Alzheimer's Clinical Syndrome Research Articles

A Critical Review of Noninvasive Brain Stimulation Technologies in Alzheimer's Dementia and Primary Progressive Aphasia.

Multiple pharmacologic agents now have been approved in the United States and other countries as treatment to slow disease and clinical progression for Alzheimer's disease. Given these treatments have not been proven to lessen the cognitive deficits already manifested in the Alzheimer's Clinical Syndrome (ACS), and none are aimed for another debilitating dementia syndrome identified as primary progressive aphasia (PPA), there is an urgent need for new, safe, tolerable, and efficacious treatments to mitigate the cognitive deficits experienced in ACS and PPA. Noninvasive brain stimulation has shown promise for enhancing cognitive functioning, and there has been interest in its potential therapeutic value in ACS and PPA. This review critically examines the evidence of five technologies in ACS and PPA: transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), transcranial random noise stimulation (tRNS), repetitive transcranial magnetic stimulation (rTMS), and noninvasive vagus nerve stimulation (nVNS). Many randomized controlled trials of tDCS and rTMS report positive treatment effects on cognition in ACS and PPA that persist out to at least 8 weeks, whereas there are few trials for tACS and none for tRNS and nVNS. However, most positive trials did not identify clinically meaningful changes, underscoring that clinical efficacy has yet to be established in ACS and PPA. Much is still to be learned about noninvasive brain stimulation in ACS and PPA, and shifting the focus to prioritize clinical significance in addition to statistical significance in trials could yield greater success in understanding its potential cognitive effects and optimal parameters.

The associations between synaptic density and "A/T/N" biomarkers in Alzheimer's disease: An 18F-SynVesT-1 PET/MR study.

A newly developed SV2A radiotracer, 18F-SynVesT-1, was used in this study to investigate synaptic density and its association with Alzheimer's disease (AD) "A/T/N" biomarkers. The study included a cohort of 97 subjects, consisting of 64 patients with cognitive impairment (CI) and 33 individuals with normal cognition (CU). All subjects underwent 18F-SynVesT-1 PET/MR and 18F-florbetapir PET/CT scans. Additionally, a subgroup of individuals also underwent 18F-MK-6240, 18F-FDG PET/CT, plasma Aβ42/Aβ40 and p-tau181 tests. The differences in synaptic density between the groups and the correlations between synaptic density and AD "A/T/N" biomarkers were analyzed. The results showed that compared to the CU group, the CI with Aβ+ (CI+) group exhibited the most pronounced synapse loss in the hippocampus, with some loss also observed in the neocortex. Furthermore, synaptic density in the hippocampus and parahippocampal gyrus showed associations with AD biomarkers detected by both imaging and plasma tests in the CI group. The associations between synaptic density and FDG uptake and hippocampal volume were also observed in the CI+ group. In conclusion, the study demonstrated significant synaptic density loss, as measured by the promising tracer 18F-SynVesT-1, and its close correlation with "A/T/N" biomarkers in patients with both Alzheimer's clinical syndrome and pathological changes.

A - 17 Preliminary Neuropsychological Outcomes in a Randomized Controlled Trial of High-Definition Transcranial Direct Current Stimulation in Alzheimer's Clinical Syndrome.

The Alzheimer's Clinical Syndrome (ACS) is marked by global cognitive decline, and neural circuit dysfunction involving the dorsal anterior cingulate cortex (dACC) has been associated with some of the episodic memory and non-memory deficits in ACS. High-definition transcranial direct current stimulation (HD-tDCS) is a promising noninvasive treatment to lessen cognitive deficits in ACS, and this preliminary double-blinded trial examined whether HD-tDCS targeting the dACC could improve cognitive performance in ACS. Ten patients diagnosed with ACS (M age = 71.500; SD = 9.755) were randomized to receive sham (n = 2), 1mA (n = 5), or 2mA (n = 3) multi-electrode (4 cathodes x 1 anode) HD-tDCS for 10 daily sessions. Episodic memory, language, attention, and executive function measures were administered pre- and immediately post-treatment, and composite memory and non-memory scores were calculated. Paired samples t-tests examined significant differences (p < 0.05) between pre-treatment and post-treatment scores for each HD-tDCS group. For all three HD-tDCS groups, there were no significant improvements between pre-treatment and post-treatment scores for memory or non-memory abilities (p's > 0.05). This preliminary study showed that HD-tDCS applied over the dACC was unassociated with cognitive improvement in ACS. Future research with a larger sample will be needed to inform if this configuration of HD-tDCS could ameliorate cognitive deficits in ACS. Moreover, evaluation of HD-tDCS applied over other brain regions may yield additional insights, and a critical step will be to identify whether any clinical characteristics such as disease stage may influence the response to stimulation in ACS.

