A simple genetic stratification method for lower cost, more expedient clinical trials in early Alzheimer's disease: A preliminary study of tau PET and cognitive outcomes.

INTRODUCTION: Identifying individuals who are most likely to accumulate tau and exhibit cognitive decline is critical for Alzheimer's disease (AD) clinical trials. METHODS: Participants (N = 235) who were cognitively normal or with mild cognitive impairment from the Alzheimer's Disease Neuroimaging Initiative were stratified by a cutoff on the polygenic hazard score (PHS) at 65th percentile (above as high-risk group and below as low-risk group). We evaluated the associations between the PHS risk groups and tau positron emission tomography and cognitive decline, respectively. Power analyses estimated the sample size needed for clinical trials to detect differences in tau accumulation or cognitive change. RESULTS: The high-risk group showed faster tau accumulation and cognitive decline. Clinical trials using the high-risk group would require a fraction of the sample size as trials without this inclusion criterion. DISCUSSION: Incorporating a PHS inclusion criterion represents a low-cost and accessible way to identify potential participants for AD clinical trials.

Optimal Weighting of Preclinical Alzheimer's Cognitive Composite (PACC) Scales to Improve their Performance as Outcome Measures for Alzheimer's Disease Clinical Trials.

Introduction: Cognitive composite scales constructed by combining existing neuropsychometric tests are seeing wide application as endpoints for clinical trials and cohort studies of Alzheimer's disease (AD) predementia conditions. Preclinical Alzheimer's Cognitive Composite (PACC) scales are composite scores calculated as the sum of the component test scores weighted by the reciprocal of their standard deviations at the baseline visit. Reciprocal standard deviation is an arbitrary weighting in this context, and may be an inefficient utilization of the data contained in the component measures. Mathematically derived optimal composite weighting is a promising alternative. Methods: Sample size projections using standard power calculation formulas were used to describe the relative performance of component measures and their composites when used as endpoints for clinical trials. Power calculations were informed by (n=1,333) amnestic mild cognitive impaired participants in the National Alzheimer's Coordinating Center (NACC) Uniform Data Set. Results: A composite constructed using PACC reciprocal standard deviation weighting was both less sensitive to change than one of its component measures and less sensitive to change than its optimally weighted counterpart. In standard sample size calculations informed by NACC data, a clinical trial using the PACC weighting would require 38% more subjects than a composite calculated using optimal weighting. Discussion: These findings illustrate how reciprocal standard deviation weighting can result in inefficient cognitive composites, and underscore the importance of component weights to the performance of composite scales. In the future, optimal weighting parameters informed by accumulating clinical trial data may improve the efficiency of clinical trials in AD.

Sex differences in Alzheimer's disease: plasma MMP-9 and markers of disease severity.

BACKGROUND: Studies have reported higher plasma matrix metalloproteinase-9 (MMP-9) levels in mild cognitive impairment (MCI) and Alzheimer's disease (AD). Despite evidence that MMP-9 activity and its influence on AD pathophysiology may be modulated by sex hormones, sex differences in the association between MMP-9 and AD biomarkers and cognition have not been explored. METHODS: Our sample included 238 amyloid-ß (Aß)-positive participants with MCI or AD dementia from the Alzheimer's Disease Neuroimaging Initiative (37.4% women, 74.6 ± 7.3 years). We used linear regression models to examine whether sex modified free and total plasma MMP-9 associations with CSF t-tau, p-tau181, and Aß42. We used linear mixed effects models to examine whether sex modified total and free plasma MMP-9 associations with cognition, using longitudinal Mini-Mental Status Examination (MMSE) and Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-cog) data. RESULTS: Total and free MMP-9 levels did not differ by sex, but AD dementia patients had higher total MMP-9 levels than participants with MCI (ß = 0.06 [-0.11 to -0.01], p = 0.031). Sex modified the association of CSF t-tau with total (ß = 128.68 [55.37 to 201.99], p < 0.001) and free MMP-9 (ß = 98.61 [33.61 to 163.62], p = 0.003), whereby higher total and free MMP-9 correlated with higher CSF t-tau in women and lower CSF t-tau in men. Higher free MMP-9 correlated with lower CSF p-tau181 among men (ß = -14.98 [-27.37 to -2.58], p = 0.018), but not women. In participants with MCI, higher free MMP-9 levels were associated with higher CSF Aß42 among men (ß = 26.88 [4.03 to 49.73], p = 0.022) but not women. In the overall sample, higher free and total MMP-9 at baseline predicted worsening MMSE scores in women (ß = -2.10 [-3.97 to -0.27], p = 0.027 and ß = -2.24 [-4.32 to -0.18], p = 0.035) but not men. Higher free MMP-9 correlated with worse ADAS-cog scores (ß = 12.34 [3.02 to 21.65], p = 0.011) in women (ß = 12.34 [3.02 to 21.65], p = 0.011) but not men with AD dementia cross-sectionally but correlated with worsening ADAS-cog scores longitudinally only in men (ß = 8.98 [0.27 to 17.68], p = 0.042). CONCLUSIONS: MMP-9 may have more detrimental effects on AD-related pathological and cognitive changes in women. If replicated, our findings could help uncover potential mechanisms contributing to women's elevated susceptibility to AD.

