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Study objectivesFast frequency sleep spindles are reduced in aging and Alzheimer's disease (AD), but the mechanisms and functional relevance of these deficits remain unclear. The study objective was to identify AD biomarkers associated with fast sleep spindle deficits in cognitively unimpaired older adults at risk for AD.MethodsFifty-eight cognitively unimpaired, β-amyloid-negative, older adults (mean ± SD; 61.4 ± 6.3 years, 38 female) enriched with parental history of AD (77.6%) and apolipoprotein E (APOE) ε4 positivity (25.9%) completed the study. Cerebrospinal fluid (CSF) biomarkers of central nervous system inflammation, β-amyloid and tau proteins, and neurodegeneration were combined with polysomnography (PSG) using high-density electroencephalography and assessment of overnight memory retention. Parallelized serial mediation models were used to assess indirect effects of age on fast frequency (13 to

Background and objectivesTo determine how fully automated Elecsys CSF immunoassays for β-amyloid (Aβ) and tau biomarkers and an ultrasensitive Simoa assay for neurofilament light chain (NFL) correlate with neuropathologic changes of Alzheimer disease (AD) and frontotemporal lobar degeneration (FTLD).MethodsWe studied 101 patients with antemortem CSF and neuropathology data. CSF samples were collected a mean of 2.9 years before death (range 0.2-7.5 years). CSF was analyzed for Aβ40, Aβ42, total tau (T-tau), tau phosphorylated at amino acid residue 181 (P-tau), P-tau/Aβ42 and Aβ42/Aβ40 ratios, and NFL. Neuropathology measures included Thal phases, Braak stages, Consortium to Establish a Registry for Alzheimer's Disease (CERAD) scores, AD neuropathologic change (ADNC), and primary and contributory pathologic diagnoses. Associations between CSF biomarkers and neuropathologic features were tested in regression models adjusted for age, sex, and time from sampling to death.ResultsCSF biomarkers were associated with neuropathologic measures of Aβ (Thal, CERAD score), tau (Braak stage), and overall ADNC. The CSF P-tau/Aβ42 and Aβ42/Aβ40 ratios had high sensitivity, specificity, and overall diagnostic performance for intermediate-high ADNC (area under the curve range 0.95-0.96). Distinct biomarker patterns were seen in different FTLD subtypes, with increased NFL and reduced P-tau/T-tau in FTLD-TAR DNA-binding protein 43 and reduced T-tau in progressive supranuclear palsy compared to other FTLD variants.DiscussionCSF biomarkers, including P-tau, T-tau, Aβ42, Aβ40, and NFL, support in vivo identification of AD neuropathology and correlate with FTLD neuropathology.Classification of evidenceThis study provides Class II evidence that distinct CSF biomarker patterns, including for P-tau, T-tau, Aβ42, Aβ40, and NFL, are associated with AD and FTLD neuropathology.

Background: Klotho, encoded by the KLOTHO gene, is an anti-aging and neuroprotective protein. KLOTHO KL-VS heterozygosity (KL-VSHET) is hypothesized to be protective against the accumulation of Alzheimer's disease (AD) neuropathological hallmarks (amyloid-β (Aβ) and tau). Objective: We examine whether being positive for Aβ (A+) or tau (T+), or A/T joint status [positive for Aβ (A + T-), tau (A-T+), both (A + T+) or neither (A-T-)] vary by KL-VS and whether serum klotho protein levels vary based on A+, T+, or A/T status in a cohort enriched for AD risk. Methods: The sample consisted of 704 cognitively unimpaired, late middle-aged, and older adults; MeanAge(SD) = 64.9(8.3). Serum klotho was available for a sub-sample of 396 participants; MeanAge(SD) = 66.8(7.4). Covariate-adjusted logistic regression examined whether A + or T+, and multinomial regression examined whether A/T status, vary by KL-VS genotype. Covariate-adjusted linear regression examined whether serum klotho levels differ based on A+, T+, or A/T status. Results: A+ prevalence was lower in KL-VSHET (p = 0.05), with no differences in T + prevalence (p = 0.52). KL-VSHET also had marginally lower odds of being A + T- (p = 0.07). Serum klotho levels did not differ based on A+, T+, or A/T status (all ps ≥ 0.40). Conclusions: KL-VSHET is associated with lower odds of being positive for Aβ, regardless of whether one is also positive for tau. Conversely, the likelihood of being tau positive did not differ based on KL-VS genotype. Our findings add to the growing KLOTHO literature and suggests the need for further research focused on understanding the mechanisms underlying KL-VS-related putative resilience to AD. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Growing evidence suggests a role for neuroinflammation in Alzheimer's disease (AD). We investigated complement pathway activity in AD patient cerebrospinal fluid (CSF) and evaluated its modulation by the anti‐tau antibody semorinemab. METHODS: Immunoassays were applied to measure CSF complement proteins C4, factor B (FB), C3 and their cleavage fragments C4a, C3a, and factor Bb (Bb) in AD patients and a separate cognitively unimpaired (CU) cohort. RESULTS: All measured CSF complement proteins were increased in AD versus CU subjects, with C4a displaying the most robust increase. Finally, semorinemab did not have a significant pharmacodynamic effect on CSF complement proteins. DISCUSSION: Elevated levels of CSF C4a, C4, C3a, C3, Bb, and FB are consistent with complement activation in AD brains. Despite showing a reduction in CSF soluble tau species, semorinemab did not impact complement protein levels or activity. Further studies are needed to determine the value of complement proteins as neuroinflammation biomarkers in AD. Highlights: Cerebrospinal fluid (CSF) complement proteins C4a, C3a, Bb, C4, C3, and factor B levels were increased in Alzheimer's disease (AD) patients compared to a separate cognitively unimpaired (CU) cohort.Baseline CSF complement protein levels were correlated with neuro‐axonal degeneration and glial activation biomarkers in AD patients.The investigational anti‐tau antibody semorinemab did not impact CSF complement protein levels or activity relative to the placebo arm. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Cerebral blood flow (CBF) is reduced in cognitively impaired (CI) Alzheimer's disease (AD) patients. We checked the sensitivity of time‐encoded arterial spin labeling (te‐ASL) in measuring CBF alterations in individuals with positive AD biomarkers and associations with relevant biomarkers in cognitively unimpaired (CU) individuals. METHODS: We compared te‐ASL with single‐postlabel delay (PLD) ASL in measuring CBF in 59 adults across the AD continuum, classified as CU amyloid beta (Aβ) negative (−), CU Aβ positive (+), and CI Aβ+. We sought associations of CBF with biomarkers of AD, cerebrovascular disease, synaptic dysfunction, neurodegeneration, and cognition in CU participants. RESULTS: te‐ASL was more sensitive at detecting CBF reduction in the CU Aβ+ and CI Aβ+ groups. In CU participants, lower CBF was associated with altered biomarkers of Aβ, tau, synaptic dysfunction, and neurodegeneration. DISCUSSION: CBF reduction occurs early in the AD continuum. te‐ASL is more sensitive than single‐PLD ASL at detecting CBF changes in AD. Highlights: Lower CBF can be detected in CU subjects in the early AD continuum.te‐ASL is more sensitive than single‐PLD ASL at detecting CBF alterations in AD.CBF is linked to biomarkers of AD, synaptic dysfunction, and neurodegeneration. [ABSTRACT FROM AUTHOR]

