Frontal variant of Alzheimer's disease with asymmetric presentation mimicking frontotemporal dementia: Case report and literature review

INTRODUCTION

Frontal variant of Alzheimer's disease (fvAD) is a rare nonamnestic syndrome of Alzheimer's disease (AD). Differentiating it from behavior variant of frontotemporal dementia (bvFTD), which has implications for treatment responses and prognosis, remains a clinical challenge.

METHODS

Molecular neuroimaging and biofluid markers were performed for the index patient for accurate premortem diagnosis of fvAD. The clinical, neuroimaging, and biofluid characteristics of the patient were compared to those reported in previous studies of fvAD from 1999 to 2019.

RESULTS

A 66-year-old man presented with progressive executive dysfunction, personality and behavioral changes, and memory decline since age 59. He had no family history of neurodegenerative disorders. A stimulus-sensitive myoclonus was noted over his left upper extremity. Neuropsychological assessment revealed moderate dementia with a Mini-Mental State Exam score of 10/30 and compromised executive and memory performance. Brain imaging showed asymmetrical atrophy and hypometabolism over the right frontal and temporal areas, mimicking bvFTD. However, we observed increased tau depositions based on ¹⁸ F-labeled T807 Tau PET in these areas and diffusely increased amyloid deposition based on ¹¹ C-labeled Pittsburgh compound B positron emission tomography (PET). Plasma biomarker measures indicated an AD profile with increased Aβ1-42 (18.66 pg/ml; cutoff: 16.42 pg/ml), Aβ1-42/Aβ1-40 ratio (0.45; cutoff: 0.30), total tau (29.78 pg/ml; cutoff: 23.89 pg/ml), and phosphorylated tau (4.11 pg/ml; cutoff: 3.08 pg/ml). These results supported a diagnosis of fvAD.

CONCLUSIONS

Our results with asymmetrical presentations extend current knowledge about this rare AD variant. Application of biofluid and molecular imaging markers could assist in early, accurate diagnosis.

Additive-color multi-harmonic generation microscopy for simultaneous label-free differentiation of plaques, tangles, and neuronal axons

Multicolor fluorescence imaging has been widely used by neuroscientists to simultaneously observe different neuropathological features of the brain. However, these optical modalities rely on exogenous labeling. Here, we demonstrate, for the first time, a label-free additive-color multi-harmonic generation microscopy to elucidate, concurrently with different hues, Alzheimer's disease (AD) neuropathological hallmarks: amyloid β (Aβ) plaques and neurofibrillary tangles (NFT). By treating third harmonic generation (THG) and second harmonic generation (SHG) as two primary colors, our study can simultaneously label-free differentiate AD hallmarks by providing different additive colors between Aβ plaques, NFT, and neuronal axons, with weaker THG presentation from NFT in most places of the brain. Interestingly our pixel-based quantification and Pearson's correlation results further corroborated these findings. Our proposed label-free technique fulfills the unmet challenge in the clinical histopathology for stain-free slide-free differential visualization of neurodegenerative disease pathologies, with a sub-femtoliter resolution in a single image field-of-view.

Composite Scores of Plasma Tau and β-Amyloids Correlate with Dementia in Down Syndrome

Dementia frequently occurs in Down syndrome (DS) patients, and early intervention is important in its management. We have previously demonstrated a positive correlation of plasma β-amyloid Aβ42 levels and negative correlations of Aβ40 and tau levels with dementia in DS. In this study, we examined more cases and constructed composite scores with both tau and amyloids to correlate with dementia in DS. Plasma Aβ42, Aβ40, and tau proteins were measured by an immunomagnetic reduction assay in DS patients. Data were randomly and repeatedly split into training and validating sets, and logistic regression was applied to calculate the area under the curve (AUC) for each biomarker. A total of 73 DS patients (among them, 23 had neurodegeneration) and 77 controls were recruited. In DS patients without dementia, plasma Aβ40 and tau levels were highly elevated, but Aβ42 levels were lower than those of the healthy controls. DS patients with dementia, compared with DS patients with no dementia, had a large decline in Aβ40 and tau but a rise in Aβ42. For biomarker scores correlating with dementia, Aβ40 revealed an AUC of 0.912; the composite score of Aβ40 × tau revealed an AUC of 0.953; and a combined composite score of 0.1 for Aβ40 × Tau +0.9 Tau × Aβ40/Aβ42 achieved the highest AUC of 0.965. Therefore, composite biomarker scores including both plasma tau and β-amyloid levels correlate with dementia in DS better than using individual biomarker scores. The pattern of tau decline and Aβ42 rise in DS patients with dementia are also different from previous findings in Alzheimer's disease.