Sex differences in plasma p-tau181 associations with Alzheimer's disease biomarkers, cognitive decline, and clinical progression.

Studies have shown that women on the Alzheimer's disease (AD) continuum have more pathological tau in the brain and cerebrospinal fluid (CSF), than men. Some studies have found that higher levels of tau biomarkers are more strongly associated with clinical AD, cognitive decline and neurodegeneration in women than in men. Despite major developments in the use of plasma tau phosphorylated at threonine 181 (p-tau181) as an AD biomarker, it is unknown whether these sex differences apply to plasma p-tau181. In 1060 Alzheimer's Disease Neuroimaging Initiative (ADNI) participants (47% women, 73.8 ± 7.6 years old), we examined sex differences in plasma p-tau181 levels and their association with other biomarkers, cognitive decline and incident AD. Linear regressions tested for an effect of sex on plasma p-tau181 levels and for plasma p-tau181 × sex interactions on CSF p-tau181, as well as entorhinal cortex tau, cortical amyloid-ß (Aß) deposition, and brain glucose metabolism, quantified using PET imaging. Linear mixed effects models tested for a sex × baseline plasma p-tau181 interaction on change in cognition over time. Finally, Cox models tested for a sex × plasma p-tau181 interaction on the risk of AD dementia in participants who were free of dementia at baseline. Despite similar plasma p-tau181 levels between sexes, women had lower brain glucose metabolism, greater brain Aß and entorhinal cortex tau deposition, higher CSF p-tau181 and faster cognitive decline in relation to higher baseline plasma p-tau181 levels compared with men. Among Aß positive, dementia-free participants, women had higher rates of incident AD dementia associated with increasing baseline plasma p-tau181 levels, relative to men. Our results suggest that sex may impact the clinical interpretation of plasma p-tau181 concentrations. If replicated, these findings could have important implications for the use of plasma p-tau181 as an accessible AD biomarker and screening tool for preventive and therapeutic clinical trials.

TDP-43 Pathology Exacerbates Cognitive Decline in Primary Age-Related Tauopathy.

OBJECTIVE: Primary age-related tauopathy (PART) refers to tau neurofibrillary tangles restricted largely to the medial temporal lobe in the absence of significant beta-amyloid plaques. PART has been associated with cognitive impairment, but contributions from concomitant limbic age-related TDP-43 encephalopathy neuropathologic change (LATE-NC) are underappreciated. METHODS: We compare prevalence of LATE-NC and vascular copathologies in age- and Braak-matched patients with PART (n = 45, Braak stage I-IV, Thal phase 0-2) or early stage Alzheimer disease neuropathologic change (ADNC; n = 51, Braak I-IV, Thal 3-5), and examine their influence on clinical and cognitive decline. RESULTS: Concomitant LATE-NC and vascular pathology were equally common, and cognition was equally impaired, in PART (Mini-Mental State Examination [MMSE] = 24.8 ± 6.9) and ADNC (MMSE = 24.2 ± 6.0). Patients with LATE-NC were more impaired than those without LATE-NC on the MMSE (by 5.8 points, 95% confidence interval [CI] = 3.0-8.6), Mattis Dementia Rating Scale (DRS; 17.5 points, 95% CI = 7.1-27.9), Clinical Dementia Rating, sum of boxes scale (CDR-sob; 5.2 points, 95% CI = 2.1-8.2), memory composite (0.8 standard deviations [SD], 95% CI = 0.1-1.6), and language composite (1.1 SD, 95% CI = 0.2-2.0), and more likely to receive a dementia diagnosis (odds ratio = 4.8, 95% CI = 1.5-18.0). Those with vascular pathology performed worse than those without on the DRS (by 10.2 points, 95% CI = 0.1-20.3) and executive composite (1.3 SD, 95% CI = 0.3-2.3). Cognition declined similarly in PART and ADNC over the 5 years preceding death; however, LATE-NC was associated with more rapid decline on the MMSE (ß = 1.9, 95% CI = 0.9-3.0), DRS (ß = 7.8, 95% CI = 3.4-12.7), CDR-sob (ß = 1.9, 95% CI = 0.4-3.7), language composite (ß = 0.5 SD, 95% CI = 0.1-0.8), and vascular pathology with more rapid decline on the DRS (ß = 5.2, 95% CI = 0.6-10.2). INTERPRETATION: LATE-NC, and to a lesser extent vascular copathology, exacerbate cognitive impairment and decline in PART and early stage ADNC. ANN NEUROL 2022;92:425-438.