INTRODUCTION: We examined whether the aging suppressor KLOTHO gene's functionally advantageous KL‐VS variant (KL‐VS heterozygosity [KL‐VSHET]) confers resilience against deleterious effects of aging indexed by cerebrospinal fluid (CSF) biomarkers of neuroinflammation (interleukin‐6 [IL‐6], S100 calcium‐binding protein B [S100B], triggering receptor expressed on myeloid cells [sTREM2], chitinase‐3‐like protein 1 [YKL‐40], glial fibrillary acidic protein [GFAP]), neurodegeneration (total α‐synuclein [α‐Syn], neurofilament light chain protein), and synaptic dysfunction (neurogranin [Ng]). METHODS: This Alzheimer disease risk‐enriched cohort consisted of 454 cognitively unimpaired adults (Mage = 61.5 ± 7.75). Covariate‐adjusted multivariate regression examined relationships between age (mean‐split[age ≥ 62]) and CSF biomarkers (Roche/NeuroToolKit), and whether they differed between KL‐VSHET (N = 122) and non‐carriers (KL‐VSNC; N = 332). RESULTS: Older age was associated with a poorer biomarker profile across all analytes (Ps ≤ 0.03). In age‐stratified analyses, KL‐VSNC exhibited this same pattern (Ps ≤ 0.05) which was not significant for IL‐6, S100B, Ng, and α‐Syn (Ps ≥ 0.13) in KL‐VSHET. Although age‐related differences in GFAP, sTREM2, and YKL‐40 were evident for both groups (Ps ≤ 0.01), the effect magnitude was markedly stronger for KL‐VSNC. DISCUSSION: Higher levels of neuroinflammation, neurodegeneration, and synaptic dysfunction in older adults were attenuated in KL‐VSHET. Highlights: Older age was associated with poorer profiles across all cerebrospinal fluid biomarkers of neuroinflammation, neurodegeneration, and synaptic dysfunction.KLOTHO KL‐VS non‐carriers exhibit this same pattern, which is does not significantly differ between younger and older KL‐VS heterozygotes for interleukin‐6, S100 calcium‐binding protein B, neurogranin, and total α‐synuclein.Although age‐related differences in glial fibrillary acidic protein, triggering receptor expressed on myeloid cells, and chitinase‐3‐like protein 1 are evident for both KL‐VS groups, the magnitude of the effect is markedly stronger for KL‐VS non‐carriers.Higher levels of neuroinflammation, neurodegeneration, and synaptic dysfunction in older adults are attenuated in KL‐VS heterozygotes. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Recent genome‐wide association studies (GWAS) have reported a genetic association with Alzheimer's disease (AD) at the TNIP1/GPX3 locus, but the mechanism is unclear. METHODS: We used cerebrospinal fluid (CSF) proteomics data to test (n = 137) and replicate (n = 446) the association of glutathione peroxidase 3 (GPX3) with CSF biomarkers (including amyloid and tau) and the GWAS‐implicated variants (rs34294852 and rs871269). RESULTS: CSF GPX3 levels decreased with amyloid and tau positivity (analysis of variance P = 1.5 × 10−5) and higher CSF phosphorylated tau (p‐tau) levels (P = 9.28 × 10−7). The rs34294852 minor allele was associated with decreased GPX3 (P = 0.041). The replication cohort found associations of GPX3 with amyloid and tau positivity (P = 2.56 × 10−6) and CSF p‐tau levels (P = 4.38 × 10−9). DISCUSSION: These results suggest variants in the TNIP1 locus may affect the oxidative stress response in AD via altered GPX3 levels. Highlights: Cerebrospinal fluid (CSF) glutathione peroxidase 3 (GPX3) levels decreased with amyloid and tau positivity and higher CSF phosphorylated tau.The minor allele of rs34294852 was associated with lower CSF GPX3. levels when also controlling for amyloid and tau category.GPX3 transcript levels in the prefrontal cortex were lower in Alzheimer's disease than controls.rs34294852 is an expression quantitative trait locus for GPX3 in blood, neutrophils, and microglia. [ABSTRACT FROM AUTHOR]

Introduction: The lack of cognitive awareness, anosognosia, is a clinical deficit in Alzheimer's disease (AD) dementia. However, an increased awareness of cognitive function, hypernosognosia, may serve as a marker in the preclinical stage. Subjective cognitive decline (SCD) might correspond to the initial symptom in the dynamic trajectory of awareness, but SCD might be absent along with low awareness of actual cognitive performance in the preclinical stage. We hypothesized that distinct meta-cognitive profiles, both hypernosognosia and anosognosia, might be identified in preclinical-AD. This research evaluated the association between cerebrospinal fluid (CSF) AD biomarkers and the awareness of episodic memory, further exploring dyadic (participant-partner) SCD reports, in the preclinical Alzheimer's continuum. Methods: We analyzed 314 cognitively unimpaired (CU) middle-aged individuals (mean age: 60, SD: 4) from the ALFA+ cohort study. Episodic memory was evaluated with the delayed recall from the Memory Binding Test (MBT). Awareness of episodic memory, meta-memory, was defined as the normalized discrepancy between objective and subjective performance. SCD was defined using self-report, and dyadic SCD profiles incorporated the study partner's report using parallel SCD-Questionnaires. The relationship between CSF Ab42/40 and CSF p-tau181 with meta-memory was evaluated with multivariable regression models. The role of SCD and the dyadic contingency was explored with the corresponding stratified analysis. Results: CSF Ab42/40 was non-linearly associated with meta-memory, showing an increased awareness up to Ab-positivity and a decreased awareness beyond this threshold. In the non-SCD subset, the non-linear association between CSF Ab42/40 and meta-memory persisted. In the SCD subset, higher Ab-pathology was linearly associated with increased awareness. Individuals presenting only study partner's SCD, defined as unaware decliners, exhibited higher levels of CSF p-tau181 correlated with lower meta-memory performance. Discussion: These results suggested that distinct meta-cognitive profiles can be identified in preclinical-AD. While most individuals might experience an increased awareness associated with the entrance in the AD continuum, hypernosognosia, some might be already losing insight and stepping into the anosognosic trajectory. This research reinforced that an early anosognosic profile, although at increased risk of AD-related decline, might be currently overlooked considering actual diagnostic criteria, and therefore its medical attention delayed. [ABSTRACT FROM AUTHOR]