Comparison Of Potential Plasma Biomarkers In Alzheimer's Disease And Neurodegenerative Dementias In Pakistani Population.

This study aimed to compare the mean plasma levels of Amyloid β42, Phosphorylated Tau and Neurofilament Light chain in patients diagnosed with Alzheimer's Clinical Syndrome (ACS), and other neurodegenerative dementias to find affordable and less-invasive means of diagnosing Alzheimer's disease (AD) early in its course. Blood samples of 36 subjects presenting with cognitive decline to the neurology OPDs of Dow and Civil hospitals, Karachi, were centrifuged, and plasma was stored at -80℃. Before analysis, it was thawed at 4℃ and protein levels were measured through ELISA. Two-thirds of the patients were females but age distribution across both the groups was not significantly different (p=0.21). No difference was observed in the mean plasma concentrations of Aβ42, P-Tau, and NFL between the two groups (p-values 0.78 and 0.27 and 0.09 respectively). Our study suggests that despite being promising in CSF, Aβ42, P-Tau, and NFL cannot differentiate between different neurodegenerative dementias when measured in plasma.

Plasma levels of phosphorylated tau and neurofilament light chain as potential biomarkers for Alzheimer’s disease: A biochemical analysis in Pakistani population

The National Institute on Aging-Alzheimer's Association's research framework in 2018 proposed a molecular construct for the diagnosis of Alzheimer’s disease (AD). Nonetheless, the clinical exclusionary strategy is still the mainstay of AD diagnosis in Pakistan. We looked at the plasma levels of amyloid beta-42 (Aβ-42), phosphorylated tau (P-tau), and neurofilament light (NFL) in patients with Alzheimer's clinical syndrome (ACS) and healthy controls (HC) from the Pakistani population to keep pace with the global efforts towards establishing accessible and affordable biochemical diagnostic markers for AD in Pakistan.Consultant neurologists screened patients who presented with cognitive impairment to three large tertiary care hospitals in Karachi, and after receiving informed consent, recruited participants with ACS and HC from the same facilities. We collected 5cc of blood in EDTA tubes along with demographic and lifestyle information of the subjects. Plasma aliquots were stored at −80°C after centrifugation. For analysis it was thawed at 4℃ and levels of the three proteins were measured through ELISA.Data from 28 ACS patients and 28 age matched healthy controls were evaluated. Among demographic factors, education and depression were related with health status (p = 0.03 and 0.003, respectively). NFL and P-tau mean values demonstrated a significant difference between the ACS and control groups (p = 0.003 and 0.006), however Aβ42 did not (p = 0.114). ROC analysis showed that plasma P-tau and NFL, with AUCs of 0.717 and 0.735, respectively, could substantially distinguish ACS from the HC group (p = 0.007 and 0.003, respectively). Both plasma P-tau (r = −0.389; p = 0.004) and NFL (r = −0.424; p = 0.001) levels were significantly and negatively correlated with individuals' MMSE scores. NFL and plasma P-tau show promise in differentiating AD patients from healthy individuals. However, similar larger studies are needed to validate our findings.

Predicting amyloid PET and tau PET stages with plasma biomarkers.

