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  • 1
    In: Alzheimer's & Dementia, Wiley, Vol. 16, No. S4 ( 2020-12)
    Abstract: Recent research suggests that brain network degeneration and immune response play important roles in Alzheimer’s Dementia (AD). Brain network connectivity become increasingly impaired as AD progresses. Glial activation in the neuropathology of AD has also been widely recognized both as a consequence and as a contributing factor for the formation of Aβ and tau aggregation. Immune surveillance in the brain and microglial activation can be reliably measured by translocator protein (TSPO) positron emission tomography (PET). Method To understand better important associations between network degeneration and immune response in AD, we initiated the ActiGliA prospective cohort study. Here we present an analysis of the initial 55 participants, including 20 participants with subjective cognitive declined, 19 patients with mild cognitive impairment and 16 AD patients. Participants were characterized using CSF biomarker information and underwent TSPO‐PET, fMRT and DTI acquisitions. We assessed topographical associations between microglia activity (TSPO‐PET covariance) with resting state functional and DTI structural connectivity changes using a 210 regions parcellation of the neocortex. PET and MRI preprocessing were performed using standard imaging pipelines. Result At baseline, elevated microglia activity was found in TSPO‐PET analysis of AD patients. Resting state fMRI graph‐theory analysis showed reduced global efficiency and increased local efficiency in AD compared to controls. No significant group differences were found in the graph‐theory analysis of structural connectivity. In a further analysis, we assessed the association between microglia activity and functional connectivity. A positive correlation of resting state functional connectivity with microglia covariance (r=0.177, p 〈 0.001), but no correlation of structural connectivity and microglia covariance were detected. Network specific TSPO uptake in resting‐state networks, demonstrating increased uptake in the language, default mode network (DMN), and visual network in the AD group compared to controls. Conclusion In line with previous findings, we confirm that brain functional connectivity is disrupted and microglial activity is elevated in AD. Preliminary results suggest an association between functional connectivity and microglia activity in AD, furthermore microglia activity is preferentially found in particular resting state networks.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2201940-6
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  • 2
    In: Alzheimer's & Dementia, Wiley, Vol. 17, No. S4 ( 2021-12)
    Abstract: The cognitive reserve (CR) hypothesis was proposed to explain inter‐individual differences in the association between observed cognitive function and estimated neurodegenerative burden, e.g. in Alzheimer’s disease (AD). Latent CR marker approaches were suggested as a promising method to predict reserve. Method Amyloid‐β (Aβ)‐negative, cognitively normal and Aβ‐positive, cognitive impaired (Clinical Dementia Rating global score 〉 = 0.5) individuals participating in the AD Neuroimaging Initiative (ADNI) were classified as healthy controls (HC, N=138) and AD spectrum (ADS, Baseline N=462, Follow‐Up N=211), respectively. A latent CR marker (CRM) was obtained by multilinear regression analysis in the entire study cohort, defined as the residual global cognitive performance remaining after accounting for neuropathological burden (CSF Aß42 and total Tau levels and APOE ε4 carrier status) and demographic variables. Mean standardized uptake value ratio (SUVR) values for regions of interests (ROIs) of left and right angular gyrus (L/R‐ANG), bilateral posterior cingulate (PCC), left and right inferior temporal gyrus (L/R‐TEMP) were derived from FDG‐PET data. In separate analyses for HC and ADS, the interactive effects of the memory cognitive composite (MEM) and latent CR marker on FDG‐PET SUVR values were tested for the five cortical ROIs at baseline and 24‐months follow‐up data. Result In ADS, higher CRM attenuated the relationship between MEM and FDG‐PET SUVR in L‐TEMP, R‐TEMP and L‐ANG at baseline, and in L‐TEMP, R‐TEMP, L‐ANG and R‐ANG in the longitudinal analyses. In HC, however, no interaction was observed. Conclusion Patients with higher CR maintained their memory performance better in the face of AD‐related glucose hypometabolism . Therefore, the present study supports the use of a residual CRM to improve our understand of inter‐individual differences in the resilience against neurodegeneration, both cross‐sectionally and longitudinally.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2201940-6