Objective: Along with the known effects of stress on brain structure and inflammatory processes, increasing evidence suggest a role of chronic stress in the pathogenesis of Alzheimer's disease (AD). We investigated the association of accumulated stressful life events (SLEs) with AD pathologies, neuroinflammation, and gray matter (GM) volume among cognitively unimpaired (CU) individuals at heightened risk of AD. Methods: This cross‐sectional cohort study included 1,290 CU participants (aged 48–77) from the ALFA cohort with SLE, lumbar puncture (n = 393), and/or structural magnetic resonance imaging (n = 1,234) assessments. Using multiple regression analyses, we examined the associations of total SLEs with cerebrospinal fluid (1) phosphorylated (p)‐tau181 and Aβ1–42/1–40 ratio, (2) interleukin 6 (IL‐6), and (3) GM volumes voxel‐wise. Further, we performed stratified and interaction analyses with sex, history of psychiatric disease, and evaluated SLEs during specific life periods. Results: Within the whole sample, only childhood and midlife SLEs, but not total SLEs, were associated with AD pathophysiology and neuroinflammation. Among those with a history of psychiatric disease SLEs were associated with higher p‐tau181 and IL‐6. Participants with history of psychiatric disease and men, showed lower Aβ1–42/1–40 with higher SLEs. Participants with history of psychiatric disease and women showed reduced GM volumes in somatic regions and prefrontal and limbic regions, respectively. Interpretation: We did not find evidence supporting the association of total SLEs with AD, neuroinflammation, and atrophy pathways. Instead, the associations appear to be contingent on events occurring during early and midlife, sex and history of psychiatric disease. ANN NEUROL 2024;95:1058–1068 [ABSTRACT FROM AUTHOR]

INTRODUCTION: We studied how biomarkers of reactive astrogliosis mediate the pathogenic cascade in the earliest Alzheimer's disease (AD) stages. METHODS: We performed path analysis on data from 384 cognitively unimpaired individuals from the ALzheimer and FAmilies (ALFA)+ study using structural equation modeling to quantify the relationships between biomarkers of reactive astrogliosis and the AD pathological cascade. RESULTS: Cerebrospinal fluid (CSF) amyloid beta (Aβ)42/40 was associated with Aβ aggregation on positron emission tomography (PET) and with CSF p‐tau181, which was in turn directly associated with CSF neurofilament light (NfL). Plasma glial fibrillary acidic protein (GFAP) mediated the relationship between CSF Aβ42/40 and Aβ‐PET, and CSF YKL‐40 partly explained the association between Aβ‐PET, p‐tau181, and NfL. DISCUSSION: Our results suggest that reactive astrogliosis, as indicated by different fluid biomarkers, influences the pathogenic cascade during the preclinical stage of AD. While plasma GFAP mediates the early association between soluble and insoluble Aβ, CSF YKL‐40 mediates the latter association between Aβ and downstream Aβ‐induced tau pathology and tau‐induced neuronal injury. Highlights: Lower CSF Aβ42/40 was directly linked to higher plasma GFAP concentrations.Plasma GFAP partially explained the relationship between soluble Aβ and insoluble Aβ.CSF YKL‐40 mediated Aβ‐induced tau phosphorylation and tau‐induced neuronal injury. [ABSTRACT FROM AUTHOR]

Background: In preclinical Alzheimer's disease (AD), previous evidence suggests that glial reactivity may affect cognitive performance. This study aimed to test whether glial markers cerebrospinal fluid (CSF) GFAP, YKL‐40, sTREM2, and plasma GFAP are associated with cognitive change in cognitively unimpaired individuals at risk of AD. We hypothesized that higher levels of glial markers may be associated with better cognitive outcomes. Method: We included 353 individuals from the ALFA+ cohort with available baseline (BL) glial biomarkers and cognition at follow‐up (FU) 3 years later (Table 1). CSF Aβ42/40, pTau181, YKL‐40, GFAP, and sTREM2, were analyzed using the exploratory Roche NeuroToolKit, a panel of automated robust prototype immunoassays. Plasma GFAP was determined with the Simoa HD‐X (Quanterix) platform using the commercial Neurology 4‐Plex E assay (N4PE). Amyloid pathology was studied with Centiloids derived from [18F]flutemetamol PET. Rate of change ([FU‐BL]/time) in the Preclinical Alzheimer's Cognitive Composite (PACC) and domain‐specific cognitive composites was used as the dependent variable, glial biomarkers at BL as predictors, and age, sex and education as covariates in linear models. Interaction terms between each glial biomarker and different AD pathology were also explored. Aβ+ was defined as CSF Aβ42/40 <0.071. Result: Higher baseline CSF sTREM2 was associated with a positive PACC rate of change (p = 0.002) (Table 2). These results remained significant after controlling for CSF Aβ42/40, pTau181 and Centiloid levels (all p < 0.01). Moreover, CSF sTREM2 at baseline was associated with a better memory outcome (p = 0.012), independently of amyloid and tau (all p < 0.02), and better executive functioning (p = 0.046), independently of tau pathology (p = 0.011). These positive associations remained in the Aβ‐ group regardless of AD pathology, but not in the Aβ+ group, in which some negative associations were observed when adjusting for Centiloids (YKL‐40, p = 0.024) (Figure 1). Conclusion: Higher TREM2‐mediated microglial response in individuals at risk of AD is associated with better cognitive performance. These associations were driven by the Aβ‐ group. These results may have important implications for the design of clinical interventions targeting TREM2 in this early stage of AD. [ABSTRACT FROM AUTHOR]

