Alzheimer's & Dementia

Introduction: Participant- and study partner-reported Cognitive Function Index scores may provide complementary information, but it remains unclear whether Alzheimer's disease biomarkers are associated with CFI scores across reporters, reporter-specific imbalance, or both. Methods: Using A4/LEARN screening data (screening sample, N = 1,686; primary dyadic analytic sample, N = 1,682; CDR global score = 0), we jointly modeled participant-reported (CFI-PT) and study partner-reported (CFI-SP) scores in long format to evaluate biomarker associations with CFI scores and biomarker x reporter interactions. As a secondary analysis, we compared tau PET with plasma p-tau217. Results: In an A4/LEARN-adapted regional extent model, reporter balance varied across amyloid regional extent categories, with the largest participant-leading contrast observed in the exploratory restricted early cortical subgroup. Tau PET was associated with higher CFI scores, but this association did not differ detectably between reporters. Plasma p-tau217 showed no clear CFI association or reporter-specific interaction in the A4-derived, amyloid-enriched subset. Discussion: Amyloid regional extent and tau PET were associated with different features of dyadic CFI data: reporter balance and CFI burden across reporters, respectively. Joint interpretation of CFI-PT and CFI-SP may support biomarker-informed interpretation of the instrument, although the cross-sectional findings require replication and longitudinal validation.

INTRODUCTIONThe growing number of assay platforms measuring blood-based biomarkers (BBMs) for Alzheimers disease (AD) has introduced challenges in interpretability and comparability across assays. Differences across studies also limit comparability of data. To address these challenges, a systematic evaluation of harmonization methods is needed to support BBM data integration within or across studies. METHODSTwo multisite studies, Alzheimers Disease Neuroimaging Initiative (ADNI, n = 219) and Human Connectome Project (HCP, n = 111), were used to evaluate harmonization methods for mitigating assay and cohort effects in plasma p-tau217 measurements. Methods includes various normalization, regression, and standardization approaches, including the recently developed CentiMarker. Assay effects were evaluated using repeated-measures data across assay platforms within each cohort, whereas cohort effects were assessed using pooled ADNI and HCP data. Harmonization performance was evaluated using distributional statistics and downstream modeling of p-tau217. RESULTSQuantile normalization and quantile mapping methods were most effective for mitigating assay effects, whereas conditional quantile mapping performed best for pooled multi-cohort data. These methods also preserved biological variability. In contrast, simple means adjustment and reference-based z-score standardization were least effective for mitigating assay effects, while simple means adjustment, z-score standardization, and quantile normalization were least effective for mitigating cohort effects. CentiMarker had minimal impact on assay or cohort effects. DISCUSSIONBased on our evaluation, we recommend (conditional) quantile mapping for p-tau217 studies integrating data across multiple assays or cohorts. In contrast, we caution against using CentiMarker and z-score-based methods, as they limit comparability and do not effectively mitigate technical variability.

Interventions targeting lifestyle and health behaviors support cognition in older adults at risk of dementia. It remains unclear if the cognitive benefit of such interventions is modified by Alzheimer's disease (AD)-related neuropathology, and if lifestyle interventions lead to changes in blood AD biomarkers. Here, we analyzed core AD plasma biomarkers (A{beta}, p-tau181, p-tau217, p-tau231, NFL, GFAP) in the two-year FINGER randomized controlled multidomain lifestyle trial, which demonstrated cognitive efficacy in an at-risk older general population (N=1260). We found that 85% of participants had p-tau217 below the pathological threshold at baseline (Lumipulse assay). Higher biomarker levels were associated with less favorable cognitive trajectories over two years, but their ability to predict brain amyloid accumulation on PET scans was modest (e.g., p-tau217 AUC 0.72). We found no indication that baseline biomarker levels significantly modified the cognitive benefits of the intervention. Changes in biomarkers were small over two years, with most participants (82%) remaining below the pathological p-tau217 threshold. Biomarker trajectories were similar in the intervention and control groups, suggesting that the cognitive benefits of the two-year lifestyle intervention in at-risk individuals without substantial impairment may primarily involve mechanistic pathways not captured by AD blood biomarkers. These findings provide new evidence to clarify the role of AD blood biomarkers for risk stratification and prediction of response to lifestyle interventions, which is crucial to inform future dementia precision prevention strategies. ClinicalTrials.gov ID NCT01041989.

