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Psychological stress is associated with dementia risk. However, the underlying mechanisms are unclear. This cross-sectional study examined the association between self-reported psychological stress and cerebrospinal fluid (CSF) biomarkers of Alzheimer's disease and neurodegeneration in 73 cognitively unimpaired middle-aged adults from the Healthy Brain Project (mean age = 58±7 years). Linear regression analyses did not reveal any significant associations of psychological stress with CSF amyloid-β 42 , phosphorylated tau-181, total tau, or neurofilament light chain. Cohen's f 2 effect sizes were small in magnitude (f 2 ≤0.08). Further research is needed to replicate our findings, particularly given that the sample reported on average low levels of stress., Competing Interests: TC reports personal fees/honoraria for lectures from Roche. KF, LC, LB, RB, NY, YYL, and MP have no known conflicts of interest to disclose., (© 2023 – The authors. Published by IOS Press.)

Background: Insomnia is one of the most common sleep disorders yet its relationship to the biology of Alzheimer's disease remains equivocal., Objective: We investigated the cross-sectional relationship between insomnia symptom severity and cerebrospinal fluid (CSF) concentrations of Alzheimer's disease biomarkers in a cognitively unimpaired middle-aged community sample., Methods: A total of 63 participants from the Healthy Brain Project (age = 59±7 years; 67% women) completed a lumbar puncture and two weeks of actigraphy to measure two of insomnia's core features: difficulty initiating sleep (prolonged sleep onset latency) and difficulty maintaining sleep (wake after sleep onset [WASO] and number of awakenings). Additionally, the Insomnia Severity Index (ISI) was completed by 58 participants. Linear and Tobit regression were used to estimate the associations between each insomnia variable and CSF Aβ42, phosphorylated tau 181 (p-tau181), total-tau, and neurofilament light chain protein (NfL), adjusting for age, sex, and APOEɛ4 genotype., Results: Higher ISI score was associated with greater average levels of CSF Aβ42 (per point: 30.7 pg/mL, 95% CI: 4.17-57.3, p = 0.023), as was higher WASO (per 10 min: 136 pg/mL, 95% CI: 48-223, p = 0.002) and more awakenings (per 5:123 pg/mL, 95% CI = 55-192, p < 0.001). Difficulty initiating sleep was not associated with CSF Aβ42, nor were insomnia features associated with p-tau181, total-tau, or NfL levels., Conclusion: Insomnia symptoms were associated with higher CSF Aβ42 levels in this relatively young, cognitively unimpaired sample. These findings may reflect increased amyloid production due to acute sleep disruption.

Background: The BetterBrains Randomized Controlled Trial (RCT) will evaluate the effectiveness of an online, person-centered, risk factor management, coaching intervention in community-dwelling, healthy adults at risk of cognitive decline. Multi-component interventions are challenging to evaluate due to program complexity and personalization to individual needs and contexts. This paper describes a multi-level process evaluation conducted alongside the BetterBrains RCT., Objective: To understand how and why the BetterBrains intervention was effective or ineffective at reducing cognitive decline in healthy adults whilst considering the context in which it was implemented., Methods: 1,510 non cognitively-deteriorated community-dwelling adults aged 40-70 years old at risk of cognitive decline will be recruited and randomly assigned to the intervention or control group. All BetterBrains intervention participants, coaches, and the research team will be included in the evaluation. A mixed-methods design will be used, guided by The Framework for Implementation Fidelity and the program logic model. Data will be sourced from interviews, focus groups, surveys, BetterBrains coach notes, participant weekly check-in surveys, and audio recordings of intervention coaching sessions. Quantitative data will be analyzed via descriptive and inferential statistics and qualitative data will be analyzed using content and thematic analysis., Results: The process evaluation will provide information about contextual and influencing factors related to the implementation of BetterBrains and the RCT outcomes., Conclusion: Understanding how BetterBrains was implemented and its associated impacts will inform the translation of the program into community and clinical settings, providing easy access to online, personalized dementia prevention services.

Background: Midlife cardiovascular risk factors (CVRF) are associated with reduced cognition and an increased risk of dementia., Objective: To further investigate this association using remote unsupervised online assessment of cognition and cardiovascular risk in middle-aged adults; and to explore the extent to which the association is altered by carriage of the APOE ɛ4 allele., Methods: The Healthy Brain Project is an online cohort of middle-aged cognitively unimpaired adults (40-70 years) who have undergone cognitive assessment and provided self-reports of demographic and health history. Cardiovascular risk was determined by ascertaining history of hypertension, hypercholesterolemia, diabetes mellitus, overweight (body mass index≥25), and current cigarette smoking. Participants (n = 2,480) were then grouped based on the number of reported CVRF into no CVRF, 1, 2, and≥3 CVRF. Associations between the number of CVRF as a continuous variable, CVRF group, and each individual CVRF with composite measures of attention, memory and subjective cognitive function were investigated., Results: Higher number of CVRF was associated with poorer attention (β= -0.042, p = 0.039) and memory (β= -0.080, p < 0.001), but not with subjective cognitive function. When considered individually, current smoking (β= -0.400, p = 0.015), diabetes (β= -0.251, p = 0.023), and hypercholesterolemia (β= -0.109, p = 0.044) were independently associated with poorer memory performance. APOE ɛ4 carriers with≥1 CVRF performed worse on memory than ɛ4 carriers with no CVRFs (β(SE) = 0.259(0.077), p = 0.004). This was not observed in ɛ4 non-carriers., Conclusion: In cognitively normal middle-aged adults, CVRF were associated with poorer cognition, particularly in the memory domain. These results support feasibility of online assessment of cardiovascular risk for cognitive impairment.