Background: Cognitively unimpaired (CU) adults with Alzheimer's disease (AD) pathologic change may be more vulnerable to developing neuropsychiatric symptoms. We reported an association of higher β‐amyloid (Aβ) and increased anxiety/depression during the COVID‐19 lockdown in CU adults (Akinci et al., 2022). Here, we investigated whether changes in Aβ1−42 predict post‐traumatic stress disorder (PTSD) symptomatology following COVID‐19 lockdown in CU adults at risk for AD. Method: We included 128 CU participants who underwent lumbar puncture 2.3±0.6 years before and 1.1±0.4 years after the lockdown. The outcome of interest was self‐reported PTSD symptomatology (Impact of Event Scale Revised) measured 1.7±0.1 years after the lockdown. The main predictor was annual rate of change in cerebrospinal fluid (CSF) Aβ1−42 measured with the NeuroToolKit panel of robust prototype assays (Roche Diagnostics International Ltd, Rotkreuz, Switzerland). Other predictors included sex, age, years of education, stressors during COVID‐19, and anxiety/depression (Hospital Anxiety and Depression Scale, HADS) and perceived stress (Perceived Stress Scale, PSS) measured during lockdown. We performed regression analyses to explore the association between annual rate of change in Aβ1‐42 with PTSD scores adjusting for demographic and stressor variables, and further adjusting for HADS and PSS scores. We then explored the mediating effect of HADS and PSS on the association between change in Aβ1‐42 and PTSD scores. Result: Participant age ranged from 53−72 and 59% were women (Table 1). Independent of demographic variables and stressors experienced during COVID‐19, the rate of annual change in Aβ1‐42 predicted PTSD scores (p =.008; Table 2). This association attenuated after introducing HADS and PSS scores into the model (p =.066). We found full mediation effects of HADS and PSS scores, explaining 46% and 40% of the effect of annual change in Aβ1‐42 on PTSD scores, respectively (Figure 1). Conclusion: CU older adults with longitudinal CSF Aβ1−42 increases are more vulnerable to developing PTSD symptomatology after a stressful event, such as the pandemic. Anxiety/depression is one plausible mechanism through which increases in Aβ might exacerbate PTSD symptomatology. The results suggest a window for stress regulation during stressful events to prevent further mental health worsening in people at risk for AD. [ABSTRACT FROM AUTHOR]

Background: Estrogens exert neuroprotective effects and regulate cognitive functioning and memory, and reduction of estrogen levels during menopause is proposed as a contributor to the increased risk for Alzheimer´s disease (AD) observed in women. However, previous results on the effects of estrogen exposure on AD biomarkers and risk of cognitive decline are conflicting. We aimed to study whether reproductive span, as a proxy of endogenous estrogen exposure, influences AD‐related biomarkers and their association with cognitive change in cognitively unimpaired (CU) women. Method: We studied 125 CU women with CSF biomarkers, amyloid PET (Centiloids), and longitudinal cognitive measures (3 years' follow‐up) (Table 1). CSF biomarkers were measured with Roche NeuroToolKit, Elecsys® immunoassays, or IP‐MS. We used longitudinal change in PACC and in a memory composite as cognitive outcomes. Reproductive span was calculated by subtracting the age at menarche from the age at menopause. ANCOVA models adjusted by age, education, and time between visits were used to test the main effect of reproductive span on biomarkers (baseline and longitudinal change), and the interaction between reproductive span and biomarkers with cognitive change as the outcome. Result: Reproductive span was not associated with baseline levels or longitudinal change of AD biomarkers. Reproductive span modified the association of Aβ PET Centiloids with change in PACC, and the association of Centiloids, CSF p‐tau181, SNAP‐25, synaptotagmin‐1, and ɑ‐Synuclein with change in the Memory Composite (Figure 1). Specifically, higher baseline levels of these biomarkers were associated with cognitive decline only in women with a shorter reproductive span. Reproductive span also modified the association between longitudinal change in CSF sTREM2, IL‐6, and NfL and cognitive change. In women with a shorter reproductive span, increases in these biomarkers were associated with greater memory declines. In women with a longer reproductive span, an increase in CSF sTREM2 was associated with improved memory performance at follow‐up (Figure 2). Conclusion: In women with a shorter reproductive span, higher baseline levels of Aβ deposition and tau and synaptic CSF biomarkers are associated with a steeper decline in memory. Our results suggest that longer estrogen exposure contributes to resilience against AD‐related pathology. [ABSTRACT FROM AUTHOR]

Background: Presence of Alzheimer's disease (AD) core pathology, β‐amyloid (Aβ) and p‐tau, has been proven to impact cognitive function even in cognitively unimpaired (CU) individuals. Although the Aβ and p‐tau (AT) effect has been mainly associated with memory function, recent evidence (Tideman, P., 2022. Neurology) suggested that Aβ levels were associated independently of p‐tau with the cross‐sectional performance in executive functioning. The aim of the present study was to explore specific associations of cerebrospinal fluid (CSF) and plasma Aβ and p‐tau baseline levels with the longitudinal change in several cognitive domains in a sample of CU individuals at increased risk of AD. Method: We analyzed the associations of baseline CSF Aβ42/40, and p‐tau181 as well as plasma Aβ42/40, and p‐tau231 levels, with domain‐specific cognitive changes 3 years after baseline in 337 CU participants from the ALFA+ study. We defined AT groups (A‐T‐, A+T‐, and A+T+) using CSF levels, and the A‐T‐ group's baseline performance served as reference to compute z‐scores for Visual Processing, Semantic Fluency, Executive Functioning, Episodic Memory, and Attentional Processing. Delta scores were computed by subtracting baseline from follow‐up scores and then compared among AT groups by means of ANCOVAs. Multiple linear regressions were performed on the whole sample using CSF Aβ42/40, p‐tau181 and plasma Aβ42/40, p‐tau231 as predictors of change in cognitive function. Result: A+T+ individuals showed a significant decline in Executive Function (p = 0.005, Cohen's d = 0.716), and Attentional Processing (p = 0.032, Cohen's d = 0.563), but not in Episodic Memory (p = 0.334) when compared with A‐T‐ individuals. In the whole sample, CSF Aβ42/40 was associated independently of p‐tau181 with a decline in Semantic Fluency (β = 6.284, p = 0.013), Attentional Processing (β = 3.828, p = 0.020), and Episodic Memory (β = 3.513, p = 0.004). Plasma p‐tau231 levels were associated with a decline in Semantic Fluency (β = ‐0.413, p = 0.045). CSF p‐tau181 and plasma Aβ42/40 were not associated with cognitive changes. Conclusion: Executive Function and Attentional Processing were more sensitive than Episodic Memory in capturing the early subtle cognitive changes in CU individuals with underlying AD pathology. Attentional Processing was the only cognitive domain associated both with the status of AD biomarkers and with the effect of CSF Aβ levels independently of p‐tau. [ABSTRACT FROM AUTHOR]

