Plasma neurofilament light chain in memory clinic practice: Evidence from a real-life study.

OBJECTIVE: To explore the accuracy of plasma neurofilament light chain (NfL) as a biomarker for diagnosis and staging of cognitive impairment, in a large cohort with of previously diagnosed patients in clinical practice. METHODS: Retrospective, cross-sectional, monocentric study, from a tertiary memory clinic. Patients underwent cerebrospinal fluid core Alzheimer's disease (AD) biomarker evaluation using ELISA or Elecsys methods, and plasma NfL analysis using the single molecule array technology. The patients' biomarker data were examined for associations with: i/cognitive status ii/presence of neurodegenerative disease and iii/diagnostic groups. Associations between core CSF biomarkers and plasma NfL were determined. RESULTS: Participants (N = 558, mean age = 69.2 ± 8.8, 56.5% women) were diagnosed with AD (n = 274, considering dementia and MCI stages), frontotemporal dementia (FTD, n = 55), Lewy body disease (LBD, n = 40, considering MCI and dementia stages), other neurodegenerative diseases, n = 57 (e.g Supranuclear Palsy, Corticobasal syndrome), non-neurodegenerative cognitive impairment (NND, n = 79, e.g. vascular lesions, epilepsy or psychiatric disorders) or subjective cognitive impairment (SCI, n = 53). Mean plasma NfL (log, pg/mL) levels were higher in neurodegenerative than non-neurodegenerative disorders (1.35 ± 0.2 vs 1.16 ± 0.23, p < 0.001), higher in all diagnostic groups than in SCI (1.06 ± 0.23) p < 0.001), and associated with the stage of cognitive impairment (p < 0.001). The addition of plasma NfL to a clinical model (age, MMSE and APOE ε4 carriership) marginally improved the discrimination of degenerative from non-degenerative disorders in ROC analysis (AUC clinical model: 0.81, 95% CI = [0.77;0.85] AUC clinical model + plasma NfL: AUC = 0.83 95% CI = [0.78;0.87], delta Akaike information criterion = -11.7). DISCUSSION: Plasma NfL could help discrimination between degenerative and non-degenerative cognitive disorders, albeit not better than comprehensive clinical evaluation.

Cerebrospinal Fluid Alpha-Synuclein Improves the Differentiation between Dementia with Lewy Bodies and Alzheimer's Disease in Clinical Practice.

Background: Alpha-synuclein, abnormally aggregated in Dementia with Lewy Bodies (DLB), could represent a potential biomarker to improve the differentiation between DLB and Alzheimer's disease (AD). Our main objective was to compare Cerebrospinal Fluid (CSF) alpha-synuclein levels between patients with DLB, AD and Neurological Control (NC) individuals. Methods: In a monocentric retrospective study, we assessed CSF alpha-synuclein concentration with a validated ELISA kit (ADx EUROIMMUN) in patients with DLB, AD and NC from a tertiary memory clinic. Between-group comparisons were performed, and Receiver Operating Characteristic analysis was used to identify the best CSF alpha-synuclein threshold. We examined the associations between CSF alpha-synuclein, other core AD CSF biomarkers and brain MRI characteristics. Results: We included 127 participants (mean age: 69.3 ± 8.1, Men: 41.7%). CSF alpha-synuclein levels were significantly lower in DLB than in AD (1.28 ± 0.52 ng/mL vs. 2.26 ± 0.91 ng/mL, respectively, p < 0.001) without differences due to the stage of cognitive impairment. The best alpha-synuclein threshold was characterized by an Area Under the Curve = 0.85, Sensitivity = 82.0% and Specificity = 76.0%. CSF alpha-synuclein was associated with CSF AT(N) biomarkers positivity (p < 0.01) but not with hippocampal atrophy or white matter lesions. Conclusion: CSF Alpha-synuclein evaluation could help to early differentiate patients with DLB and AD in association with existing biomarkers.

Head-to-head comparison of clinical performance of CSF phospho-tau T181 and T217 biomarkers for Alzheimer's disease diagnosis.