Plasma pS129-α-Synuclein Is a Surrogate Biofluid Marker of Motor Severity and Progression in Parkinson's Disease

Phosphorylated α-synuclein accounts for more than 90% of α-synuclein found in Lewy bodies of Parkinson’s disease (PD). We aimed to examine whether plasma Ser129-phosphorylated α-synuclein (pS129-α-synuclein) is a surrogate marker of PD progression. This prospective study enrolled 170 participants (122 PD patients, 68 controls). We measured plasma levels of total and pS129-α-synuclein using immunomagnetic reduction-based immunoassay. PD patients received evaluations of motor and cognition at baseline and at a mean follow-up interval of three years. Changes in the Movement Disorder Society revision of the Unified Parkinson’s Disease Rating Scale motor score (MDS-UPDRS part III) and Mini-Mental State Examination (MMSE) score were used to assess motor and cognition progression. Our results showed that plasma levels of total and pS129-α-synuclein were significantly higher in PD patients than controls (total: 1302.3 ± 886.6 fg/mL vs. 77.8 ± 36.6 fg/mL, p < 0.001; pS129-α-synuclein: 12.9 ± 8.7 fg/mL vs. 0.8 ± 0.6 fg/mL, p < 0.001), as was the pS129-α-synuclein/total α-synuclein ratio (2.8 ± 1.1% vs. 1.1 ± 0.6%, p = 0.01). Among PD patients, pS129-α-synuclein levels were higher with advanced motor stage (p < 0.001) and correlated with MDS-UPDRS part III scores (r = 0.27, 95% CI: 0.09–0.43, p = 0.004). However, we found no remarkable difference between PD patients with and without dementia (p = 0.75). After a mean follow-up of 3.5 ± 2.1 years, PD patients with baseline pS129-α-synuclein > 8.5 fg/mL were at higher risk of motor symptom progression of at least 3 points in the MDS-UPDRS part III scores than those with pS129-α-synuclein < 8.5 fg/mL (p = 0.03, log rank test). In conclusion, our data suggest that plasma pS129-α-synuclein levels correlate with motor severity and progression, but not cognitive decline, in patients with PD.

Age-Dependent Relationship Between Plasma Aβ40 and Aβ42 and Total Tau Levels in Cognitively Normal Subjects

Both amyloid plaques and neurofibrillary tangles are pathological hallmarks in the brains of patients with Alzheimer’s disease (AD). However, the constituents of these hallmarks, amyloid beta (Aβ) 40, Aβ42, and total Tau (t-Tau), have been detected in the blood of cognitively normal subjects by using an immunomagnetic reduction (IMR) assay. Whether these levels are age-dependent is not known, and their interrelation remains undefined. We determined the levels of these biomarkers in cognitively normal subjects of different age groups. A total of 391 cognitively normal subjects aged 23–91 were enrolled from hospitals in Asia, Europe, and North America. Healthy cognition was evaluated by NIA-AA guidelines to exclude subjects with mild cognitive impairment (MCI) and AD and by cognitive assessment using the Mini Mental State Examination and Clinical Dementia Rating (CDR). We examined the effect of age on plasma levels of Aβ40, Aβ42, and t-Tau and the relationship between these biomarkers during aging. Additionally, we explored age-related reference intervals for each biomarker. Plasma t-Tau and Aβ42 levels had modest but significant correlations with chronological age (r = 0.127, p = 0.0120 for t-Tau; r = −0.126, p = 0.0128 for Aβ42), ranging from ages 23 to 91. Significant positive correlations were detected between Aβ42 and t-Tau in the groups aged 50 years and older, with Rho values ranging from 0.249 to 0.474. Significant negative correlations were detected between Aβ40 and t-Tau from age 40 to 91 (r ranged from −0.293 to −0.582) and between Aβ40 and Aβ42 in the age groups of 30–39 (r = −0.562, p = 0.0235), 50–59 (r = −0.261, p = 0.0142), 60–69 (r = −0.303, p = 0.0004), and 80–91 (r = 0.459, p = 0.0083). We also provided age-related reference intervals for each biomarker. In this multicenter study, age had weak but significant effects on the levels of Aβ42 and t-Tau in plasma. However, the age group defined by decade revealed the emergence of a relationship between Aβ40, Aβ42, and t-Tau in the 6th and 7th decades. Validation of our findings in a large-scale and longitudinal study is warranted.

