Cross-sectional and longitudinal comparisons of biomarkers and cognition among asymptomatic middle-aged individuals with a parental history of either autosomal dominant or late-onset Alzheimer's disease.

BACKGROUND: Comparisons of late-onset Alzheimer's disease (LOAD) and autosomal dominant AD (ADAD) are confounded by age. METHODS: We compared biomarkers from cerebrospinal fluid (CSF), magnetic resonance imaging, and amyloid imaging with Pittsburgh Compound-B (PiB) across four groups of 387 cognitively normal participants, 42 to 65 years of age, in the Dominantly Inherited Alzheimer Network (DIAN) and the Adult Children Study (ACS) of LOAD: DIAN mutation carriers (MCs) and non-carriers (NON-MCs), and ACS participants with a positive (FH+) and negative (FH-) family history of LOAD. RESULTS: At baseline, MCs had the lowest age-adjusted level of CSF Aß42 and the highest levels of total and phosphorylated tau-181, and PiB uptake. Longitudinally, MC had similar increase in PiB uptake to FH+, but drastically faster decline in hippocampal volume than others, and was the only group showing cognitive decline. DISCUSSION: Preclinical ADAD and LOAD share many biomarker signatures, but cross-sectional and longitudinal differences may exist.

Development of a Comprehensive Battery to Collect Social and Structural Determinants of Health (SSDOH) in Cognitively Normal or Very Mildly Impaired Persons.

INTRODUCTION: Research addressing Alzheimer disease and related dementias must examine nonbiological factors influencing the risk for and expression of Alzheimer disease and related dementias. These factors address the interplay of cognition with lived experiences and social and structural determinants of health (SSDOH). However, coordinated measures of SSDOH are limited. METHODS: The Knight Alzheimer Disease Research Center (ADRC) at Washington University in St. Louis developed and piloted a comprehensive battery to measure SSDOH. One hundred and twelve participants, very mildly cognitively impaired or unimpaired, enrolled in memory studies completed the electronic SSDOH battery. The Clinical Dementia Rating (CDR) determined the presence or absence of cognitive impairment. RESULTS: Four domains demonstrated above acceptable intraclass correlation scores for test-retest reliability (≥0.70), including adverse childhood events, discrimination, social status, and early education. Twenty very mildly impaired participants completed the electronic pilot study. CONCLUSION: Our findings indicate that participants with early-stage symptomatic Alzheimer disease are able to participate in electronic SSDOH data collection. In collaboration with the University of Pennsylvania ADRC, we replaced/modified certain assessments to increase intraclass correlation. The resulting battery, Social and Structural Life-courses Influencing Aging and Dementia (SS-DIAD), can serve as a SSDOH collection tool and is currently utilized in cognitively impaired and unimpaired research participants at both ADRCs.

Different rates of cognitive decline in autosomal dominant and late-onset Alzheimer disease.

As prevention trials advance with autosomal dominant Alzheimer disease (ADAD) participants, understanding the similarities and differences between ADAD and "sporadic" late-onset AD (LOAD) is critical to determine generalizability of findings between these cohorts. Cognitive trajectories of ADAD mutation carriers (MCs) and autopsy-confirmed LOAD individuals were compared to address this question. Longitudinal rates of change on cognitive measures were compared in ADAD MCs (n = 310) and autopsy-confirmed LOAD participants (n = 163) before and after symptom onset (estimated/observed). LOAD participants declined more rapidly in the presymptomatic (preclinical) period and performed more poorly at symptom onset than ADAD participants on a cognitive composite. After symptom onset, however, the younger ADAD MCs declined more rapidly. The similar but not identical cognitive trajectories (declining but at different rates) for ADAD and LOAD suggest common AD pathologies but with some differences.

African Americans Have Differences in CSF Soluble TREM2 and Associated Genetic Variants.

