A rapidly growing literature strongly suggests that exercise, specifically aerobic exercise, may attenuate cognitive impairment and reduce dementia risk. We used PubMed (keywords exercise and ...cognition) and manuscript bibliographies to examine the published evidence of a cognitive neuroprotective effect of exercise. Meta-analyses of prospective studies documented a significantly reduced risk of dementia associated with midlife exercise; similarly, midlife exercise significantly reduced later risks of mild cognitive impairment in several studies. Among patients with dementia or mild cognitive impairment, randomized controlled trials (RCTs) documented better cognitive scores after 6 to 12 months of exercise compared with sedentary controls. Meta-analyses of RCTs of aerobic exercise in healthy adults were also associated with significantly improved cognitive scores. One year of aerobic exercise in a large RCT of seniors was associated with significantly larger hippocampal volumes and better spatial memory; other RCTs in seniors documented attenuation of age-related gray matter volume loss with aerobic exercise. Cross-sectional studies similarly reported significantly larger hippocampal or gray matter volumes among physically fit seniors compared with unfit seniors. Brain cognitive networks studied with functional magnetic resonance imaging display improved connectivity after 6 to 12 months of exercise. Animal studies indicate that exercise facilitates neuroplasticity via a variety of biomechanisms, with improved learning outcomes. Induction of brain neurotrophic factors by exercise has been confirmed in multiple animal studies, with indirect evidence for this process in humans. Besides a brain neuroprotective effect, physical exercise may also attenuate cognitive decline via mitigation of cerebrovascular risk, including the contribution of small vessel disease to dementia. Exercise should not be overlooked as an important therapeutic strategy.
Summary Background Neurofibrillary pathology has a stereotypical progression in Alzheimer's disease (AD) that is encapsulated in the Braak staging scheme; however, some AD cases are atypical and do ...not fit into this scheme. We aimed to compare clinical and neuropathological features between typical and atypical AD cases. Methods AD cases with a Braak neurofibrillary tangle stage of more than IV were identified from a brain bank database. By use of thioflavin-S fluorescence microscopy, we assessed the density and the distribution of neurofibrillary tangles in three cortical regions and two hippocampal sectors. These data were used to construct an algorithm to classify AD cases into typical, hippocampal sparing, or limbic predominant. Classified cases were then compared for clinical, demographic, pathological, and genetic characteristics. An independent cohort of AD cases was assessed to validate findings from the initial cohort. Findings 889 cases of AD, 398 men and 491 women with age at death of 37–103 years, were classified with the algorithm as hippocampal sparing (97 cases 11%), typical (665 75%), or limbic predominant (127 14%). By comparison with typical AD, neurofibrillary tangle counts per 0.125 mm2 in hippocampal sparing cases were higher in cortical areas (median 13, IQR 11–16) and lower in the hippocampus (7.5, 5.2–9.5), whereas counts in limbic-predominant cases were lower in cortical areas (4.3, 3.0–5.7) and higher in the hippocampus (27, 22–35). Hippocampal sparing cases had less hippocampal atrophy than did typical and limbic-predominant cases. Patients with hippocampal sparing AD were younger at death (mean 72 years SD 10) and a higher proportion of them were men (61 63%), whereas those with limbic-predominant AD were older (mean 86 years SD 6) and a higher proportion of them were women (87 69%). Microtubule-associated protein tau ( MAPT ) H1H1 genotype was more common in limbic-predominant AD (54 70%) than in hippocampal sparing AD (24 46%; p=0.011), but did not differ significantly between limbic-predominant and typical AD (204 59%; p=0.11). Apolipoprotein E ( APOE ) ε4 allele status differed between AD subtypes only when data were stratified by age at onset. Clinical presentation, age at onset, disease duration, and rate of cognitive decline differed between the AD subtypes. These findings were confirmed in a validation cohort of 113 patients with AD. Interpretation These data support the hypothesis that AD has distinct clinicopathological subtypes. Hippocampal sparing and limbic-predominant AD subtypes might account for about 25% of cases, and hence should be considered when designing clinical, genetic, biomarker, and treatment studies in patients with AD. Funding US National Institutes of Health via Mayo Alzheimer's Disease Research Center, Mayo Clinic Study on Aging, Florida Alzheimer's Disease Research Center, and Einstein Aging Study; and State of Florida Alzheimer's Disease Initiative.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Objective
This study aimed to determine the frequency of frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD‐U) in the setting of hippocampal sclerosis (HpScl) and Alzheimer's ...disease (AD) using immunohistochemistry for TAR DNA binding protein 43 (TDP‐43), a putative marker for FTLD‐U.