Blood-based neurofilament light (NfL) is associated with all-cause mortality, but whether this reflects neuroaxonal injury or overlaps with cognitive and functional decline remains unclear. We followed 559 individuals aged 92-107 from three oldest-old cohorts for up to 16 years: cognitively healthy Dutch centenarians and two population-based Danish cohorts. Plasma biomarkers (A{beta}42/40, A{beta}40, A{beta}42, pTau-181, pTau-181/A{beta}42, NfL, and GFAP; Dutch cohort; NfL, Danish cohorts), cognition, and activities of daily living (ADL) were evaluated against mortality. NfL was the only biomarker consistently associated with mortality (HR 1.21-1.38), whereas AD-specific biomarkers did not predict mortality despite reflecting post-mortem AD neuropathology. NfL remained associated with mortality independently of cognition and ADL; ADL mediated 13-21% across cohorts and cognition 28%, only where cognitive impairment was widespread. Mortality at extreme age is more closely linked to neuroaxonal injury than to upstream AD pathology, with NfL capturing biological vulnerability beyond cognitive and functional decline.

Background: Plasma p-tau217 identifies Alzheimer's disease pathology, but performance in mixed cohorts may not extend to conditional tau-positivity discrimination within amyloid-positive individuals or to MRI-defined hippocampal neurodegeneration. We compared plasma prediction across PET- and MRI-defined AT(N) outcomes and conducted separate axis-specific assessments. Methods: This retrospective secondary study used Alzheimer's Disease Neuroimaging Initiative (ADNI) data. Tasks were amyloid positivity (A; 1,097 participants, 496 positive), tau positivity (T; 929, 195), T within A+ (361, 161), study-defined hippocampal neurodegeneration (N; 1,303, 248), and joint A+T+ (852, 161). Repeated nested cross-validation used fold-internal preprocessing and calibration. Post-hoc assessments comprised a Bio-Hermes A-axis staged random-forest analysis using Lilly p-tau217 and C2N amyloid-beta 40/amyloid-beta 42 (908 participants; 328 and 324 positive under the primary and alternative PET classifications), and an A4 ordinal p-tau217 analysis against an A4-specific medial-temporal tau-PET endpoint in A+ participants. Results: ADNI random-forest AUROCs were 0.9425 (95% CI 0.9271 to 0.9562) for A, 0.9495 (0.9325 to 0.9645) for T, 0.8852 (0.8485 to 0.9163) for T within A+, 0.7865 (0.7553 to 0.8151) for N, and 0.9614 (0.9484 to 0.9726) for joint A+T+. At thresholds targeting 90% sensitivity, specificity was 87.5% for T overall and 60.7% within A+. In Bio-Hermes, adding amyloid-beta 40 and amyloid-beta 42 to p-tau217 increased AUROC from 0.894 to 0.916 (paired difference 0.022, 95% conditional interval 0.010 to 0.035) and changed Brier score by -0.011 (-0.017 to -0.005); the alternative PET classification was concordant. In A4, ordinal p-tau217 had AUROC 0.7356 (95% CI 0.6775 to 0.7907), average precision 0.5657 (0.4732 to 0.6677), and Spearman rho = 0.4718 (0.3824 to 0.5528). Conclusions: ADNI identified task-dependent performance boundaries, particularly attenuated conditional T discrimination within A+. Separate-cohort evidence supported moderate single-marker conditional-T discrimination in A4 and modest complementary A-axis information from plasma amyloid-beta in Bio-Hermes, but only within those respective axes and assay implementations.