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  • 3
    In: Alzheimer's & Dementia, Wiley, Vol. 17, No. S5 ( 2021-12)
    Abstract: The cognitive reserve (CR) hypothesis explains inter‐individual differences in the association between observed cognitive function and estimated neurodegenerative burden. Latent CR marker approach were suggested as a promising method to estimate cognitive reserve. We aimed to compare different CR marker approaches and test a clinical latent CR marker score. Method Amyloid‐β (Aβ)‐negative and cognitively normal participants were included as healthy controls (HC) and Aβ‐positive and clinically impaired participants were included as AD spectrum (ADS) from the AD Neuroimaging Initiative (ADNI) study as two separate CSF data‐only discovery and a PET data‐only replication cohorts. A latent CR marker factor (CRM‐Factor) was obtained as the latent global cognitive domain score (gCDS) through a principal component analysis remaining after accounting for neuropathological burden and demographic variables. A residual CR marker (CRM‐Residual) was calculated as residualized gCDS in a multilinear regression analysis. We then estimated a CR marker score (CRM‐Score) as predictions from a multiple regression model with CRM‐Factor as dependent variable and demographics, total Mini‐Mental State Examination score and binarized biomarker status as predictors. Markers have been derived at baseline. We tested the moderation of each CR marker on the individual trajectories of memory decline in separate linear mixed models. Result Higher years of education were predicted by the CR markers when tested separately. CRM‐Residual levels were strongly associated with CRM‐Factor, while CRM‐Residual was moderately associated with CRM‐Factor and CRM‐Score. In linear mixed models, patients in ADS with higher CR revealed a slower memory decline, mainly in preclinical AD. Conclusion Our results support the operational value and effectivity of the latent CR marker approach. We defined a novel latent CR Marker Score that may be operationalized in independent cohorts without conducting a data‐driven analysis. In line with previous studies, latent CR markers estimated differences in cognitive trajectories predominantly in the MCI stage. Our marker score approach can offer a standardized clinical scoring for simple, cohort‐independent and effective estimation the individual CR in clinical and epidemiological studies, making a better individual risk assessment and estimating therapeutic effects to strengthen the CR.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2201940-6
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  • 4
    In: Alzheimer's & Dementia, Wiley, Vol. 18, No. S6 ( 2022-12)
    Abstract: Recent evidence suggests substantial heterogeneity in Alzheimer's disease (AD). Distinct subtypes have been identified using tau pet positron emissions tomography. There is only limited knowledge about the longitudinal cognitive and clinical trajectories of these subtypes. Method Three hundred and twenty‐one participants were included with 155 amyloid‐β (Aβ) negative and cognitively normal healthy controls (HC, 74 years, 85 female) and 166 Aβ positive patients with mild cognitive impairment or AD dementia (Alzheimer’s disease spectrum, ADS, 75 years, 76 female). We identified distinct subtypes using an unbiased, data‐driven and similarity‐based Louvain clustering algorithm, modified using a consensus method. Longitudinal trajectories in cognitive domain scores and clinical severity were compared between tau subtypes using mixed effect models. Result Four distinct tau PET imaging subtypes were identified, including a posterior, a limbic, a medio‐temoral lobe (MTL) sparing and a temporal subtype (Figure 1). In longitudinal analyses, the subtypes differed substantially in disease progression in the different cognitive domains, i.e. episodic memory, executive functioning, language and visual memory. The temporal subtype showed the steepest decline in visual memory and language, the medial temporal lobe sparing subtype showed only minor language degradation and the limbic subtype showed relatively preserved executive functioning but decline in all other cognitive domains. The MTLs was by far worst affected by clinical progression. The remaining subtypes showed only slight deterioration in clinical severity (Figure 2). Conclusion Our results suggest characteristic differences in longitudinal cognitive and clinical trajectories of the tau PET imaging subtypes. Analyzing the heterogeneity in AD using tau PET spatial distribution patterns, significantly improves our understanding of the biological underpinnings of individual differences in clinical presentation and progression. An in‐depth understanding of the subtype’s characteristics in the longitudinal trajectories contributes significantly to improved prevention strategies and individualized precision treatments.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 2201940-6