Methods
Initially, 21 cases of HpScl associated with a variety of other pathological processes and 74 cases of AD were screened for FTLD‐U with TDP‐43 immunohistochemistry. A confirmation study was performed on 93 additional AD cases. Specificity of TDP‐43 antibodies was assessed using double‐immunolabeling confocal microscopy, immunoelectron microscopy, and biochemistry.
Results
TDP‐43 immunoreactivity was detected in 71% of HpScl and 23% of AD cases. Double immunostaining of AD cases for TDP‐43 and phospho‐tau showed that the TDP‐43–immunoreactive inclusions were usually distinct from neurofibrillary tangles. At the ultrastructural level, TDP‐43 immunoreactivity in AD was associated with granular and filamentous cytosolic material and only occasionally associated with tau filaments. Western blots of AD cases showed a band that migrated at a higher molecular weight than normal TDP‐43 that was not present in AD cases without TDP‐43 immunoreactivity.
Interpretation
These results suggest that as many as 20% of AD cases and more than 70% of HpScl cases have pathology similar to that found in FTLD‐U. Whether this represents concomitant FTLD‐U or is analogous to colocalization of α‐synuclein and tau in AD, reflecting a propensity for codeposition of abnormal protein conformers, remains to be determined. Ann Neurol 2007;61:435–445
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Objective
This study was undertaken to evaluate the frequency of modifiable dementia risk factors and their association with cognitive impairment and rate of decline in diverse participants engaged ...in studies of memory and aging.
Methods
Modifiable dementia risk factors and their associations with cognitive impairment and cognitive decline were determined in community‐dwelling African American (AA; n = 261) and non‐Hispanic White (nHW; n = 193) participants who completed ≥2 visits at the Mayo Clinic Alzheimer Disease Research Center in Jacksonville, Florida. Risk factors and their associations with cognitive impairment (global Clinical Dementia Rating CDR ≥ 0.5) and rates of decline (CDR Sum of Boxes) in impaired participants were compared in AA and nHW participants, controlling for demographics, APOE ɛ4 status, and Area Deprivation Index.
Results
Hypertension, hypercholesterolemia, obesity, and diabetes were overrepresented in AA participants, but were not associated with cognitive impairment. Depression was associated with increased odds of cognitive impairment in AA (odds ratio OR = 4.30, 95% confidence interval CI = 2.13–8.67) and nHW participants (OR = 2.79, 95% CI = 1.21–6.44) but uniquely associated with faster decline in AA participants (β = 1.71, 95% CI = 0.69–2.73, p = 0.001). Fewer AA participants reported antidepressant use (9/49, 18%) than nHW counterparts (57/78, 73%, p < 0.001). Vitamin B12 deficiency was also associated with an increased rate of cognitive decline in AA participants (β = 2.65, 95% CI = 0.38–4.91, p = 0.023).