INTRODUCTION: Phosphorylated tau (p-tau) in cerebrospinal fluid (CSF) is an established Alzheimer's disease (AD) biomarker. Novel immunoassays targeting N-terminal and mid-region p-tau181 and p-tau217 fragments are available, but head-to-head comparison in clinical settings is lacking. METHODS: N-terminal-directed p-tau217 (N-p-tau217), N-terminal-directed p-tau181 (N-p-tau181), and standard mid-region p-tau181 (Mid-p-tau181) biomarkers in CSF were evaluated in three cohorts (n = 503) to assess diagnostic performance, concordance, and associations with amyloid beta (Aß). RESULTS: CSF N-p-tau217 and N-p-tau181 had better concordance (88.2%) than either with Mid-p-tau181 (79.7%-82.7%). N-p-tau217 and N-p-tau181 were significantly increased in early mild cognitive impairment (MCI)-AD (A+T-N-) without changes in Mid-p-tau181 until AD-dementia. N-p-tau217 and N-p-tau181 identified Aß pathophysiology (area under the curve [AUC] = 94.8%-97.1%) and distinguished MCI-AD from non-AD MCI (AUC = 82.6%-90.5%) signficantly better than Mid-p-tau181 (AUC = 91.2% and 70.6%, respectively). P-tau biomarkers equally differentiated AD from non-AD dementia (AUC = 99.1%-99.8%). DISCUSSION: N-p-tau217 and N-p-tau181 could improve diagnostic accuracy in prodromal-AD and clinical trial recruitment as both identify Aß pathophysiology and differentiate early MCI-AD better than Mid-p-tau181.

Age and the association between apolipoprotein E genotype and Alzheimer disease: A cerebrospinal fluid biomarker-based case-control study.

BACKGROUND: The ε4 allele of apolipoprotein E (APOE) gene and increasing age are two of the most important known risk factors for developing Alzheimer disease (AD). The diagnosis of AD based on clinical symptoms alone is known to have poor specificity; recently developed diagnostic criteria based on biomarkers that reflect underlying AD neuropathology allow better assessment of the strength of the associations of risk factors with AD. Accordingly, we examined the global and age-specific association between APOE genotype and AD by using the A/T/N classification, relying on the cerebrospinal fluid (CSF) levels of ß-amyloid peptide (A, ß-amyloid deposition), phosphorylated tau (T, pathologic tau), and total tau (N, neurodegeneration) to identify patients with AD. METHODS AND FINDINGS: This case-control study included 1,593 white AD cases (55.4% women; mean age 72.8 [range = 44-96] years) with abnormal values of CSF biomarkers from nine European memory clinics and the American Alzheimer's Disease Neuroimaging Initiative (ADNI) study. A total of 11,723 dementia-free controls (47.1% women; mean age 65.6 [range = 44-94] years) were drawn from two longitudinal cohort studies (Whitehall II and Three-City), in which incident cases of dementia over the follow-up were excluded from the control population. Odds ratio (OR) and population attributable fraction (PAF) for AD associated with APOE genotypes were determined, overall and by 5-year age categories. In total, 63.4% of patients with AD and 22.6% of population controls carried at least one APOE ε4 allele. Compared with non-ε4 carriers, heterozygous ε4 carriers had a 4.6 (95% confidence interval 4.1-5.2; p < 0.001) and ε4/ε4 homozygotes a 25.4 (20.4-31.2; p < 0.001) higher OR of AD in unadjusted analysis. This association was modified by age (p for interaction < 0.001). The PAF associated with carrying at least one ε4 allele was greatest in the 65-70 age group (69.7%) and weaker before 55 years (14.2%) and after 85 years (22.6%). The protective effect of APOE ε2 allele for AD was unaffected by age. Main study limitations are that analyses were based on white individuals and AD cases were drawn from memory centers, which may not be representative of the general population of patients with AD. CONCLUSIONS: In this study, we found that AD diagnosis based on biomarkers was associated with APOE ε4 carrier status, with a higher OR than previously reported from studies based on only clinical AD criteria. This association differs according to age, with the strongest effect at 65-70 years. These findings highlight the need for early interventions for dementia prevention to mitigate the effect of APOE ε4 at the population level.

Psychosis in Neurodegenerative Dementias: A Systematic Comparative Review.

Background: Psychosis, characterized by delusions and/or hallucinations, is frequently observed during the progression of Alzheimer's disease (AD) and other neurodegenerative dementias (ND) (i.e., dementia with Lewy bodies (DLB), and frontotemporal dementia (FTD)) and cause diagnostic and management difficulties. Objective: This review aims at presenting a concise and up-to-date overview of psychotic symptoms that occur in patients with ND with a comparative approach. Methods: A systematic review was conducted following the PRISMA guidelines. 98 original studies investigating psychosis phenotypes in neurodegenerative dementias were identified (40 cohort studies, 57 case reports). Results: Psychosis is a frequently observed phenomenon during the course of ND, with reported prevalence ranging from 22.5% to 54.1% in AD, 55.9% to 73.9% in DLB, and 18% to 42% in FTD. Throughout all stages of these diseases, noticeable patterns emerge depending on their underlying causes. Misidentification delusions (16.6-78.3%) and visual hallucinations (50-69.6%) are frequently observed in DLB, while paranoid ideas and somatic preoccupations seem to be particularly common in AD and FTD, (respectively 9.1-60.3% and 3.10-41.5%). Limited data were found regarding psychosis in the early stages of these disorders. Conclusions: Literature data suggest that different ND are associated with noticeable variations in psychotic phenotypes, reflecting disease-specific tendencies. Further studies focusing on the early stages of these disorders are necessary to enhance our understanding of early psychotic manifestations associated with ND and help in differential diagnosis issues.