Blood NfL: A biomarker for disease severity and progression in Parkinson disease

OBJECTIVE

To examine whether plasma neurofilament light chain (NfL) levels were associated with motor and cognitive progression in Parkinson disease (PD).

METHODS

This prospective follow-up study enrolled 178 participants, including 116 with PD, 22 with multiple system atrophy (MSA), and 40 healthy controls. We measured plasma NfL levels with electrochemiluminescence immunoassay. Patients with PD received evaluations of motor and cognition at baseline and at a mean follow-up interval of 3 years. Changes in the Unified Parkinson's Disease Rating Scale (UPDRS) part III motor score and Mini-Mental State Examination score were used to assess motor and cognition progression.

RESULTS

Plasma NfL levels were significantly higher in the MSA group than in the PD and healthy groups (35.8 ± 6.2, 17.6 ± 2.8, and 10.6 ± 2.3 pg/mL, respectively, p < 0.001). In the PD group, NfL levels were significantly elevated in patients with advanced Hoehn-Yahr stage and patients with dementia (p < 0.001). NfL levels were modestly correlated with UPDRS part III scores (r = 0.42, 95% confidence interval 0.46-0.56, p < 0.001). After a mean follow-up of 3.4 ± 1.2 years, a Cox regression analysis adjusted for age, sex, disease duration, and baseline motor or cognitive status showed that higher baseline NfL levels were associated with higher risks for either motor or cognition progression (p = 0.029 and p = 0.015, respectively).

CONCLUSIONS

Plasma NfL levels correlated with disease severity and progression in terms of both motor and cognitive functions in PD.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that plasma NfL level distinguishes PD from MSA and is a surrogate biomarker for PD progression.

The Social Functioning Scale for Alzheimer's Disease: A Short Informant-based Measure of Functional Status in Patients with Alzheimer's Disease in Taiwan

OBJECTIVE

Evaluating social-functioning impairments in patients with Alzheimer's disease (AD) objectively is essential for clinical service. However, the existing instruments lack representative content, consensus on purposes of use, and adequate scoring systems and samples. This study was thus to develop a social functioning scale for patients: the Social Functioning Scale for Alzheimer's Disease (SFSAD).

METHOD

Questionnaires were analyzed from 142 AD patients, 30 patients with amnestic mild cognitive impairment (aMCI), and 50 normal controls.

RESULTS

Based on the literature review and experts' opinions, the final scale includes 20 items in four subscales. The SFSAD showed high internal consistency coefficients (Cronbach's α = .97) and test-retest reliability (r = .99) coefficients. The content validity was desirable, and the criterion-related validity was demonstrated by a significant association with the MMSE, the IADL, and the Barthel ADL. The discriminant validity of the scale was also demonstrated as the level of social-functioning impairment was significantly related to the degree of dementia, and for construct validity, our findings supported the structure of the four-factor hypothesized model.

CONCLUSIONS

The SFSAD is thus a practical, psychometrically sound, and easy-to-administer measure to evaluate social functioning of AD and aMCI in brisk clinical settings.