Background: Blood-based biomarkers are increasingly used to identify Alzheimer's disease (AD)-related pathology, but differences in p217tau assay methodology, training cohorts, and model-development context can substantially influence machine-learning (ML) predictions. Whether emerging biomarker platforms preserve biologically meaningful AD-related information across independently developed ML frameworks remains incompletely understood. Objective: To evaluate the biological coherence and translational consistency of plasma biomarker measurements generated using the 5ADCSI platform by applying multiple externally trained ML frameworks and developing a consensus-risk approach that integrates framework predictions while quantifying prediction uncertainty. Methods: Plasma biomarker measurements from 472 participants in the Louisville Twins Study were analyzed using three independently trained ML frameworks: an A4-derived model using the Lilly p217tau MSD assay and two ADNI-derived models using Quanterix Simoa p217tau measured with either the AlzPath or Janssen antibody. Framework-specific predictions of amyloid positivity probability and predicted centiloid burden were integrated into consensus amyloid risk, consensus centiloid burden, and composite consensus AD-risk scores. Prediction uncertainty and rank instability were used to characterize framework agreement and participant-level classification stability. Results: All three frameworks recognized biologically coherent AD-related signal despite differences in training cohort and assay methodology. Agreement was strongest between the A4-MSD and ADNI-AlzPath frameworks, whereas agreement involving the ADNI-Jan framework was weaker. Consensus-risk modeling identified a reproducibly high-risk subgroup characterized by elevated consensus-risk scores, low prediction uncertainty, and low rank instability. Participants prioritized by the consensus framework were enriched for APOE {varepsilon}4 burden, p-tau217, p-tau217/A{beta}42, and GFAP, while discordant high-risk participants exhibited substantially greater framework disagreement. Conclusions: Plasma biomarker measurements generated using the 5ADCSI platform preserve biologically meaningful AD-related information that is consistently recognized across multiple independent ML frameworks. Consensus-risk modeling provides a practical strategy for integrating complementary information from external biological reference models while explicitly characterizing prediction uncertainty, thereby supporting evaluation of emerging blood-based biomarker platforms when direct pathological validation is unavailable.

Background: Alzheimer's disease (AD) is a complex neurodegenerative disorder strongly influenced by genetic factors, with apolipoprotein E (APOE) {epsilon}4 allele being the most established risk variant. Although DNA-based genotyping remains standard, plasma proteotyping may provide scalable, isoform-specific alternatives. Methods: Plasma APOE4 protein were quantified using the NULISAseq CNS panel across four cohorts (ADRC, HeartSCORE, LATTICE, and ALPS). DNA-based APOE genotyping was the reference standard. Proteotyping thresholds for APOE {epsilon}4 carrier status and copy number were derived in ADRC and externally validated in the other cohorts. Logistic, proportional-odds, and Cox proportional-hazards models compared genotype- and proteotype-defined groups in relation to amyloid positivity, cross-sectional CDR global scores, and time to CDR-SB worsening, respectively. Results: Plasma APOE4 accurately classified APOE {epsilon}4 carrier status in ADRC (AUC=0.977, 95%CI 0.967-0.985; threshold 5.78 NULISA protein quantification [NPQ] value) and achieved near-perfect external validation in HeartSCORE, LATTICE, and ALPS (all AUCs=1.000, 95%CI 1.000-1.000). Plasma APOE4 also well-differentiated heterozygous from homozygous {epsilon}4 carriers (ADRC AUC=0.879, 95%CI 0.834-0.921; threshold 12.23 NPQ value). Genotype- and proteotype-defined {epsilon}4 carrier status showed similar associations with amyloid positivity (OR=4.40 vs 4.45), higher CDR global scores (OR=1.50 for both), and CDR-SB worsening (HR=1.22 for both). Discussion: Plasma APOE4 proteotyping accurately distinguished genotype-defined APOE {epsilon}4 carrier status and copy number while demonstrating AD-related associations comparable to DNA genotyping.

Current biobanking guidelines require in-person blood collection and immediate processing for Alzheimer's disease (AD) biomarker assessment. We recently reported that the P100 blood collection tubes containing protease inhibitors improve protein biomarker stability over delayed centrifugation periods. However, whether this comparability extends beyond a small set of biomarkers to the broad panels enabled by high-plex platforms has not been established. Here, we performed a head-to-head comparison of 127 neurodegeneration-related biomarkers in paired P100 vs. standard ethylenediaminetetraacetic acid (EDTA) plasma samples from n = 43 community-dwelling older adult participants using the NUcleic acid-Linked Immuno-Sandwich Assay (NULISA) proteomic technology. The NULISA assay demonstrated excellent technical reproducibility (intra- and inter-plate coefficients of variation [CVs] <10%). Biomarker levels in P100 and EDTA tubes were strongly correlated, with mean and median Spearman coefficients exceeding rho = 0.8. Six conventional AD biomarkers showed strong P100-EDTA correlations (rho > 0.8) with minimal mean differences and no significant proportional bias in Bland-Altman analysis, including plasma A42, GFAP, MAPT, NEFL, p-tau181, and p-tau231, while p-tau217 showed a P100-EDTA correlation of rho = 0.57. Two biomarker ratios (A{beta}42/A{beta}40 and p-tau217/A{beta}42) also showed minimal bias with no proportional bias detected. Receiver operating characteristic analysis using amyloid status, assessed with positron emission tomography in a subset of participants, showed comparable classification performance between the two tube types, with classification concordance up to 92% and no significant DeLong differences for most (80%) biomarkers. These findings indicate that, on the NULISA platform, P100 tubes yield analytical and classification performance comparable to conventional EDTA tubes, supporting their use for blood-based neurodegeneration biomarker research where immediate sample processing is not feasible.