Plasma neurofilament light chain as prognostic marker of cognitive decline in neurodegenerative diseases, a clinical setting study.

BACKGROUND: Analysis of selected research cohorts has highlighted an association between plasma neurofilament light (NfL) protein and cross-sectional cognitive impairment as well as longitudinal cognitive decline. However, the findings have yielded inconsistent results regarding its possible application in clinical practice. Despite its potential prognostic significance, the role of plasma NfL in daily clinical practice with unselected patients suffering from cognitive impairment remains largely unexplored. METHODS: This retrospective, cross-sectional and longitudinal monocentric study enrolled 320 patients with Alzheimer's disease ([AD], n = 158), dementia with Lewy body ([DLB], n = 30), frontotemporal dementia ([FTD], n = 32), non-neurodegenerative diseases ([NND], n = 59) or subjective cognitive decline ([SCD], n = 41). Plasma NfL levels were measured at baseline on the Simoa platform. AD, DLB, and FTD patients were also analyzed altogether as a 'degenerative conditions' subgroup, whereas SCD and NND were grouped as a 'non-degenerative conditions' subgroup. We assessed the relationship between plasma NfL levels and cross-sectional cognitive performance, including global cognition and six specific cognitive domains. A subset of 239 patients had follow-up mini-mental state examinations (MMSE) up to 60 months. Models were adjusted on age, education level, glomerular filtration rate and body mass index. RESULTS: In 320 patients, baseline plasma NfL levels were negatively associated with global cognition (ß=-1.28 (-1.81 ; -0.75) P < 0.001), memory (ß=-1.48 (-2.38 ; -0.59), P = 0.001), language (ß=-1.72(-2.49 ; -0.95) P < 0.001), praxis (ß=-2.02 (-2.91 ; -1.13) P < 0.001) and executive functions (ß=-0.81, P < 0.001). Across diagnosis, plasma NfL levels were negatively associated with cross-sectional global cognition in all but the SCD subgroup, specifically with executive functions and memory in AD (respectively ß=-0.71(-1.21 ; -0.211), P = 0.005 and ß=-1.29 (-2.17 ; -0.42), P = 0.004), and with attention in LBD (ß=-0.81(-1.16 ; -0.002), P = 0.03). Linear mixed-effects models showed that plasma NfL predicted MMSE decline in the global population (ßPlasmaNfLxTime=-0.15 (-0.26 ; -0.04), P = 0.006), as in the neurodegenerative condition subgroup (ßPlasmaNfLxTime=-0.21 (-0.37 ; - 0.06), P = 0.007), but not in non-neurodegenerative condition subgroup. CONCLUSION: In our clinical cohort, plasma NfL was associated with faster cognitive decline in neurodegenerative dementia, which corroborates data obtained in research cohorts. Yet, plasma NfL was not predictive of accelerated cognitive decline in individuals without neurodegeneration, suggesting its use as a neurodegeneration-specific predictive biomarker.

Plasma biomarkers of amyloid, tau, axonal, and neuroinflammation pathologies in dementia with Lewy bodies.

BACKGROUND: Increasing evidence supports the use of plasma biomarkers of amyloid, tau, neurodegeneration, and neuroinflammation for diagnosis of dementia. However, their performance for positive and differential diagnosis of dementia with Lewy bodies (DLB) in clinical settings is still uncertain. METHODS: We conducted a retrospective biomarker study in two tertiary memory centers, Paris Lariboisière and CM2RR Strasbourg, France, enrolling patients with DLB (n = 104), Alzheimer's disease (AD, n = 76), and neurological controls (NC, n = 27). Measured biomarkers included plasma Aß40/Aß42 ratio, p-tau181, NfL, and GFAP using SIMOA and plasma YKL-40 and sTREM2 using ELISA. DLB patients with available CSF analysis (n = 90) were stratified according to their CSF Aß profile. RESULTS: DLB patients displayed modified plasma Aß ratio, p-tau181, and GFAP levels compared with NC and modified plasma Aß ratio, p-tau181, GFAP, NfL, and sTREM2 levels compared with AD patients. Plasma p-tau181 best differentiated DLB from AD patients (ROC analysis, area under the curve [AUC] = 0.80) and NC (AUC = 0.78), and combining biomarkers did not improve diagnosis performance. Plasma p-tau181 was the best standalone biomarker to differentiate amyloid-positive from amyloid-negative DLB cases (AUC = 0.75) and was associated with cognitive status in the DLB group. Combining plasma Aß ratio, p-tau181 and NfL increased performance to identify amyloid copathology (AUC = 0.79). Principal component analysis identified different segregation patterns of biomarkers in the DLB and AD groups. CONCLUSIONS: Amyloid, tau, neurodegeneration and neuroinflammation plasma biomarkers are modified in DLB, albeit with moderate diagnosis performance. Plasma p-tau181 can contribute to identify Aß copathology in DLB.

