Citations

Abstract Background Subjective cognitive decline (SCD) has gained recent interest as a potential harbinger of neurodegenerative diseases such as Alzheimer’s disease (AD) and cerebrovascular disease (CVD). In addition, SCD can be related to depressive symptomatology. However, the association between AD and CVD biomarkers, depressive symptomatology, and SCD is still unclear. We investigated the association of AD and CVD biomarkers and depressive symptomatology with SCD in individuals with subjective memory complaints (SCD-memory group) and individuals with subjective concentration complaints (SCD-concentration group). Methods We recruited a population-based cohort of 217 individuals (all aged 70 years, 53% female participants, 119 SCD-memory individuals, 23 SCD-concentration individuals, and 89 controls). AD and CVD were assessed through cerebrospinal fluid levels of the Aβ42/40 ratio and phosphorylated tau, and white matter signal abnormalities on magnetic resonance imaging, respectively. Associations between biomarkers, depressive symptomatology, and SCD were tested via logistic regression and correlation analyses. Results We found a significant association between depressive symptomatology with SCD-memory and SCD-concentration. Depressive symptomatology was not associated with AD and CVD biomarkers. Both the phosphorylated tau biomarker and depressive symptomatology predicted SCD-memory, and the Aβ42/40 ratio and depressive symptomatology predicted SCD-concentration. Conclusions The role of depressive symptomatology in SCD may differ depending on the stage within the spectrum of preclinical AD (as determined by amyloid-beta and tau positivity), and does not seem to reflect AD pathology. Our findings contribute to the emerging field of subclinical depressive symptomatology in SCD and clarify the association of different types of subjective complaints with distinct syndromic and biomarker profiles.

AbstractBackgroundDementia with Lewy bodies (DLB) is the second most common neurodegenerative dementia, after Alzheimer’s disease (AD). While alpha‐synuclein pathology is the hallmark of DLB, AD and cerebrovascular pathologies are common in DLB patients. However, the contribution of these pathologies towards neurodegeneration in DLB is largely unknown. We investigated associations of amyloid‐beta, tau, and cerebrovascular biomarkers with regional gray matter (GM) volume in DLB patients and cognitively unimpaired (CU) controls.MethodWe included 30 DLB patients (69.3±10.2 years old, 87% men) and 100 CU individuals balanced on age and sex (Table 1). We used 11C‐Pittsburgh Compound‐B (PiB) and 18F‐Flortaucipir positron emission tomography (PET) to assess amyloid‐beta and tau in‐vivo. We used structural MRI to assess white matter hyperintensity (WMH) volume, a marker of cerebrovascular lesion load, and regional GM volume (a marker of neurodegeneration). We used correlations and ANCOVA in the whole dataset and structural equation modelling in the DLB patients to investigate associations of WMH volume and regional amyloid‐beta and tau PET standardized uptake value ratios (SUVRs) with regional GM volume.ResultDLB patients showed lower GM volume across all cortical and subcortical regions except for cuneus, putamen, and pallidum (Fig.1). Greater WMH volume was associated with lower volume in the medial and orbital frontal cortices, insula, fusiform cortex, and thalamus in DLB patients (Fig.2). Greater PiB SUVR was associated with lower volume in the inferior temporal cortex, while Flortaucipir SUVR did not correlate with GM volume (Fig.2). Structural equation modelling showed that higher age and positivity for the APOE e4 genotype were significant predictors of greater WMH, and WMH in turn was a significant predictor of GM volume in medial and orbital frontal cortices, insula, and inferior temporal cortex (Fig.3). In contrast, we observed two distinct paths for the fusiform cortex, with age having an effect through PiB and Flortaucipir SUVRs on the one path, and through WMH on the other path (Fig.3).ConclusionDLB patients have widespread cortical atrophy, most of which likely is influenced by alpha‐synuclein pathology. Although amyloid‐beta, tau, and cerebrovascular pathologies often coexist in DLB, their contributions to neurodegeneration seem to be region specific.

