dementia. The analysis identifies three CSF proteins (apolipoprotein E, neuronal pentraxin-2, and fatty-acid-binding protein), four lipids (DEDE.18.2, DEDE.20.4, LPC.O.20.1, and LPC.P.18.1), and five serum gut metabolites (Hyodeoxycholic acid, Glycohyodeoxycholic acid, Hippuric acid, Glyceric acid, and Glycodeoxycholic acid) capable of predicting dementia prevalence from cognitively unimpaired participants, achieving Area Under the Curve (AUC) values of 0.879 (95% CI: 0.802-0.956), 0.766 (95% CI: 0.700-0.835), and 0.717 (95% CI: 0.657-0.777), respectively. Furthermore, exclusively three CSF proteins exhibit the potential to predict mild cognitive impairment prevalence from cognitively unimpaired subjects, with an AUC of 0.760 (95% CI: 0.691-0.828). In conclusion, we present novel combinations of lipids, gut metabolites, and CSF proteins that showed discriminative abilities between the states of cognitive decline and underscore the potential of these molecules in elucidating the mechanisms of cognitive decline.

Association between retinal microvascular abnormalities and late-life brain amyloid-ß deposition: the ARIC-PET study.

BACKGROUND: Retinal microvascular signs are accessible measures of early alterations in microvascular dysregulation and have been associated with dementia; it is unclear if they are associated with AD (Alzheimer's disease) pathogenesis as a potential mechanistic link. This study aimed to test the association of retinal microvascular abnormalities in mid and late life and late life cerebral amyloid. METHODS: Participants from the ARIC-PET (Atherosclerosis Risk in Communities-Positron Emission Tomography) study with a valid retinal measure (N = 285) were included. The associations of mid- and late-life retinal signs with late-life amyloid-ß (Aß) by florbetapir PET were tested. Two different measures of Aß burden were included: (1) elevated amyloid (SUVR > 1.2) and (2) continuous amyloid SUVR. The retinal measures' association with Aß burden was assessed using logistic and robust linear regression models. A newly created retinal score, incorporating multiple markers of retinal abnormalities, was also evaluated in association with greater Aß burden. RESULTS: Retinopathy in midlife (OR (95% CI) = 0.36 (0.08, 1.40)) was not significantly associated with elevated amyloid burden. In late life, retinopathy was associated with increased continuous amyloid standardized value uptake ratio (SUVR) (ß (95%CI) = 0.16 (0.02, 0.32)) but not elevated amyloid burden (OR (95%CI) = 2.37 (0.66, 9.88)) when accounting for demographic, genetic and clinical risk factors. A high retinal score in late life, indicating a higher burden of retinal abnormalities, was also significantly associated with increased continuous amyloid SUVR (ß (95% CI) = 0.16 (0.04, 0.32)) independent of vascular risk factors. CONCLUSIONS: Retinopathy in late life may be an easily obtainable marker to help evaluate the mechanistic vascular pathway between retinal measures and dementia, perhaps acting via AD pathogenesis. Well-powered future studies with a greater number of retinal features and other microvascular signs are needed to test these findings.

High Throughput Plasma Proteomics and Risk of Heart Failure and Frailty in Late Life.