Is the clinical phenotype impact the prognosis in dementia with Lewy bodies?

INTRODUCTION: The first predominant clinical symptoms of dementia with Lewy bodies (DLB) are highly variable; however, the prognosis based on initial predominant symptoms remains poorly understood. METHODS: Multicenter retrospective study in 4 French expert neurological centers. Patients were categorized in 3 groups according to their first more predominant symptoms: cognitive, psychiatric, or motor. RESULTS: Analysis of 310 DLB patients. The mean age was 73.5 years old (SD 7.5) including 32.3% of women. The mean follow-up was 7.25 years (SD 3.6). We observed that the full clinical picture was more frequent in the motor group than in the cognitive group (p = 0.01); male gender and age at onset were associated with a significant excess risk of instantaneous mortality (p = 0.01). CONCLUSION: Initial symptoms may affect the clinical course of patients, but no significant difference in mortality was observed.

Plasma Leptin Is Associated With Amyloid CSF Biomarkers and Alzheimer's Disease Diagnosis in Cognitively Impaired Patients.

BACKGROUND: Metabolic dysfunction and dysregulation of leptin signaling have been linked to Alzheimer's disease (AD)'s pathophysiology. The objectives of this study were to examine the associations between plasma leptin, cerebrospinal fluid (CSF), beta-amyloid (Aß), and tau biomarkers (AT[N] status) and with the stage of cognitive impairment. METHODS: Cross-sectional analysis of data from cognitively impaired patients from a tertiary memory clinic. Plasma leptin levels were compared according to the stage of cognitive impairment and biomarker profiles, using the AT(N) classification. Linear regression models were performed to examine the relationship between leptin and CSF biomarkers. Results were adjusted for age, gender, body mass index (BMI), and APOE ε4. In a subgroup of A+T+ individuals, we compared the 2-year evolution of Mini-Mental State Examination scores, according to the participants' tertile of plasma leptin levels. RESULTS: We included 1 036 participants (age 68.7 ± 9.1, females = 54.1%). A+T+ and A+T- patients had significantly lower plasma leptin levels than amyloid negative participants (p < .01). CSF Aß concentration was significantly associated with lower plasma leptin ß = -4.3 (1.5), p = .005 unadjusted; and ß = -3.4 (1.6), p = .03 after adjustment for age, female gender, BMI, and APOE ε4. Patients with major neurocognitive disorder due to AD had a difference of leptin of -7.3 ng/mL 95% confidence interval (CI; -11.8; -2.8), p = .0002, compared to individuals with other causes of cognitive impairment. Leptin was not associated with the slope of cognitive decline. CONCLUSION: Plasma leptin levels were associated with CSF Aß and with the diagnosis of AD confirmed by CSF biomarkers, suggesting a molecular interplay between leptin metabolism and brain amyloid deposition.

Quantification of the trans-synaptic partners neurexin-neuroligin in CSF of neurodegenerative diseases by parallel reaction monitoring mass spectrometry.

BACKGROUND: Synaptic proteins are increasingly studied as biomarkers for synaptic dysfunction and loss, which are early and central events in Alzheimer's disease (AD) and strongly correlate with the degree of cognitive decline. In this study, we specifically investigated the synaptic binding partners neurexin (NRXN) and neuroligin (Nlgn) proteins, to assess their biomarker's potential. METHODS: we developed a parallel reaction monitoring mass spectrometric method for the simultaneous quantification of NRXNs and Nlgns in cerebrospinal fluid (CSF) of neurodegenerative diseases, focusing on AD. Specifically, NRXN-1α, NRXN-1ß, NRXN-2α, NRXN-3α and Nlgn1, Nlgn2, Nlgn3 and Nlgn4 proteins were targeted. FINDINGS: The proteins were investigated in a clinical cohort including CSF from controls (n=22), mild cognitive impairment (MCI) due to AD (n=44), MCI due to other conditions (n=46), AD (n=77) and a group of non-AD dementia (n=28). No difference in levels of NRXNs and Nlgns was found between AD (both at dementia and MCI stages) or controls or the non-AD dementia group for any of the targeted proteins. NRXN and Nlgn proteins correlated strongly with each other, but only a weak correlation with the AD core biomarkers and the synaptic biomarkers neurogranin and growth-associated protein 43, was found, possibly reflecting different pathogenic processing at the synapse. INTERPRETATION: we conclude that NRXN and Nlgn proteins do not represent suitable biomarkers for synaptic pathology in AD. The panel developed here could aid in future investigations of the potential involvement of NRXNs and Nlgns in synaptic dysfunction in other disorders of the central nervous system. FUNDING: a full list of funding can be found under the acknowledgments section.