Sex and APOE ɛ4 modify the effect of cardiovascular risk on tau in cognitively normal older adults.

The interaction between APOE ɛ4 and vascular risk factors on cognitive function is stronger in women than in men. These effects may be mediated by the amount of tau pathology in the brain. Therefore, we examined whether APOE ɛ4 and sex modify cross-sectional associations between cardiovascular risk and tau deposition in cognitively normal older adults from the Alzheimer's Disease Neuroimaging Initiative. We calculated the Framingham Heart Study cardiovascular disease risk score for 141 participants (74 women, 47 APOE ɛ4 carriers) with complete medical history data, processed tau-PET data and a Clinical Dementia Rating global score of 0.0 at the time of the tau-PET scan, implying no significant cognitive or functional impairment. We used linear regression models to examine the effects of sex, APOE ɛ4, cardiovascular risk and their interactions on tau deposition in the entorhinal cortex, inferior temporal cortex and a composite meta-region of interest of temporal lobe areas. We found a significant three-way interaction among sex, APOE ɛ4 status and cardiovascular disease risk on tau deposition in the entorhinal cortex (ß = 0.04; 95% CI, 0.01-0.07; P = 0.008), inferior temporal cortex (ß = 0.02; 95% CI, 0.0-0.05; P = 0.029) and meta-region (ß = 0.02; 95% CI, 0.0-0.04; P = 0.042). After stratifying by APOE ɛ4 status to examine interactions between sex and cardiovascular disease risk on tau in APOE ɛ4 carriers and non-carriers, we found a significant two-way interaction between sex and cardiovascular disease risk on tau in the entorhinal cortex (ß = 0.05; 95% CI, 0.02-0.08; P = 0.001), inferior temporal cortex (ß = 0.03; 95% CI, 0.01-0.05; P =0.009) and meta-region (ß = 0.02; 95% CI, 0.01-0.04; P = 0.008) only among APOE ɛ4 carriers. In analyses stratified by sex, higher cardiovascular risk scores were associated with higher levels of tau in the entorhinal cortex (ß = 0.05; 95% CI, 0.02-0.08; P = 0.002), inferior temporal cortex (ß = 0.02; 95% CI, 0.0-0.05; P = 0.023) and meta-region (ß = 0.02; 95% CI, 0.01-0.04; P = 0.013) in female APOE ɛ4 carriers but not in male carriers. Our findings suggest that cognitively normal older women carrying at least one APOE ɛ4 allele, may be particularly vulnerable to the effects of cardiovascular disease risk on early tau deposition.

Perceived Stress in Older Dementia Caregivers: Mediation by Loneliness and Depression.

Coupled with aging, chronic stress experienced by dementia caregivers often leads to deteriorating health. Comparing caregivers and non-caregivers, we tested whether depression and loneliness mediate the relationship between caregiver status and a measure of chronic stress, the Perceived Stress Scale. Seventy-six cognitively normal older adults (mean age 72.7) were identified as caregivers or non-caregivers based on the functional independence of a paired family member. Caregivers reported more perceived stress, depression, and loneliness than non-caregivers. Using multiple mediation analyses, we found that loneliness and depression mediated the relationship of caregiver status with perceived stress. The loneliness effect on perceived stress was both direct and via its relationship with depressive symptoms. The findings suggest loneliness as a likely point of intervention to reduce caregiver stress. Initiatives to enable caregivers to maintain or develop social relationships apart from caregiver responsibilities may mitigate stress and its negative impact on mental and physical health.