Importance: Heart failure (HF) and frailty frequently coexist and may share a common pathobiology, although the underlying mechanisms remain unclear. Understanding these mechanisms may provide guidance for preventing and treating both conditions. Objective: To identify shared pathways between incident HF and frailty in late life using large-scale proteomics. Design, Setting, and Participants: In this cohort study, 4877 aptamers (Somascan v4) were measured among participants in the community-based longitudinal Atherosclerosis Risk In Communities (ARIC) cohort study at visit 3 (V3; 1993-1995; n = 10 638) and at visit 5 (V5; 2011-2013; n = 3908). Analyses were externally replicated among 3189 participants in the Cardiovascular Health Study (CHS). Data analysis was conducted from February 2022 to June 2023. Exposures: Protein aptamers, measured at study V3 and V5. Main Outcomes and Measures: Outcomes assessed included incident HF hospitalization after V3 and after V5, prevalent frailty at V5, and incident frailty between V5 and visit 6 (V6; 2016-2017; n = 4131). Frailty was assessed using the Fried criteria. Analyses were adjusted for age, gender, race, field center, hypertension, diabetes, smoking status, body mass index, estimated glomerular filtration rate, prevalent coronary heart disease, prevalent atrial fibrillation, and history of myocardial infarction. Mendelian randomization (MR) analysis was performed to assess potential causal effects of candidate proteins on HF and frailty. Results: A total of 4877 protein aptamers were measured among 10 638 participants at V3 (mean [SD] age, 60 [6] years; 4886 [46%] men). Overall, 286 proteins were associated with incident HF after V3 (822 events; P < 1.0 × 10-5), 83 of which were also associated with incident after V5 (336 events; P < 1.7 × 10-4). Among HF-free participants at V5 (n = 3908; mean [SD] age, 75 [5] years; 1861 [42%] men), 48 of 83 HF-associated proteins were associated with prevalent frailty (223 cases; P < 6.0 × 10-4), 18 of which were also associated with incident frailty at V6 (152 cases; P < 1.0 × 10-3). These proteins enriched fibrosis and inflammation pathways and demonstrated stronger associations with incident HF with preserved ejection fraction (HFpEF) than HF with reduced ejection fraction. All 18 proteins were associated with both prevalent frailty and incident HF in CHS. MR identified potential causal effects of several proteins on frailty and HF. Conclusions and Relevance: In this study, the proteins associated with risk of HF and frailty enrich for pathways related to inflammation and fibrosis as well as risk of HFpEF. Several of these proteins could potentially contribute to the shared pathophysiology of frailty and HF.

Plasma metabolomic markers underlying skeletal muscle mitochondrial function relationships with cognition and motor function.

BACKGROUND: Lower skeletal muscle mitochondrial function is associated with future cognitive impairment and mobility decline, but the biological underpinnings for these associations are unclear. We examined metabolomic markers underlying skeletal muscle mitochondrial function, cognition and motor function. METHODS: We analysed data from 560 participants from the Baltimore Longitudinal Study of Aging (mean age: 68.4 years, 56% women, 28% Black) who had data on skeletal muscle oxidative capacity (post-exercise recovery rate of phosphocreatine, kPCr) via 31P magnetic resonance spectroscopy and targeted plasma metabolomics using LASSO model. We then examined which kPCr-related markers were also associated with cognition and motor function in a larger sample (n = 918, mean age: 69.4, 55% women, 27% Black). RESULTS: The LASSO model revealed 24 metabolites significantly predicting kPCr, with the top 5 being asymmetric dimethylarginine, lactic acid, lysophosphatidylcholine a C18:1, indoleacetic acid and triacylglyceride (17:1_34:3), also significant in multivariable linear regression. The kPCr metabolite score was associated with cognitive or motor function, with 2.5-minute usual gait speed showing the strongest association (r = 0.182). Five lipids (lysophosphatidylcholine a C18:1, phosphatidylcholine ae C42:3, cholesteryl ester 18:1, sphingomyelin C26:0, octadecenoic acid) and 2 amino acids (leucine, cystine) were associated with both cognitive and motor function measures. CONCLUSION: Our findings add evidence to the hypothesis that mitochondrial function is implicated in the pathogenesis of cognitive and physical decline with aging and suggest that targeting specific metabolites may prevent cognitive and mobility decline through their effects on mitochondria. Future omics studies are warranted to confirm these findings and explore mechanisms underlying mitochondrial dysfunction in aging phenotypes.

Maintenance of Normal Blood Pressure From Middle to Older Age: Results From the Atherosclerosis Risk in Communities Study.

BACKGROUND: It is unknown whether maintaining normal blood pressure (BP) from middle to older age is associated with improved health outcomes. METHODS: We estimated the proportion of Atherosclerosis Risk in Communities study participants who maintained normal BP from 1987 to 1989 (visit 1) through 1996 to 1998 and 2011 to 2013 (over 4 and 5 visits, respectively). Normal BP was defined as systolic BP <120 mm Hg and diastolic BP <80 mm Hg, without antihypertensive medication. We estimated the risk of cardiovascular disease, dementia, and poor physical functioning after visit 5. In exploratory analyses, we examined participant characteristics associated with maintaining normal BP. RESULTS: Among 2699 participants with normal BP at baseline (mean age 51.3 years), 47.1% and 15.0% maintained normal BP through visits 4 and 5, respectively. The hazard ratios comparing participants who maintained normal BP through visit 4 but not visit 5 and through visit 5 versus those who did not maintain normal BP through visit 4 were 0.80 (95% CI, 0.63-1.03) and 0.60 (95% CI, 0.42-0.86), respectively, for cardiovascular disease, and 0.85 (95% CI, 0.71-1.01) and 0.69 (95% CI, 0.54-0.90), respectively, for poor physical functioning. Maintaining normal BP through visit 5 was more common among participants with normal body mass index versus obesity at visit 1, those with normal body mass index at visits 1 and 5, and those with overweight at visit 1 and overweight or normal body mass index at visit 5, compared with those with obesity at visits 1 and 5. CONCLUSIONS: Maintaining normal BP was associated with a lower risk of cardiovascular disease and poor physical functioning.