Background: The apolipoprotein E (APOE) ɛ4 allele is associated with dose-response effects on cognitive dysfunction and dementia risk in older adults. However, its effects on cognition in middle-aged adults remains unclear., Objective: We examined effects of ɛ4 heterozygosity and homozygosity on objective and subjective cognition in middle-aged adults enrolled in the Healthy Brain Project (HBP) and in older adults from the Australian Imaging, Biomarkers and Lifestyle (AIBL) study., Methods: HBP participants (1,000 non-carriers; 450 ɛ4 heterozygotes; 50 ɛ4 homozygotes) completed unsupervised assessments of the Cogstate Brief Battery (CBB), ratings of subjective cognitive function and provided a saliva sample. AIBL cognitively normal participants (650 non-carriers; 204 ɛ4 heterozygotes; 31 ɛ4 homozygotes) completed in-person assessments of the CBB, ratings of subjective cognitive function and provided a blood sample., Results: Greater memory impairment was observed in middle-aged ɛ4 homozygotes compared with ɛ4 heterozygotes and non-carriers. When data from middle-aged (HBP) and older (AIBL) adults were pooled, the effect of ɛ4 homozygosity and memory impairment increased with age. In both middle-aged and older adults, ɛ4 heterozygotes did not differ from non-carriers on any measure of objective or subjective cognition., Conclusion: Memory impairment in ɛ4 homozygotes is evident in adults aged 50-60 years, and this can be detected through unsupervised cognitive assessments. The effect of ɛ4 homozygosity increases with older age. APOEɛ4 homozygosity has a negative impact on memory as early as midlife, but due to the subtle magnitude of effect, our findings support the necessity of online platforms in large cohorts to assess these complex relationships.

Background: Several modifiable risk factors for dementia have been identified, although the extent to which their modification leads to improved cognitive outcomes remains unclear., Objective: The primary aim is to test the hypothesis that a behavior modification intervention program targeting personalized risk factors prevents cognitive decline in community-dwelling, middle-aged adults with a family history of dementia., Methods: This is a prospective, risk factor management, blinded endpoint, randomized, controlled trial, where 1510 cognitively normal, community-dwelling adults aged 40-70 years old will be recruited. Participants will be screened for risk factors related to vascular health (including physical inactivity), mental health, sleep, and cognitive/social engagement. The intervention is an online person-centered risk factor management program: BetterBrains. Participants randomized to intervention will receive telehealth-based person-centered goal setting, motivational interviewing, and follow-up support, health care provider communication and community linkage for management of known modifiable risk factors of dementia. Psychoeducational health information will be provided to both control and intervention groups., Results: The primary outcome is favorable cognitive performance at 24-months post-baseline, defined as the absence of decline on one or more of the following cognitive tests: (a) Cogstate Detection, (b) Cogstate One Card Learning, (c) Cogstate One Back, and (d) Cognitive Function Instrument total score., Conclusion: We will test the hypothesis that the BetterBrains intervention program can prevent cognitive decline. By leveraging existing community services and using a risk factor management pathway that tailors the intervention to each participant, we maximize likelihood for engagement, long-term adherence, and for preserving cognitive function in at-risk individuals.

Background: Cerebrovascular disease often coexists with Alzheimer's disease (AD). While both diseases share common risk factors, their interrelationship remains unclear. Increasing the understanding of how cerebrovascular changes interact with AD is essential to develop therapeutic strategies and refine biomarkers for early diagnosis., Objective: We investigate the prevalence and risk factors for the comorbidity of amyloid-β (Aβ) and cerebrovascular disease in the Australian Imaging, Biomarkers and Lifestyle Study of Ageing, and further examine their cross-sectional association., Methods: A total of 598 participants (422 cognitively normal, 89 with mild cognitive impairment, 87 with AD) underwent positron emission tomography and structural magnetic resonance imaging for assessment of Aβ deposition and cerebrovascular disease. Individuals were categorized based on the comorbidity status of Aβ and cerebrovascular disease (V) as Aβ-V-, Aβ-V+, Aβ+V-, or Aβ+V+., Results: Advancing age was associated with greater likelihood of cerebrovascular disease, high Aβ load and their comorbidity. Apolipoprotein E ɛ4 carriage was only associated with Aβ positivity. Greater total and regional WMH burden were observed in participants with AD. However, no association were observed between Aβ and WMH measures after stratification by clinical classification, suggesting that the observed association between AD and cerebrovascular disease was driven by the common risk factor of age., Conclusion: Our observations demonstrate common comorbid condition of Aβ and cerebrovascular disease in later life. While our study did not demonstrate a convincing cross-sectional association between Aβ and WMH burden, future longitudinal studies are required to further confirm this.