Interpretation
Modifiable dementia risk factors are common in AA and nHW participants, representing important risk mitigation targets. Depression was associated with dementia in AA and nHW participants, and with accelerated declines in cognitive function in AA participants. Optimizing depression screening and treatment may improve cognitive trajectories and outcomes in AA participants. ANN NEUROL 2024;95:518–529
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Abstract Introduction A classification framework for posterior cortical atrophy (PCA) is proposed to improve the uniformity of definition of the syndrome in a variety of research settings. Methods ...Consensus statements about PCA were developed through a detailed literature review, the formation of an international multidisciplinary working party which convened on four occasions, and a Web-based quantitative survey regarding symptom frequency and the conceptualization of PCA. Results A three-level classification framework for PCA is described comprising both syndrome- and disease-level descriptions. Classification level 1 (PCA) defines the core clinical, cognitive, and neuroimaging features and exclusion criteria of the clinico-radiological syndrome. Classification level 2 (PCA-pure, PCA-plus) establishes whether, in addition to the core PCA syndrome, the core features of any other neurodegenerative syndromes are present. Classification level 3 (PCA attributable to AD PCA-AD, Lewy body disease PCA-LBD, corticobasal degeneration PCA-CBD, prion disease PCA-prion) provides a more formal determination of the underlying cause of the PCA syndrome, based on available pathophysiological biomarker evidence. The issue of additional syndrome-level descriptors is discussed in relation to the challenges of defining stages of syndrome severity and characterizing phenotypic heterogeneity within the PCA spectrum. Discussion There was strong agreement regarding the definition of the core clinico-radiological syndrome, meaning that the current consensus statement should be regarded as a refinement, development, and extension of previous single-center PCA criteria rather than any wholesale alteration or redescription of the syndrome. The framework and terminology may facilitate the interpretation of research data across studies, be applicable across a broad range of research scenarios (e.g., behavioral interventions, pharmacological trials), and provide a foundation for future collaborative work.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
APOE4 is the strongest genetic risk factor associated with late-onset Alzheimer's disease (AD). To address the underlying mechanism, we develop cerebral organoid models using induced pluripotent stem ...cells (iPSCs) with APOE ε3/ε3 or ε4/ε4 genotype from individuals with either normal cognition or AD dementia. Cerebral organoids from AD patients carrying APOE ε4/ε4 show greater apoptosis and decreased synaptic integrity. While AD patient-derived cerebral organoids have increased levels of Aβ and phosphorylated tau compared to healthy subject-derived cerebral organoids, APOE4 exacerbates tau pathology in both healthy subject-derived and AD patient-derived organoids. Transcriptomics analysis by RNA-sequencing reveals that cerebral organoids from AD patients are associated with an enhancement of stress granules and disrupted RNA metabolism. Importantly, isogenic conversion of APOE4 to APOE3 attenuates the APOE4-related phenotypes in cerebral organoids from AD patients. Together, our study using human iPSC-organoids recapitulates APOE4-related phenotypes and suggests APOE4-related degenerative pathways contributing to AD pathogenesis.
Objective
The objective of this study was to describe clinical features, 18F‐fluorodeoxyglucose (FDG)‐positron emission tomography (PET) metabolism and digital pathology in patients with logopenic ...progressive aphasia (LPA) and pathologic diagnosis of diffuse Lewy body disease (DLBD) and compare to patients with LPA with other pathologies, as well as patients with classical features of probable dementia with Lewy bodies (pDLB).
Methods
This is a clinicopathologic case‐control study of 45 patients, including 20 prospectively recruited patients with LPA among whom 6 were diagnosed with LPA‐DLBD. We analyzed clinical features and compared FDG‐PET metabolism in LPA‐DLBD to an independent group of patients with clinical pDLB and regional α‐synuclein burden on digital pathology to a second independent group of autopsied patients with DLBD pathology and antemortem pDLB (DLB‐DLBD).
Results
All patients with LPA‐DLBD were men. Neurological, speech, and neuropsychological characteristics were similar across LPA‐DLBD, LPA‐Alzheimer's disease (LPA‐AD), and LPA‐frontotemporal lobar degeneration (LPA‐FTLD). Genetic screening of AD, DLBD, and FTLD linked genes were negative with the exception of APOE ε4 allele present in 83% of LPA‐DLBD patients. Seventy‐five percent of the patients with LPA‐DLBD showed a parietal‐dominant pattern of hy pometabolism; LPA‐FTLD – temporal‐dominant pattern, whereas LPA‐AD showed heterogeneous patterns of hypometabolism. LPA‐DLBD had more asymmetrical hypometabolism affecting frontal lobes, with relatively spared occipital lobe in the nondominantly affected hemisphere, compared to pDLB. LPA‐DLBD had minimal atrophy on gross brain examination, higher cortical Lewy body counts, and higher α‐synuclein burden in the middle frontal and inferior parietal cortices compared to DLB‐DLBD.