OBJECTIVE: To evaluate for racial differences in triggering receptor expressed on myeloid cells 2 (TREM2), a key immune mediator in Alzheimer disease, the levels of CSF soluble TREM2 (sTREM2), and the frequency of associated genetic variants were compared in groups of individuals who self-reported their race as African American (AA) or non-Hispanic White (NHW). METHODS: Community-dwelling older research participants underwent measurement of CSF sTREM2 concentrations and genetic analyses. RESULTS: The primary cohort included 91 AAs and 868 NHWs. CSF sTREM2 levels were lower in the AA compared with the NHW group (1,336 ± 470 vs 1,856 ± 624 pg/mL, p < 0.0001). AAs were more likely to carry TREM2 coding variants (15% vs 3%, p < 0.0001), which were associated with lower CSF sTREM2. AAs were less likely to carry the rs1582763 minor allele (8% vs 37%, p < 0.0001), located near MS4A4A, which was associated with higher CSF sTREM2. These findings were replicated in an independent cohort of 23 AAs and 917 NHWs: CSF sTREM2 levels were lower in the AA group (p = 0.03), AAs were more likely to carry coding TREM2 variants (22% vs 4%, p = 0.002), and AAs were less likely to carry the rs1582763 minor allele (16% vs 37%, p = 0.003). CONCLUSIONS: On average, AAs had lower CSF sTREM2 levels compared with NHWs, potentially because AAs are more likely to carry genetic variants associated with lower CSF sTREM2 levels. Importantly, CSF sTREM2 reflects TREM2-mediated microglial activity, a critical step in the immune response to amyloid plaques. These findings suggest that race may be associated with risk for genetic variants that influence Alzheimer disease-related inflammation.

Lack of association between acute stroke, post-stroke dementia, race, and ß-amyloid status.

INTRODUCTION: Stroke and Alzheimer disease share risk factors and often co-occur, and both have been reported to have a higher prevalence in African Americans as compared to non-Hispanic whites. However, their interaction has not been established. The objective of this study was to determine if preclinical Alzheimer disease is a risk factor for stroke and post-stroke dementia and whether racial differences moderate this relationship. METHODS: This case-control study was analyzed in 2019 using retrospective data from 2007 to 2013. Participants were adults age 65 and older with and without acute ischemic stroke. Recruitment included word of mouth and referrals in Saint Louis, MO, with stroke participants recruited from acutely hospitalized patients and non-stroke participants from community living older adults who were research volunteers. Our assessment included radiologic reads of infarcts, microbleeds, and white matter hyperintensitites (WMH); a Pittsburgh Compound B PET measure of cortical ß-amyloid binding; quantitative measures of hippocampal and WMH volume; longitudinal Mini Mental State Examination (MMSE) scores; and Clinical Dementia Rating (CDR) 1 year post-stroke. RESULTS: A total of 243 participants were enrolled, 81 of which had a recent ischemic stroke. Participants had a mean age of 75, 57% were women, and 52% were African American. Cortical amyloid did not differ significantly by race, stroke status, or CDR post-stroke. There were racial differences in MMSE scores at baseline (mean 26.8 for African Americans, 27.9 for non-Hispanic whites, p = 0.03), but not longitudinally. African Americans were more likely to have microbleeds (32.8% vs 22.6%, p = 0.04), and within the acute stroke group, African Americans were more likely to have small infarcts (75.6% vs 56.8%, p = 0.049). CONCLUSION: Preclinical Alzheimer disease did not show evidence of being a risk factor for stroke nor predictive of post-stroke dementia. We did not observe racial differences in ß-amyloid levels. However, even after controlling for several vascular risk factors, African Americans with clinical stroke presentations had greater levels of vascular pathology on MRI.

Reduced non-rapid eye movement sleep is associated with tau pathology in early Alzheimer's disease.

In Alzheimer's disease (AD), deposition of insoluble amyloid-ß (Aß) is followed by intracellular aggregation of tau in the neocortex and subsequent neuronal cell loss, synaptic loss, brain atrophy, and cognitive impairment. By the time even the earliest clinical symptoms are detectable, Aß accumulation is close to reaching its peak and neocortical tau pathology is frequently already present. The period in which AD pathology is accumulating in the absence of cognitive symptoms represents a clinically relevant time window for therapeutic intervention. Sleep is increasingly recognized as a potential marker for AD pathology and future risk of cognitive impairment. Previous studies in animal models and humans have associated decreased non-rapid eye movement (NREM) sleep slow wave activity (SWA) with Aß deposition. In this study, we analyzed cognitive performance, brain imaging, and cerebrospinal fluid (CSF) AD biomarkers in participants enrolled in longitudinal studies of aging. In addition, we monitored their sleep using a single-channel electroencephalography (EEG) device worn on the forehead. After adjusting for multiple covariates such as age and sex, we found that NREM SWA showed an inverse relationship with AD pathology, particularly tauopathy, and that this association was most evident at the lowest frequencies of NREM SWA. Given that our study participants were predominantly cognitively normal, this suggested that changes in NREM SWA, especially at 1 to 2 Hz, might be able to discriminate tau pathology and cognitive impairment either before or at the earliest stages of symptomatic AD.