Social relationships, amyloid burden, and dementia: The ARIC-PET study.

INTRODUCTION: This study aimed to assess whether social relationships in mid-life reduce the risk of dementia related to amyloid burden. METHODS: Participants in the Atherosclerosis Risk in Communities (ARIC) study were assessed for social support and isolation (visit 2; 1990-1992). A composite measure, "social relationships," was generated. Brain amyloid was evaluated with florbetapir positron emission tomography (PET); (visit 5; 2012-2014). Incident dementia cases were identified following visit 5 through 2019 using ongoing surveillance. Relative contributions of mid-life social relationships and elevated brain amyloid to incident dementia were evaluated with Cox regression models. RESULTS: Among 310 participants without dementia, strong mid-life social relationships were associated independently with lower dementia risk. Elevated late-life brain amyloid was associated with greater dementia risk. DISCUSSION: Although mid-life social relationships did not moderate the relationship between amyloid burden and dementia, these findings affirm the importance of strong social relationships as a potentially protective factor against dementia.

Alzheimer's and neurodegenerative disease biomarkers in blood predict brain atrophy and cognitive decline.

BACKGROUND: Although blood-based biomarkers have been identified as cost-effective and scalable alternatives to PET and CSF markers of neurodegenerative disease, little is known about how these biomarkers predict future brain atrophy and cognitive decline in cognitively unimpaired individuals. Using data from the Baltimore Longitudinal Study of Aging (BLSA), we examined whether plasma biomarkers of Alzheimer's disease (AD) pathology (amyloid-ß [Aß42/40], phosphorylated tau [pTau-181]), astrogliosis (glial fibrillary acidic protein [GFAP]), and neuronal injury (neurofilament light chain [NfL]) were associated with longitudinal brain volume loss and cognitive decline. Additionally, we determined whether sex, APOEε4 status, and plasma amyloid-ß status modified these associations. METHODS: Plasma biomarkers were measured using Quanterix SIMOA assays. Regional brain volumes were measured by 3T MRI, and a battery of neuropsychological tests assessed five cognitive domains. Linear mixed effects models adjusted for demographic factors, kidney function, and intracranial volume (MRI analyses) were completed to relate baseline plasma biomarkers to baseline and longitudinal brain volume and cognitive performance. RESULTS: Brain volume analyses included 622 participants (mean age ± SD: 70.9 ± 10.2) with an average of 3.3 MRI scans over 4.7 years. Cognitive performance analyses included 674 participants (mean age ± SD: 71.2 ± 10.0) with an average of 3.9 cognitive assessments over 5.7 years. Higher baseline pTau-181 was associated with steeper declines in total gray matter volume and steeper regional declines in several medial temporal regions, whereas higher baseline GFAP was associated with greater longitudinal increases in ventricular volume. Baseline Aß42/40 and NfL levels were not associated with changes in brain volume. Lower baseline Aß42/40 (higher Aß burden) was associated with a faster decline in verbal memory and visuospatial performance, whereas higher baseline GFAP was associated with a faster decline in verbal fluency. Results were generally consistent across sex and APOEε4 status. However, the associations of higher pTau-181 with increasing ventricular volume and memory declines were significantly stronger among individuals with higher Aß burden, as was the association of higher GFAP with memory decline. CONCLUSIONS: Among cognitively unimpaired older adults, plasma biomarkers of AD pathology (pTau-181) and astrogliosis (GFAP), but not neuronal injury (NfL), serve as markers of future brain atrophy and cognitive decline.

Associations of plasma proteomics and age-related outcomes with brain age in a diverse cohort.

