Publications in Dementia by NOMIS researchers

Objective: The amyloid cascade hypothesis of Alzheimer disease (AD) has been increasingly challenged. Here, we aim to refocus the amyloid cascade hypothesis on its original premise that the accumulation of amyloid beta (Aβ) peptide is the primary and earliest event in AD pathogenesis as based on current evidence, initiating several pathological events and ultimately leading to AD dementia. Background: An ongoing debate about the validity of the amyloid cascade hypothesis for AD has been triggered by clinical trials with investigational disease-modifying drugs targeting Aβ that have not demonstrated consistent clinically meaningful benefits. Updated Hypothesis: It is an open question if monotherapy targeting Aβ pathology could be markedly beneficial at a stage when the brain has been irreversibly damaged by a cascade of pathological changes. Interventions in cognitively unimpaired individuals at risk for dementia, during amyloid-only and pre-amyloid stages, are more appropriate for proving or refuting the amyloid hypothesis. Our updated hypothesis states that anti-Aβ investigational therapies are likely to be most efficacious when initiated in the preclinical (asymptomatic) stages of AD and specifically when the disease is driven primarily by amyloid pathology. Given the young age at symptom onset and the deterministic nature of the mutations, autosomal dominant AD (ADAD) mutation carriers represent the ideal population to evaluate the efficacy of putative disease-modifying Aβ therapies. Major Challenges for the Hypothesis: Key challenges of the amyloid hypothesis include the recognition that disrupted Aβ homeostasis alone is insufficient to produce the AD pathophysiologic process, poor correlation of Aβ with cognitive impairment, and inconclusive data regarding clinical efficacy of therapies targeting Aβ. Challenges of conducting ADAD research include the rarity of the disease and uncertainty of the generalizability of ADAD findings for the far more common “sporadic” late-onset AD. Linkage to Other Major Theories: The amyloid cascade hypothesis, modified here to pertain to the preclinical stage of AD, still needs to be integrated with the development and effects of tauopathy and other co-pathologies, including neuroinflammation, vascular insults, synucleinopathy, and many others.

Introduction: Females may have greater susceptibility to Alzheimer’s disease (AD)-pathology. We examined the effect of sex on pathology, neurodegeneration, and memory in cognitively-unimpaired Presenilin-1 (PSEN1) E280A mutation carriers and non-carriers. Methods: We analyzed baseline data from 167 mutation carriers and 75 non-carriers (ages 30 to 53) from the Alzheimer’s Prevention Initiative Autosomal Dominant AD Trial, including florbetapir- and fludeoxyglucose-PET, MRI based hippocampal volume and cognitive testing. Results: Females exhibited better delayed recall than males, controlling for age, precuneus glucose metabolism, and mutation status, although the effect was not significant among PSEN1 mutation carriers only. APOE ε4 did not modify the effect of sex on AD biomarkers and memory. Discussion: Our findings suggest that, among cognitively-unimpaired individuals at genetic risk for autosomal-dominant AD, females may have greater cognitive resilience to AD pathology and neurodegeneration than males. Further investigation of sex-specific differences in autosomal-dominant AD is key to elucidating mechanisms of AD risk and resilience.

Introduction: The Alzheimer’s Prevention Initiative Autosomal-Dominant Alzheimer’s Disease (API ADAD) Trial evaluated the anti-oligomeric amyloid beta (Aβ) antibody therapy crenezumab in cognitively unimpaired members of the Colombian presenilin 1 (PSEN1) E280A kindred. We report availability, methods employed to protect confidentiality and anonymity of participants, and process for requesting and accessing baseline data. Methods: We developed mechanisms to share baseline data from the API ADAD Trial in consultation with experts and other groups sharing data from Alzheimer’s disease (AD) prevention trials, balancing the need to protect anonymity and trial integrity with making data broadly available to accelerate progress in the field. We pressure-tested deliberate and inadvertent potential threats under specific assumptions, employed a system to suppress or mask both direct and indirect identifying variables, limited and firewalled data managers, and put forth specific principles requisite to receive data. Results: Baseline demographic, PSEN1 E280A and apolipoprotein E genotypes, florbetapir and fluorodeoxyglucose positron emission tomography, magnetic resonance imaging, clinical, and cognitive data can now be requested by interested researchers. Discussion: Baseline data are publicly available; treatment data and biological samples, including baseline and treatment-related blood-based biomarker data will become available in accordance with our original trial agreement and subsequently developed Collaboration for Alzheimer’s Prevention principles. Sharing of these data will allow exploration of important questions including the differential effects of initiating an investigational AD prevention therapy both before as well as after measurable Aβ plaque deposition.