Background: Up to 30% of individuals harboring core Alzheimer's disease (AD) neuropathology, amyloid-beta (Abeta; A) and tau (T)-remain cognitively unimpaired. Objective: We examine whether MRI measures of cerebral blood flow (CBF) and white matter hyperintensities (WMH) differentiate cognitively impaired (AD or mild cognitive impairment (MCI);AD+MCI) from non-demented individuals with (NDAN) and without (Controls) core AD neuropathology. Methods: A retrospective cohort study (2018-2023) using data from The Wisconsin Registry for Alzheimer's Prevention and Wisconsin Alzheimer's Disease Research Center studies employed linear models comparing group differences in regional gray matter (GM) CBF and whole brain WMH volume. Participants (N=500) underwent 3T MRI, amyloid- (11C-Pittsburgh Compound B) and tau- (18F-MK6240) PET, and neuropsychological assessments. We categorized participants based on PET and cognitive status as Controls (n=416; cognitively unimpaired, A-T-), NDAN (n=38; cognitively unimpaired, A+T+), or AD+MCI (n=46; cognitively impaired, A+T+). Results: Participants were 67 years old (mean), 68% female, and 37% APOE 4+. NDAN, like Controls, had significantly higher CBF than AD+MCI in GM regions susceptible to neurofibrillary tangle formation in early AD (frontal and temporal cortices, and limbic regions (ps<0.05)). Largest CBF differences (22-34%) were observed in GM regions that accumulate amyloid early but remain largely tangle-free during early AD progression, namely the occipital and parietal cortices. WMH volume differentiated AD+MCI from Controls (p=0.002) but not NDAN (p=0.16). Conclusion: CBF differentiated NDAN from AD+MCI, highlighting vascular contributions to cognitive resilience. Most pronounced CBF preservation in NDAN was observed in parietal and occipital cortices, regions typically free of tau until late stages of AD progression.

Clinical trajectories after a diagnosis of mild cognitive impairment (MCI) vary widely, so prognostic models must account for both the timing of subsequent diagnoses and unequal follow-up. Using the Alzheimer's Disease Neuroimaging Initiative (ADNI), we developed a Cox proportional-hazards model for time from an MCI-aligned plasma index visit to a subsequent dementia diagnosis, using age at study entry and log- transformed plasma p-tau217. Coefficients and baseline survival were estimated in 401 participants with 85 events and then frozen and applied without refitting to an independent cohort from the National Alzheimer's Coordinating Center (NACC). NACC p-tau217 measurements were reported on the Quanterix HD-X platform and were mapped to the ADNI development-assay scale using a prespecified transformation derived from paired ADNI measurements. The two-predictor model reached a pooled out- of-fold C-index of 0.775 in ADNI (apparent C-index, 0.778) and 0.652 (95% CI, 0.526-0.765) in 104 NACC participants with 25 incident dementia diagnoses. At two years, observed risk was 0.214 compared with a mean predicted risk of 0.089, an observed-to-expected ratio of 2.40. Neither adding APOE {epsilon} 4 count, sex, or education nor expanding the model with GFAP, NfL, and the A{beta}42/A{beta}40 ratio materially improved discrimination in ADNI; APOE {epsilon} 4 also provided no detectable incremental gain in NACC. The model showed moderate discrimination in NACC, although the wide confidence interval includes values near chance and the middle and higher risk tertiles did not clearly separate; C-indices were similar in the bridged primary and direct-scale sensitivity analyses, and mean two-year predicted risk was lower than observed only in the bridged analysis.

