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Objective: We aimed to test the hypothesis that elevated neocortical β-amyloid (Aβ), a hallmark feature of Alzheimer's disease (AD), predicts sex-specific cognitive trajectories in clinically normal older adults, with women showing greater risk of decline than men. Method: Florbetapir Aβ positron emission tomography (PET) was acquired in 149 clinically normal older adults (52% female, Mage = 74). Participants underwent cognitive testing at baseline and during annual follow-up visits over a timespan of up to 5.14 years. Mixed-effects regression models evaluated whether relations between baseline neocortical Standardized Uptake Value Ratio (SUVR) and composite scores of episodic memory, executive functioning, and processing speed were moderated by sex (male/female) and apolipoprotein E (APOE) status (ε4 carrier/noncarrier). Results: Higher baseline SUVR was associated with longitudinal decline in episodic memory in women (b = -1.32, p < .001) but not men (b = -0.30, p = .28). Female APOE ε4 carriers with elevated SUVR showed particularly precipitous declines in episodic memory (b = -4.33, p < .001) whereas other cognitive domains were spared. SUVR did not predict changes in executive functioning or processing speed, regardless of sex (ps >.63), though there was a main effect of SUVR on processing speed (b = 2.50, p = .003). Conclusions: Clinically normal women with elevated Aβ are more vulnerable to episodic memory decline than men. Understanding sex-related differences in AD, particularly in preclinical stages, is crucial for guiding precision medicine approaches to early detection and intervention. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

BackgroundCentral nervous system levels of tumor necrosis factor-alpha (TNF-α), a pro-inflammatory cytokine, regulate the neuroinflammatory response and may play a role in age-related neurodegenerative diseases. The longitudinal relation between peripheral levels of TNF-α and typical brain aging is understudied. We hypothesized that within-person increases in systemic TNF-α would track with poorer brain health outcomes in functionally normal adults.MethodsPlasma-based TNF-α concentrations (pg/mL; fasting morning draws) and magnetic resonance imaging were acquired in 424 functionally intact adults (mean age = 71) followed annually for up to 8.4 years (mean follow-up = 2.2 years). Brain outcomes included total gray matter volume and white matter hyperintensities. Cognitive outcomes included composites of memory, executive functioning, and processing speed, as well as Mini-Mental State Examination total scores. Longitudinal mixed-effects models were used, controlling for age, sex, education, and total intracranial volume, as appropriate.ResultsTNF-α concentrations significantly increased over time (p < .001). Linear increases in within-person TNF-α were longitudinally associated with declines in gray matter volume (p < .001) and increases in white matter hyperintensities (p = .003). Exploratory analyses suggested that the relation between TNF-α and gray matter volume was curvilinear (TNF-α 2p = .002), such that initial increases in inflammation were associated with more precipitous atrophy. There was a negative linear relationship of within-person changes in TNF-α to Mini-Mental State Examination scores over time (p = .036) but not the cognitive composites (all ps >.05).ConclusionSystemic inflammation, as indexed by plasma TNF-α, holds potential as a biomarker for age-related declines in brain health.

IntroductionWe investigated plasma proteomic markers of astrocytopathy, brain degeneration, plasticity, and inflammation in sporadic early-onset versus late-onset Alzheimer's disease (EOAD and LOAD).MethodsPlasma was analyzed using ultra-sensitive immuno-based assays from 33 EOAD, 30 LOAD, and 36 functionally normal older adults.ResultsPrinciple component analyses identified 3 factors: trophic (BDNF, VEGF, TGFβ), degenerative (GFAP, NfL), and inflammatory (TNFα, IL-6, IP-10, IL-10). Trophic factor was elevated in both AD groups and associated with cognition and gray matter volumes. Degenerative factor was elevated in EOAD, with higher levels associated with worse functioning in this group. Biomarkers of inflammation were not significantly different between groups and were only associated with age.DisucssionPlasma proteomic biomarkers provide novel means of investigating molecular processes in vivo and their contributions to clinical outcomes. We present initial investigations of several of these fluid biomarkers, capturing aspects of astrocytopathy, neuronal injury, cellular plasticity, and inflammation in EOAD versus LOAD.