Committee on High-quality Alzheimer's Disease Studies (CHADS) consensus report.

BACKGROUND: Consensus guidance for the development and identification of high-quality Alzheimer's disease clinical trials is needed for protocol development and conduct of clinical trials. METHODS: An ad hoc consensus committee was convened in conjunction with the Alzheimer's Association to develop consensus recommendations. RESULTS: Consensus was readily reached for the need to provide scientific justification, registration of trials, institutional review board oversight, conflict of interest disclosure, funding source disclosure, defined trial population, recruitment resources, definition of the intervention, specification of trial duration, appropriate payment for participant engagement, risk-benefit disclosure as part of the consent process, and the requirement to disseminate and/or publish trial results even if the study is negative. CONCLUSIONS: This consensus guidance should prove useful for the protocol development and conduct of clinical trials, and may further provide a platform for the development of education materials that may help guide appropriate clinical trial participation decisions for potential trial participants and the general public.

Association of Neurofibrillary Tangle Distribution With Age at Onset-Related Clinical Heterogeneity in Alzheimer Disease: An Autopsy Study.

BACKGROUND AND OBJECTIVE: Patients with earlier age at onset of sporadic Alzheimer disease (AD) are more likely than those with later onset to present with atypical clinical and cognitive features. We sought to determine whether this age-related clinical and cognitive heterogeneity is mediated by different topographic distributions of tau-aggregate neurofibrillary tangles (NFTs) or by variable amounts of concomitant non-AD neuropathology. METHODS: The relative distribution of NFT density in hippocampus and midfrontal neocortex was calculated, and α-synuclein, TAR DNA binding protein 43 (TDP-43), and microvascular copathologies were staged, in patients with severe AD and age at onset of 51-60 (n = 40), 61-70 (n = 41), and >70 (n = 40) years. Regression, mediation, and mixed effects models examined relationships of pathologic findings with clinical features and longitudinal cognitive decline. RESULTS: Patients with later age at onset of AD were less likely to present with nonmemory complaints (odds ratio [OR] 0.46 per decade, 95% confidence interval [CI] 0.22-0.88), psychiatric symptoms (ß = -0.66, 95% CI -1.15 to -0.17), and functional impairment (ß = -1.25, 95% CI -2.34 to -0.16). TDP-43 (OR 2.00, 95% CI 1.23-3.35) and microvascular copathology (OR 2.02, 95% CI 1.24-3.40) were more common in later onset AD, and α-synuclein copathology was not related to age at onset. NFT density in midfrontal cortex (ß = -0.51, 95% CI -0.72 to -0.31) and midfrontal/hippocampal NFT ratio (ß = -0.18, 95% CI -0.26 to -0.10) were lower in those with later age at onset. Executive function (ß = 0.48, 95% CI 0.09-0.90) and visuospatial cognitive deficits (ß = 0.97, 95% CI 0.46-1.46) were less impaired in patients with later age at onset. Mediation analyses showed that the effect of age at onset on severity of executive function deficits was mediated by midfrontal/hippocampal NFT ratio (ß = 0.21, 95% CI 0.08-0.38) and not by concomitant non-AD pathologies. Midfrontal/hippocampal NFT ratio also mediated an association between earlier age at onset and faster decline on tests of global cognition, executive function, and visuospatial abilities. DISCUSSION: Worse executive dysfunction and faster cognitive decline in people with sporadic AD with earlier rather than later age at onset is mediated by greater relative midfrontal neocortical to hippocampal NFT burden and not by concomitant non-AD neuropathology.

A phase II study repurposing atomoxetine for neuroprotection in mild cognitive impairment.