An one-pot two-step automated synthesis of [18F]T807 injection, its biodistribution in mice and monkeys, and a preliminary study in humans

[18F]T807 is a potent tau protein imaging agent. In order to fulfill the demand from preclinical and clinical studies, we developed an automated one-pot two-step synthesis of this potent tau imaging agent and studied its stability, and dosimetry in mice and monkeys. We also conducted a preliminary study of this imaging agent in humans. Using this one-pot two-step method, the radiochemical yield (RCY) of [18F]T807 was 20.5 ± 6.1% (n = 15) at the end of bombardment (EOB) in a synthesis time of 70±5 min. The chemical and radiochemical purities were >90% and the specific activities were 151 ± 52 GBq/μmol. The quality of [18F]T807 synthesized by this method met the U.S. Pharmacopoeia (USP) criteria. The stability test showed that the [18F]T807 injection was stable at room temperature for up to 4 h after the end of synthesis (EOS). The estimated effective dose of the [18F]T807 injection extrapolated from monkeys was 19 μSv/MBq (n = 2), while the estimated effective doses of the [18F]T807 injection extrapolated from fasted and non-fasted mice were 123 ± 27 (n = 3) and 94 ± 19 (n = 4) μSv/MBq, respectively. This one-pot two-step automated method produced the [18F]T807 injection with high reproducibility and high quality. PET imaging and radiation dosimetry evaluation in mice and Formosan rock monkeys suggested that the [18F]T807 injection synthesized by this method is suitable for use in human PET imaging studies. Thus, this method could fulfill the demand for the [18F]T807 injection in both preclinical and clinical studies of tauopathies, especially for nearby study sites without cyclotrons.

Cognitive dysfunction predicts worse health-related quality of life for older stroke survivors: a nationwide population-based survey in Taiwan

OBJECTIVES

This study investigated the associations of cognitive status with specific/overall health-related quality of life (HRQoL) in older stroke survivors in Taiwan.

METHOD

A subsample of 592 older stroke survivors in a nationwide population-based survey of cognitive-dysfunction prevalencewas analyzed. HRQoL was assessed using the EuroQol five-dimension questionnaire (EQ-5D).

RESULTS

Stroke survivors with dementia were 5.60 times more likely to have mobility problems, 12.20 times to have self-care problems, 16.61 times to have problems in usual activities, 4.31 times to have pain/discomfort, and 3.28 times to have anxiety/depression than stroke survivors with normal cognitive function. Stroke survivors with mild cognitive dysfunction (MCD) were 2.57 times more likely to have mobility problems, 3.17 times to have self-care problems, 3.31 times to have problems in usual activities, 2.11 times to have pain/discomfort, and 2.35 times to have anxiety/depression than those with normal cognitive function. Both dementia (b = -15.13, p < .001) and MCD (b = -6.24, p < .001) significantly contributed to lower EQ-5D VAS; both dementia (b = -.15, p < .001) and MCD (b = -.10, p < .001) significantly contributed to lower EQ-5D index.

CONCLUSION

Dementia and MCD strongly predicted worse overall and specific HRQoL dimensions, especially self-care and usual activities for older stroke survivors.

Long-Term Storage Effects on Stability of Aβ1-40, Aβ1-42, and Total Tau Proteins in Human Plasma Samples Measured with Immunomagnetic Reduction Assays

Background

The stability of Alzheimer's disease (AD) biomarkers in plasma, measured by immunomagnetic reduction (IMR) after long-term storage at −80°C, has not been established before.

Method

Ninety-nine human plasma samples from 53 normal controls (NCs), 5 patients with amnestic mild cognitive impairment (aMCI), and 41 AD patients were collected. Each plasma sample was aliquoted and stored as single-use aliquots at −80°C. The baseline measurements for Aβ_1–40, Aβ_1–42, and total Tau protein (T-Tau) concentrations for each sample were done within 3 months of blood draw by IMR. They are referred to as baseline concentrations. A separate aliquot from each sample was assayed with IMR to assess the stability of the measured analytes during storage at −80°C between 1.1 and 5.4 years. This is referred to as a repeated result.

