Impact of demographics and comorbid conditions on plasma biomarkers concentrations and their diagnostic accuracy in a memory clinic cohort.

Plasma biomarkers have emerged as promising tools for identifying amyloid beta (Aß) pathology. Before implementation in routine clinical practice, confounding factors modifying their concentration beyond neurodegenerative diseases should be identified. We studied the association of a comprehensive list of demographics, comorbidities, medication and laboratory parameters with plasma p-tau181, glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) on a prospective memory clinic cohort and studied their impact on diagnostic accuracy for discriminating CSF/amyloid PET-defined Aß status. Three hundred sixty patients (mean age 66.5 years, 55% females, 53% Aß positive) were included. Sex, age and Aß status-adjusted models showed that only estimated glomerular filtration rate (eGFR, standardized ß -0.115 [-0.192 to -0.035], p = 0.005) was associated with p-tau181 levels, although with a much smaller effect than Aß status (0.685 [0.607-0.763], p < 0.001). Age, sex, body mass index (BMI), Charlson comorbidity index (CCI) and eGFR significantly modified GFAP concentration. Age, blood volume (BV) and eGFR were associated with NfL levels. p-tau181 predicted Aß status with 87% sensitivity and specificity with no relevant increase in diagnostic performance by adding any of the confounding factors. Using two cut-offs, plasma p-tau181 could have spared 62% of amyloid-PET/CSF testing. Excluding patients with chronic kidney disease did not change the proposed cut-offs nor the diagnostic performance. In conclusion, in a memory clinic cohort, age, sex, eGFR, BMI, BV and CCI slightly modified plasma p-tau181, GFAP and NfL concentrations but their impact on the diagnostic accuracy of plasma biomarkers for Aß status discrimination was minimal.

The APOE4 effect: structural brain differences in Alzheimer's disease according to the age at symptom onset.

BACKGROUND AND PURPOSE: How the APOE genotype can differentially affect cortical and subcortical memory structures in biomarker-confirmed early-onset (EOAD) and late-onset (LOAD) Alzheimer's disease (AD) was assessed. METHOD: Eighty-seven cerebrospinal fluid (CSF) biomarker-confirmed AD patients were classified according to their APOE genotype and age at onset. 28 were EOAD APOE4 carriers (+EOAD), 21 EOAD APOE4 non-carriers (-EOAD), 23 LOAD APOE4 carriers (+LOAD) and 15 LOAD APOE4 non-carriers (-LOAD). Grey matter (GM) volume differences were analyzed using voxel-based morphometry in Papez circuit regions. Multiple regression analyses were performed to determine the relation between GM volume loss and cognition. RESULTS: Significantly more mammillary body atrophy in +EOAD compared to -EOAD is reported. The medial temporal and posterior cingulate cortex showed less GM in +LOAD compared to -LOAD. Medial temporal GM volume loss was also found in +EOAD compared to -LOAD. With an exception for +EOAD, medial temporal GM was strongly associated with episodic memory in the three groups, whilst posterior cingulate cortex GM volume was more related with visuospatial abilities. Visuospatial abilities and episodic memory were also associated with the anterior thalamic nucleus in -LOAD. CONCLUSIONS: Our results show that the APOE genotype has a significant effect on GM integrity as a function of age of disease onset. Specifically, whilst LOAD APOE4 genotype is mostly associated with increased medial temporal and parietal atrophy compared to -LOAD, for EOAD APOE4 might have a more specific effect on subcortical (mammillary body) structures. The findings suggest that APOE genotype needs to be taken into account when classifying patients by age at onset.

Early-onset Alzheimer's disease shows a distinct neuropsychological profile and more aggressive trajectories of cognitive decline than late-onset.