Assessment of Racial Disparities in Biomarkers for Alzheimer Disease.

Importance: Racial differences in molecular biomarkers for Alzheimer disease may suggest race-dependent biological mechanisms. Objective: To ascertain whether there are racial disparities in molecular biomarkers for Alzheimer disease. Design, Setting, and Participants: A total of 1255 participants (173 African Americans) were enrolled from January 1, 2004, through December 31, 2015, in longitudinal studies at the Knight Alzheimer Disease Research Center at Washington University and completed a magnetic resonance imaging study of the brain and/or positron emission tomography of the brain with Pittsburgh compound B (radioligand for aggregated amyloid-ß) and/or cerebrospinal fluid (CSF) assays for the concentrations of amyloid-ß42, total tau, and phosphorylated tau181. Independent cross-sectional analyses were conducted from April 22, 2016, to August 27, 2018, for each biomarker modality with an analysis of variance or analysis of covariance including age, sex, educational level, race, apolipoprotein E (APOE) ε4 allele status, and clinical status (normal cognition or dementia). All biomarker assessments were conducted without knowledge of the clinical status of the participants. Main Outcomes and Measures: The primary outcomes were hippocampal volumes adjusted for differences in intracranial volumes, global cerebral amyloid burden as transformed into standardized uptake value ratios (partial volume corrected), and CSF concentrations of amyloid-ß42, total tau, and phosphorylated tau181. Results: Of the 1255 participants (707 women and 548 men; mean [SD] age, 70.8 [9.9] years), 116 of 173 African American participants (67.1%) and 724 of 1082 non-Hispanic white participants (66.9%) had normal cognition. There were no racial differences in the frequency of cerebral ischemic lesions noted on results of brain magnetic resonance imaging, mean cortical standardized uptake value ratios for Pittsburgh compound B, or for amyloid-ß42 concentrations in CSF. However, in individuals with a reported family history of dementia, mean (SE) total hippocampal volumes were lower for African American participants than for white participants (6418.26 [138.97] vs 6990.50 [44.10] mm3). Mean (SE) CSF concentrations of total tau were lower in African American participants than in white participants (293.65 [34.61] vs 443.28 [18.20] pg/mL; P < .001), as were mean (SE) concentrations of phosphorylated tau181 (53.18 [4.91] vs 70.73 [2.46] pg/mL; P < .001). There was a significant race by APOE ε4 interaction for both CSF total tau and phosphorylated tau181 such that only APOE ε4-positive participants showed the racial differences. Conclusions and Relevance: The results of this study suggest that analyses of molecular biomarkers of Alzheimer disease should adjust for race. The lower CSF concentrations of total tau and phosphorylated tau181 in African American individuals appear to reflect a significant race by APOE ε4 interaction, suggesting a differential effect of this Alzheimer risk variant in African American individuals compared with white individuals.

Longitudinal decreases in multiple cerebrospinal fluid biomarkers of neuronal injury in symptomatic late onset Alzheimer's disease.

INTRODUCTION: Individuals in early stages of Alzheimer's disease are a targeted population for secondary prevention trials aimed at preserving normal cognition. Understanding within-person biomarker(s) change over time is critical for trial enrollment and design. METHODS: Longitudinal cerebrospinal fluid samples from the Alzheimer's Disease Neuroimaging Initiative were assayed for novel markers of neuronal/synaptic injury (visinin-like protein 1, Ng, and SNAP-25) and neuroinflammation (YKL-40) and compared with ß amyloid 42, tau, and phospho-tau181. General linear mixed models were used to compare within-person rates of change in three clinical groups (cognitively normal, mild cognitive impairment, and Alzheimer's disease) further defined by ß amyloid status. RESULTS: Levels of injury markers were highly positively correlated. Despite elevated baseline levels as a function of clinical status and amyloid-positivity, within-person decreases in these measures were observed in the early symptomatic, amyloid-positive Alzheimer's disease group. DISCUSSION: Knowledge of within-person biomarker change will impact interpretation of biomarker outcomes in clinical trials that are dependent on disease stage.

Upward drift in cerebrospinal fluid amyloid ß 42 assay values for more than 10 years.