Background: In this study, we evaluated the association between tau PET and fluid biomarkers and explored biological mechanisms associated with elevated tau in cognitively unimpaired(CU) individuals. Method: Seventy‐nine CU individuals from the ALFA+ cohort had [18F]RO‐948 and [18F]flutemetamol PET, T1‐weighted MRI, CSF and plasma biomarkers. Longitudinal changes in cognition were measured using cognition composites(Table1). Participants were categorized into AT stages using CSF biomarkers and pre‐established cut‐offs(Table 1). [18F]RO‐948 SUVR was measured in entorhinal(BraakI/II), limbic(BraakIII/IV), and neocortical(BraakV/VI) regions using the inferior cerebellum as reference. Regional positivity thresholds per Braak region were calculated as mean+2SD of the A‐T‐ group. [18F]flutemetamol PET scans were quantified in Centiloids(CL). Associations between [18F]RO‐948 SUVRs and AD biomarkers (Figure1) were assessed using Pearson correlations. Receiver Operating Curve(ROC) analyses were conducted to determine the capacity of biomarkers to predict BraakI/II positivity. In those with CL>cut‐off for tau‐PET positivity, differences in non‐core AD fluid biomarkers(Figure2) and longitudinal cognition were sought between tau BraakI/II positive and negative individuals. The mediating effect of non‐core AD biomarkers on the AD pathophysiological cascade were sought. FDR‐corrected p‐values<0.05 were considered significant. Result: Nine cases(11.4%) were positive in BraakI/II. Following a hierarchical pattern, four of them were also positive for BraakIII/IV and one for BraakV/VI. Fluid biomarkers presented correlations with tau PET SUVR in all Braak stages (Figure1) and predictive capacity for tau‐PET positivity in BraakI/II(Table2). In individuals with CL>32.53, BraakI/II positives had higher levels of CSF‐GFAP(p<0.01) and CSF‐NFL(p = 0.03), and presented declines in PACC and in visual, attention, and memory composites (Figure1). CSF‐GFAP partially mediated the association between CL and tau‐PET (16%) and between tau‐PET and CSF‐NfL (30%). Conclusion: Early in the AD continuum, [18F]RO‐948 PET conformed to the Braak hierarchical model. CSF and plasma biomarkers showed moderate associations with tau PET SUVR but good capacity to predict tau PET positivity in BraakI/II. Tau‐PET positivity in this region was associated with higher astrogliosis, neurodegeneration and cognitive decline as compared to tau‐PET negatives with similar levels of amyloid deposition. Astrogliosis partially explained the observed associations between amyloid deposition and the presence of tau tangles in medial temporal regions and, even strongly, between the latter and neurodegeneration. [ABSTRACT FROM AUTHOR]

Background: MRI‐derived brain‐age prediction is a promising biomarker of biological brain aging. Accelerated brain aging has been found in Alzheimer's disease (AD) and other neurodegenerative diseases. However, no previous studies have investigated the relationship between specific pathophysiological pathways in AD and biological brain aging. Here, we studied whether glial activation and synaptic dysfunction are associated with biological brain aging in the earliest stages of the Alzheimer's continuum. Method: We included 418 cognitively unimpaired individuals (CU) from the ALFA+ study with available structural MRI, and CSF biomarkers of amyloid‐β (Aβ42/40) and tau pathology (p‐tau181), synaptic dysfunction (neurogranin, GAP43, SYT1, SNAP25), glial activation (sTREM2, YKL40, GFAP, interleukin‐6 and S100b) and α‐synuclein (Table 1). Aβ42/40, neurogranin and the glial activation biomarkers were measured using the Roche NeuroToolKit. We computed brain‐age delta as the difference between chronological and predicted brain‐age. The latter was estimated using a previously pretrained machine learning algorithm on cerebral morphological measurements on individuals from the UKBioBank cohort (N = 22.000). General linear modeling was used to test the associations between CSF biomarkers and brain‐age delta, adjusting by p‐tau, age, APOE status and sex. For the biomarkers whose associations were significant, we evaluated the interaction term "biomarker" × AT status while adjusting by age, APOE status and sex. AT staging was performed using pre‐established cut‐off values. We then used hippocampal volume as a marker of AD‐related neurodegeneration and repeated the same association studies with CSF biomarkers, adjusting by p‐tau, age, APOE status, sex and TIV. Result: Brain‐age delta was negatively associated with CSF sTREM2 (Padjusted<0.001), meaning that younger‐appearing brains showed higher levels of this biomarker (Table 1). None of the other biomarkers survived multiple comparisons. Hippocampal volume was not significantly associated with any of the CSF biomarkers (Table 2). There was no significant interaction between AT status and CSF sTREM2 for brain‐age delta, nor for hippocampal volume. Conclusion: These results showed that higher levels of CSF sTREM2 were associated with younger‐appearing brains in CU individuals independently of AT status, which might indicate a protective effect of this microglial phenotype in brain aging. This effect might not be AD‐related. [ABSTRACT FROM AUTHOR]

Background: Vascular dysfunction often occurs concurrently with Alzheimer's disease (AD). Breakdown of the blood–brain barrier (BBB) and vascular injury may be related to amyloid and tau pathology. In preliminary analyses, we examined the relationship between cerebrospinal fluid (CSF) biomarkers of AD, neurodegeneration, and glial activation, and two novel CSF markers of vascular dysfunction: soluble platelet‐derived growth factor receptor beta (sPDGFRβ) a marker of BBB integrity, and angiopoietin‐2 (Ang2), a marker of vascular injury. Method: CSF samples from participants enrolled in the Wisconsin Registry for Alzheimer's Prevention (WRAP) or the Wisconsin Alzheimer's Disease Research Center (WADRC) studies were assayed for markers of AD, neurodegeneration, and gliosis, using Roche NeuroToolKit® immunoassays (Roche Diagnostics International Ltd, Switzerland). A subset of serially sampled participants (N = 209, Nobs = 531) who spanned the AD clinical spectrum (cognitively unimpaired, MCI, dementia) underwent sPDGFRβ measurement (ELISA); a sample of N = 121 (Nobs= 276) was also assayed for Ang2 (ELISA) (Table 1). Pearson correlations were calculated for all CSF biomarkers. Linear mixed‐effects models with random intercepts, age‐at‐lumbar‐puncture as the measure of time, and CSF vascular biomarker as the outcome were used to test associations with tau positivity (>24.8 pg/mL), and cognitive status. Result: sPDGFRβ correlated with all CSF biomarkers (rs range.18 to.45, ps<.001, Figure 1A) except AB42/40. Ang2 correlated with all CSF biomarkers (rs range.21 to.45 ps <.001, Figure 1B) except AB42/40, and S100B. sPDGFRβ and Ang2 correlated most strongly with Aβ40 and biomarkers of synaptic function (neurogranin and α‐synuclein). Tau positivity was associated with sPDGFRβ in the whole sample (estimate = 64.5, p<.001) and excluding participants with MCI/dementia (estimate = 77.7, p<.001). Tau positivity was associated with Ang2 (estimate = 18.1, p =.007), however the association was not significant after excluding participants with MCI/dementia. There was no difference in sPDGFRβ across the AD clinical spectrum. Ang2 was higher among participants with MCI than cognitively unimpaired participants (estimate = 21.0, p =.037, Figure 2). Conclusion: CSF markers of vascular injury were elevated in MCI and were moderately related to tau pathology and markers of neuronal injury and neuroinflammation, but not amyloid pathology, providing insight into the association of of vascular injury to AD related disease [ABSTRACT FROM AUTHOR]