The locus coeruleus is the initial site of Alzheimer's disease neuropathology, with hyperphosphorylated Tau appearing in early adulthood followed by neurodegeneration in dementia. Locus coeruleus dysfunction contributes to Alzheimer's pathobiology in experimental models, which can be rescued by increasing norepinephrine transmission. To test norepinephrine augmentation as a potential disease-modifying therapy, we performed a biomarker-driven phase II trial of atomoxetine, a clinically-approved norepinephrine transporter inhibitor, in subjects with mild cognitive impairment due to Alzheimer's disease. The design was a single-centre, 12-month double-blind crossover trial. Thirty-nine participants with mild cognitive impairment and biomarker evidence of Alzheimer's disease were randomized to atomoxetine or placebo treatment. Assessments were collected at baseline, 6- (crossover) and 12-months (completer). Target engagement was assessed by CSF and plasma measures of norepinephrine and metabolites. Prespecified primary outcomes were CSF levels of IL1α and TECK. Secondary/exploratory outcomes included clinical measures, CSF analyses of amyloid-ß42, Tau, and pTau181, mass spectrometry proteomics and immune-based targeted inflammation-related cytokines, as well as brain imaging with MRI and fluorodeoxyglucose-PET. Baseline demographic and clinical measures were similar across trial arms. Dropout rates were 5.1% for atomoxetine and 2.7% for placebo, with no significant differences in adverse events. Atomoxetine robustly increased plasma and CSF norepinephrine levels. IL-1α and TECK were not measurable in most samples. There were no significant treatment effects on cognition and clinical outcomes, as expected given the short trial duration. Atomoxetine was associated with a significant reduction in CSF Tau and pTau181 compared to placebo, but not associated with change in amyloid-ß42. Atomoxetine treatment also significantly altered CSF abundances of protein panels linked to brain pathophysiologies, including synaptic, metabolism and glial immunity, as well as inflammation-related CDCP1, CD244, TWEAK and osteoprotegerin proteins. Treatment was also associated with significantly increased brain-derived neurotrophic factor and reduced triglycerides in plasma. Resting state functional MRI showed significantly increased inter-network connectivity due to atomoxetine between the insula and the hippocampus. Fluorodeoxyglucose-PET showed atomoxetine-associated increased uptake in hippocampus, parahippocampal gyrus, middle temporal pole, inferior temporal gyrus and fusiform gyrus, with carry-over effects 6 months after treatment. In summary, atomoxetine treatment was safe, well tolerated and achieved target engagement in prodromal Alzheimer's disease. Atomoxetine significantly reduced CSF Tau and pTau, normalized CSF protein biomarker panels linked to synaptic function, brain metabolism and glial immunity, and increased brain activity and metabolism in key temporal lobe circuits. Further study of atomoxetine is warranted for repurposing the drug to slow Alzheimer's disease progression.

Differential blood DNA methylation across Lewy body dementias.

INTRODUCTION: Dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD) are characterized by cognitive alterations, visual hallucinations, and motor impairment. Diagnosis is based on type and timing of clinical manifestations; however, determination of clinical subtypes is challenging. The utility of blood DNA methylation as a biomarker for Lewy body disorders (LBD) is mostly unexplored. METHODS: We performed a cross-sectional analysis of blood methylation in 42 DLB and 50 PDD cases applying linear models to compare groups and logistic least absolute shrinkage and selection operator regression to explore the discriminant power of methylation signals. RESULTS: DLB blood shows differential methylation compared to PDD. Some methylation changes associate with core features of LBD. Sets of probes show high predictive value to discriminate between variants. DISCUSSION: Our study is the first to explore LBD blood methylation. Despite overlapping clinical presentation, we detected differential epigenetic signatures that, if confirmed in independent cohorts, could be developed into useful biomarkers.

Age-at-Onset and APOE-Related Heterogeneity in Pathologically Confirmed Sporadic Alzheimer Disease.

OBJECTIVE: To characterize age-related clinical heterogeneity in Alzheimer disease (AD) and determine whether it is modified by APOE genotype or concomitant non-AD pathology, we analyzed data from 1,750 patients with sporadic, pathologically confirmed severe AD. METHODS: In this retrospective cohort study, regression and mixed effects models assessed effects of estimated age at onset, APOE genotype, and their interaction on standardized clinical, cognitive, and pathologic outcome measures from the National Alzheimer's Coordinating Center database. RESULTS: A bimodal distribution of age at onset frequency in APOE ε4- cases showed best separation at age 63. Using this age cutoff, cases were grouped as ε4- early-onset AD (EOAD) (n = 169), ε4+ EOAD (n = 273), ε4- late-onset AD (LOAD) (n = 511), and ε4+ LOAD (n = 797). Patients with EOAD were more likely than patients with LOAD to present with noncognitive behavioral or motor symptoms or nonmemory cognitive complaints, and had more executive dysfunction, but less language impairment on objective cognitive testing. Age at onset and ε4- genotype were independently associated with lower baseline Mini-Mental State Examination scores and greater functional impairment and patients with EOAD had faster cognitive and functional decline than patients with LOAD regardless of APOE genotype. Patients with EOAD were more likely than patients with LOAD to receive a non-AD clinical diagnosis even though they were more likely to have pure AD without concomitant vascular or other non-AD neurodegenerative pathology. CONCLUSIONS: Early-onset sporadic AD is associated with a greater likelihood of an atypical, non-memory-dominant clinical presentation, especially in the absence of the APOE ε4 allele, which may lead to misattribution to non-AD underlying pathology.

