Search

Background/Objectives: Advance care planning (ACP) traditionally involves asking individuals about their treatment preferences during a brief period of incapacity near the end of life. Because dementia leads to prolonged incapacity, with many decisions arising before a terminal event, it has been suggested that dementia‐specific ACP is necessary. We sought to elicit the perspectives of older adults with early cognitive impairment and their caregivers on traditional and dementia‐specific ACP. Design Qualitative study with separate focus groups for patients and caregivers. Setting: Memory disorder clinics. Participants: Twenty eight persons aged 65+ with mild cognitive impairment or early dementia and 19 caregivers. Measurements Understanding of dementia trajectory and types of planning done; how medical decisions would be made in the future; thoughts about these decisions. Results: No participants had engaged in any written form of dementia‐specific planning. Barriers to dementia‐specific ACP emerged, including lack of knowledge about the expected trajectory of dementia and potential medical decisions, the need to stay focused in the present because of fear of loss of self, disinterest in planning because the patient will not be aware of decisions, and the expectation that involved family members would take care of issues. Some patients had trouble engaging in the discussion. Patients had highly variable views on what the quality of their future life would be and on the leeway their surrogates should have in decision making. Conclusions: Even among patients with early cognitive impairment seen in specialty clinics and their caregivers, most were unaware of the decisions they could face, and there were many barriers to planning for these decisions. These issues would likely be magnified in more representative populations, and highlight challenges to the use of dementia‐specific advance directive documents. [ABSTRACT FROM AUTHOR]

Background: Attempts to associate amyloid-β (Aβ) pathogenesis with synaptic loss in Alzheimer's disease (AD) have thus far been limited to small numbers of postmortem studies. Aβ plaque burden is not well-correlated with indices of clinical severity or neurodegeneration—at least in the dementia stage—as deposition of Aβ reaches a ceiling. In this study, we examined in vivo the association between fibrillar Aβ deposition and synaptic density in early AD using positron emission tomography (PET). We hypothesized that global Aβ deposition would be more strongly inversely associated with hippocampal synaptic density in participants with amnestic mild cognitive impairment (aMCI; a stage of continued Aβ accumulation) compared to those with dementia (a stage of relative Aβ plateau). Methods: We measured SV2A binding ([11C]UCB-J) and Aβ deposition ([11C]PiB) in 14 participants with aMCI due to AD and 24 participants with mild AD dementia. Distribution volume ratios (DVR) with a cerebellar reference region were calculated for both tracers to investigate the association between global Aβ deposition and SV2A binding in hippocampus. Exploratory analyses examined correlations between both global and regional Aβ deposition and SV2A binding across a broad range of brain regions using both ROI- and surface-based approaches. Results: We observed a significant inverse association between global Aβ deposition and hippocampal SV2A binding in participants with aMCI (r = − 0.55, P = 0.04), but not mild dementia (r = 0.05, P = 0.82; difference statistically significant by Fisher z = − 1.80, P = 0.04). Exploratory analyses across other ROIs and whole brain analyses demonstrated no broad or consistent associations between global Aβ deposition and regional SV2A binding in either diagnostic group. ROI-based analyses of the association between regional Aβ deposition and SV2A binding also revealed no consistent pattern but suggested a "paradoxical" positive association between local Aβ deposition and SV2A binding in the hippocampus. Conclusions: Our findings lend support to a model in which fibrillar Aβ is still accumulating in the early stages of clinical disease but approaching a relative plateau, a point at which Aβ may uncouple from neurodegenerative processes including synaptic loss. Future research should investigate the relationship between Aβ deposition and synaptic loss in larger cohorts beginning preclinically and followed longitudinally in conjunction with other biomarkers. [ABSTRACT FROM AUTHOR]