Staging the severity of Alzheimer's disease pathology using biomarkers is useful for therapeutic trials and clinical prognosis. Disease staging with amyloid and tau PET has face validity; however, this would be more practical with plasma biomarkers. Our objectives were, first, to examine approaches for staging amyloid and tau PET and, second, to examine prediction of amyloid and tau PET stages using plasma biomarkers. Participants (n = 1136) were enrolled in either the Mayo Clinic Study of Aging or the Alzheimer's Disease Research Center; had a concurrent amyloid PET, tau PET and blood draw; and met clinical criteria for cognitively unimpaired (n = 864), mild cognitive impairment (n = 148) or Alzheimer's clinical syndrome with dementia (n = 124). The latter two groups were combined into a cognitively impaired group (n = 272). We used multinomial regression models to estimate discrimination [concordance (C) statistics] among three amyloid PET stages (low, intermediate, high), four tau PET stages (Braak 0, 1-2, 3-4, 5-6) and a combined amyloid and tau PET stage (none/low versus intermediate/high severity) using plasma biomarkers as predictors separately within unimpaired and impaired individuals. Plasma analytes, p-tau181, Aβ1-42 and Aβ1-40 (analysed as the Aβ42/Aβ40 ratio), glial fibrillary acidic protein and neurofilament light chain were measured on the HD-X Simoa Quanterix platform. Plasma p-tau217 was also measured in a subset (n = 355) of cognitively unimpaired participants using the Lilly Meso Scale Discovery assay. Models with all Quanterix plasma analytes along with risk factors (age, sex and APOE) most often provided the best discrimination among amyloid PET stages (C = 0.78-0.82). Models with p-tau181 provided similar discrimination of tau PET stages to models with all four plasma analytes (C = 0.72-0.85 versus C = 0.73-0.86). Discriminating a PET proxy of intermediate/high from none/low Alzheimer's disease neuropathological change with all four Quanterix plasma analytes was excellent but not better than p-tau181 only (C = 0.88 versus 0.87 for unimpaired and C = 0.91 versus 0.90 for impaired). Lilly p-tau217 outperformed the Quanterix p-tau181 assay for discriminating high versus intermediate amyloid (C = 0.85 versus 0.74) but did not improve over a model with all Quanterix plasma analytes and risk factors (C = 0.85 versus 0.83). Plasma analytes along with risk factors can discriminate between amyloid and tau PET stages and between a PET surrogate for intermediate/high versus none/low neuropathological change with accuracy in the acceptable to excellent range. Combinations of plasma analytes are better than single analytes for many staging predictions with the exception that Quanterix p-tau181 alone usually performed equivalently to combinations of Quanterix analytes for tau PET discrimination.

Outcome measures for Alzheimer's disease: A global inter-societal Delphi consensus.

We aim to provide guidance on outcomes and measures for use in patients with Alzheimer's clinical syndrome. A consensus group of 20 voting members nominated by 10 professional societies, and a non-voting chair, used a Delphi approach and modified GRADE criteria. Consensus was reached on priority outcomes (n=66), measures (n=49) and statements (n=37) across nine domains. A number of outcomes and measurement instruments were ranked for: Cognitive abilities; Functional abilities/dependency; Behavioural and neuropsychiatric symptoms; Patient quality of life (QoL); Caregiver QoL; Healthcare and treatment-related outcomes; Medical investigations; Disease-related life events; and Global outcomes. This work provides indications on the domains and ideal pertinent measurement instruments that clinicians may wish to use to follow patients with cognitive impairment. More work is needed to develop instruments that are more feasible in the context of the constraints of clinical routine.

Subjective Cognitive Complaints: Comparing the Relation between Self-Reported Versus Informant-Reported Subjective Cognitive Complaints and Cognitive Performances in Cognitively Unimpaired, Mild Cognitive Impairment and Populations with Dementia.

Subjective cognitive decline is proposed to be associated with future mild cognitive impairment and dementia. A better understanding of the roles of self-reported and informant-reported subjective cognitive complaints can provide a more delicate picture in dementia recognition and early diagnosis. To evaluate the accuracy of self-reported and informant-reported subjective cognitive complaints and the relation of subjective cognitive complaints and neuropsychological function in cognitively unimpaired, mild cognitive impairment and populations with dementia. We conducted a cross-sectional survey and evaluate the relations between subjective cognitive complaint scores and cognitive function in the different diagnostic groups. We recruited individuals diagnosed with cognitively unimpaired or mild cognitive impairment or dementia with Alzheimer's clinical syndrome from a memory clinic in a tertiary medical center in Taiwan. Participants, age greater than 50 years old, were enrolled in this study. Participants' informants were also enrolled for the cognitive questionnaire assessment. Participants' and informants' subjective cognitive complaint scores were collected based on a 12-item questionnaire. Neuropsychological assessments of global cognitive function, memory, language, executive function, visuospatial function and calculation were performed. The relations between subjective cognitive complaint scores and cognitive function in the different diagnostic groups were assessed by linear regression model. There were 1536 individuals and 1028 informants enrolled in this study. Self-reported subjective cognitive complaint scores from early and late mild cognitive impairment and dementia with Alzheimer's clinical syndrome participants showed no significant differences, but informants' subjective cognitive complaint scores showed a significant increase. Informant-reported subjective cognitive complaint scores related to neuropsychological tests in population with dementia. Neither self-reported nor informant-reported subjective cognitive complaint scores related to neuropsychological tests in cognitively unimpaired and mild cognitive impairment populations. Self-reported subjective cognitive complaints alone may not be sufficient to demonstrate clinical significance in different stages of cognitive impairment. Incorporating informant-reported subjective cognitive complaints, along with considering individual's anxiety and depressive status, are crucial in assessing cognitive statuses in clinical practice.