Power formulas for mixed effects models with random slope and intercept comparing rate of change across groups.

We have previously derived power calculation formulas for cohort studies and clinical trials using the longitudinal mixed effects model with random slopes and intercepts to compare rate of change across groups [Ard & Edland, Power calculations for clinical trials in Alzheimer's disease. J Alzheim Dis 2011;21:369-77]. We here generalize these power formulas to accommodate 1) missing data due to study subject attrition common to longitudinal studies, 2) unequal sample size across groups, and 3) unequal variance parameters across groups. We demonstrate how these formulas can be used to power a future study even when the design of available pilot study data (i.e., number and interval between longitudinal observations) does not match the design of the planned future study. We demonstrate how differences in variance parameters across groups, typically overlooked in power calculations, can have a dramatic effect on statistical power. This is especially relevant to clinical trials, where changes over time in the treatment arm reflect background variability in progression observed in the placebo control arm plus variability in response to treatment, meaning that power calculations based only on the placebo arm covariance structure may be anticonservative. These more general power formulas are a useful resource for understanding the relative influence of these multiple factors on the efficiency of cohort studies and clinical trials, and for designing future trials under the random slopes and intercepts model.

Community memory screening as a strategy for recruiting older adults into Alzheimer's disease research.

BACKGROUND: Growing awareness of Alzheimer's disease (AD) has prompted a demand for quick and effective ways to screen for memory loss and cognitive decline in large numbers of individuals in the community. Periodic Memory Screening Day events provide free, brief cognitive screening aimed at those 65 years and older, and can serve as an opportunity to gauge participants' attitudes towards AD research and recruit them into ongoing research projects. METHODS: Over 6 single-day events in 2 years, more than 574 individuals were individually screened using the MoCA and a story recall task (immediate and delayed), given feedback about their performance, and introduced to AD research and opportunities to participate. RESULTS: Screening classified 297 individuals (52.0%) as having "No Decline," 192 (33.6%) as "Possible decline," and 82 (14.4%) as "Likely decline." Those with "Likely decline" were older and less educated, had more memory concerns, were more likely to be men, and were less likely to have a positive family history of dementia than those with "No Decline." Subsequent validation of screening procedures against a full clinical evaluation showed 72% classification accuracy with a skew towards over-calling Possible and Likely decline and thereby guiding questionable individuals to a more thorough evaluation. Of those screened, 378 (66%) agreed to additional research and consented to being listed in a research registry, and a majority (70-85%) of those consenting reported they were amenable to various AD research procedures including lumbar puncture, MRI, and autopsy. Overall, 19.1% of those screened met inclusion criteria for ongoing studies and were successfully recruited into AD research. CONCLUSIONS: Conducting a few concentrated community memory screening events each year may help meet the public's demand for brief assessment of memory concerns and can be a relatively effective and efficient recruitment strategy for AD research.

Cognitive decline profiles differ in Parkinson disease dementia and dementia with Lewy bodies.

OBJECTIVE: To examine whether domain-specific patterns of cognitive impairment and trajectories of decline differed in patients with clinically diagnosed Parkinson disease dementia (PDD) (N = 29) and autopsy-confirmed dementia with Lewy bodies (DLB) (N = 58) or Alzheimer disease (AD) (N = 174) and to determine the impact of pooling patients with PDD and DLB in clinical trials targeting cognition. METHODS: Patients were matched on demographics and level of global cognitive impairment. Patterns of cross-sectional performance and longitudinal decline were examined in 4 cognitive domains: Visuospatial, Memory, Executive, and Language. Power analyses were performed to determine the numbers of participants needed to adequately power a hypothetical clinical trial to slow cognitive decline in pure PDD, pure DLB, or a mixed PDD/DLB group. RESULTS: Both DLB and PDD were more impaired and declined more rapidly than AD in the Visuospatial domain. Patients with PDD exhibited the most impairment and fastest decline in Executive, although patients with DLB also declined faster than AD. Memory was more impaired in AD than DLB and in both compared with PDD; however, all 3 groups declined at comparable rates. In contrast, PDD declined at a slower rate on Language measures than DLB or AD. Power analyses suggest that Visuospatial and Executive outcome measures would be most sensitive in PDD, but Memory and Language in DLB. CONCLUSION: DLB and PDD differ from each other, and from AD, in a cognitive domain-specific manner. As such, different outcome measures may be most sensitive to detecting changes in DLB vs PDD, suggesting that the 2 should be analyzed separately in clinical trials.