Background: Epidemiologic studies show that multiparity (≥3 children) is associated with a higher risk of clincal AD in cognitively unimpaired (CU) women. However, studies exploring the impact of parity on AD biomarkers are scarce. We explored the association between number of children and imaging and fluid AD biomarkers, and the related interaction with neurodegeneration and cognition. Method: We included 210 CU parous women from the ALFA+ cohort with 34 nulliparous women and 152 men with children as controls. The number of children was dichotomized as <3 children vs ≥3 children. All CSF biomarkers were measured using the Roche NeuroToolKit and Elecsys® immunoassays (both Roche Diagnostics International Ltd), except p‐tau231 and GAP‐43 (ELISA). All plasma biomarkers were measured using the Simoa HD‐X (Quanterix Corp) except sICAM1 (MSD). Jack's cortical thickness AD signature was used as a marker of neurodegeneration. Cognitive change (3‐year follow‐up) was measured with a PACC‐like composite as well as for individual cognitive domains. Biomarkers differences between parity groups were analyzed with ANCOVA adjusted by age. Independent linear models with biomarkers, AD signature and cognitive change as dependent variable were constructed. The number of children was set as predictor, and age, APOE‐ε4, and age at first birth as covariates in all models. Interaction terms between number of children and biomarkers were modeled. p‐values <0.05 were considered as significant. Result: Several biomarkers were significantly higher in grand multiparours women (Table 1). Linear regression results (Table 2, Fig. 1A) showed that multiparity was associated with higher CSF p‐tau181 levels. Moreover, multiparity interacted with CSF p‐tau181 to predict thinner cortical thickness in AD‐sensitive regions and a steeper decline in executive function (Table 2, Fig. 1B & 1C). No significant associations in men and nulliparous women were found. Conclusion: Having ≥3 children increases the risk of higher CSF p‐tau181 levels in CU middle‐aged women, with CSF p‐tau181 having a more deleterious effect on cortical thickness and change on executive function performance. These findings contribute to our understanding of the higher risk for AD observed in CU multiparous women, who show higher susceptibility and more adverse downstream consequences to tau pathology. [ABSTRACT FROM AUTHOR]

Background: Type 2 diabetes (T2D) and metabolic syndrome (MetS) are associated with increased risk of dementia, as well as altered gut microbiome composition (Ott et al., 1999; Ley et al., 2006). However, the extent to which gut microbiome alterations moderate brain pathology in these conditions remains unclear. Here, we examined the extent to which MetS associates with altered cerebrospinal fluid (CSF) biomarkers of Alzheimer's Disease (AD), glial activation, and neurodegeneration, and whether MetS interacts with gut microbiome composition to impact brain pathology. Method: Cognitively unimpaired adults (n = 88, Wisconsin Registry for Alzheimer's Prevention and Wisconsin Alzheimer's Disease Research Center; Table 1) underwent fasting blood collection and lumbar puncture, and provided a stool sample. Twenty‐six percent (n = 23) of participants met MetS criteria. Fecal microbiota composition was characterized using 16S rRNA sequencing. QIIME2 was used to denoise and classify features, followed by Phyloseq to filter rare taxa, agglomerate taxa at the phylum rank, and compute relative abundances. Analyses centered on Firmicutes:Bacteroidetes, given its previously observed alterations in T2D and MetS (Stadlbauer et al., 2015). CSF biomarkers were quantified using a robust prototype assay as part of the Roche NeuroToolKit research platform. Multiple regression models were used to determine associations between MetS and CSF biomarkers in addition to Firmicutes:Bacteroidetes, and any MetS by Firmicutes:Bacteroidetes effects on CSF biomarkers. Results are reported as significant when p < 0.05, uncorrected. Result: A significant negative association between MetS and CSF YKL‐40 was observed (Figs. 1a, 1b), but no significant association between MetS and Firmicutes:Bacteroidetes (Fig 1c), nor associations with other CSF biomarkers (Table 2). MetS showed a significant interaction with Firmicutes:Bacteroidetes on YKL‐40 (Fig. 1d), as control participants with a higher ratio showed increased YKL‐40. Conclusion: In a cognitively unimpaired cohort, MetS was associated with lower CSF YKL‐40 (a marker of astrocytic activation) and moderated the relationship between Firmicutes:Bacteroidetes and CSF YKL‐40. While the direction of the findings was unexpected, T2D is associated with inhibition of astrocyte activation (Jing et al., 2013), and astroglial function is modulated by gut microbiota. Follow‐up studies are currently testing how gut microbiome modulates neuroimmune function in the context of AD. [ABSTRACT FROM AUTHOR]

Background: Biochemical changes, which may precede morphological changes, could be of great relevance in profiling preclinical AD. We aimed to investigate metabolic changes using magnetic resonance spectroscopy (MRS) in three AD‐relevant regions: right hippocampus, right angular gyrus, and right precuneus, focusing on myoinositol due to its role in glial activity (osmoregulation‐neuroinflammation). Method: Three hundred sixty‐six participants from the ALFA+ cohort underwent three single‐voxel MRS (PRESS sequence, TR = 2000ms; TE = 100ms chosen to invert myoinositol peak for more precise quantitation; volume of interest (VOI): 20×20×20mm3 [25×20×16mm3 for hippocampus]). Figure 1 shows VOI location and MRS samples. Concentrations of N‐acetyl‐containing compounds (NAA) that is a neuronal marker, total creatine (Cr) related to brain energy, myoinositol (mI), choline‐containing compounds (Cho) related to cell proliferation, and glutamate/glutamine were calculated with LCModel in arbitrary units (using water reference) with the default settings and basis set adapted to the acquisition conditions. Concentrations were corrected for VOI CSF content. Remaining VOI gray matter percentage was used as a confounder in all analyses, jointly with age, sex, and APOE‐e4 status (carrier/non‐carrier). We investigated the correlation of MRS metabolite concentrations with CSF concentrations of Aβ42/40 and ptau‐181 as biomarkers for AD (Elecsys®; Roche Diagnostics). For completeness, we also checked the dependency of MRS metabolites on age. MRS not meeting QA criteria were discarded (Cramer‐Rao lower bounds >20 for any of the metabolites or imprecise VOI location). The statistical threshold was set to p<0.05 for all the analyses. Result: Table 1 shows characteristics of the subsamples with MRS in each location. Higher myoinositol levels in hippocampus and angular gyrus were associated with lower CSF Ab42/40, but not in the precuneus, where it was associated with higher Cr/Cho ratio. Higher Cr and NAA were positively associated with higher CSF p‐tau181 levels in the angular gyrus. NAA was negatively associated with age on cortical regions, as well as Cr on the angular gyrus. Table 2 summarizes the main results. Conclusion: MRS allowed determination of differential metabolite changes in AD‐related regions in preclinical AD. Further research is warranted to better characterize the nature of these metabolic changes and determine their impact on longitudinal outcomes of these participants. [ABSTRACT FROM AUTHOR]