Results

IMR shows that plasma levels of Aβ_1–40 and Aβ_1–42 exhibit stability over 5-year storage at −80°C and that plasma levels of T-Tau are less stable (approximately 1.5 years).

Conclusion

Although the measured concentrations of T-Tau in human plasma may alter during storage, the diagnostic utility of the results are only slightly affected when the product of Aβ_1–42 and T-Tau concentrations are used. The results show that the overall agreement between baseline and repeated measurements in the ability of discriminating NCs from aMCI/AD patients is higher than 80%.

Relationships Between Cognitive Dysfunction and Health-Related Quality of Life Among Older Persons in Taiwan: A Nationwide Population-Based Survey

BACKGROUND

To examine the relationships between cognitive dysfunction status and quality of life.

METHODS

Secondary analysis of a nationwide population-based survey (≥65 years) in Taiwan. The 5-dimension EuroQoL questionnaire (EQ-5D) was completed by 10 013 participants.

RESULTS

Participants with mild cognitive impairment (MCI; odds ratio = 4.88), very mild dementia (VMD; 7.96), or dementia (32.85) were more likely than those with normal cognition to report self-care problems. Participants with MCI (3.86), VMD (9.26), or dementia (31.61) were more likely to have usual-activity problems, and those with MCI (3.04), VMD (3.82), or dementia (9.23) were more likely to have mobility problems. Participants with MCI (2.10 and 2.14), VMD (2.77 and 2.18), or dementia (3.04 and 3.02) were more likely to report pain/discomfort and anxiety/depression.

CONCLUSION

Dementia was negatively associated with EQ-5D, especially self-care, usual activities, and mobility. Mild cognitive impairment or VMD was also negatively associated, with VMD more negatively associated. Developing interventions for patients with specific cognitive dysfunctions is critical.

Mild cognitive impairment in combination with comorbid diabetes mellitus and hypertension is negatively associated with health-related quality of life among older persons in Taiwan

PURPOSE

To fill the gap in knowledge about associations of health-related quality of life (HRQoL) with comorbid diabetes mellitus (DM), hypertension (HTN), and/or mild cognitive impairment (MCI) in the elderly, we explored associations of comorbid DM, HTN, and/or MCI with HRQoL.

METHODS

Data for this study were from a population-based cross-sectional survey of elderly Taiwanese (≥ 65 years old). Participants (N = 4,634; 47.9% male) were categorized into eight chronic-illness groups: DM only (n = 224); HTN only (n = 1226); DM and HTN (n = 365); MCI only (n = 497); DM and MCI (n = 58); HTN and MCI (n = 303); DM, HTN, and MCI (n = 101); and none (healthy; n = 1860). Associations were examined between the eight chronic-illness groups and HRQoL (measured by EQ-5D scores) using binary logistic regression analyses and generalized linear models adjusted for covariates. Index scores were calculated from EQ-5D scores using Taiwan's general population-preference weights.

RESULTS

Compared to the healthy group, after adjusting covariates, MCI alone or with other comorbidities was significantly, negatively associated with HRQoL. Among all chronic-illness groups, comorbid DM, HTN, and MCI exhibited the lowest HRQoL. After adjusting covariates, between-group odds ratios for index scores were significant when comparing comorbid DM and MCI to DM only, comparing comorbid HTN and MCI to HTN only and comorbid DM, comparing HTN and MCI to comorbid DM and HTN, suggesting that MCI additively affects HRQoL.

CONCLUSIONS

HRQoL of older Taiwanese adults was negatively associated with having MCI. Thus, clinicians managing older persons with chronic illnesses should assess their cognitive function to identify high-risk groups needing HRQoL assistance.

Association of Polypharmacy With Mild Cognitive Impairment and Cognitive Ability: A Nationwide Survey in Taiwan

BACKGROUND

Polypharmacy, defined as the concomitant use of 5 or more medications, has a documented negative association with cognitive impairment such as delirium and is associated, potentially, with a higher risk of dementia. However, whether polypharmacy contributes to increased risk of mild cognitive impairment (MCI) or decreased cognitive capacity requires further investigation. This nationwide population survey investigated the association among polypharmacy, MCI, and dementia.