OBJECTIVES: Early- and late-onset Alzheimer's disease (EOAD and LOAD) share the same neuropathological traits but show distinct cognitive features. We aimed to explore baseline and longitudinal outcomes of global and domain-specific cognitive function in a well characterized cohort of patients with a biomarker-based diagnosis. METHODS: In this retrospective cohort study, 195 participants were included and classified according to their age, clinical status, and CSF AD biomarker profile: 89 EOAD, 37 LOAD, 46 young healthy controls (age ≤ 65 years), and 23 old healthy controls (>65 years). All subjects underwent clinical and neuropsychological assessment, neuroimaging, APOE genotyping and lumbar puncture. RESULTS: We found distinct neuropsychological profiles between EOAD and LOAD at the time of diagnosis. Both groups showed similar performances on memory and language domains, but the EOAD patients displayed worsened deficits in visual perception, praxis, and executive tasks (p < 0.05). Longitudinally, cognitive decline in EOAD was more pronounced than LOAD in the global outcomes at the expense of these non-amnestic domains. We found that years of education significantly influenced the decline in most of the neuropsychological tests. Besides, the APOE ε4 status showed a significant effect on the decline of memory-related tasks within the EOAD cohort (p < 0.05). INTERPRETATION: Age of onset is a main factor shaping the cognitive trajectories in AD patients, with younger age driving to a steeper decline of the non-memory domains. Years of education are related to a transversal decline in all cognitive domains and APOE ε4 status to a specific decline in memory performance in EOAD.

Sex differences in early-onset Alzheimer's disease.

BACKGROUND AND PURPOSE: Sex is believed to drive heterogeneity in Alzheimer's disease (AD), although evidence in early-onset AD (EOAD; <65 years) is scarce. METHODS: We included 62 EOAD patients and 44 healthy controls (HCs) with core AD cerebrospinal fluid (CSF) biomarkers, neurofilament light chain levels, neuropsychological assessment, and 3-T magnetic resonance imaging. We measured cortical thickness (CTh) and hippocampal subfield volumes (HpS) using FreeSurfer. Adjusted linear models were used to analyze sex-differences and the relationship between atrophy and cognition. RESULTS: Compared to same-sex HCs, female EOAD subjects showed greater cognitive impairment and broader atrophy burden than male EOAD subjects. In a direct female-EOAD versus male-EOAD comparison, there were slight differences in temporal CTh, with no differences in cognition or HpS. CSF tau levels were higher in female EOAD than in male EOAD subjects. Greater atrophy was associated with worse cognition in female EOAD subjects. CONCLUSIONS: At diagnosis, there are sex differences in the pattern of cognitive impairment, atrophy burden, and CSF tau in EOAD, suggesting there is an influence of sex on pathology spreading and susceptibility to the disease in EOAD.

Differential Gene Expression in Sporadic and Genetic Forms of Alzheimer's Disease and Frontotemporal Dementia in Brain Tissue and Lymphoblastoid Cell Lines.

Sporadic early-onset Alzheimer's disease (EOAD) and autosomal dominant Alzheimer's disease (ADAD) provide the opportunity to investigate the physiopathological mechanisms in the absence of aging, present in late-onset forms. Frontotemporal dementia (FTD) causes early-onset dementia associated to tau or TDP43 protein deposits. A 15% of FTD cases are caused by mutations in C9orf72, GRN, or MAPT genes. Lymphoblastoid cell lines (LCLs) have been proposed as an alternative to brain tissue for studying earlier phases of neurodegenerative diseases. The aim of this study is to investigate the expression profile in EOAD, ADAD, and sporadic and genetic FTD (sFTD and gFTD, respectively), using brain tissue and LCLs. Sixty subjects of the following groups were included: EOAD, ADAD, sFTD, gFTD, and controls. Gene expression was analyzed with Clariom D microarray (Affymetrix). Brain tissue pairwise comparisons revealed six common differentially expressed genes (DEG) for all the patients' groups compared with controls: RGS20, WIF1, HSPB1, EMP3, S100A11 and GFAP. Common up-regulated biological pathways were identified both in brain and LCLs (including inflammation and glial cell differentiation), while down-regulated pathways were detected mainly in brain tissue (including synaptic signaling, metabolism and mitochondrial dysfunction). CD163, ADAMTS9 and LIN7A gene expression disruption was validated by qPCR in brain tissue and NrCAM in LCLs in their respective group comparisons. In conclusion, our study highlights neuroinflammation, metabolism and synaptic signaling disturbances as common altered pathways in different AD and FTD forms. The use of LCLs might be appropriate for studying early immune system and inflammation, and some neural features in neurodegenerative dementias.