Exploring the link between GBA1 mutations and Dementia with Lewy bodies, A mini-review.

IMPORTANCE: Dementia with Lewy bodies (DLB) is a neurodegenerative disease linked to abnormal accumulation of phosphorylated α-synuclein. GBA1 is the gene encoding the lysosomal enzyme glucocerebrosidase (GCase), whose mutations are a risk factor of DLB. OBJECTIVE: To report all available data exploring the association between GBA1 mutations and DLB. EVIDENCE REVIEW: All publications focused on GCase and DLB in humans between 2003 and 2022 were identified on PubMed, Cochrane and ClinicalTrials.gov. FINDINGS: 29 studies were included and confirmed the strong association between GBA1 mutations and DLB (Odds Ratio [OR]: 8.28). GBA1 mutation carriers presented a more malignant phenotype, with earlier symptom onset, more severe motor and cognitive dysfunctions, more visual hallucinations and rapid eye movement sleep disorder. GBA1 mutations were associated with "purer" neuropathological DLB. No therapeutic recommendations exist and clinical trials targeting GCase are just starting in DLB patients. CONCLUSIONS AND RELEVANCE: This review reports a link between GBA1 mutations and the DLB phenotype with limited evidence due to the small number of studies.

Plasma neuregulin 1 as a synaptic biomarker in Alzheimer's disease: a discovery cohort study.

BACKGROUND: Synaptic dysfunction is an early core feature of Alzheimer's disease (AD), closely associated with cognitive symptoms. Neuregulin 1 (NRG1) is a growth and differentiation factor with a key role in the development and maintenance of synaptic transmission. Previous reports have shown that changes in cerebrospinal fluid (CSF) NRG1 concentration are associated with cognitive status and biomarker evidence of AD pathology. Plasma biomarkers reflecting synaptic impairment would be of great clinical interest. OBJECTIVE: To measure plasma NRG1 concentration in AD patients in comparison with other neurodegenerative disorders and neurological controls (NC) and to study its association with cerebrospinal fluid (CSF) core AD and synaptic biomarkers. METHODS: This retrospective study enrolled 127 participants including patients with AD at mild cognitive impairment stage (AD-MCI, n = 27) and at dementia stage (n = 35), non-AD dementia (n = 26, Aß-negative), non-AD MCI (n = 19), and neurological controls (n=20). Plasma and CSF NRG1, as well as CSF core AD biomarkers (Aß 42/Aß 40 ratio, phospho-tau, and total tau), were measured using ELISA. CSF synaptic markers were measured using ELISA for GAP-43 and neurogranin and through immunoprecipitation mass spectrometry for SNAP-25. RESULTS: Plasma NRG1 concentration was higher in AD-MCI and AD dementia patients compared with neurological controls (respectively P = 0.005 and P < 0.001). Plasma NRG1 differentiated AD MCI patients from neurological controls with an area under the curve of 88.3%, and AD dementia patients from NC with an area under the curve of 87.3%. Plasma NRG1 correlated with CSF NRG1 (ß = 0.372, P = 0.0056, adjusted on age and sex). Plasma NRG1 was associated with AD CSF core biomarkers in the whole cohort and in Aß-positive patients (ß = -0.197-0.423). Plasma NRG1 correlated with CSF GAP-43, neurogranin, and SNAP-25 (ß = 0.278-0.355). Plasma NRG1 concentration correlated inversely with MMSE in the whole cohort and in Aß-positive patients (all, ß = -0.188, P = 0.038; Aß+: ß = -0.255, P = 0.038). CONCLUSION: Plasma NRG1 concentration is increased in AD patients and correlates with CSF core AD and synaptic biomarkers and cognitive status. Thus, plasma NRG1 is a promising non-invasive biomarker to monitor synaptic impairment in AD.

A Pragmatic, Data-Driven Method to Determine Cutoffs for CSF Biomarkers of Alzheimer Disease Based on Validation Against PET Imaging.