Background: Plasma phosphorylated tau at threonine 217 (p-Tau217) is a leading blood-based biomarker for Alzheimer's disease (AD). Robust analytical characterization on high-throughput platforms is essential for research use and clinical translation. Objective: To evaluate the analytical performance of an automated plasma p-Tau217 immunoassay and characterize its discrimination of PET-defined amyloid status. Methods: We performed analytical validation of the Access Research Use Only (RUO) plasma p-Tau217 immunoassay on the Beckman Coulter DxI 9000 Access Immunoassay Analyzer and evaluated biomarker discrimination of PET-defined amyloid pathology in a subset of the Bio-Hermes-001 cohort spanning the symptomatic cognitive continuum (mild cognitive impairment or mild AD dementia; cognitively unimpaired participants excluded; n = 449). Analytical precision, sensitivity, linearity, specificity, interference, and sample stability were assessed per Clinical and Laboratory Standards Institute guidelines. Discrimination of PET-defined amyloid status was evaluated using receiver operating characteristic curve and indeterminate zone analyses. Results: The assay demonstrated high precision (within-laboratory CV </=7.1%), excellent sensitivity (limit of detection 0.018-0.021 pg/mL), linearity across the analytical measuring range (R-squared > 0.99), strong epitope specificity (</=1.0% cross-reactivity with other tau phosphoisoforms), and minimal interference from over 60 endogenous and exogenous substances. In 449 research participants plasma p-Tau217 showed strong discrimination between amyloid-positive and amyloid-negative groups (AUC 0.881; 95% CI 0.846-0.915). Application of indeterminate zones systematically improved classification metrics at the cost of fewer definitive classifications. Conclusions: These findings support the Access p-Tau217 (RUO) assay as a robust, high-throughput assay for plasma biomarker-based discrimination of PET-defined amyloid pathology in AD applications.

Detection and characterisation of dementia and Mild Cognitive Impairment (MCI) is essential for diagnosis and to support recruitment of patients into trials of disease-targeted therapies. Computerised systems offer a means of improving detection in community and primary care settings in a scalable way. This study presents further validation of the self-test PROTECT Cognitive Test System of eight assessments of memory, attention and executive function in 36,941 participants (35,822 healthy, 1046 MCI, 73 dementia). PROTECT shows robust separation of dementia and non-dementia participants (p < 0.001), and good discriminative ability for dementia (Area Under the Curve = 0.966) with 90.90% sensitivity and 87.80% specificity. An optimised detection algorithm robustly identified MCI (P<0.001) and predicted 24-month decline across cognitive domains in both amnestic MCI and non-amnestic MCI phenotypes compared with healthy controls. PROTECT cognitive data also correlated strongly with the plasma biomarkers p-tau217 and Neurofilament Light (n = 46). The system provides a means of improving dementia and MCI detection using self-testing, offering a scalable triage and monitoring tool for clinical pathways and trials.

ABSTRACT Importance: The biological mechanisms underlying the associations of social isolation and loneliness with dementia risk are not well understood. Objective: To evaluate the relationship of prospectively measured social isolation and loneliness with AD/ADRD blood-based biomarkers. Design: Observational study using the U.S. Health and Retirement Study (2010-2016). Venous blood draws were conducted in 2016 and AD/ADRD biomarkers were released in 2025. We estimated associations of social isolation and loneliness patterns between 2012 and 2014 with continuous biomarkers using linear regressions, accounting for socio-demographic and health covariates. We evaluated effect modification by sex and APOE {varepsilon}4 carrier status. Setting: Population-based Participants: Community-dwelling HRS participants aged 50 years or older (n = 3862). Exposures: Primary exposures were four-category multi-wave variables of persistent, resolving, new-onset, or no social isolation/loneliness across the two exposure waves. Social isolation was classified as "severe" and "moderate-to-severe" based on a 5-item scale including marital status, household size, proximity to children, religious service attendance, and volunteering. Past-week loneliness was measured with a single-item question (yes/no). Main Outcomes and Measures: Neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), and the ratio of amyloid beta 42 to amyloid beta 40 (A{beta}42/40), measured in plasma via a Multiplex Simoa Assay and phosphorylated tau (p-tau181), measured in serum via a Simoa Assay. Results: At the analytic baseline, respondents were a mean age of 64 (9.5) years, 59% female, and 25% APOE {varepsilon}4 carriers. Across the two exposure waves, 4% experienced persistent severe social isolation, 16% experienced persistent moderate-to-severe social isolation, and 8% reported persistent loneliness. Multiple patterns of social isolation (vs. no social isolation) were associated with higher NfL, including persistent severe social isolation ({beta}: 0.31), new-onset moderate-to-severe social isolation ({beta}: 0.14), and resolving moderate-to-severe social isolation ({beta}: 0.20). Persistent severe social isolation was associated with lower GFAP ({beta}: -0.31) while persistent loneliness and, for men, new-onset loneliness were associated with higher GFAP ({beta}_persistent: 0.16; {beta}_(new onset_men): 0.25). New-onset severe social isolation was associated with a lower A{beta}42/40 ratio ({beta}: -0.25) while resolving moderate-to-severe social isolation and, for men, persistent severe social isolation were each associated with higher p-tau181 ({beta}_resolving: 0 .11; {beta}_(persistent_men): 0.41). There was some additional variation by APOE {varepsilon}4 carriership, although selective survival is a concern. Conclusions: Social isolation was associated with elevated blood-based biomarkers of neuronal injury, with variation by patterns of exposure over time. Associations between social isolation and loneliness with biomarkers related to astrocyte damage and Alzheimer's disease were less consistent, and varied in sign and magnitude by exposure and sex.