Shortening heparan sulfate chains prolongs survival and reduces parenchymal plaques in prion disease caused by mobile, ADAM10-cleaved prions.

Cofactors are essential for driving recombinant prion protein into pathogenic conformers. Polyanions promote prion aggregation in vitro, yet the cofactors that modulate prion assembly in vivo remain largely unknown. Here we report that the endogenous glycosaminoglycan, heparan sulfate (HS), impacts prion propagation kinetics and deposition sites in the brain. Exostosin-1 haploinsufficient (Ext1+/-) mice, which produce short HS chains, show a prolonged survival and a redistribution of plaques from the parenchyma to vessels when infected with fibrillar prions, and a modest delay when infected with subfibrillar prions. Notably, the fibrillar, plaque-forming prions are composed of ADAM10-cleaved prion protein lacking a glycosylphosphatidylinositol anchor, indicating that these prions are mobile and assemble extracellularly. By analyzing the prion-bound HS using liquid chromatography-mass spectrometry (LC-MS), we identified the disaccharide signature of HS differentially bound to fibrillar compared to subfibrillar prions, and found approximately 20-fold more HS bound to the fibrils. Finally, LC-MS of prion-bound HS from human patients with familial and sporadic prion disease also showed distinct HS signatures and higher HS levels associated with fibrillar prions. This study provides the first in vivo evidence of an endogenous cofactor that accelerates prion disease progression and enhances parenchymal deposition of ADAM10-cleaved, mobile prions.

Brain Injury and Later-Life Cognitive Impairment and Neuropathology: The Honolulu-Asia Aging Study.

BACKGROUND: Findings are inconsistent regarding the role of traumatic head injury in the subsequent development of neurologic outcomes. OBJECTIVE: Examine the relationship between head injury and later cognitive impairment. METHODS: A sample of 3,123 Japanese-American men was assessed for history of head injury and evaluated for cognitive impairment using the Cognitive Abilities Screening Instrument (CASI). For a subsample of 676 respondents, neuropathologic results from those with and without head injury were compared. RESULTS: Although the crude model showed an association between history of head injury and later severe cognitive impairment, the relationship lost significance in the adjusted model (OR = 1.320, CI: 0.90-1.93), regardless of time between injury and impairment. Similar to cognitive impairment, hippocampal sclerosis was observed significantly more in the brains of respondents with a history of head injury in the crude model, but the relationship weakened in the adjusted model (OR = 1.462, CI: 0.68-3.12). After adjustment, decedents with a head injury demonstrated marginally higher brain weight (OR = 1.003, CI: 1.00-1.01). CONCLUSION: We did not find a relationship between head injury and subsequent cognitive decline in this cohort. The neuropathology results also displayed no strong association between history of head injury and specific brain lesions and characteristics. These results support other findings in prospective cohorts. However, they could be influenced by the demographic make-up of the sample (male Japanese-Americans) or by the observation that the majority reported only a single head injury.

Sex-specific composite scales for longitudinal studies of incipient Alzheimer's disease.

INTRODUCTION: The impact of Alzheimer's disease (AD) on cognitive decline differs by sex. Composite scores are useful as singular outcomes in clinical trials, yet to date these have not been developed to measure sex-specific change. METHOD: We derived optimal composites from component scales available in the AD Neuroimaging Initiative (ADNI) database among cognitively normal and mild cognitively impaired subjects who are cerebrospinal fluid amyloid-ß positive for early AD. Maximally sensitive composites were constructed separately for men and women using standard formulas. We compared the statistical power of the composites with the ADNI Prodromal Alzheimer's Cognitive Composite. RESULTS: Among 9 cognitive measures and clinical dementia rating sum of boxes, the optimal sex-specific composites included 5 measures, including the clinical dementia rating and 4 distinct cognitive measures. The sex-specific composites consistently outperformed sex-agnostic composites and the ADNI Prodromal Alzheimer's Cognitive Composite. DISCUSSION: Sex-specific composite scales may improve the power of longitudinal studies of early AD and clinical trials.