BACKGROUND AND OBJECTIVES: To elaborate a new algorithm to establish a standardized method to define cutoffs for CSF biomarkers of Alzheimer disease (AD) by validating the algorithm against CSF classification derived from PET imaging. METHODS: Low and high levels of CSF phosphorylated tau were first identified to establish optimal cutoffs for CSF ß-amyloid (Aß) peptide biomarkers. These Aß cutoffs were then used to determine cutoffs for CSF tau and phosphorylated tau markers. We compared this algorithm to a reference method, based on tau and amyloid PET imaging status (ADNI study), and then applied the algorithm to 10 large clinical cohorts of patients. RESULTS: A total of 6,922 patients with CSF biomarker data were included (mean [SD] age: 70.6 [8.5] years, 51.0% women). In the ADNI study population (n = 497), the agreement between classification based on our algorithm and the one based on amyloid/tau PET imaging was high, with Cohen's kappa coefficient between 0.87 and 0.99. Applying the algorithm to 10 large cohorts of patients (n = 6,425), the proportion of persons with AD ranged from 25.9% to 43.5%. DISCUSSION: The proposed novel, pragmatic method to determine CSF biomarker cutoffs for AD does not require assessment of other biomarkers or assumptions concerning the clinical diagnosis of patients. Use of this standardized algorithm is likely to reduce heterogeneity in AD classification.

COVID-19 in adults with dementia: clinical features and risk factors of mortality-a clinical cohort study on 125 patients.

BACKGROUND: There is limited evidence on the characteristics and outcome of patients with dementia hospitalised for novel coronavirus infection (COVID-19). METHOD: We conducted a prospective study in 2 gerontologic COVID units in Paris, France, from March 14, 2020, to May 7, 2020. Patients with dementia hospitalised for confirmed COVID-19 infection were systematically enrolled. A binary logistic regression analysis was performed to identify factors associated with mortality at 21 days. RESULTS: We included 125 patients. Median age was 86 (IQI 82-90); 59.4% were female. Most common causes of dementia were Alzheimer's disease, mixed dementia and vascular dementia. 67.2% had ≥ 2 comorbidities; 40.2% lived in a long-term care facility. The most common symptoms at COVID-19 onset were confusion and delirium (82.4%), asthenia (76.8%) and fever (72.8%) before polypnea (51.2%) and desaturation (50.4%). Falls were frequent at the initial phase of the disease (35.2%). The fatality rate at 21 days was 22.4%. Chronic kidney disease and CRP at admission were independent factors of death. Persisting confusion, mood and behavioural disorders were observed in survivors (19.2%). CONCLUSION: COVID-19 in demented individuals is associated with severe outcome in SARS-CoV-2 infection and is characterised by specific clinical features and complications, with confusion and delirium at the forefront. COVID-19 testing should be considered in front of any significant change from baseline.

Differences Between Plasma and Cerebrospinal Fluid Glial Fibrillary Acidic Protein Levels Across the Alzheimer Disease Continuum.

Importance: Glial fibrillary acidic protein (GFAP) is a marker of reactive astrogliosis that increases in the cerebrospinal fluid (CSF) and blood of individuals with Alzheimer disease (AD). However, it is not known whether there are differences in blood GFAP levels across the entire AD continuum and whether its performance is similar to that of CSF GFAP. Objective: To evaluate plasma GFAP levels throughout the entire AD continuum, from preclinical AD to AD dementia, compared with CSF GFAP. Design, Setting, and Participants: This observational, cross-sectional study collected data from July 29, 2014, to January 31, 2020, from 3 centers. The Translational Biomarkers in Aging and Dementia (TRIAD) cohort (Montreal, Canada) included individuals in the entire AD continuum. Results were confirmed in the Alzheimer's and Families (ALFA+) study (Barcelona, Spain), which included individuals with preclinical AD, and the BioCogBank Paris Lariboisière cohort (Paris, France), which included individuals with symptomatic AD. Main Outcomes and Measures: Plasma and CSF GFAP levels measured with a Simoa assay were the main outcome. Other measurements included levels of CSF amyloid-ß 42/40 (Aß42/40), phosphorylated tau181 (p-tau181), neurofilament light (NfL), Chitinase-3-like protein 1 (YKL40), and soluble triggering receptor expressed on myeloid cells 2 (sTREM2) and levels of plasma p-tau181 and NfL. Results of amyloid positron emission tomography (PET) were available in TRIAD and ALFA+, and results of tau PET were available in TRIAD. Results: A total of 300 TRIAD participants (177 women [59.0%]; mean [SD] age, 64.6 [17.6] years), 384 ALFA+ participants (234 women [60.9%]; mean [SD] age, 61.1 [4.7] years), and 187 BioCogBank Paris Lariboisière participants (116 women [62.0%]; mean [SD] age, 69.9 [9.2] years) were included. Plasma GFAP levels were significantly higher in individuals with preclinical AD in comparison with cognitively unimpaired (CU) Aß-negative individuals (TRIAD: Aß-negative mean [SD], 185.1 [93.5] pg/mL, Aß-positive mean [SD], 285.0 [142.6] pg/mL; ALFA+: Aß-negative mean [SD], 121.9 [42.4] pg/mL, Aß-positive mean [SD], 169.9 [78.5] pg/mL). Plasma GFAP levels were also higher among individuals in symptomatic stages of the AD continuum (TRIAD: CU Aß-positive mean [SD], 285.0 [142.6] pg/mL, mild cognitive impairment [MCI] Aß-positive mean [SD], 332.5 [153.6] pg/mL; AD mean [SD], 388.1 [152.8] pg/mL vs CU Aß-negative mean [SD], 185.1 [93.5] pg/mL; Paris: MCI Aß-positive, mean [SD], 368.6 [158.5] pg/mL; AD dementia, mean [SD], 376.4 [179.6] pg/mL vs CU Aß-negative mean [SD], 161.2 [67.1] pg/mL). Plasma GFAP magnitude changes were consistently higher than those of CSF GFAP. Plasma GFAP more accurately discriminated Aß-positive from Aß-negative individuals than CSF GFAP (area under the curve for plasma GFAP, 0.69-0.86; area under the curve for CSF GFAP, 0.59-0.76). Moreover, plasma GFAP levels were positively associated with tau pathology only among individuals with concomitant Aß pathology. Conclusions and Relevance: This study suggests that plasma GFAP is a sensitive biomarker for detecting and tracking reactive astrogliosis and Aß pathology even among individuals in the early stages of AD.