CSF P-Tau181 and Other Biomarkers in Patients With Neuronal Intranuclear Inclusion Disease.

CSF tau phosphorylated at threonine 181 (p-tau181) is a widely used biomarker for Alzheimer disease (AD) and has recently been regarded to reflect β-amyloid and/or p-tau deposition in the AD brain. Neuronal intranuclear inclusion disease (NIID) is a neurodegenerative disease characterized by intranuclear inclusions in neurons, glial cells, and other somatic cells. Symptoms include dementia, neuropathy, and others. CSF biomarkers were not reported. The objective of this study was to investigate whether CSF biomarkers including p-tau181 are altered in patients with NIID. This was a retrospective observational study. CSF concentrations of p-tau181, total tau, amyloid-beta 1-42 (Aβ42), monoamine metabolites homovanillic acid (HVA), and 5-hydroxyindole acetic acid (5-HIAA) were compared between 12 patients with NIID, 120 patients with Alzheimer clinical syndrome biologically confirmed based on CSF biomarker profiles, and patients clinically diagnosed with other neurocognitive disorders (dementia with Lewy bodies [DLB], 24; frontotemporal dementia [FTD], 13; progressive supranuclear palsy [PSP], 21; and corticobasal syndrome [CBS], 13). Amyloid PET using Pittsburgh compound B (PiB) was performed in 6 patients with NIID. The mean age of patients with NIID, AD, DLB, FTD, PSP, and CBS was 71.3, 74.6, 76.8, 70.2, 75.5, and 71.9 years, respectively. CSF p-tau181 was significantly higher in NIID (72.7 ± 24.8 pg/mL) compared with DLB, PSP, and CBS and was comparable between NIID and AD. CSF p-tau181 was above the cutoff value (50.0 pg/mL) in 11 of 12 patients with NIID (91.7%). Within these patients, only 2 patients showed decreased CSF Aβ42, and these patients showed negative or mild local accumulation in PiB PET, respectively. PiB PET scans were negative in the remaining 4 patients tested. The proportion of patients with increased CSF p-tau181 and normal Aβ42 (A-T+) was significantly higher in NIID (75%) compared with DLB, PSP, and CBS (4.2%, 4.8%, and 7.7%, respectively). CSF HVA and 5-HIAA concentrations were significantly higher in patients with NIID compared with disease controls. CSF p-tau181 was increased in patients with NIID without amyloid accumulation. Although the deposition of p-tau has not been reported in NIID brains, the molecular mechanism of tau phosphorylation or secretion of p-tau may be altered in NIID.

Language performance as a prognostic factor for developing Alzheimer's clinical syndrome and mild cognitive impairment: Results from the population-based HELIAD cohort.

There is limited research on the prognostic value of language tasks regarding mild cognitive impairment (MCI) and Alzheimer's clinical syndrome (ACS) development in the cognitively normal (CN) elderly, as well as MCI to ACS conversion. Participants were drawn from the population-based Hellenic Longitudinal Investigation of Aging and Diet (HELIAD) cohort. Language performance was evaluated via verbal fluency [semantic (SVF) and phonemic (PVF)], confrontation naming [Boston Naming Test short form (BNTsf)], verbal comprehension, and repetition tasks. An additional language index was estimated using both verbal fluency tasks: SVF-PVF discrepancy. Cox proportional hazards analyses adjusted for important sociodemographic parameters (age, sex, education, main occupation, and socioeconomic status) and global cognitive status [Mini Mental State Examination score (MMSE)] were performed. A total of 959 CN and 118 MCI older (>64 years) individuals had follow-up investigations after a mean of ∼3 years. Regarding the CN group, each standard deviation increase in the composite language score reduced the risk of ACS and MCI by 49% (8-72%) and 32% (8-50%), respectively; better SVF and BNTsf performance were also independently associated with reduced risk of ACS and MCI. On the other hand, using the smaller MCI participant set, no language measurement was related to the risk of MCI to ACS conversion. Impaired language performance is associated with elevated risk of ACS and MCI development. Better SVF and BNTsf performance are associated with reduced risk of ACS and MCI in CN individuals, independent of age, sex, education, main occupation, socioeconomic status, and MMSE scores at baseline.

Sensitivity of the Social Behavior Observer Checklist to Early Symptoms of Patients With Frontotemporal Dementia.