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  • 5
    In: Annals of Neurology, Wiley, Vol. 92, No. 5 ( 2022-11), p. 768-781
    Abstract: Alzheimer disease (AD) is characterized by amyloid β (Aβ) plaques and neurofibrillary tau tangles, but increasing evidence suggests that neuroinflammation also plays a key role, driven by the activation of microglia. Aβ and tau pathology appear to spread along pathways of highly connected brain regions, but it remains elusive whether microglial activation follows a similar distribution pattern. Here, we assess whether connectivity is associated with microglia activation patterns. Methods We included 32 Aβ‐positive early AD subjects (18 women, 14 men) and 18 Aβ‐negative age‐matched healthy controls (10 women, 8 men) from the prospective ActiGliA (Activity of Cerebral Networks, Amyloid and Microglia in Aging and Alzheimer's Disease) study. All participants underwent microglial activation positron emission tomography (PET) with the third‐generation mitochondrial 18 kDa translocator protein (TSPO) ligand [ 18 F]GE‐180 and magnetic resonance imaging (MRI) to measure resting‐state functional and structural connectivity. Results We found that inter‐regional covariance in TSPO‐PET and standardized uptake value ratio was preferentially distributed along functionally highly connected brain regions, with MRI structural connectivity showing a weaker association with microglial activation. AD patients showed increased TSPO‐PET tracer uptake bilaterally in the anterior medial temporal lobe compared to controls, and higher TSPO‐PET uptake was associated with cognitive impairment and dementia severity in a disease stage‐dependent manner. Interpretation Microglial activation distributes preferentially along highly connected brain regions, similar to tau pathology. These findings support the important role of microglia in neurodegeneration, and we speculate that pathology spreads throughout the brain along vulnerable connectivity pathways. ANN NEUROL 2022;92:768–781
    Type of Medium: Online Resource
    ISSN: 0364-5134 , 1531-8249
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 2037912-2
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  • 6
    In: Nutrition and Healthy Aging, IOS Press, Vol. 8, No. 1 ( 2023-08-24), p. 143-156
    Abstract: BACKGROUND: There is evidence that adherence to Mediterranean-like diet reduces cognitive decline and brain atrophy in Alzheimer's disease (AD). However, lengthy dietary assessments, such as food frequency questionnaires (FFQs), discourage more frequent use. OBJECTIVE: Here we aimed to validate a 6-items short questionnaire for a Mediterranean-like diet (6-QMD) and explore its associations with memory performance and hippocampal atrophy in healthy elders and individuals at risk for AD. METHODS: We analyzed 938 participants (N = 234 healthy controls and N = 704 participants with an increased AD risk) from the DZNE-Longitudinal Cognitive Impairment and Dementia Study (DELCODE). The 6-QMD was validated against the Mediterranean Diet (MeDi) score and the Mediterranean-DASH Diet Intervention for Neurodegenerative Delay (MIND) score, both derived from a detailed FFQ. Furthermore, associations between the 6-QMD and memory function as well as hippocampal atrophy were evaluated using linear regressions. RESULTS: The 6-QMD was moderately associated with the FFQ-derived MeDi adherence score (ρ = 0.25, p  〈  0.001) and the MIND score (ρ = 0.37, p=  〈  0.001). Higher fish and olive oil consumption and lower meat and sausage consumption showed significant associations in a linear regression, adjusted for diagnosis, age, sex and education, with memory function (β = 0.1, p = 0.008) and bilateral hippocampal volumes (left: β = 0.15, p  〈  0.001); (right: β = 0.18, p  〈  0.001)). CONCLUSIONS: The 6-QMD is a useful and valid brief tool to assess the adherence to MeDi and MIND diets, capturing associations with memory function and brain atrophy in healthy elders and individuals at increased AD dementia risk, making it a valid alternative in settings with time constraints.