Baseline MRI atrophy predicts 2-year cognitive outcomes in early-onset Alzheimer's disease.

BACKGROUND: MRI atrophy predicts cognitive status in AD. However, this relationship has not been investigated in early-onset AD (EOAD, < 65 years) patients with a biomarker-based diagnosis. METHODS: Forty eight EOAD (MMSE ≥ 15; A + T + N +) and forty two age-matched healthy controls (HC; A - T - N -) from a prospective cohort underwent full neuropsychological assessment, 3T-MRI scan and lumbar puncture at baseline. Participants repeated the cognitive assessment annually. We used linear mixed models to investigate whether baseline cortical thickness (CTh) or subcortical volume predicts two-year cognitive outcomes in the EOAD group. RESULTS: In EOAD, hemispheric CTh and ventricular volume at baseline were associated with global cognition, language and attentional/executive functioning 2 years later (p < 0.0028). Regional CTh was related to most cognitive outcomes (p < 0.0028), except verbal/visual memory subtests. Amygdalar volume was associated with letter fluency test (p < 0.0028). Hippocampal volume did not show significant associations. CONCLUSION: Baseline hemispheric/regional CTh, ventricular and amygdalar volume, but not the hippocampus, predict two-year cognitive outcomes in EOAD.

Longitudinal brain atrophy and CSF biomarkers in early-onset Alzheimer's disease.

There is evidence of longitudinal atrophy in posterior brain areas in early-onset Alzheimer's disease (EOAD; aged < 65 years), but no studies have been conducted in an EOAD cohort with fluid biomarkers characterization. We used 3T-MRI and Freesurfer 6.0 to investigate cortical and subcortical gray matter loss at two years in 12 EOAD patients (A + T + N + ) compared to 19 controls (A-T-N-) from the Hospital Clínic Barcelona cohort. We explored group differences in atrophy patterns and we correlated atrophy and baseline CSF-biomarkers levels in EOAD. We replicated the correlation analyses in 14 EOAD (A + T + N + ) and 55 late-onset AD (LOAD; aged ≥ 75 years; A + T + N + ) participants from the Alzheimer's disease Neuroimaging Initiative. We found that EOAD longitudinal atrophy spread with a posterior-to-anterior gradient and beyond hippocampus/amygdala. In EOAD, higher initial CSF NfL levels correlated with higher ventricular volumes at baseline. On the other hand, higher initial CSF Aß42 levels (within pathological range) predicted higher rates of cortical loss in EOAD. In EOAD and LOAD subjects, higher CSF t-tau values at baseline predicted higher rates of subcortical atrophy. CSF p-tau did not show any significant correlation. In conclusion, posterior cortices, hippocampus and amygdala capture EOAD atrophy from early stages. CSF Aß42 might predict cortical thinning and t-tau/NfL subcortical atrophy.

Screening of dementia genes by whole-exome sequencing in Spanish patients with early-onset dementia: likely pathogenic, uncertain significance and risk variants.

Early-onset Alzheimer's disease (EOAD) and frontotemporal dementia (FTD) have a high proportion of genetically determined cases. Next-generation sequencing technologies have triggered the discovery of new mutations and genetic variants in dementia-causal genes. We performed whole-exome sequencing and selective analysis of known genes causative of EOAD and FTD in a well-characterized Spanish cohort of 103 patients (60 EOAD, 43 FTD) to find genetic variants associated to patients' phenotype. In EOAD patients, a new likely pathogenic variant in PSEN1 gene (p.G378R) was found. In FTD patients, 2 likely pathogenic variants were found, one in MAPT gene (p.P397S) and one in VCP gene (p.R159H). In our series, 2% of early-onset dementia without criteria for clinical genetic testing according to current guidelines presented a likely pathogenic mutation. We have also detected 13 additional variants of uncertain significance in causal genes, as well as rare variants in risk genes for dementia (ABCA7, SORL1, SQSTM1, and TREM2). Next-generation technologies in neurodegenerative diseases constitute a powerful tool that significantly contributes to patients' diagnosis.