Changes in social behavior are common symptoms of frontotemporal lobar degeneration (FTLD) and Alzheimer disease syndromes. For early identification of individual patients and differential diagnosis, sensitive clinical measures are required that are able to assess patterns of behaviors and detect syndromic differences in both asymptomatic and symptomatic stages. We investigated whether the examiner-based Social Behavior Observer Checklist (SBOCL) is sensitive to early behavior changes and reflects disease severity within and between neurodegenerative syndromes. Asymptomatic individuals and patients with neurodegenerative disease were selected from the multisite ALLFTD cohort study. In a sample of participants with at least 1 time point of SBOCL data, we investigated whether the Disorganized, Reactive, and Insensitive subscales of the SBOCL change as a function of disease stage within and between these syndromes. In a longitudinal subsample with both SBOCL and neuroimaging data, we examined whether change over time on each subscale corresponds to progressive gray matter atrophy. A total of 1,082 FTLD pathogenic variant carriers and noncarriers were enrolled (282 asymptomatic, 341 behavioral variant frontotemporal dementia, 114 semantic and 95 nonfluent variant primary progressive aphasia, 137 progressive supranuclear palsy, and 113 Alzheimer disease syndrome). The Disorganized score increased between asymptomatic to very mild (p = 0.016, estimate = -1.10, 95% CI = -1.99 to -0.22), very mild to mild (p = 0.013, estimate = -1.17, 95% CI = -2.08 to -0.26), and mild to moderate/severe (p < 0.001, estimate = -2.00, 95% CI = -2.55 to -1.45) disease stages in behavioral variant frontotemporal dementia regardless of pathogenic variant status. Asymptomatic GRN pathogenic gene variant carriers showed more reactive behaviors (preoccupation with time: p = 0.001, estimate = 1.11, 95% CI = 1.06 to 1.16; self-consciousness: p = 0.003, estimate = 1.77, 95% CI = 1.52 to 2.01) than asymptomatic noncarriers (estimate = 1.01, 95% CI = 0.98 to 1.03; estimate = 1.31, 95% CI = 1.20 to 1.41). The Insensitive score increased to a clinically abnormal level in advanced stages of behavioral variant frontotemporal dementia (p = 0.003, estimate = -0.73, 95% CI = -1.18 to -0.29). Higher scores on each subscale corresponded with higher caregiver burden (p < 0.001). Greater change over time corresponded to greater fronto-subcortical atrophy in the semantic-appraisal and fronto-parietal intrinsically connected networks. The SBOCL is sensitive to early symptoms and reflects disease severity, with some evidence for progression across asymptomatic and symptomatic stages of FTLD syndromes; thus, it may hold promise for early measurement and monitoring of behavioral symptoms in clinical practice and treatment trials. This study provides Class II evidence that the SBOCL is sensitive to early behavioral changes in FTLD pathogenic variants and early symptomatic individuals in a highly educated patient cohort.

CSF-Derived CD4+ T-Cell Diversity Is Reduced in Patients With Alzheimer Clinical Syndrome.

Background and ObjectivesPatients with Alzheimer dementia display evidence of amyloid-related neurodegeneration. Our focus was to determine whether such patients also display evidence of a disease-targeting adaptive immune response mediated by CD4+ T cells. To test this hypothesis, we evaluated the CSF immune profiles of patients with Alzheimer clinical syndrome (ACS), who display clinically defined dementia.MethodsInnate and adaptive immune profiles of patients with ACS were measured using multicolor flow cytometry. CSF-derived CD4+ and CD8+ T-cell receptor repertoire genetics were measured using next-generation sequencing. Brain-specific autoantibody signatures of CSF-derived antibody pools were measured using array technology or ELISA. CSF from similar-age healthy controls (HCs) was used as a comparator cohort.ResultsInnate cells were expanded in the CSF of patients with ACS in comparison to HCs, and innate cell expansion increased with age in the patients with ACS, but not HCs. Despite innate cell expansion in the CSF, the frequency of total CD4+ T cells reduced with age in the patients with ACS. T-cell receptor repertoire genetics indicated that T-cell clonal expansion is enhanced, and diversity is reduced in the patients with ACS compared with similar-age HCs.DiscussionExamination of CSF indicates that CD4+ T cell–mediated adaptive immune responses are altered in patients with ACS. Understanding the underlying mechanisms affecting adaptive immunity will help move us toward the goal of slowing cognitive decline.

Oculomotor Behaviors and Integrative Memory Functions in the Alzheimer's Clinical Syndrome.