Background: Synaptic density PET is an emerging technology with potential as a biomarker for tracking disease progression and therapeutic efficacy in studies of Alzheimer's disease (AD). Simplified methods of image acquisition and quantification would facilitate the use of synaptic density imaging in multicenter longitudinal studies. Therefore, we validated a simplified tissue‐to‐reference ratio method using standardized uptake value ratios (SUVR) for estimating synaptic density using [11C]UCB‐J PET. Method: [11C]UCB‐J binding was measured in 31 participants with early AD and 16 cognitively normal (CN) participants aged 55‐85 years. All participants underwent 90 minute dynamic PET scans on the HRRT after bolus injection of [11C]UCB‐J. Parametric images of binding potential (BPND) were generated using SRTM2 (0‐60 minutes) with a centrum semiovale reference region and converted to distribution volume ratios (DVR) with a cerebellum reference region. Parametric images of SUVR were generated by summing frames from 30‐60 or 60‐90 minutes and normalizing to the cerebellum. Regional group differences were assessed using unpaired t tests and Cohen's d, while associations between DVR and SUVR were assessed using Pearson's correlation. Result: Widespread reductions in cortical and subcortical synaptic density were observed in AD (vs. CN) participants using measures of DVR, SUVR30‐60min, and SUVR60‐90min. In the entire sample, stronger regional correlations between measures of DVR and SUVR60‐90min(r=0.97, p<0.00001) were observed compared to DVR and SUVR30‐60min(r=0.91, p<0.00001; Figure 1). The correlation between DVR and SUVR60‐90minwas also stronger for within‐group correlations (DVR vs. SUVR60‐90minrCN=0.97, rAD=0.97; DVR vs. SUVR30‐60minrCN=0.90, rAD=0.91). The within‐region correlation between measures of DVR and SUVR60‐90minranged from 0.77 to 0.97 (p<0.00001) in the entire sample. Effect sizes to determine group differences in SV2A binding across all regions were highly correlated between both DVR and SUVR60‐90min(r=0.93, p<0.00001) and DVR and SUVR30‐60min(r=0.93, p<0.00001; Figure 2). Conclusion: A simplified method of quantifying synaptic density with SUVR using a shortened (60‐90 minute) scan window and cerebellum reference region is highly correlated with measures of DVR generated with SRTM2 kinetic modeling. This simplified tissue‐to‐reference ratio methodology may be of practical use for multicenter and longitudinal studies seeking to measure synaptic density in AD. [ABSTRACT FROM AUTHOR]

Background: Attempts to associate amyloid-β (Aβ) pathogenesis with synaptic loss in Alzheimer's disease (AD) have thus far been limited to small numbers of postmortem studies. Aβ plaque burden is not well-correlated with indices of clinical severity or neurodegeneration-at least in the dementia stage-as deposition of Aβ reaches a ceiling. In this study, we examined in vivo the association between fibrillar Aβ deposition and synaptic density in early AD using positron emission tomography (PET). We hypothesized that global Aβ deposition would be more strongly inversely associated with hippocampal synaptic density in participants with amnestic mild cognitive impairment (aMCI; a stage of continued Aβ accumulation) compared to those with dementia (a stage of relative Aβ plateau)., Methods: We measured SV2A binding ([ 11 C]UCB-J) and Aβ deposition ([ 11 C]PiB) in 14 participants with aMCI due to AD and 24 participants with mild AD dementia. Distribution volume ratios (DVR) with a cerebellar reference region were calculated for both tracers to investigate the association between global Aβ deposition and SV2A binding in hippocampus. Exploratory analyses examined correlations between both global and regional Aβ deposition and SV2A binding across a broad range of brain regions using both ROI- and surface-based approaches., Results: We observed a significant inverse association between global Aβ deposition and hippocampal SV2A binding in participants with aMCI (r = - 0.55, P = 0.04), but not mild dementia (r = 0.05, P = 0.82; difference statistically significant by Fisher z = - 1.80, P = 0.04). Exploratory analyses across other ROIs and whole brain analyses demonstrated no broad or consistent associations between global Aβ deposition and regional SV2A binding in either diagnostic group. ROI-based analyses of the association between regional Aβ deposition and SV2A binding also revealed no consistent pattern but suggested a "paradoxical" positive association between local Aβ deposition and SV2A binding in the hippocampus., Conclusions: Our findings lend support to a model in which fibrillar Aβ is still accumulating in the early stages of clinical disease but approaching a relative plateau, a point at which Aβ may uncouple from neurodegenerative processes including synaptic loss. Future research should investigate the relationship between Aβ deposition and synaptic loss in larger cohorts beginning preclinically and followed longitudinally in conjunction with other biomarkers.