Background: Quantifying the contribution of cerebrovascular disease to the clinical and pathological profile of Alzheimer's disease is challenging., Objective: We aimed to determine the influence of cerebrovascular disease, amyloid-β (Aβ), and their comorbidity on cognitive decline, hippocampal atrophy, and Aβ deposition, by evaluating data from the Australian Imaging, Biomarker and Lifestyle Study of Ageing., Methods: Two-hundred and eighteen participants underwent Aβ PET, MRI, and cognitive assessment at 18-month intervals for up to 90 months. Aβ status was determined on baseline PET. Participants were also classified as V+ on baseline MRI if they had≥1 large cortical infarcts, subcortical infarcts, or cortical cerebral microinfarcts; or white matter hyperintensity volume greater than the 90th percentile of healthy controls. Linear mixed models were conducted comparing slopes of change in cognition, hippocampal volume, and Aβ load between the four resultant groups., Results: Mean age at baseline was 74 years (range 59-96). One-hundred and fifteen participants were cognitively normal, 54 had mild cognitive impairment, and 49 had Alzheimer's disease. Compared to the Aβ-/V- group, the Aβ+/V- and Aβ+/V+ groups showed significantly faster cognitive decline and hippocampal atrophy over 90 months. V+ status was associated with greater cognitive decline (Cohen's d = 0.85, p < 0.001) and hippocampal atrophy (d = 2.05, p < 0.001) in the Aβ+ group but not in the Aβ- group. V+ status was not associated with Aβ accumulation in any group., Conclusion: Comorbidity of cerebrovascular disease and Aβ was associated with cognitive decline and neurodegeneration. Cerebrovascular disease was not associated with the rate of Aβ accumulation.

Background: Characterizing the earliest demonstrable cognitive decline in middle-aged adults at risk of Alzheimer's disease (AD) will allow for the better understanding of the early disease trajectory, and the provision of therapies prior to clinical symptom onset. We developed an online platform- healthybrainproject.org.au (Healthy Brain Project; HBP)- to recruit, assess, and monitor at-risk middle-aged adults., Objective: Describe the HBP methodology and report baseline characteristics and adherence indices of participants., Methods: Between February 2017 and August 2018, 4,000 community-based middle-aged Australian adults with a first or second-degree family history of dementia enrolled at our website (healthybrainproject.org.au). Participants were directed to complete five modules: "Basics", "Health History", "How You Feel", "How You Live", and "How You Think". Of these, 1,816 participants have received a saliva sampling kit for genetic analysis., Results: Participants had a mean (SD) age of 55.5 (6.8) years, 11.8 (3.4) years of education, and annual personal income of AUD$68,830 ($35,044). Participants took 26.4 (49.7) days after enrolment to complete questionnaires and cognitive tests. Most participants were from Victoria (63%), followed by New South Wales (14%). Most participants (74%) were female and 76% identified as Caucasian. Approximately 36% of participants completed all modules (n = 1,450), and 56% (n = 2,221) completed 4 out of 5 modules. Most saliva kits (89%) had been returned., Conclusion: The HBP joins a handful of online registries worldwide that assess and monitor a large cohort of individuals at risk of AD. Our study extends on these efforts by focusing on midlife, where the earliest signs of cognitive and pathological changes will manifest.

Background: Preclinical Alzheimer's disease (AD) is defined by cerebral amyloid-β positivity (Aβ+) in cognitively normal (CN) older adults., Objective: To estimate the risk of progression to the symptomatic stages of AD due to PET Aβ+ and the extent that progression was influenced by other demographic, genetic, and clinical characteristics in a large prospective study., Methods: Fine-Gray subdistribution modeling was used to examine the risk of progression from CN to MCI/dementia due to Aβ+, APOEɛ4 carriage, and their interaction in the Australian Imaging, Biomarkers and Lifestyle (AIBL) flagship study of aging CN cohort (n = 599) over 8 years., Results: 17.7% Aβ+ and 8.1% Aβ-progressed over 8 years (OR: 2.43). Risk of progression for Aβ+ was 65-104% greater than Aβ-. Aβ+ APOEɛ4 carriers were at 348% greater risk than all other participants. Significant risk factors of progression in Aβ+ were age (HR: 1.05), PET SUVR (HR: 2.49) and APOE ɛ4 carriage (HR: 2.63); only age was a significant risk factor in Aβ-(HR: 1.09). Aβ-progressors were not near the threshold for Aβ+. These relationships were not moderated by hypertension, diabetes, obesity, or stroke/TIA., Conclusion: Aβ+ is an important prognostic marker for progression from CN to MCI/dementia in older adults and APOEɛ4 carriage provides further predictive value in the presence of Aβ+. These data suggest that Aβ-associated clinical progression is consistent with clinical-pathological models of AD, whereas progression in the absence of elevated Aβ deposition may be the result of neuropathological processes other than AD that accumulate with age.