Biological information drawn from eye-tracking metrics is providing evidence regarding drivers of cognitive decline in Alzheimer's disease. In particular, pupil size has proved useful to investigate cognitive performance during online activities. To investigate the oculomotor correlates of impaired performance of patients with mild Alzheimer's Clinical Syndrome (ACS) on a recently developed memory paradigm, namely the Short-Term Memory Binding Test (STMBT). We assessed a sample of eighteen healthy controls (HC) and eighteen patients with a diagnosis of mild ACS with the STMBT while we recorded their oculomotor behaviors using pupillometry and eye-tracking. As expected, a group (healthy controls versus ACS) by condition (Unbound Colours versus Bound Colours) interaction was found whereby behavioral group differences were paramount in the Bound Colours condition. Healthy controls' pupils dilated significantly more in the Bound Colours than in the Unbound Colours condition, a discrepancy not observed in ACS patients. Furthermore, ROC analysis revealed the abnormal pupil behaviors distinguished ACS patients from healthy controls with values of sensitivity and specify of 100%, thus outperforming both recognition scores and gaze duration. The biological correlates of Short-Term Memory Binding impairments appear to involve a network much wider than we have thought to date, which expands across cortical and subcortical structures. We discuss these findings focusing on their implications for our understanding of neurocognitive phenotypes in the preclinical stages of Alzheimer's disease and potential development of cognitive biomarkers that can support ongoing initiatives to prevent dementia.

The relationship of glucose-stimulated insulin secretion to cerebral glucose metabolism and cognition in healthy middle-aged and older adults

Insulin resistance (IR) has been related to reduced cerebral glucose metabolism in regions identified as hypometabolic in Alzheimer's clinical syndrome. Insulin secretion (IS) has been less studied than IR despite findings that decreased IS is an early indicator of future type 2 diabetes and a potential predictor of Alzheimer's clinical syndrome. We investigated whether higher IR and lower IS would be associated with greater age-related reductions in regional cerebral glucose metabolism and worse cognitive performance. Two-hour oral glucose tolerance testing and 18F-fluorodeoxyglucose positron emission tomography were performed on 1–2 occasions on a sample of healthy middle-aged and older adults from the Wisconsin Alzheimer's Disease Research Center. Neuropsychological tests were completed during Alzheimer's Disease Research Center Clinical Core visits. Pattern of findings suggested that lower (not higher) IS was related to higher regional cerebral glucose metabolism in middle aged but not older adults, and lower (not higher) IS was also related to better immediate recall. In the context of healthy insulin sensitivity, lower IS may be beneficial to brain health.

Association Between Metformin and Prevention of Dementia in T2DM Adult Patients

Introduction: In 2020 the World Health Organization estimated that the number of people with dementia was 50 million in the world. Furthermore, it is expected about 10 million new cases every year. Alzheimer’s disease (AD) is the most common form of dementia, which represents more than 50% of the cases. Type 2 diabetes mellitus (T2DM) is a major risk factor for AD and dementia. Even in people without clinical dementia, diabetes is associated with decreased cognitive performance and with increased brain atrophy. If comparing general population and people with diabetes, patients with T2DM had a 73% higher risk of developing dementia and a 56% increased risk of developing AD. Typically, the first medication prescribed for T2DM is metformin and it has been associated with the reduction of cognitive decline and the risk of dementia in patients with T2DM when compared with diabetic patients without medication. A randomized, double-blinded, placebo-controlled study demonstrated that during metformin treatment there was an improvement of executive functioning, learning, memory, and attentional abilities. A possible explanations for the protective effect of metformin in patients with T2DM is that it prevents hyperinsulinemia and the formation of amyloid-β plaques in the brain and the onset of AD. Metformin does not only decrease the plasma glucose level in several mechanisms, but it also characterized to beneficially effect serum lipid profiles, reduce inflammatory cell adhesion to endothelium, and exert anti-inflammatory, anti-apoptotic and anti-oxidative properties. Method: A Clinical Scientific Research was made about correlation among dementia and metformin. Were searched and found in PubMed a total of 61 articles between 2015–2020, but only free access and those who correlated metformin and dementia were used. Results: Studies showed that T2DM patients taking metformin had decreased risk of developing dementia or AD if compared to others diabetic patients that were not taking metformin. However, it is being hard to test antidiabetic therapies in AD, because the mechanisms which tie T2DM to Alzheimer clinical syndrome are not totally known. Therefore, to be as effective as possible it is necessary to treat the patients before they develop extensive amyloid and tau tangle burden. Conclusion: Diabetic patients taking metformin have a protector factor to don’t develop dementia or AD, when compared to those who don’t take metformin since they started the treatment before accumulation of amyloid and tau protein in the brain.