Diagnostic Accuracy of MRI Visual Rating Scales in the Diagnosis of Early Onset Cognitive Impairment.

BACKGROUND: The diagnosis of incipient symptomatic stages of early-onset dementia is challenging. The magnetic resonance imaging (MRI) is an easy-access biomarker. OBJECTIVE: We aim to determine the distribution and diagnostic performance of the existing atrophy visual rating scales on MRI in initial stages of the most frequent neurodegenerative early onset dementias. METHODS: We evaluated the visual atrophy scales usefulness in two hundred subjects: seventy sporadic early onset Alzheimer's disease (AD) patients (48 amnestic and 22 non-amnestic), 14 patients with autosomal-dominant AD (ADAD), 25 sporadic frontotemporal dementia patients [11 with behavioral variant (bvFTD), nine with semantic variant of primary progressive aphasia (svPPA), and 5 with non-fluent primary progressive aphasia (nfvPPA)], 7 with genetically determined FTD (genetic FTD), 25 mild cognitive impairment due to non-degenerative disorders, and 59 healthy controls. All had MMSE≥18, 3T-brain MRI, and biomarker-supported diagnosis. Two raters evaluated six frontal, temporal, and parietal scales. Inter-rater reliability and diagnostic performance in terms of area under the receiver-operator curves and balanced accuracy were analyzed. RESULTS: Best scales to discriminate AD from controls were the anterior cingulate scale for amnestic and the posterior atrophy scale for sporadic non-amnestic AD and ADAD. The anterior temporal scale was the best for sporadic bvFTD and svPPA and the anterior cingulate scale was for nfvPPA. All scales performed well for the genetic FTD. However, no scale demonstrated good performance at discriminating AD from FTD or non-degenerative disorders. CONCLUSIONS: The clinicians should interpret with caution atrophy scale assessment in subjects with early-onset cognitive impairment given that none of the evaluated scales met the requirements for being a diagnostic biomarker.

Contribution of CSF biomarkers to early-onset Alzheimer's disease and frontotemporal dementia neuroimaging signatures.

Prior studies have described distinct patterns of brain gray matter and white matter alterations in Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD), as well as differences in their cerebrospinal fluid (CSF) biomarkers profiles. We aim to investigate the relationship between early-onset AD (EOAD) and FTLD structural alterations and CSF biomarker levels. We included 138 subjects (64 EOAD, 26 FTLD, and 48 controls), all of them with a 3T MRI brain scan and CSF biomarkers available (the 42 amino acid-long form of the amyloid-beta protein [Aß42], total-tau protein [T-tau], neurofilament light chain [NfL], neurogranin [Ng], and 14-3-3 levels). We used FreeSurfer and FSL to obtain cortical thickness (CTh) and fraction anisotropy (FA) maps. We studied group differences in CTh and FA and described the "AD signature" and "FTLD signature." We tested multiple regression models to find which CSF-biomarkers better explained each disease neuroimaging signature. CTh and FA maps corresponding to the AD and FTLD signatures were in accordance with previous literature. Multiple regression analyses showed that the biomarkers that better explained CTh values within the AD signature were Aß and 14-3-3; whereas NfL and 14-3-3 levels explained CTh values within the FTLD signature. Similarly, NfL levels explained FA values in the FTLD signature. Ng levels were not predictive in any of the models. Biochemical markers contribute differently to structural (CTh and FA) changes typical of AD and FTLD.

Hippocampal atrophy has limited usefulness as a diagnostic biomarker on the early onset Alzheimer's disease patients: A comparison between visual and quantitative assessment.