AbstractBackgroundSubjective cognitive decline (SCD) is topic of mayor interest when identifying individuals at risk for future cognitive impairment and dementia. The degeneration of the cholinergic system is linked to the onset of cognitive symptoms in mild cognitive impairment (MCI) and dementia. Yet, it is uncertain whether the neurodegeneration of the cholinergic system is already present in SCD individuals. This review is the first to synthetize the available data on the association of SCD with multiple markers of degeneration in the cholinergic system.MethodFollowing the PRISMA guidelines, original articles focused on the association of SCD and the cholinergic system were extracted from three databases: Pubmed, WOS and Scopus, in November 2021. Two researchers reviewed the studies independently in a 2‐stepwise approach. The quality of the studies and risk of bias were assessed using FLC 3.0, that allows to systematically evaluate the studies and summarize them easily.ResultAmong 119 studies found in our systematic search, 11 were included in the current review. Seven were cross‐sectional and 4 had a longitudinal design. Most of the studies operationalized SCD based on amnestic cognitive complaints (n = 9, 82%). The cholinergic system measures were based on neuroimaging markers for volume of the basal forebrain and/or functional connectivity, transcranial magnetic stimulation, or biofluid markers (i.e. cerebrospinal fluid (CSF) and plasma). The studies focused on association of SCD with basal brain atrophy, 75% reported reduce volumes in SCD; From those focused on functional connectivity of the cholinergic system, 33% reported poorer connectivity in SCD.ConclusionBased on scientific evidence, neurodegeneration of the cholinergic system is already evident during SCD. Using multiple cholinergic biomarkers, degeneration of cholinergic system in SCD seems to occur with significant structural and functional degeneration of cholinergic nuclei in the basal forebrain and their connections with other brain areas. These findings have implications on identifying individuals with increased vulnerability to cognitive impairment and for targeting individuals that might benefit from cholinergic‐target treatments. Further research is needed to elucidate potential contributors to the cholinergic degeneration in SCD and its impact on cognition and clinical progression.

AbstractAlterations of cerebral glucose metabolism can be detected in patients with isolated rapid eye movement sleep behaviour disorder, a prodromal feature of neurodegenerative diseases with α-synuclein pathology. However, metabolic characteristics that determine clinical progression in isolated rapid eye movement sleep behaviour disorder and their association with other biomarkers need to be elucidated. We investigated the pattern of cerebral glucose metabolism on 18F-fluorodeoxyglucose PET in patients with isolated rapid eye movement sleep behaviour disorder, differentiating between those who clinically progressed and those who remained stable over time. Second, we studied the association between 18F-fluorodeoxyglucose PET and lower dopamine transporter availability in the putamen, another hallmark of synucleinopathies. Patients with isolated rapid eye movement sleep behaviour disorder from the Mayo Clinic Alzheimer’s Disease Research Center and Center for Sleep Medicine (n = 22) and age-and sex-matched clinically unimpaired controls (clinically unimpaired; n = 44) from the Mayo Clinic Study of Aging were included. All participants underwent 18F-fluorodeoxyglucose PET and dopamine transporter imaging with iodine 123-radiolabeled 2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane on single-photon emission computerized tomography. A subset of patients with isolated rapid eye movement sleep behaviour disorder with follow-up evaluations (n = 17) was classified as isolated rapid eye movement sleep behaviour disorder progressors (n = 7) if they developed mild cognitive impairment or Parkinson’s disease; or isolated rapid eye movement sleep behaviour disorder stables (n = 10) if they remained with a diagnosis of isolated rapid eye movement sleep behaviour disorder with no cognitive impairment. Glucose metabolic abnormalities in isolated rapid eye movement sleep behaviour disorder were determined by comparing atlas-based regional 18F-fluorodeoxyglucose PET uptake between isolated rapid eye movement sleep behaviour disorder and clinically unimpaired. Associations between 18F-fluorodeoxyglucose PET and dopamine transporter availability in the putamen were analyzed with Pearson’s correlation within the nigrostriatal pathway structures and with voxel-based analysis in the cortex. Patients with isolated rapid eye movement sleep behaviour disorder had lower glucose metabolism in the substantia nigra, retrosplenial cortex, angular cortex, and thalamus, and higher metabolism in the amygdala and entorhinal cortex compared with clinically unimpaired. Patients with isolated rapid eye movement sleep behaviour disorder who clinically progressed over time were characterized by higher glucose metabolism in the amygdala and entorhinal cortex, and lower glucose metabolism in the cerebellum compared with clinically unimpaired. Lower dopamine transporter availability in the putamen was associated with higher glucose metabolism in the pallidum within the nigrostriatal pathway; and with higher 18F-fluorodeoxyglucose uptake in the amygdala, insula, and temporal pole on a voxel-based analysis, although these associations did not survive after correcting for multiple comparisons. Our findings suggest that cerebral glucose metabolism in isolated rapid eye movement sleep behaviour disorder is characterized by hypometabolism in regions frequently affected during the prodromal stage of synucleinopathies, potentially reflecting synaptic dysfunction. Hypermetabolism is also seen in isolated rapid eye movement sleep behaviour disorder, suggesting that synaptic metabolic disruptions may be leading to a lack of inhibition, compensatory mechanisms, or microglial activation, especially in regions associated with nigrostriatal degeneration.