INTRODUCTION: The best-established cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease are levels of amyloid ß 42 (Aß42), total tau (tau), and phosphorylated tau 181 (ptau). We examined whether a widely used commercial immunoassay for CSF Aß42, tau, and ptau provided stable measurements for more than ∼10 years. METHODS: INNOTEST assay values for CSF Aß42, tau, and ptau from Washington University in St. Louis and VU Medical Center, Amsterdam, were evaluated. RESULTS: Aß42 values as measured by the INNOTEST assay drifted upward by approximately 3% per year over the past decade. Tau values remained relatively stable, whereas results for ptau were mixed. DISCUSSION: Assay drift may reduce statistical power or even confound analyses. The drift in INNOTEST Aß42 values may reduce diagnostic accuracy for Alzheimer's disease in the clinic. We recommend methods to account for assay drift in existing data sets and to reduce assay drift in future studies.

ApoE4 markedly exacerbates tau-mediated neurodegeneration in a mouse model of tauopathy.

APOE4 is the strongest genetic risk factor for late-onset Alzheimer disease. ApoE4 increases brain amyloid-ß pathology relative to other ApoE isoforms. However, whether APOE independently influences tau pathology, the other major proteinopathy of Alzheimer disease and other tauopathies, or tau-mediated neurodegeneration, is not clear. By generating P301S tau transgenic mice on either a human ApoE knock-in (KI) or ApoE knockout (KO) background, here we show that P301S/E4 mice have significantly higher tau levels in the brain and a greater extent of somatodendritic tau redistribution by three months of age compared with P301S/E2, P301S/E3, and P301S/EKO mice. By nine months of age, P301S mice with different ApoE genotypes display distinct phosphorylated tau protein (p-tau) staining patterns. P301S/E4 mice develop markedly more brain atrophy and neuroinflammation than P301S/E2 and P301S/E3 mice, whereas P301S/EKO mice are largely protected from these changes. In vitro, E4-expressing microglia exhibit higher innate immune reactivity after lipopolysaccharide treatment. Co-culturing P301S tau-expressing neurons with E4-expressing mixed glia results in a significantly higher level of tumour-necrosis factor-α (TNF-α) secretion and markedly reduced neuronal viability compared with neuron/E2 and neuron/E3 co-cultures. Neurons co-cultured with EKO glia showed the greatest viability with the lowest level of secreted TNF-α. Treatment of P301S neurons with recombinant ApoE (E2, E3, E4) also leads to some neuronal damage and death compared with the absence of ApoE, with ApoE4 exacerbating the effect. In individuals with a sporadic primary tauopathy, the presence of an ε4 allele is associated with more severe regional neurodegeneration. In individuals who are positive for amyloid-ß pathology with symptomatic Alzheimer disease who usually have tau pathology, ε4-carriers demonstrate greater rates of disease progression. Our results demonstrate that ApoE affects tau pathogenesis, neuroinflammation, and tau-mediated neurodegeneration independently of amyloid-ß pathology. ApoE4 exerts a 'toxic' gain of function whereas the absence of ApoE is protective.

Gastrointestinal dysfunctions as a risk factor for sleep disorders in children with idiopathic autism spectrum disorder: A retrospective cohort study.

Sleep disorders often co-occur with autism spectrum disorder. They further exacerbate autism spectrum disorder symptoms and interfere with children's and parental quality of life. This study examines whether gastrointestinal dysfunctions increase the odds of having sleep disorders in 610 children with idiopathic autism spectrum disorder, aged 2-18 years, from the Autism Genetic Resource Exchange research program. The adjusted odds ratio for sleep disorder among those with gastrointestinal dysfunctions compared to those without was 1.74 (95% confidence interval: 1.22-2.48). In addition, the odds of having multiple sleep disorder symptoms among children with gastrointestinal dysfunctions, adjusted for age, gender, behavioral problems, bed wetting, current and past supplements, and current and past medications for autism spectrum disorder symptoms were 1.75 (95% confidence interval: 1.10-2.79) compared to children without gastrointestinal dysfunctions. Early detection and treatment of gastrointestinal dysfunctions in autism spectrum disorder may be means to reduce prevalence and severity of sleep problems and improve quality of life and developmental outcomes in this population.

Neuropsychological measures that detect early impairment and decline in preclinical Alzheimer disease.