INTRODUCTION: A hallmark of Alzheimer's disease (AD) is the aggregation of proteins (amyloid beta [A] and hyperphosphorylated tau [T]) in the brain, making cerebrospinal fluid (CSF) proteins of particular interest. METHODS: We conducted a CSF proteome‐wide analysis among participants of varying AT pathology (n = 137 participants; 915 proteins) with nine CSF biomarkers of neurodegeneration and neuroinflammation. RESULTS: We identified 61 proteins significantly associated with the AT category (P < 5.46 × 10−5) and 636 significant protein‐biomarker associations (P < 6.07 × 10−6). Proteins from glucose and carbon metabolism pathways were enriched among amyloid‐ and tau‐associated proteins, including malate dehydrogenase and aldolase A, whose associations with tau were replicated in an independent cohort (n = 717). CSF metabolomics identified and replicated an association of succinylcarnitine with phosphorylated tau and other biomarkers. DISCUSSION: These results implicate glucose and carbon metabolic dysregulation and increased CSF succinylcarnitine levels with amyloid and tau pathology in AD. Highlights: Cerebrospinal fluid (CSF) proteome enriched for extracellular, neuronal, immune, and protein processing.Glucose/carbon metabolic pathways enriched among amyloid/tau‐associated proteins.Key glucose/carbon metabolism protein associations independently replicated.CSF proteome outperformed other omics data in predicting amyloid/tau positivity.CSF metabolomics identified and replicated a succinylcarnitine–phosphorylated tau association. [ABSTRACT FROM AUTHOR]

Wordlist and story recall tests are routinely employed in clinical practice for dementia diagnosis. In this study, our aim was to establish how well-standard clinical metrics compared to process scores derived from wordlist and story recall tests in predicting biomarker determined Alzheimer's disease, as defined by CSF ptau/Aβ42 ratio. Data from 295 participants (mean age = 65 ± 9.) were drawn from the University of Wisconsin – Madison Alzheimer's Disease Research Center (ADRC) and Wisconsin Registry for Alzheimer's Prevention (WRAP). Rey's Auditory Verbal Learning Test (AVLT; wordlist) and Logical Memory Test (LMT; story) data were used. Bayesian linear regression analyses were carried out with CSF ptau/Aβ42 ratio as outcome. Sensitivity analyses were carried out with logistic regressions to assess diagnosticity. LMT generally outperformed AVLT. Notably, the best predictors were primacy ratio, a process score indexing loss of information learned early during test administration, and recency ratio, which tracks loss of recently learned information. Sensitivity analyses confirmed this conclusion. Our study shows that story recall tests may be better than wordlist tests for detection of dementia, especially when employing process scores alongside conventional clinical scores. [ABSTRACT FROM AUTHOR]

Introduction: Metabolomics technology facilitates studying associations between small molecules and disease processes. Correlating metabolites in cerebrospinal fluid (CSF) with Alzheimer's disease (AD) CSF biomarkers may elucidate additional changes that are associated with early AD pathology and enhance our knowledge of the disease. Methods: The relative abundance of untargeted metabolites was assessed in 161 individuals from the Wisconsin Registry for Alzheimer's Prevention. A metabolome-wide association study (MWAS) was conducted between 269 CSF metabolites and protein biomarkers reflecting brain amyloidosis, tau pathology, neuronal and synaptic degeneration, and astrocyte or microglial activation and neuroinflammation. Linear mixed-effects regression analyses were performed with random intercepts for sample relatedness and repeated measurements and fixed effects for age, sex, and years of education. The metabolome-wide significance was determined by a false discovery rate threshold of 0.05. The significant metabolites were replicated in 154 independent individuals from then Wisconsin Alzheimer's Disease Research Center. Mendelian randomization was performed using genome-wide significant single nucleotide polymorphisms from a CSF metabolites genome-wide association study. Results: Metabolome-wide association study results showed several significantly associated metabolites for all the biomarkers except Aß42/40 and IL-6. Genetic variants associated with metabolites and Mendelian randomization analysis provided evidence for a causal association of metabolites for soluble triggering receptor expressed on myeloid cells 2 (sTREM2), amyloid ß (Aß40), asynuclein, total tau, phosphorylated tau, and neurogranin, for example, palmitoyl sphingomyelin (d18:1/16:0) for sTREM2, and erythritol for Aß40 and a -synuclein. Discussion: This study provides evidence that CSF metabolites are associated with AD-related pathology, and many of these associations may be causal. [ABSTRACT FROM AUTHOR]