Abstract Background and objectives. Sex is an important contributing factor to neuroimaging phenotypes in brain disorders. However, little is known about the contribution of sex differences to the neurodegeneration in dementia with Lewy bodies (DLB). We investigated sex differences in probable DLB patients by using both visual rating scales of lobar atrophy and automated estimations of regional atrophy. Methods. We included 442 probable DLB patients from the European-DLB consortium and the Mayo Clinic who have magnetic resonance imaging (MRI) data available. We assessed sex differences and the sex-by-age interaction in two largely independent samples through visual rating scales of lobar atrophy (n = 333; mean age 73 ± 8 years, 62% males) and automated regional estimations of gray matter (GM) volume and mean cortical thickness (CTh) (n = 165; mean age 69 ± 9 years, 72% males). We used binary logistic regression and ANOVA for statistical analysis. Results. We found a statistically significantly higher likelihood of frontal atrophy measured by the global cortical atrophy-frontal subscale (GCA-F) in males (40% of males had an abnormal GCA-F score versus 29% of females, P-value = 0.006). Using automated estimations, we found smaller GM volumes in 6 cortical regions in males compared with females, as well as smaller GM volume in the entorhinal cortex and thinner olfactory cortices in females, compared with males. The sex-by-age interaction showed statistically significant results in 6 cortical volumes and 7 mean CTh estimations (P-value ≤ 0.05), accentuated in the right middle frontal gyrus (FDR-adjusted P-value = 0.047). These cross-sectional interactions indicated that while females have statistically significantly less atrophy than males at younger ages, differences become non-significant at older ages, with females showing the same level of atrophy than males around the age of 75. Conclusions. This study demonstrates sex differences on brain atrophy in probable DLB. While male DLB patients have a more widespread pattern of cortical atrophy at younger ages, these sex differences tend to disappear with increasing age. Longitudinal studies will help establish these cross-sectional findings and inform on sex and age considerations to the use of MRI in clinical routine, as the field moves towards precision medicine.

Abstract Background Donepezil is an approved therapy for the treatment of Alzheimer’s disease (AD). Results across clinical trials have been inconsistent, which may be explained by design-methodological issues, the pathophysiological heterogeneity of AD, and diversity of included study participants. We investigated whether response to Donepezil differs in mild cognitive impaired (MCI) individuals demonstrating different magnetic resonance imaging (MRI) subtypes. Methods From the Hippocampus Study double-blind, randomized clinical trial, we included 173 MCI individuals (donepezil = 83; placebo = 90) with structural MRI data, at baseline and at clinical follow-up assessments (6-12-month). Efficacy outcomes were the annualized percentage change (APC) in hippocampal, ventricular, and total grey matter volumes, as well as in the AD cortical thickness signature. Participants were classified into MRI subtypes as typical-AD, limbic-predominant, hippocampal-sparing, or minimal atrophy at baseline. We compared two subtyping approaches: the conventional categorical approach and an approach based on continuous dimensions. Results Donepezil treated MCI individuals showed slower atrophy rates compared to the placebo group, but only if they belonged to the minimal atrophy or hippocampal sparing subtypes. Importantly, only the continuous subtyping approach, but not the conventional categorical approach, captured this differential response. Conclusions Our data suggest that individuals with MCI, with hippocampal sparing or minimal atrophy subtype, may have improved benefit from donepezil, as compared with MCI individuals with typical or limbic predominant patterns of atrophy. The newly proposed continuous subtyping approach may have advantages compared to the conventional categorical approach. Future research is warranted to demonstrate the potential of subtype stratification for disease prognosis and response to treatment. Trial registration: Clinical Trial.gov Number: NCT00403520, Submission Date: November 21, 2006.

AbstractBackgroundβ‐amyloid plaques, a pathological hallmark of Alzheimer’s disease, are common in dementia with Lewy bodies (DLB). However, little is known about when β‐amyloid levels increase throughout the Lewy body disease (LBD) continuum, from an early prodromal stage of isolated REM sleep behavior disorder (iRBD), to a stage of mild cognitive impairment‐Lewy bodies (MCI‐LB), and finally DLB. Our objective was to investigate β‐amyloid deposition throughout the LBD continuum, as well as the influence of sex and APOE ε4 status, as potential factors contributing to Alzheimer’s disease pathological changes.MethodPatients with iRBD (n=24), MCI‐LB (n=62), and DLB (n=82) from the Mayo Clinic Alzheimer’s Disease Research Center and Center for Sleep Medicine were included. β‐amyloid levels were measured by Pittsburgh compound B (PiB) PET and global cortical standard uptake value ratio (SUVR) was calculated. Global cortical PiB SUVR values from each clinical group were compared to each other and to cognitively unimpaired individuals (CU; n=100) balanced on age and sex from the Mayo Clinic Study of Aging (MCSA). Clinical groups were compared using ANCOVA after adjusting by age.ResultMCI‐LB and DLB patients had significantly higher global cortical PiB SUVR than CU participants, while PiB SUVR in iRBD patients was comparable to that of CU participants (Figure 1). DLB patients also had significantly higher global cortical PiB SUVR compared to iRBD patients (p=0.004). In MCI‐LB and DLB, global cortical PiB SUVR was higher in APOE ε4 carriers compared to APOE ε4 non‐carriers (p<0.001), and women had higher global cortical PiB SUVR compared to men (p=0.024).ConclusionIn this cross‐sectional study, β‐amyloid pathology gradually increased throughout the clinically defined LBD continuum. Whereas β‐amyloid levels are comparable to cognitively unimpaired individuals in iRBD, a significant elevation in β‐amyloid levels coincides with cognitive impairment observed in MCI‐LB and DLB. Specifically, women and APOE ε4 carriers tend to have higher β‐amyloid levels than men and APOE ε4 non‐carriers. These findings have important implications for targeting patients within the LBD continuum, who may benefit from amyloid modifying therapies.