NIA-AA diagnostic criteria include volumetric or visual rating measures of hippocampal atrophy (HA) as a diagnostic biomarker of Alzheimer's disease (AD). We aimed to determine its utility as a diagnostic biomarker for early onset Alzheimer's disease (EOAD) by assessing Medial Temporal Atrophy (MTA) and hippocampal volume (HV) determination. MTA score and HV quantified by FreeSurfer were assessed in 140 (aged ≤65) subjects with biomarker supported diagnosis: 38 amnesic (A-EOAD), 20 non-amnesic (NA-EOAD), 30 late onset AD (LOAD), 20 fronto-temporal dementia (FTD) and 32 healthy controls (HC). The results showed that the proportion of MTA ≥ 1.5 was higher on LOAD and FTD than EOAD and HC but none of the MTA thresholds (≥1, ≥1.5 and ≥ 2) showed acceptable diagnostic accuracy. LOAD had lower HV than the other groups. A-EOAD HV was lower than NA-EOAD and HC but equal to FTD. The 6258 mm3 cut-off showed good diagnostic accuracy between A-EOAD and HC. Both tools showed a moderate inverse correlation. In conclusion, MTA has a limited diagnostic utility as an EOAD biomarker as it does not discriminate AD from FTD or HC in initial symptomatic stages. HV may discriminate A-EOAD from HC but not from FTD.

Regional patterns of 18F-florbetaben uptake in presenilin 1 mutation carriers.

Individuals with autosomal dominant Alzheimer's disease (ADAD) present amyloid deposits before symptoms onset. We aimed to investigate efficacy and safety of 18F-florbetaben (FBB) for assessing amyloid deposition in ADAD. We acquired FBB positron emission tomography and magnetic resonance imaging of 25 individuals from PSEN1 families (NCT02362880). We studied individual uptake patterns, group differences, and correlation with estimated years to symptoms onset, as well as adverse events. We found that asymptomatic carriers (N = 14) showed increased FBB uptake across the cerebral cortex and in the caudate. FBB accumulation appeared more than 15 years before onset in the precuneus and bankssts, among other regions, overlapping regions showing increased cortical thickness in the same subjects. FBB uptake correlated with estimated years to symptoms onset in several areas, especially the rostral anterior cingulate. Symptomatic carriers (N = 7) had an elevated FBB uptake plateau. No adverse events were reported. Overall, we found progressive FBB uptake in ADAD starting 2 decades before symptoms. The rostral anterior cingulate is a candidate area to track Aß deposition in addition to the precuneus.

Cerebrospinal Fluid Biomarkers Predict Clinical Evolution in Patients with Subjective Cognitive Decline and Mild Cognitive Impairment.

BACKGROUND: Determination of Alzheimer's disease (AD) by cerebrospinal fluid (CSF) biomarkers - 42-amino-acid amyloid-ß (Aß42), total tau and phosphorylated tau (p-tau) - has demonstrated high validity for detecting AD neuropathological changes. However, their prognostic utility to predict the onset of dementia in predementia subjects is still questioned. We aimed to study the prospective clinical evolution of a group of subjects with subjective cognitive decline (SCD) or mild cognitive impairment (MCI) and to determine the prognostic capacity of AD CSF biomarkers. METHODS: 149 subjects with MCI or SCD, not meeting dementia criteria, underwent a prospective clinical, neuropsychological and CSF biomarker study. Patients were initially classified as SCD or MCI following internationally accepted criteria. CSF sampling was obtained and analysed following consensus protocols. Neuropsychological and clinical evaluations were conducted at the follow-up. Statistical analysis considering the final clinical diagnosis, regression analysis to define risk factors and survival curves for progression were made. RESULTS: 72.4% of subjects (83% MCI and 27% SCD) with a pathological CSF ratio (Aß42/p-tau) met criteria for dementia during the 5-year follow-up versus 18.7% of subjects from the group with a normal ratio. The pathological CSF ratio was a powerful marker of risk for AD dementia (OR 27.1; 95% CI 10.3-71.2). Kaplan-Meier survival curves showed that only 15% of subjects with a pathological CSF ratio remained free of AD dementia at 5 years of follow-up. All subjects who reverted to normal cognition presented a normal CSF profile at baseline. CONCLUSION: An abnormal AD CSF biomarker profile in predementia subjects is a powerful predictor of cognitive and/or functional decline in the medium term.