Background: Genetic scores for late-onset Alzheimer's disease (LOAD) have been associated with preclinical cognitive decline and biomarker variations. Compared with an overall polygenic risk score (PRS), a pathway-specific PRS (p-PRS) may be more appropriate in predicting a specific biomarker or cognitive component underlying LOAD pathology earlier in the lifespan. Objective: In this study, we leveraged longitudinal data from the Wisconsin Registry for Alzheimer's Prevention and explored changing patterns in cognition and biomarkers at various age points along six biological pathways. Methods: PRS and p-PRSs with and without APOE were constructed separately based on the significant SNPs associated with LOAD in a recent genome-wide association study meta-analysis and compared to APOE alone. We used a linear mixed-effects model to assess the association between PRS/p-PRSs and cognitive trajectories among 1,175 individuals. We also applied the model to the outcomes of cerebrospinal fluid biomarkers in a subset. Replication analyses were performed in an independent sample. Results: We found p-PRSs and the overall PRS can predict preclinical changes in cognition and biomarkers. The effects of PRS/p-PRSs on rate of change in cognition, amyloid-β, and tau outcomes are dependent on age and appear earlier in the lifespan when APOE is included in these risk scores compared to when APOE is excluded. Conclusion: In addition to APOE, the p-PRSs can predict age-dependent changes in amyloid-β, tau, and cognition. Once validated, they could be used to identify individuals with an elevated genetic risk of accumulating amyloid-β and tau, long before the onset of clinical symptoms. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Apolipoprotein E (APOE) ε4‐carrier status or ε4 allele count are included in analyses to account for the APOE genetic effect on Alzheimer's disease (AD); however, this does not account for protective effects of APOE ε2 or heterogeneous effect of ε2, ε3, and ε4 haplotypes. METHODS: We leveraged results from an autopsy‐confirmed AD study to generate a weighted risk score for APOE (APOE‐npscore). We regressed cerebrospinal fluid (CSF) amyloid and tau biomarkers on APOE variables from the Wisconsin Registry for Alzheimer's Prevention (WRAP), Wisconsin Alzheimer's Disease Research Center (WADRC), and Alzheimer's Disease Neuroimaging Initiative (ADNI). RESULTS: The APOE‐npscore explained more variance and provided a better model fit for all three CSF measures than APOE ε4‐carrier status and ε4 allele count. These findings were replicated in ADNI and observed in subsets of cognitively unimpaired (CU) participants. DISCUSSION: The APOE‐npscore reflects the genetic effect on neuropathology and provides an improved method to account for APOE in AD‐related analyses. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Our objective was determining the optimal combinations of cerebrospinal fluid (CSF) biomarkers for predicting disease progression in Alzheimer's disease (AD) and other neurodegenerative diseases. METHODS: We included 1,983 participants from three different cohorts with longitudinal cognitive and clinical data, and baseline CSF levels of Aβ42, Aβ40, phosphorylated tau at threonine‐181 (p‐tau), neurofilament light (NfL), neurogranin, α‐synuclein, soluble triggering receptor expressed on myeloid cells 2 (sTREM2), glial fibrillary acidic protein (GFAP), YKL‐40, S100b, and interleukin 6 (IL‐6) (Elecsys NeuroToolKit). RESULTS: Change of modified Preclinical Alzheimer's Cognitive Composite (mPACC) in cognitively unimpaired (CU) was best predicted by p‐tau/Aβ42 alone (R2 ≥ 0.31) or together with NfL (R2 = 0.25), while p‐tau/Aβ42 (R2 ≥ 0.19) was sufficient to accurately predict change of the Mini‐Mental State Examination (MMSE) in mild cognitive impairment (MCI) patients. P‐tau/Aβ42 (AUC ≥ 0.87) and p‐tau/Aβ42 together with NfL (AUC ≥ 0.75) were the best predictors of conversion to AD and all‐cause dementia, respectively. DISCUSSION: P‐tau/Aβ42 is sufficient for predicting progression in AD, with very high accuracy. Adding NfL improves the prediction of all‐cause dementia conversion and cognitive decline. [ABSTRACT FROM AUTHOR]

Introduction: There is a great need for fully automated plasma assays that can measure amyloid beta (Aβ) pathology and predict future Alzheimer's disease (AD) dementia. Methods: Two cohorts (n = 920) were examined: Panel A+ (n = 32 cognitively unimpaired [CU], n = 106 mild cognitive impairment [MCI], and n = 89 AD) and BioFINDER‐1 (n = 461 CU, n = 232 MCI). Plasma Aβ42/Aβ40, phosphorylated tau (p‐tau)181, two p‐tau217 variants, ApoE4 protein, neurofilament light, and GFAP were measured using Elecsys prototype immunoassays. Results: The best biomarker for discriminating Aβ‐positive versus Aβ‐negative participants was Aβ42/Aβ40 (are under the curve [AUC] 0.83–0.87). Combining Aβ42/Aβ40, p‐tau181, and ApoE4 improved the AUCs significantly (0.90 to 0.93; P< 0.01). Adding additional biomarkers had marginal effects (ΔAUC ≤0.01). In BioFINDER, p‐tau181, p‐tau217, and ApoE4 predicted AD dementia within 6 years in CU (AUC 0.88) and p‐tau181, p‐tau217, and Aβ42/Aβ40 in MCI (AUC 0.87). Discussion: The high accuracies for Aβ pathology and future AD dementia using fully automated instruments are promising for implementing plasma biomarkers in clinical trials and clinical routine. [ABSTRACT FROM AUTHOR]

Background: Alzheimer's disease (AD) and related dementias are public health concerns often with long preclinical phases. Thus, intervention and prevention methods in midlife could prove efficacious. Cerebrospinal fluid (CSF) biomarkers can change early in the disease process and have been utilized for dementia diagnostics. Multiple health‐related lifestyle factors have been associated with risk for AD, yet existing research on lifestyle factors has focused on clinical outcomes such as cognitive decline, mild cognitive impairment and/or AD dementia; their associations with early changes in CSF are less understood. Our aim was to determine whether physical activity (PA), a modifiable lifestyle factor, is associated with biomarkers for neurodegeneration, glial activation, and inflammation. Method: Participants were N = 204 cognitively unimpaired adults (aged 45–80 years) from the Wisconsin Registry for Alzheimer's Prevention and the Wisconsin Alzheimer's Disease Research Center, two on‐going, longitudinal studies of preclinical AD. PA was defined as the weekly metabolic equivalent (MET), calculated by scoring amount and intensity of mild, moderate, and vigorous exercises per week (range 0–79 METS). We assessed CSF biomarkers using robust exploratory prototype assays from the NeuroToolKit research platform (Roche Diagnostics International, Switzerland). Participants also completed demographic and health questionnaires (Table 1). We used linear regression models to assess associations between PA and CSF biomarkers, adjusting for age at biomarker assessment, sex, education, and chronic health conditions (diabetes, hypertension, cardiovascular disease). Result: Preliminary results showed that participants who engage in more PA had higher CSF S100B concentrations, a pro‐inflammatory calcium‐binding protein (standardized b change per MET = 0.0013, 95% confidence interval: 0.0003–0.0023; p =.01). No other PA‐biomarker associations were significant. Conclusion: Higher PA was significantly associated with higher CSF concentration of S100B, a marker of (astro‐)glial activation. Future studies will need to examine whether PA is associated with higher S100B in individuals along the disease continuum of AD, and whether this is reflected in the blood. Longer follow‐ups may be needed to determine associations of PA with other biomarkers, where we had limited variation in this primarily healthy study cohort. [ABSTRACT FROM AUTHOR]