INTRODUCTION: Accurately identifying risk of Alzheimers Dementia (AD) is essential for supporting people living with symptoms in clinical settings, as well as recruiting adults in prospective medical research. Various algorithms have been created to calculate AD risk based on evidenced risk factors which are weighted toward a total score. As daily life conditions determining risk change at scale, it remains unclear how effective gold standard algorithms remain in modern cohorts. METHODS: In the Bio-Hermes-001 diverse cohort, we assessed algorithm discrimination and calibration in six outcomes: classifying AB PET binary outcome (negative N = 603, positive N = 342); phosphorylated tau-217 binary outcome (pTau-217 negative N = 166, positive N = 469); participants with Healthy Cognition (N = 417) from probable AD (N = 272); HC from Mild Cognitive Impairment (N = 312), HC from pooled MCI or AD; and MCI from AD. Approximately a third of the cohort are individuals from populations typically underrepresented in dementia research (HC: 19%; MCI: 24%; AD: 33%). RESULTS: Hosmer-Lemeshow tests and Brier score demonstrate acceptable calibration of all algorithms except the oldest algorithm. However, Receiver Operating Characteristic (ROC) curves and the associated area under the curve (AUC) estimates evidenced that in this cohort only the BDSI exceeded conventional thresholds for good discrimination (.8 AUC in HC-AD classification, with AUC approximately .7 in the other clinical, AB PET, and pTau-217 comparisons). When the functional item is removed from the BDSI score, it remains acceptably calibrated, but DeLong tests reflect statistically significant reduction in discriminatory performance for all group comparisons. The two earliest published algorithms were only chance-level accurate. DISCUSSION: In a contemporary, diverse cohort, most established dementia risk algorithms had limited power in discriminating amyloid positivity, pTau-217 positivity, and current cognitive status despite acceptable calibration. Including a functional measure markedly improved discrimination across both clinical and biomarker-defined outcomes, suggesting that proximal indicators of cognitive vulnerability are critical for identifying individuals with underlying AD-related pathology.

INTRODUCTION: Characterizing the prognostic utility of blood-based biomarkers for Alzheimer's disease (AD) in predicting longitudinal cognitive trajectories is essential; however, population-based evidence is needed. METHODS: We evaluated plasma phosphorylated tau at threonine 217 (p-tau217) and plasma neurofilament light chain (NfL) in 4,971 dementia-free individuals aged 70 years and older from the population-based Norwegian HUNT study. Predefined cut offs categorized biomarker ranges (p-tau217: low, intermediate, high; NfL: low, high), in addition to continuous biomarker analysis. RESULTS: Adjusted for other risk factors, higher baseline p-tau217 and NfL ranges indicated a significantly increased dementia risk after four years compared to low ranges (intermediate p-tau217: risk ratio [RR] 1.23, 95% CI 1.01-1.50; high p-tau217: RR 2.05, 95% CI 1.73-2.44; high NfL: RR 1.72, 95% CI 1.31-2.27; jointly high p-tau217 and NfL: RR 3.32, 95% CI 2.61-4.23). The estimated cumulative risk of all-cause dementia was 10.6% (95% CI 9.3-12.1) for low p-tau217, 16.9% (95% CI 14.6-19.5) for intermediate p-tau217, 33.0% (95% CI 29.9-36.1) for high p-tau217, 15.7% (95% CI 14.4-17.0) for low NfL, 35.4% (95% CI 30.6-40.5) for high NfL, and 47.8% (95% CI 40.7-55.0) for jointly high p-tau217 and NfL. The association of p-tau217 with incident dementia differed by sex. DISCUSSION: These findings support the use of blood-based biomarkers for population-level dementia risk stratification, underscore the value of combining markers to improve prognostic precision, and can aid clinicians using plasma p-tau217 or NfL in interpreting dementia risk.