AbstractBackgroundReduced striatal uptake on ioflupane SPECT is considered an indicative biomarker for Dementia with Lewy Bodies (DLB), and has been proposed as an indicative biomarker for Mild Cognitive Impairment with Lewy Bodies (MCI‐LB). Little data exists on the profile of uptake on key striatal regions of interest (ROIs) in DLB or MCI‐LB.MethodParticipants with DLB or MCI‐LB at baseline based on the presence of ≥2 core clinical DLB features, and ≥2 ioflupane SPECT scans performed approximately annually, were identified from the Mayo ADRC database. Minimum brain laterality z‐score values for the putamen (whole, anterior and posterior), caudate and striatum were determined using DaTQUANT 2 software. Baseline clinical and scan data was used for all analyses, and the annualized minimum putamen z‐change was determined on serial scans. The scan was considered abnormal if the minimum putamen z‐score was <‐0.98 based on clinicopathologic data.Result27 participants were included (21 DLB and 6 MCI‐LB, 96% male). Compared to MCI‐LB, DLB had a lower mean MoCA score and a trend toward a higher UPDRS score compared to MCI‐LB; there were no statistically significant differences in age, sex, onset age or duration of cognitive decline, or presence of other core DLB features. The majority (89%) had an abnormal scan at baseline. All ROI z‐scores showed the expected general trend of DLB<MCI‐LB, and the annualized z‐change was more negative in DLB, but none of the findings reached statistical significance.ConclusionThese findings suggest in MCI‐LB and DLB that 1) an abnormal ioflupane SPECT scan is frequently present at diagnosis, 2) z‐scores become more negative over time, and 3) the annualized z‐change is similar. Similar findings in larger cohorts would support the use of ioflupane SPECT as a biomarker in both MCI‐LB and DLB clinical trials.

AbstractBackgroundSubjective cognitive decline (SCD) implies self‐reported cognitive complaints in absence of objective cognitive impairment. SCD has been postulated as an early marker of Alzheimer’s Disease (AD). However, longitudinal studies have linked SCD to future vascular dementia. Thus, we conducted a systematic review and meta‐analysis aiming to synthesise and analyse the available data on the association between SCD and the presence of underlying cerebrovascular pathology measured by MRI.MethodOur study was performed following the PRISMA statement. The search strategy included terms for “subjective cognitive decline” and “white matter signal abnormalities”. It was conducted in 3 databases (PubMed, Scopus and Web of Science) from origin by December 8th, 2021. Two authors screened the studies in a 2‐stepwise approach. Primary studies including cognitively unimpaired adults with subjective cognitive complaints meeting the SCD‐I criteria for SCD that evaluated cerebrovascular pathology based on white matter signal abnormalities (WMSA) on MR images were selected. Study quality was assessed using the FLC 3.0 tool. Meta‐analysis comparing case‐control mean difference of WMSA was performed.ResultOf 240 articles identified, 16 research articles were selected. Of those, 8 case‐control studies were selected for the meta‐analysis. The sample size of the SCD group across the studies ranged from 8 to 906 participants, with age ranged from 40 to 84 years. All eight studies comprised a total of 2.637 SCD individuals. Study quality was deemed moderate (n=6) to high (n=10). The meta‐analysis showed a significant overall effect‐size between the mean WMSA burden of SCD and the controls, that was not significantly heterogeneous (Q(gl=7)=14.20; p=0,04; I2=42,5%). SCD was significantly associated with higher CVP burden based on neuroimaging measures.ConclusionThis is the first study to synthesise and analyse the current evidence on the association between SCD and WMSA. Our findings show the usefulness of SCD as a marker of underlying cerebrovascular pathology. Thus, the potential role of SCD as a preclinical stage of vascular cognitive impairment needs further investigation. Changes in lifestyle (e.g. exercise, diet, smoking cessation), cognitive stimulation or pharmacotherapy may be key to avoid an evolution towards cognitive deterioration in SCD.