    Type of Medium: Online Resource
    ISSN: 2451-9480 , 2451-9502
    Language: Unknown
    Publisher: IOS Press
    Publication Date: 2023
    detail.hit.zdb_id: 2879828-4
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  • 7
    In: Neurobiology of Aging, Elsevier BV, Vol. 122 ( 2023-02), p. 33-44
    Type of Medium: Online Resource
    ISSN: 0197-4580
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2023
    detail.hit.zdb_id: 1498414-3
    SSG: 12
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  • 8
    In: Alzheimer's & Dementia, Wiley, Vol. 19, No. S2 ( 2023-06)
    Abstract: Cognitive reserve (CR) is a concept that addresses the differences in trajectories of cognitive decline while facing neurodegenerative changes in the brain. Common proxies of CR include demographic or socio‐behavioral measures such as sex and educational/occupational attainment. Recent studies have quantified CR using a residual approach, a direct and cross‐sectional measurement of the discrepancy between estimated cognition and neurodegenerative burden. The associations between these two approaches remain largely unclear. Methods Data of 801 participants from the German DELCODE study was used, including 215 healthy controls and 586 individuals with increased risk of AD dementia (61 subjective cognitive decline, 150 mild cognitive impairment and 75 aged 80 years and older with a first‐degree relative with AD). To differentiate similar clusters in tested lifestyle factors, we conducted a dimension reduction method using principal component analysis and consequently derived 8 component factor scores. A residualized memory CR score (CR MEM ) was calculated as residuals from a multilinear regression model. Functional connectivity was analyzed using resting‐state fMRI data. Results Partial correlation analyses revealed significant positive correlations between CR MEM and component factors 1 (retirement and living), 3 (educational attainment) and 4 (social network and occupational attainment) in the entire cohort and at risk for AD dementia individuals. Higher CR MEM was associated with higher functional connectivity between the hippocampus and regions related to the default‐mode network. Factor scores 3 and 4 were associated with increased rostral hippocampus‐right angular gyrus functional connectivity. A mediation analysis showed a significant indirect effect of factor 3 on the relationship between CR MEM and rostral hippocampus‐right angular gyrus functional connectivity. Conclusion CR‐favorable socio‐behavioral factors are correlated with higher CR MEM in healthy aging and AD‐risk groups. Educational attainment might present a rather specific proxy of CR for individuals at AD‐risk. In contrast, mid‐life (occupational attainment) and late‐life factors (retirement years, social network and living status) predict CR both in AD‐risk and healthy aging groups. However, only in the AD‐risk group, hippocampal functional connectivity was higher in individuals with higher CR MEM , mediated in favor of higher educational and female sex, suggesting a close relationship to neural reserve.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2201940-6
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  • 9
    In: Alzheimer's & Dementia, Wiley, Vol. 16, No. S4 ( 2020-12)
    Abstract: Cognitive reserve (CR) refers to the individual differences in cognition relative to brain aging or neurodegenerative changes. Recently, various studies tried to quantify a marker that represents CR. Among others, the residual approach suggested being relatively reliable as it has been studied not only with cross‐sectional but also with longitudinal observations. However, it is unknown if brain connectivity changes in the resting‐state are related to reserve factors e.g. lifestyle factors. Method In the present study we defined a CR Marker based on residuals calculated through a multimodal (multi‐linear) regression model adapted from a recent study using pathological changes of AD such as atrophy, demographic and genetic information as predictors. The data of 546 participants including healthy controls, participants with subjective cognitive decline, 62 patients with MCI, and 64 patients with AD from the German multicentric DELCODE cohort was assessed. To examine neural substrates of defined CR marker, we constructed a weighted undirected partial correlation matrix in the GraphVar toolbox and analyzed graph theoretical metrics in global topography with various network thresholds. Permutation‐based FDR‐correction has been used in statistical analyses with graph measures. Then we examined the possible associations between CR and lifestyle factors specifically the Lifetime Experiences Questionnaire(LEQ). Result CR was positively correlated (r=0.247, p=0.012) with higher scores in LEQ which includes leisure, educational and physical activities across the lifespan. We demonstrated that LEQ interacts with CR in functional connectivity changes, we used a multivariate regression model, in which LEQ was binarized using median values of total normalized scores. At the global level, interaction between CR and binarized LEQ score has been found with clustering coefficient (p=0.02), transitivity (p=0.017), but not with global efficiency(p=0.45). Moreover, component of LEQ scores corresponding to young adulthood, mid‐life, and late‐life didn’t interact with CR. However, LEQ of late‐life showed interaction at marginal level(uncorrected p=0.03). Conclusion Overall, CR and lifestyle differences appear to be reflected by changes in brain connectivity with increased global information processing capacity in participants exhibit higher CR. These findings foster understanding of early AD and will be useful to help identify individuals with vulnerability or resistance to AD pathology.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2201940-6
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  • 10
    Online Resource
    Online Resource
    Elsevier BV ; 2022
    In:  Multiple Sclerosis and Related Disorders Vol. 58 ( 2022-02), p. 103457-
    In: Multiple Sclerosis and Related Disorders, Elsevier BV, Vol. 58 ( 2022-02), p. 103457-
    Type of Medium: Online Resource
    ISSN: 2211-0348
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2022
    detail.hit.zdb_id: 2645330-7
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