Introduction: The API AutosomalDominant AD (ADAD) Colombia Trial is a placebo-controlled clinical trial of crenezumab in 252 cognitively unimpaired 30 to 60-year-old Presenilin 1 (PSEN1) E280A kindred members, including mutation carriers randomized to active treatment or placebo and non-carriers who receive placebo. Methods: Of the 252 enrolled, we present data on a total of 242 mutation carriers and non-carriers matched by age range, excluding data on 10 participants to protect participant confidentiality, genetic status, and trial integrity. Results: We summarize demographic, clinical, cognitive, and behavioral data from 167 mutation carriers and 75 non-carriers, 30 to 53 years of age. Carriers were significantly younger than non-carriers ((mean age ± SD) 37 ± 5 vs 42 ± 6), had significantly lower Mini Mental Status Exam (MMSE) scores (28.8 ± 1.4 vs 29.2 ± 1.0), and had consistently lower memory scores. Discussion: Although PSEN1 E280A mutation carriers in the Trial are cognitively unimpaired, they have slightly lower MMSE and memory scores than non-carriers. Their demographic characteristics are representative of the local population.

Introduction: Recruitment for Alzheimer’s disease (AD) prevention research studies is challenging because of lack of awareness among cognitively healthy adults coupled with the high screen fail rate due to participants not having a genetic risk factor or biomarker evidence of the disease. Participant recruitment registries offer one solution for efficiently and effectively identifying, characterizing, and connecting potential eligible volunteers to studies. Methods: Individuals aged 55-75 years who live in the United States and self-report not having a diagnosis of cognitive impairment such as MCI or dementia are eligible to join GeneMatch. Participants enroll online and are provided a cheek swab kit for DNA extraction and apolipoprotein E (APOE) genotyping. Participants are not told their APOE results, although the results may be used in part to help match participants to AD prevention studies. Results: As of August 2018, 75,351 participants had joined GeneMatch. Nearly 30% of participants have one APOE4 allele, and approximately 3% have two APOE4 alleles. The percentages of APOE4 heterozygotes and homozygotes are inversely associated with age (P <.001). Discussion: GeneMatch, the first trial-independent research enrollment program designed to recruit and refer cognitively healthy adults to AD prevention studies based in part on APOE test results, provides a novel mechanism to accelerate prescreening and enrollment for AD prevention trials.

Background There is growing interest in the evaluation of preclinical Alzheimer’s disease (AD) treatments. As a result, there is a need to identify a cognitive composite that is sensitive to track preclinical AD decline to be used as a primary endpoint in treatment trials. Methods Longitudinal data from initially cognitively normal, 70- to 85-year-old participants in three cohort studies of aging and dementia from the Rush Alzheimer’s Disease Center were examined to empirically define a composite cognitive endpoint that is sensitive to detect and track cognitive decline before the onset of cognitive impairment. The mean-to-standard deviation ratios (MSDRs) of change over time were calculated in a search for the optimal combination of cognitive tests/subtests drawn from the neuropsychological battery in cognitively normal participants who subsequently progressed to clinical stages of AD during 2- and 5-year periods, using data from those who remained unimpaired during the same period to correct for aging and practice effects. Combinations that performed well were then evaluated for representation of relevant cognitive domains, robustness across individual years before diagnosis, and occurrence of selected items within top performing combinations. Results The optimal composite cognitive test score comprised seven cognitive tests/subtests with an MSDR = 0.964. By comparison, the most sensitive individual test score was Logical Memory Delayed Recall with an MSDR = 0.64. Conclusions We have identified a composite cognitive test score representing multiple cognitive domains that has improved power compared with the most sensitive single test item to track preclinical AD decline and evaluate preclinical AD treatments. We are confirming the power of the composite in independent cohorts and with other analytical approaches, which may result in refinements, have designated it as the primary endpoint in the Alzheimer’s Prevention Initiative’s preclinical treatment trials for individuals at high imminent risk for developing symptoms due to late-onset AD.