Machine learning models are increasingly being used to estimate "brain age" from neuroimaging data. The gap between chronological age and the estimated brain age gap (BAG) is potentially a measure of accelerated and resilient brain aging. Brain age calculated in this fashion has been shown to be associated with mortality, measures of physical function, health, and disease. Here, we estimate the BAG using a voxel-based elastic net regression approach, and then, we investigate its associations with mortality, cognitive status, and measures of health and disease in participants from Atherosclerosis Risk in Communities (ARIC) study who had a brain MRI at visit 5 of the study. Finally, we used the SOMAscan assay containing 4877 proteins to examine the proteomic associations with the MRI-defined BAG. Among N = 1849 participants (age, 76.4 (SD 5.6)), we found that increased values of BAG were strongly associated with increased mortality and increased severity of the cognitive status. Strong associations with mortality persisted when the analyses were performed in cognitively normal participants. In addition, it was strongly associated with BMI, diabetes, measures of physical function, hypertension, prevalent heart disease, and stroke. Finally, we found 33 proteins associated with BAG after a correction for multiple comparisons. The top proteins with positive associations to brain age were growth/differentiation factor 15 (GDF-15), Sushi, von Willebrand factor type A, EGF, and pentraxin domain-containing protein 1 (SEVP 1), matrilysin (MMP7), ADAMTS-like protein 2 (ADAMTS), and heat shock 70 kDa protein 1B (HSPA1B) while EGF-receptor (EGFR), mast/stem-cell-growth-factor-receptor (KIT), coagulation-factor-VII, and cGMP-dependent-protein-kinase-1 (PRKG1) were negatively associated to brain age. Several of these proteins were previously associated with dementia in ARIC. These results suggest that circulating proteins implicated in biological aging, cellular senescence, angiogenesis, and coagulation are associated with a neuroimaging measure of brain aging.

From Practice to Public Health: Broadening Neuropsychology's Reach & Value-An Introduction to the National Academy of Neuropsychology's 2022 Annual Conference Special Issue.

This special issue is centered around presentations from the National Academy of Neuropsychology 2022 Annual Conference. The theme of the conference, "From Practice to Public Health: Broadening Neuropsychology's Reach & Value" is pivotal for the field's future. With an ever-shifting technological landscape and recent changes in clinical practice post-COVID, we are left wondering how neuropsychology will develop. How will we use biomedical and technological advances, such as blood-based Alzheimer's disease biomarkers or passive digital recordings, to improve clinical care and further expand our understanding of disease mechanisms? As neuropsychologists, how can we use our expertise to empirically inform public health policy? The diagnosis and treatment of post-acute sequelae of COVID-19, the identification and characterization of post-pandemic educational setbacks, and the adaptation of new technological and diagnostic advances into clinical practice workflows represent a vital set of new challenges and opportunities poised to disrupt traditional modes of practice. The articles in this special issue convey the role of neuropsychology in addressing these emerging issues and illustrate how and why neuropsychology is well positioned to be at the forefront of clinical practice and scientific advancements.

Plasma biomarkers for Alzheimer's and related dementias: A review and outlook for clinical neuropsychology.

Recent technological advances have improved the sensitivity and specificity of blood-based biomarkers for Alzheimer's disease and related dementias. Accurate quantification of amyloid-ß peptide, phosphorylated tau (pTau) isoforms, as well as markers of neurodegeneration (neurofilament light chain [NfL]) and neuro-immune activation (glial fibrillary acidic protein [GFAP] and chitinase-3-like protein 1 [YKL-40]) in blood has allowed researchers to characterize neurobiological processes at scale in a cost-effective and minimally invasive manner. Although currently used primarily for research purposes, these blood-based biomarkers have the potential to be highly impactful in the clinical setting - aiding in diagnosis, predicting disease risk, and monitoring disease progression. Whereas plasma NfL has shown promise as a non-specific marker of neuronal injury, plasma pTau181, pTau217, pTau231, and GFAP have demonstrated desirable levels of sensitivity and specificity for identification of individuals with Alzheimer's disease pathology and Alzheimer's dementia. In this forward looking review, we (i) provide an overview of the most commonly used blood-based biomarkers for Alzheimer's disease and related dementias, (ii) discuss how comorbid medical conditions, demographic, and genetic factors can inform the interpretation of these biomarkers, (iii) describe ongoing efforts to move blood-based biomarkers into the clinic, and (iv) highlight the central role that clinical neuropsychologists may play in contextualizing and communicating blood-based biomarker results for patients.