METHODS

Through random sampling based on the proportion of all Taiwan counties, subjects were recruited and received in-person interviews between December 2011 and March 2013. Demographic data and clinical information included medical histories, medication use, and mental status measured by the Taiwanese Mini-Mental State Examination (TMSE) and Clinical Dementia Rating (CDR). Data on lifestyle and habits were collected, and subjects were distributed to cognitively normal, MCI, or all-cause dementia groups based on criteria by the National Institute on Aging and the Alzheimer's Association.

RESULTS

A total of 7,422 people aged 65 years or older were recruited. After adjustment for age, sex, body mass index, education, medical comorbidities, and lifestyle and habits, polypharmacy was associated with a 1.75-fold increased odds of MCI and 2.33-fold increased odds of dementia. Polypharmacy was associated with a 0.51-point decrease in TMSE scores (P = .001) and a 0.10-point increase in CDR score (P < .001). Additionally, for those without specific vascular comorbidities, polypharmacy had a greatly more negative impact on cognitive capacity.

CONCLUSIONS

Polypharmacy is common in the elderly and is associated with significantly lower cognitive capacity and higher risks of MCI and dementia, especially for persons without diabetes, hypertension, hyperlipidemia, or cerebrovascular diseases.

Task-Switching Performance Improvements After Tai Chi Chuan Training Are Associated With Greater Prefrontal Activation in Older Adults

Studies have shown that Tai Chi Chuan (TCC) training has benefits on task-switching ability. However, the neural correlates underlying the effects of TCC training on task-switching ability remain unclear. Using task-related functional magnetic resonance imaging (fMRI) with a numerical Stroop paradigm, we investigated changes of prefrontal brain activation and behavioral performance during task-switching before and after TCC training and examined the relationships between changes in brain activation and task-switching behavioral performance. Cognitively normal older adults were randomly assigned to either the TCC or control (CON) group. Over a 12-week period, the TCC group received three 60-min sessions of Yang-style TCC training weekly, whereas the CON group only received one telephone consultation biweekly and did not alter their life style. All participants underwent assessments of physical functions and neuropsychological functions of task-switching, and fMRI scans, before and after the intervention. Twenty-six (TCC, N = 16; CON, N = 10) participants completed the entire experimental procedure. We found significant group by time interaction effects on behavioral and brain activation measures. Specifically, the TCC group showed improved physical function, decreased errors on task-switching performance, and increased left superior frontal activation for Switch > Non-switch contrast from pre- to post-intervention, that were not seen in the CON group. Intriguingly, TCC participants with greater prefrontal activation increases in the switch condition from pre- to post-intervention presented greater reductions in task-switching errors. These findings suggest that TCC training could potentially provide benefits to some, although not all, older adults to enhance the function of their prefrontal activations during task-switching.

Plasma β-Amyloids and Tau Proteins in Patients with Vascular Cognitive Impairment

Increases in plasma of β-amyloids (Aβ) and tau proteins have been noted in patients with Alzheimer's dementia (AD). Our study investigated the associations of plasma Aβ and tau proteins with dementia in stroke patients. This cross-sectional study recruited 24 controls (mean age: 67.4 ± 7.5 years, 33.3% male), 27 stroke patients without dementia (mean age: 70.7 ± 6.9 years, 60.7% male), 34 stroke patients with dementia (mean age: 78.3 ± 5.3 years, 45.5% male, Clinical Dementia Ranking (CDR): 1.46 ± 0.63), and 21 AD patients (mean age: 77.1 ± 9.1 years, 42.9% male, CDR: 1.43 ± 0.60) from a medical center. Dementia was defined as a CDR scale score of ≥ 1. The plasma levels of Aβ-40, Aβ-42, and tau were analyzed using immunomagnetic reduction. One-way analysis of variance was used to compare the differences in measured protein levels between the groups. The results indicated that plasma levels of tau and Aβ-42, but not Aβ-40, in stroke patients were significantly higher than in the controls. After adjustment for age, sex, diabetes mellitus, hypertension, and hyperlipidemia, only plasma level of Aβ-42 remained significantly higher in stroke patients with dementia than in those without dementia (OR 1.85, 1.25-2.75, p = 0.002). In summary, our results suggest that plasma Aβ-42 is a potential biomarker for dementia in stroke patients.