INTRODUCTION: The utility of blood-based Alzheimer's disease (AD) biomarkers in predicting clinical trajectories remains uncertain. METHODS: We assessed the diagnostic and prognostic performance of p-tau181, p-tau217, GFAP, and NfL in a large memory-clinic cohort (n=3,645) with comprehensive baseline clinical evaluation and annual follow-up for up to three decades. RESULTS: P-tau217, p-tau181 and GFAP were associated with amyloid-beta (A{beta}) pathology, while all biomarkers were elevated in AD and all-cause dementia. P-tau217 significantly outperformed others in detecting A{beta} pathology and clinical AD but performed similarly to NfL and GFAP for all-cause dementia. Prognostically, p-tau217 demonstrated the strongest association with cognitive decline, followed by GFAP and NfL, and best predicted progression status at 5- and 10-year intervals. All biomarkers provided added prognostic value beyond demographic and genetic covariates. DISCUSSION: These findings support plasma biomarkers for disease identification and risk stratification while underscoring the need for population-specific approaches.

Familial Alzheimer's disease (fAD) is an early-onset form of AD caused by autosomal-dominant variants in APP, PSEN1, or PSEN2, with PSEN1 accounting for most genetically defined cases [1]. The hippocampus is among the earliest and most severely affected brain regions in AD [2,3]. Human induced pluripotent stem cell (iPSC)-derived brain organoids recapitulate key features of early human brain development and provide a tractable model for studying how fAD mutations perturb neurodevelopmental processes [4]. However, their interpretation is complicated by heterogeneous regional identity, variable maturation state, and cell-type composition across protocols [5,6]. Existing single-cell studies of human hippocampus cover prenatal [7] and postnatal [8-10] stages but do not provide a continuous developmental reference. By elevating the atlas approach in utilizing single-cell RNA-sequencing data, we obtain standardized information on the organoid cell class and type composition and maturation states. Here, we constructed the Human Developing Hippocampus Atlas (HuDeHA), an integrated single-cell reference comprising 658,059 cells spanning post-conceptional week 3 to 15.3 years, and used it to benchmark iPSC-derived brain organoids carrying PSEN1 E280A which is associated with fAD in a large Colombian population. Reference-based mapping revealed altered cellular composition in PSEN1 E280A organoids, including reduced radial glia and increased neural crest-derived neurons. These changes were accompanied by cross-lineage transcriptional alterations, including broad upregulation of the ventral patterning factor MEIS2 and reduced expression of the {beta}-binding protein transthyretin (TTR) in choroid-plexus and ependymal-associated populations. Reconstructed neuronal-lineage trajectories showed a shift toward mature states in PSEN1 E280A organoids. Together, these findings establish HuDeHA as a resource for developmental benchmarking of hippocampus-relevant organoid systems and describe cell-lineage-specific developmental changes in PSEN1 E280A organoids that may inform interpretation of early cellular alterations in fAD.

Background: Alzheimer's disease (AD) is characterized by amyloid beta and tau accumulation accompanied by altered inflammatory responses. Sex is an important modifier of AD risk and pathology, however, its influence on relationships between peripheral inflammatory markers and cerebrospinal fluid (CSF) AD biomarkers remains unclear. The aim of this study was to determine whether sex modifies peripheral inflammatory biomarker relationships associated with AD pathology and clinical stage. Materials and Methods: Twelve CSF biomarkers and 41 plasma biomarkers spanning AD pathology, neurodegeneration, and inflammation were measured on the Luminex platform in a cross-sectional cohort of 261 participants from the Cleveland Clinic Lou Ruvo Center for Brain Health Biobank. Associations were evaluated in sex-adjusted, sex-interaction, and sex-stratified models, accounting for age, APOE4 carrier status, and diagnosis. Results: Plasma IL-5 was inversely associated with clinical stage, and 10 plasma inflammatory markers, including Flt-3L, MCP-1, soluble TREM2 (sTREM2), TNF, IL-8, IL-5, IL-12P40, IL-1RA, fractalkine, and G-CSF, were inversely associated with the CSF pTau181/A{beta}42 ratio in pooled models adjusted for sex. Although formal biomarker x sex interactions did not survive FDR correction, significant associations between the CSF pTau181/A{beta}42 ratio and plasma MCP-1 and IL-12P40 were observed in females but not males. Discussion: Our findings identify a group of peripheral inflammatory markers associated with AD pathology and suggest that some of these relationships may vary by sex, warranting larger studies to clarify the role of sex in AD pathobiology.