Identifying which neuropsychological measures detect early cognitive changes associated with Alzheimer disease (AD), brain pathology would be helpful clinically for the diagnosis of early AD and for the design of clinical trials. We evaluated which neuropsychological measures in our cognitive battery are most strongly associated with cerebrospinal fluid (CSF) biomarkers of AD brain pathology. We studied a large cohort (n = 233) of middle-to older-aged community-dwelling individuals (mean age 61 years) who had no clinical symptoms of dementia and underwent baseline CSF collection at baseline. Participants completed a battery of 9 neuropsychological measures at baseline and then every 1 to 3 years. CSF tau/Aß42 was associated with baseline performance on 5/9 neuropsychological measures, especially measures of episodic memory, and longitudinal performance on 7/9 neuropsychological measures, especially measures of global cognition. The free recall portion of the Free and Cued Selective Reminding Task (FCSRT-free) detected declining cognition in the high CSF tau/Aß42 group the earliest, followed by another measure of episodic memory and a sequencing task.

Prevalence of non-febrile seizures in children with idiopathic autism spectrum disorder and their unaffected siblings: a retrospective cohort study.

BACKGROUND: Autism spectrum disorder (ASD) is a heterogeneous disorder characterized not only by deficits in communication and social interactions but also a high rate of co-occurring disorders, including metabolic abnormalities, gastrointestinal and sleep disorders, and seizures. Seizures, when present, interfere with cognitive development and are associated with a higher mortality rate in the ASD population. METHODS: To determine the relative prevalence of non-febrile seizures in children with idiopathic ASD from multiplex and simplex families compared with the unaffected siblings in a cohort of 610 children with idiopathic ASD and their 160 unaffected siblings, participating in the Autism Genetic Resource Exchange project, the secondary analysis was performed comparing the life-time prevalence of non-febrile seizures. Statistical models to account for non-independence of observations, inherent with the data from multiplex families, were used in assessing potential confounding effects of age, gender, and history of febrile seizures on odds of having non-febrile seizures. RESULTS: The life-time prevalence of non-febrile seizures was 8.2% among children with ASD and 2.5% among their unaffected siblings. In a logistic regression analysis that adjusted for familial clustering, children with ASD had 5.27 (95%CI: 1.51-18.35) times higher odds of having non-febrile seizures compared to their unaffected siblings. In this comparison, age, presence of gastrointestinal dysfunction, and history of febrile seizures were significantly associated with the prevalence of non-febrile seizures. CONCLUSION: Children with idiopathic ASD are significantly more likely to have non-febrile seizures than their unaffected siblings, suggesting that non-febrile seizures may be ASD-specific. Further studies are needed to determine modifiable risk factors for non-febrile seizures in ASD.

Imaging and cerebrospinal fluid biomarkers in early preclinical alzheimer disease.

OBJECTIVE: Deposition of amyloid ß (Aß)-containing plaques as evidenced by amyloid imaging and cerebrospinal fluid (CSF) Aß1-42 (Aß42) is an early indicator of preclinical Alzheimer disease (AD). To better understand their relationship during the earliest preclinical stages, we investigated baseline CSF markers in cognitively normal individuals at different stages of amyloid deposition defined by longitudinal amyloid imaging with Pittsburgh compound B (PIB): (1) PIB-negative at baseline and follow-up (PIB(-) ; normal), (2) PIB-negative at baseline but PIB-positive at follow-up (PIB converters; early preclinical AD), and (3) PIB-positive at baseline and follow-up (PIB(+) ; preclinical AD). METHODS: Cognitively normal individuals (n = 164) who had undergone baseline PIB scan and CSF collection within 1 year of each other and at least 1 additional PIB follow-up were included. Amyloid status was defined dichotomously using an a priori mean cortical cutoff. RESULTS: PIB converters (n = 20) at baseline exhibited significantly lower CSF Aß42 compared to those who remained PIB-negative (n = 123), but higher compared to the PIB(+) group (n = 21). A robust negative correlation (r = -0.879, p = 0.0001) between CSF Aß42 and absolute (but subthreshold) PIB binding was observed during this early preclinical stage. The negative correlation was not as strong once individuals were PIB-positive (r = -0.456, p = 0.038), and there was no correlation in the stable PIB(-) group (p = 0.905) or in the group (n = 10) with early symptomatic AD (p = 0.537). INTERPRETATION: CSF Aß42 levels are tightly coupled with cortical amyloid load in the earliest stages of preclinical AD, and begin to decrease dramatically prior to the point when an abnormal threshold of cortical accumulation is detected with amyloid imaging. Ann Neurol 2016;80:379-387.