Diagnostic accuracy of Instrumental Activities of Daily Living for dementia in community-dwelling older adults

BACKGROUND

many people living with dementia remain underdiagnosed and unrecognised. Screening strategies are important for early detection.

OBJECTIVE

to examine whether the Lawton's Instrumental Activities of Daily Living (IADL) scale, compared with other cognitive screening tools-the Mini-Mental State Examination (MMSE), and the Ascertain Dementia 8-item Informant Questionnaire (AD8)-can identify older (≥ 65 years) adults with dementia.

DESIGN

population-based cross-sectional observational study.

SETTING

all 19 counties in Taiwan.

PARTICIPANTS

community-dwelling older adults (n = 10,340; mean age 74.87 ± 6.03).

METHODS

all participants underwent a structured in-person interview. Dementia was identified using National Institute on Aging-Alzheimer's Association core clinical criteria for all-cause dementia. Receiver operator characteristic curves were used to determine the discriminant abilities of the IADL scale, MMSE and AD8 to differentiate participants with and without dementia.

RESULTS

we identified 917 (8.9%) participants with dementia, and 9,423 (91.1%) participants without. The discriminant abilities of the MMSE, AD8 and IADL scale (cutoff score: 6/7; area under curve = 0.925; sensitivity = 89%; specificity = 81%; positive likelihood ratio = 4.75; accuracy = 0.82) were comparable. Combining IADL with AD8 scores significantly improved overall accuracy: specificity = 93%; positive likelihood ratio = 11.74; accuracy = 0.92.

CONCLUSIONS

our findings support using IADL scale to screen older community-dwelling residents for dementia: it has discriminant power comparable to that of the AD8 and MMSE. Combining the IADL and the AD8 improves specificity.

The Relation Between Brain Amyloid Deposition, Cortical Atrophy, and Plasma Biomarkers in Amnesic Mild Cognitive Impairment and Alzheimer's Disease

Background: Neuritic plaques and neurofibrillary tangles are the pathological hallmarks of Alzheimer’s disease (AD), while the role of brain amyloid deposition in the clinical manifestation or brain atrophy remains unresolved. We aimed to explore the relation between brain amyloid deposition, cortical thickness, and plasma biomarkers.

Methods: We used ¹¹C-Pittsburgh compound B-positron emission tomography to assay brain amyloid deposition, magnetic resonance imaging to estimate cortical thickness, and an immunomagnetic reduction assay to measure plasma biomarkers. We recruited 39 controls, 25 subjects with amnesic mild cognitive impairment (aMCI), and 16 subjects with AD. PiB positivity (PiB+) was defined by the upper limit of the 95% confidence interval of the mean cortical SUVR from six predefined regions (1.0511 in this study).

Results: All plasma biomarkers showed significant between-group differences. The plasma Aβ₄₀ level was positively correlated with the mean cortical thickness of both the PiB+ and PiB- subjects. The plasma Aβ₄₀ level of the subjects who were PiB+ was negatively correlated with brain amyloid deposition. In addition, the plasma tau level was negatively correlated with cortical thickness in both the PiB+ and PiB- subjects. Moreover, cortical thickness was negatively correlated with brain amyloid deposition in the PiB+ subjects. In addition, the cut-off point of plasma tau for differentiating between controls and AD was higher in the PiB- group than in the PiB+ group (37.5 versus 25.6 pg/ml, respectively). Lastly, ApoE4 increased the PiB+ rate in the aMCI and control groups.

Conclusion: The contributions of brain amyloid deposition to cortical atrophy are spatially distinct. Plasma Aβ₄₀ might be a protective indicator of less brain amyloid deposition and cortical atrophy. It takes more tau pathology to reach the same level of cognitive decline in subjects without brain amyloid deposition, and ApoE4 plays an early role in amyloid pathogenesis.