Complement-mediated neuroinflammation has been implicated in Alzheimer's disease (AD), but its role during the pre-symptomatic phase of the disease remains unclear. In the PREVENT-AD cohort of cognitively unimpaired individuals at increased familial risk of AD, we investigated whether CSF complement proteins relate to early AD pathology and synaptic dysfunction, then assessed our results' reproducibility across the clinical AD spectrum. Baseline CSF C1q, C3, C3b, and Factor H were measured in relation to CSF AD biomarkers, synaptic proteins, cognition, MRI volumetry, and amyloid and tau PET. Key findings were then examined in 708 participants from ADNI spanning cognitively normal, mild cognitive impairment (MCI), and dementia stages of AD. In PREVENT-AD, C1q was positively associated with CSF P-tau181, T-tau, and multiple synaptic markers including ADAM23, GAP43, SNAP25, and SYT1. Factor H showed similarly strong positive associations with P-tau181, T-tau, ADAM22, ADAM23, GAP43, and SYT1. By contrast, C3 showed minimal associations, while C3b displayed weaker positive relationships with P-tau181, T-tau, ADAM22, and ADAM23. Complement proteins were not robustly associated with amyloid or tau PET, and only C1q related to lower global cognitive performance. In ADNI, C1q emerged as the most consistent analyte, showing positive associations with tau, neurofilament light, and synaptic markers across all diagnostic groups. C3 exhibited predominantly negative associations, whereas C3b and Factor H showed stage-dependent relationships, particularly with evident neurodegeneration and synaptic injury in symptomatic individuals. These findings identify complement dysregulation, especially involving C1q, as an early correlate of tau-linked synaptic pathology, and support a role for complement activation in the AD molecular cascade.

IMPORTANCE Autopsy evidence on sex-specific associations of education with neuropathology and cognition is limited. OBJECTIVE To test sex differences in education associations with neuropathologic burden and cognition. DESIGN Cohort study of data collected from September 2005 through August 2024. SETTING Multicenter autopsy cohort from the National Alzheimer's Coordinating Center. PARTICIPANTS Adults aged 55 years or older; cross-sectional eligibility required a final CDR-SB assessment within 2 years before death, and longitudinal eligibility additionally required at least 3 assessments. EXPOSURES Years of formal education. MAIN OUTCOMES AND MEASURES Neuropathologic measures and the Clinical Dementia Rating Scale Sum of Boxes (CDR-SB). Linear regression and mixed-effects models tested associations and interactions of education with sex, neuropathology, and linear and quadratic time. Benjamini-Hochberg correction addressed multiple comparisons. RESULTS Among 2592 participants (mean [SD] age at death, 81.6 [10.8] years; 1188 [45.8%] female), 1969 contributed to longitudinal analyses. In female participants, higher education was associated with lower Thal amyloid phase, diffuse plaques, neuritic plaques, and Braak stage ({beta} range, -0.097 to -0.071; qFDR<.026); none was significant among male participants. Education-by-sex interactions supported differences in Thal amyloid phase, and diffuse and neuritic plaques ({beta} range, -0.119 to -0.097; qFDR<.045). Education was unrelated to final CDR-SB among female ({beta}, -0.007; 95% CI, -0.052 to 0.038; P=.767) and male participants ({beta}, -0.026; 95% CI, -0.071 to 0.019; P=.254), with no education-by-sex interaction (P=.660). The education-by-Braak-stage-by-sex interaction indicated that higher education was associated with a weaker Braak stage-CDR-SB association among females than males ({beta}, -0.104; 95% CI, -0.171 to -0.038; qFDR=.022). Longitudinally, education was unrelated to linear CDR-SB change in either sex. Education-by-quadratic-time associations were observed among females ({beta}, 0.002; 95% CI, 0.001-0.003; P<.001) and male participants ({beta}, 0.001; 95% CI, 0-0.002; P=.037). The corresponding interaction with sex was also significant (P=.043). CONCLUSIONS AND RELEVANCE Among female participants, higher education was associated with lower selected Alzheimer's disease neuropathologic measures and weaker associations of tau pathology with cognition. Longitudinal trajectories were nonlinear, with slower earlier decline followed by later acceleration at higher education levels.