Interpretation
Whereas AD is the most frequent underlying pathology of LPA, DLBD can also be present and may contribute to the LPA phenotype possibly due to α‐synuclein‐associated functional impairment of the dominant parietal lobe. ANN NEUROL 2021;89:520–533
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
This study was undertaken to apply established and emerging cerebrospinal fluid (CSF) biomarkers to improve diagnostic accuracy in patients with rapidly progressive dementia (RPD). Overlap in ...clinical presentation and results of diagnostic tests confounds etiologic diagnosis in patients with RPD. Objective measures are needed to improve diagnostic accuracy and to recognize patients with potentially treatment-responsive causes of RPD.
Biomarkers of Alzheimer disease neuropathology (amyloid-β 42/40 ratio, phosphorylated tau p-tau181, p-tau231), neuroaxonal/neuronal injury (neurofilament light chain NfL, visinin-like protein-1 VILIP-1, total tau), neuroinflammation (chitinase-3-like protein YKL-40, soluble triggering receptor expressed on myeloid cells 2 sTREM2, glial fibrillary acidic protein GFAP, monocyte chemoattractant protein-1 MCP-1), and synaptic dysfunction (synaptosomal-associated protein 25kDa, neurogranin) were measured in CSF obtained at presentation from 78 prospectively accrued patients with RPD due to neurodegenerative, vascular, and autoimmune/inflammatory diseases; 35 age- and sex-matched patients with typically progressive neurodegenerative disease; and 72 cognitively normal controls. Biomarker levels were compared across etiologic diagnoses, by potential treatment responsiveness, and between patients with typical and rapidly progressive presentations of neurodegenerative disease.
Alzheimer disease biomarkers were associated with neurodegenerative causes of RPD. High NfL, sTREM2, and YKL-40 and low VILIP-1 identified patients with autoimmune/inflammatory diseases. MCP-1 levels were highest in patients with vascular causes of RPD. A multivariate model including GFAP, MCP-1, p-tau181, and sTREM2 identified the 44 patients with treatment-responsive causes of RPD with 89% accuracy. Minimal differences were observed between typical and rapidly progressive presentations of neurodegenerative disease.
Selected CSF biomarkers at presentation were associated with etiologic diagnoses and treatment responsiveness in patients with heterogeneous causes of RPD. The ability of cross-sectional biomarkers to inform upon mechanisms that drive rapidly progressive neurodegenerative disease is less clear. ANN NEUROL 2024;95:299-313.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Objective
Previous studies suggest that the brain‐derived neurotrophic factor (BDNF) Val66Met (rs6265) polymorphism may influence symptom onset in Alzheimer's disease (AD). Our recent cross‐sectional ...findings suggest that Met66 may influence clinical expression in dominantly inherited AD (DIAD) through its effects on tau. However, it remains unclear whether carriage of Met66 in DIAD results in faster increases in cerebrospinal fluid (CSF) tau and ptau181, and whether these increases are associated with accelerated brain volume loss and memory decline.
Methods
A total of 211 subjects (101 mutation noncarriers, 110 mutation carriers), who were cognitively normal, as defined by a Clinical Dementia Rating global score of 0, completed assessments of cognitive function, neuroimaging, and CSF sampling over 3.5 years as part of the Dominantly Inherited Alzheimer's Network.
Results
In mutation carriers, Met66 carriers showed faster memory decline (4×), hippocampal volume loss (16×), and CSF tau and ptau181 increases (6×) than Val66 homozygotes. BDNF did not influence rates of cortical β‐amyloid accumulation or change in CSF Aβ42 levels in mutation carriers. In mutation noncarriers, BDNF genotype had no effect on change in cognition, brain volume, cortical β‐amyloid accumulation, or change in any CSF measures of tau, ptau181, and CSF Aβ42.
Interpretation
As in sporadic AD, the deleterious effects of β‐amyloid on cognitive function, brain volume loss, and CSF tau in DIAD mutation carriers are less in Val66 homozygotes. The BDNF Val66Met polymorphism should be considered as a potential moderator of clinical trial outcomes in current treatment and prevention trials in DIAD and sporadic AD. Ann Neurol 2018;84:424–435
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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