Associations Between Mid-Life Psychosocial Measures and Estimated Late Life Amyloid Burden: The Atherosclerosis Risk in Communities (ARIC)-PET Study.

Background: Psychosocial factors are modifiable risk factors for Alzheimer's disease (AD). One mechanism linking psychosocial factors to AD risk may be through biological measures of brain amyloid; however, this association has not been widely studied. Objective: To determine if mid-life measures of social support and social isolation in the Atherosclerosis Risk in Communities (ARIC) Study cohort are associated with late life brain amyloid burden, measured using florbetapir positron emission tomography (PET). Methods: Measures of social support and social isolation were assessed in ARIC participants (visit 2: 1990-1992). Brain amyloid was evaluated with florbetapir PET standardized uptake value ratios (SUVRs; visit 5: 2012-2014). Results: Among 316 participants without dementia, participants with intermediate (odds ratio (OR), 0.47; 95% CI, 0.25-0.88), or low social support (OR, 0.43; 95% CI, 0.22-0.83) in mid-life were less likely to have elevated amyloid SUVRs, relative to participants with high social support. Participants with moderate risk for social isolation in mid-life (OR, 0.32; 95% CI, 0.14-0.74) were less likely to have elevated amyloid burden than participants at low risk for social isolation. These associations were not significantly modified by sex or race. Conclusions: Lower social support and moderate risk of social isolation in mid-life were associated with lower odds of elevated amyloid SUVR in late life, compared to participants with greater mid-life psychosocial measures. Future longitudinal studies evaluating mid-life psychosocial factors, in relation to brain amyloid as well as other health outcomes, will strengthen our understanding of the role of these factors throughout the lifetime.

Association of Plasma Markers of Alzheimer's Disease, Neurodegeneration, and Neuroinflammation with the Choroid Plexus Integrity in Aging.

The choroid plexus (CP) is a vital brain structure essential for cerebrospinal fluid (CSF) production. Moreover, alterations in the CP's structure and function are implicated in molecular conditions and neuropathologies including multiple sclerosis, Alzheimer's disease, and stroke. Our goal is to provide the first characterization of the association between variation in the CP microstructure and macrostructure/volume using advanced magnetic resonance imaging (MRI) methodology, and blood-based biomarkers of Alzheimer's disease (Aß42/40 ratio; pTau181), neuroinflammation and neuronal injury (GFAP; NfL). We hypothesized that plasma biomarkers of brain pathology are associated with disordered CP structure. Moreover, since cerebral microstructural changes can precede macrostructural changes, we also conjecture that these differences would be evident in the CP microstructural integrity. Our cross-sectional study was conducted on a cohort of 108 well-characterized individuals, spanning 22-94 years of age, after excluding participants with cognitive impairments and non-exploitable MR imaging data. Established automated segmentation methods were used to identify the CP volume/macrostructure using structural MR images, while the microstructural integrity of the CP was assessed using our advanced quantitative high-resolution MR imaging of longitudinal and transverse relaxation times (T1 and T2). After adjusting for relevant covariates, positive associations were observed between pTau181, NfL and GFAP and all MRI metrics. These associations reached significance (p<0.05) except for CP volume vs. pTau181 (p=0.14), CP volume vs. NfL (p=0.35), and T2 vs. NFL (p=0.07). Further, negative associations between Aß42/40 and all MRI metrics were observed but reached significance only for Aß42/40 vs. T2 (p=0.04). These novel findings demonstrate that reduced CP macrostructural and microstructural integrity is positively associated with blood-based biomarkers of AD pathology, neurodegeneration/neuroinflammation and neurodegeneration. Degradation of the CP structure may co-occur with AD pathology and neuroinflammation ahead of clinically detectable cognitive impairment, making the CP a potential structure of interest for early disease detection or treatment monitoring.

Organ-specific aging in the plasma proteome predicts disease.

In their recent Nature paper, Oh et al. use 4979 plasma proteins collected across multiple cohorts, publicly available gene expression data, and machine learning models to identify 11 organ-specific aging scores that are linked to organ-specific disease and mortality risk, including heart failure, cognitive decline, and Alzheimer's disease.