CSF levels of the BACE1 substrate NRG1 correlate with cognition in Alzheimer's disease.

BACKGROUND: The presynaptic protein neuregulin1 (NRG1) is cleaved by beta-site APP cleaving enzyme 1 (BACE1) in a similar way as amyloid precursor protein (APP) NRG1 can activate post-synaptic receptor tyrosine-protein kinase erbB4 (ErbB4) and was linked to schizophrenia. The NRG1/ErbB4 complex is neuroprotective, can trigger synaptogenesis and plasticity, increases the expression of NMDA and GABA receptors, and can induce neuroinflammation. This complex can reduce memory formation. In Alzheimer's disease (AD) brains, NRG1 accumulates in neuritic plaques. It is difficult to determine if NRG1 has beneficial and/or detrimental effects in AD. BACE1 levels are increased in AD brains and cerebrospinal fluid (CSF) and may lead to enhanced NRG1 secretion, but no study has assessed CSF NRG1 levels in AD and mild cognitive impairment (MCI) patients. METHODS: This retrospective study included 162 patients suffering from AD dementia (54), MCI with progression to AD dementia (MCI-AD) (27), non-AD MCI (30), non-AD dementias (30), and neurological controls (27). All patients had neurological examinations, brain MRI, and neuropsychological evaluations. After written informed consent and using enzyme-linked immunosorbent assays (ELISAs), CSF samples were evaluated for Aß1-42, Aß1-40, total tau (T-tau), phosphorylated tau on threonine 181 (P-tau), BACE1, growth-associated protein 43 (GAP 43), neurogranin (Ng), and NRG1. RESULTS: Levels of NRG1 were significantly increased in the CSF of AD (+ 36%) and MCI-AD (+ 28%) patients compared to neurological controls and also non-AD MCI and non-AD dementias. In addition, in AD and MCI-AD patients, NRG1 levels positively correlated with Aß1-42 but not with T-tau, P-tau, and BACE1 levels and negatively correlated with MMSE scores. A longitudinal follow-up study of AD patients revealed a trend (p = 0.08) between CSF NRG1 levels and cognitive decline. In the overall population, NRG1 correlated with MMSE and the synaptic biomarkers GAP 43 and neurogranin. CONCLUSIONS: Our results showed that CSF NRG1 levels are increased in AD and MCI-AD as compared to controls and other dementias. CSF NRG1 levels are associated with cognitive evolution, and a major outcome of our findings is that synaptic NRG1 could be involved in the pathophysiology of AD. Modulating brain NRG1 activity may represent a new therapeutic target in AD.

COVID-19 in Older Adults: A Series of 76 Patients Aged 85 Years and Older with COVID-19.