Altered resting state activity associated with anosognosia in Alzheimer's clinical syndrome: Findings from the DELCODE study

AbstractBackgroundAnosognosia, or lack of awareness of cognitive impairments, is a common phenomenon in Alzheimer’s clinical syndrome (ACS). Not just patients with dementia(AD) but also patients with mild cognitive impairment(MCI) may have diminished awareness of their deficits. Previous studies have shown that anosognosia is associated with dysfunction and reduced connectivity in the default mode network of the brain and insula. However, less is known about the level of awareness and its neural correlations in individuals with subjective cognitive decline(SCD). This study investigated the underlying neural mechanisms of anosognosia at different stages of ACS.Method504 participants (59 AD, 88 MCI, 176 SCD and 181 healthy controls[HCs]) from the DELCODE, a longitudinal multicenter observational study, were included. Cognitive awareness was assessed with a discrepancy score between participants’ report about their own cognitive abilities and report provided by informants. Resting‐state fMRI data of all subjects were analyzed and the fractional amplitude of low frequency fluctuations(fALFF) were calculated as an index of regional spontaneous neural activity. Voxel‐ and clusterwise correlations were conducted using SPM12, controlling for multiple comparisons(GRF). Age, gender and site (9 sites total) were controlled for in each statistical model.ResultCompared to HCs, subjects with SCD showed heightened awareness for cognitive changes and on the contrary, MCI and AD subjects had higher anosognosia scores. Within‐group comparisons revealed that MCI subjects with anosognosia had reduced neural activity in the left anterior insula compared to MCI subjects without anosognosia (GRF corrected, p&lt;0.005). Moreover, SCD subjects with heightened awareness showed reduced right amygdala activity(GRF corrected, p&lt;0.005), whereas higher activity was observed in the dorsomedial prefrontal cortex (dmPFC) compared to SCD subjects without heightened awareness(GRF corrected, p&lt;0.001).ConclusionThis is the first study evaluating the association between cognitive awareness at different stages of ACS and regional neural activity using fALFF. Consistent with prior findings, MCI subjects with anosognosia showed reduced neural activity in the anterior insula. Heightened awareness in SCD was associated with higher activity in the dmPFC. Future work should examine the interplay between amyloid pathology and fALFF measures for cognitive awareness, in order to specify neural correlates of cognitive awareness in the Alzheimer’s continuum.

Neuropathologic burden and the degree of frailty in relation to global cognition and dementia.

To test the hypothesis that degree of frailty and neuropathologic burden independently contribute to global cognition and odds of dementia. This was a secondary analysis of a prospective cohort study of older adults living in Illinois. Participants underwent an annual neuropsychological and clinical evaluation. We included 625 participants (mean age 89.7 ± 6.1 years; 67.5% female) who died and underwent autopsy. We quantified neuropathology using an index measure of 10 neuropathologic features: β-amyloid deposition, hippocampal sclerosis, Lewy bodies, tangle density, TDP-43, cerebral amyloid angiopathy, arteriolosclerosis, atherosclerosis, and gross and chronic cerebral infarcts. Clinical consensus determined dementia status, which we coded as no cognitive impairment, mild cognitive impairment, or dementia. A battery of 19 tests spanning multiple domains quantified global cognition. We operationalized frailty using a 41-item frailty index. We employed regression analyses to model relationships between neuropathology, frailty, and dementia. Both frailty and a neuropathology index were independently associated with global cognition and dementia status. These results held after controlling for traditional pathologic measures in a sample of participants with Alzheimer clinical syndrome. Frailty improved the fit of the model for dementia status (χ2[2] 72.64; p < 0.0001) and explained an additional 11%-12% of the variance in the outcomes. Dementia is a multiply determined condition, to which both general health, as captured by frailty, and neuropathology significantly contribute. This integrative view of dementia and health has implications for prevention and therapy; specifically, future research should evaluate frailty as a means of dementia risk reduction.

Profiles of cognitive impairment in the continuum from normal cognition to Alzheimer's clinical syndrome: Contributions of the short-term memory binding tests.