BACKGROUND: Clinical presentation and risk factors of death in COVID-19 in oldest adults have not been well characterized. OBJECTIVES: To describe clinical features and outcome of COVID-19 in patients older than 85 years and study risk factors for mortality. DESIGN: Prospective cohort. PARTICIPANTS AND SETTING: Patients aged 85 years and older, admitted in noncritical care units at the University Hospital Lariboisière Fernand-Widal (Paris, France) for confirmed severe acute respiratory syndrome coronavirus 2 infection were included and followed up for 21 days. MEASUREMENTS: Clinical and laboratory findings were collected. Cox survival analysis was performed to explore factors associated with death. RESULTS: From March 14 to April 11, 2020, 76 patients (median age = 90 (86-92) years; women = 55.3%) were admitted for confirmed COVID-19. Of the patients, 64.5% presented with three or more comorbidities. Most common symptoms were asthenia (76.3%), fever (75.0%) and confusion and delirium (71.1%). An initial fall was reported in 25.0% of cases, and digestive symptoms were reported in 22.4% of cases. COVID-19 was severe in 51.3% of cases, moderate in 32.9%, and mild in 15.8%. Complications included acute respiratory syndrome (28.9%), cardiac decompensation (14.5%), and hypotensive shock (9.0%). Fatality at 21 days was 28.9%, after a median course of disease of 13 (8-17) days. Males were overrepresented in nonsurvivors (68.2%). In survivors, median length of stay was 12 (9-19.5) days. Independent predictive factors of death were C-reactive protein level at admission and lymphocyte count at nadir. CONCLUSION: Specific clinical features, multiorgan injury, and high case fatality rate are observed in older adults with COVID-19. However, rapid diagnosis, appropriate care, and monitoring seem to improve prognosis.

Cerebrospinal Fluid and Plasma Biomarkers do not Differ in the Presenile and Late-Onset Behavioral Variants of Frontotemporal Dementia.

BACKGROUND: Memory troubles and hippocampal atrophy are considered more frequent and focal atrophy less severe in late-onset (>65 years) than in presenile behavioral variant of frontotemporal dementia (bvFTD). OBJECTIVE: To compare cerebrospinal fluid (CSF) and plasma biomarkers in late-onset and presenile bvFTD. METHODS: Multicentric retrospective study (2007-2017) on patients with clinical diagnosis of bvFTD. RESULTS: This study included 44 patients (67%) with presenile and 22 (33%) with late-onset bvFTD (comparable mean disease duration; n = 11 with causal mutations). Hippocampal atrophy was more frequent (80% versus 25.8%) and severe in late-onset bvFTD (median Scheltens score: 3 [0-4] versus 1 [0-3]), without difference after adjustment for age. Lobar atrophy and focal hypometabolism/hypoperfusion were not different between groups. The median CSF Aß1-42 and phosphorylated tau (P-tau) concentrations were in the normal range and comparable between groups. Axonal neurodegeneration biomarkers were within the normal range (CSF T-tau; plasma T-tau in late-onset bvFTD) or higher (plasma neurofilament light chain (NFL); plasma T-tau in presenile bvFTD) than the normal values, but globally not different between bvFTD groups. Plasma glial fibrillary acid protein (GFAP) was strongly increased in both bvFTD groups compared with the values in controls of the same age. CONCLUSION: The CSF and plasma biomarker profiles did not suggest a more aggressive neurodegeneration in the presenile group (comparable T-tau, NFL, and GFAP levels) or the co-existence of Alzheimer's disease in the late-onset group (comparable and within normal range CSF Aß1-42 and P-tau). The severity of the neurodegenerative process seems comparable in presenile and late-onset bvFTD.

[Biomarkers of Alzheimer's disease in older and oldest old patients]. / Quel est l'intérêt aujourd'hui des biomarqueurs de la maladie d'Alzheimer, chez les patients âgés et très âgés ?

Alzheimer's disease (AD) is the most common neurodegenerative disorder in older patients, leading to progressive cognitive impairment. Brain amyloid and tau deposits are the main pathological features of the disease and may appear several decades before the onset of clinical symptoms. The biomarkers of AD, measured in the plasma or in the cerebrospinal fluid, reflect the brain accumulation of beta-amyloid and tau. Therefore, they enable early and more accurate etiological diagnosis when combined with brain neuroimaging and neuropsychological assessment. The new definition of AD brings biomarkers forward, shifting the focus from symptoms to brain changes in living patients. The growing body of evidence from longitudinal studies has established their ability to improve the accuracy of AD diagnosis but also to predict the progression of cognitive impairment. The biomarkers of AD are also important for recruiting participants who are at increased risk of developing AD dementia in drug trials. Beyond their role in clinical research, these tools have been increasingly used for several years in clinical practice in secondary and tertiary-referral memory clinics. However, interpreting the results of AD biomarkers may be delicate in the oldest old patients with comorbidity. A tailored, patient-centered decision is mandatory in these situations. Complicated ethical issues may also arise in using these biomarkers in asymptomatic subjects. In the absence of clear guidelines for their utilization, we hereby discuss their potential interests and limitations in older adults.