Short-term memory binding (STMB) tests assess conjunctive binding, in which participants should remember the integration of features, such as shapes (or objects) and colors, forming a unique representation in memory. In this study, we investigated two STMB paradigms: change detection (CD) and free recall (FR). To investigate the cognitive profile in the CD and FR tasks of three diagnostic groups: cognitively unimpaired (CU), mild cognitive impairment (MCI), and Alzheimer's clinical syndrome (ACS). In addition, we aimed to calculate and compare the accuracy of the CD and FR tasks to identify MCI and ACS. Participants were 24 CU, 24 MCI, and 37 ACS. The cognitive scores of the clinical groups were compared using analysis of variance (ANOVA) and receiver-operating characteristic (ROC) analyses were carried out to verify the accuracy of the STMB tasks. In the CD task, CU was different from MCI and ACS (CU > MCI = ACS), while in the FR task all groups were different (CU > MCI > ACS). The ROC analyses showed an area under the curve (AUC) of 0.855 comparing CU with MCI for the CD task and 0.975 for the FR. The AUC comparing CU and ACS was 0.924 for the CD and 0.973 for the FR task. The FR task showed better accuracy to identify MCI patients, and the same accuracy to detect ACS. The present findings indicate that impairments in CD and FR of bound representations are features of the cognitive profiles of MCI and ACS patients.

Dysautonomia in Alzheimer's Disease.

Alzheimer's disease is the most common neurodegenerative disorder, and its prevalence increases with age. Although there is a large amount of scientific literature focusing on Alzheimer's disease cardinal cognitive features, autonomic nervous system dysfunction remains understudied despite being common in the elderly. In this article, we reviewed the evidence for autonomic nervous system involvement in Alzheimer's disease. We identified four major potential causes for dysautonomia in Alzheimer's disease, out of which two are well-studied (comorbidities and medication) and two are rather hypothetical (Alzheimer's pathology and brain co-pathology). Although there appears to be some evidence linking Alzheimer's disease pathology to autonomic nervous system dysfunction, there is an important gap between two types of studies; histopathologic studies do not address dysautonomia manifestations, whereas clinical studies do not employ histopathologic diagnostic confirmation. Moreover, brain co-pathology is emerging as an important confounding factor. Therefore, we consider the correlation between dysautonomia and Alzheimer's disease to be an open question that needs further study. Nevertheless, given its impact on morbidity and mortality, we emphasize the importance of assessing autonomic dysfunction in patients with Alzheimer clinical syndrome.

Association of Sleep-Disordered Breathing With Alzheimer Disease Biomarkers in Community-Dwelling Older Adults

Increasing evidence suggests that sleep-disordered breathing (SDB) increases the risk of developing Alzheimer clinical syndrome. However, the brain mechanisms underlying the link between SDB and Alzheimer disease are still unclear. To determine which brain changes are associated with the presence of SDB in older individuals who are cognitively unimpaired, including changes in amyloid deposition, gray matter volume, perfusion, and glucose metabolism. This cross-sectional study was conducted using data from the Age-Well randomized clinical trial of the Medit-Ageing European project, acquired between 2016 and 2018 at Cyceron Center in Caen, France. Community-dwelling older adults were assessed for eligibility and were enrolled in the Age-Well clinical trial if they did not meet medical or cognitive exclusion criteria and were willing to participate. Participants who completed a detailed neuropsychological assessment, polysomnography, a magnetic resonance imaging, and florbetapir and fluorodeoxyglucose positron emission tomography scans were included in the analyses. Based on an apnea-hypopnea index cutoff of 15 events per hour, participants were classified as having SDB or not. Voxelwise between-group comparisons were performed for each neuroimaging modality, and secondary analyses aimed at identifying which SDB parameter (sleep fragmentation, hypoxia severity, or frequency of respiratory disturbances) best explained the observed brain changes and assessing whether SDB severity and/or SDB-associated brain changes are associated with cognitive and behavioral changes. Of 157 participants initially assessed, 137 were enrolled in the Age-Well clinical trial, and 127 were analyzed in this study. The mean (SD) age of the 127 participants was 69.1 (3.9) years, and 80 (63.0%) were women. Participants with SDB showed greater amyloid burden (t114 = 4.51; familywise error-corrected P = .04; Cohen d, 0.83), gray matter volume (t119 = 4.12; familywise error-corrected P = .04; Cohen d, 0.75), perfusion (t116 = 4.62; familywise error-corrected P = .001; Cohen d, 0.86), and metabolism (t79 = 4.63; familywise error-corrected P = .001; Cohen d, 1.04), overlapping mainly over the posterior cingulate cortex and precuneus. No association was found with cognition, self-reported cognitive and sleep difficulties, or excessive daytime sleepiness symptoms. The SDB-associated brain changes in older adults who are cognitively unimpaired include greater amyloid deposition and neuronal activity in Alzheimer disease-sensitive brain regions, notably the posterior cingulate cortex and precuneus. These results support the need to screen and treat for SDB, especially in asymptomatic older populations, to reduce Alzheimer disease risk. ClinicalTrials.gov Identifier: NCT02977819.