Cerebral perfusion declines across the lifespan and is altered in the early stages of several age-related neuropathologies. Little is known, however, about the longitudinal evolution of perfusion in healthy older adults, particularly when perfusion is quantified using magnetic resonance imaging with arterial spin labeling (ASL). The objective was to characterize longitudinal perfusion in typically aging adults and elucidate associations with cognition and brain structure. Adults who were functionally intact at baseline (n = 161, ages 47-89) underwent ASL imaging to quantify whole-brain gray matter perfusion; a subset (n = 136) had repeated imaging (average follow-up: 2.3 years). Neuropsychological testing at each visit was summarized into executive function, memory, and processing speed composites. Global gray matter volume, white matter microstructure (mean diffusivity), and white matter hyperintensities were also quantified. We assessed baseline associations among perfusion, cognition, and brain structure using linear regression, and longitudinal relationships using linear mixed effects models. Greater baseline perfusion, particularly in the left dorsolateral prefrontal cortex and right thalamus, was associated with better executive functions. Greater whole-brain perfusion loss was associated with worsening brain structure and declining processing speed. This study helps validate noninvasive MRI-based perfusion imaging and underscores the importance of cerebral blood flow in cognitive aging.

Frontotemporal dementia refers to a group of progressive neurodegenerative syndromes usually caused by the accumulation of pathological tau or TDP-43 proteins. The effects of these proteins in the brain are complex, and each can present with several different clinical syndromes. Clinical efficacy trials of drugs targeting these proteins must use endpoints that are meaningful to all participants despite the variability in symptoms across patients. There are many candidate clinical measures, including neuropsychological scores and functional measures. Brain imaging is another potentially attractive outcome that can be precisely quantified and provides evidence of disease modification. Most imaging studies in frontotemporal dementia have been cross-sectional, and few have compared longitudinal changes in cortical volume with changes in other measures such as perfusion and white matter integrity. The current study characterized longitudinal changes in 161 patients with three frontotemporal dementia syndromes: behavioural variant frontotemporal dementia (n = 77) and the semantic (n = 45) and non-fluent (n = 39) variants of primary progressive aphasia. Visits included comprehensive neuropsychological and functional assessment, structural MRI (3 T), diffusion tensor imaging, and arterial spin labelled perfusion imaging. The goal was to identify measures that are appropriate as clinical trial outcomes for each group, as well as those that might be appropriate for trials that would include more than one of these groups. Linear mixed effects models were used to estimate changes in each measure, and to examine the correlation between imaging and clinical changes. Sample sizes were estimated based on the observed effects for theoretical clinical trials using bootstrapping techniques to provide 95% confidence intervals for these estimates. Declines in functional and neuropsychological measures, as well as frontal and temporal cortical volumes and white matter microstructure were detected in all groups. Imaging changes were statistically significantly correlated with, and explained a substantial portion of variance in, the change in most clinical measures. Perfusion and diffusion tensor imaging accounted for variation in clinical decline beyond volume alone. Sample size estimates for atrophy and diffusion imaging were comparable to clinical measures. Corpus callosal fractional anisotropy led to the lowest sample size estimates for all three syndromes. These findings provide further guidance on selection of trial endpoints for studies in frontotemporal dementia and support the use of neuroimaging, particularly structural and diffusion weighted imaging, as biomarkers. Diffusion and perfusion imaging appear to offer additional utility for explaining clinical change beyond the variance explained by volume alone, arguing for considering multimodal imaging in treatment trials.

Although leukocyte telomere length (TL) shortens over the lifespan and is associated with diseases of aging, little is known about the relationships between TL, memory, and brain structure. Sixty-nine functionally normal older adults (mean age = 71.7) were assessed at 2 time points (mean interval = 2.9 years). Linear mixed models assessed relationships between TL and hippocampal volume, fractional anisotropy, and mean diffusivity (MD) of the fornix and verbal and visual episodic memory. Unstandardized coefficients are reported in the following, and p values are not corrected for multiple comparisons. A negative baseline trend was observed between TL and fornix MD (b = -0.01, p = 0.06), but no other cross-sectional associations were significant (ps > 0.16). Greater TL shortening at follow-up was associated with greater hippocampal volume loss (b = 27.09, p < 0.001), even after controlling for global volume loss (b = 10.83, p = 0.002). Greater telomere attrition was also associated with larger increases in fornix MD (b = -0.01, p = 0.012) and decreases in fornix fractional anisotropy (b = 0.004, p = 0.002). TL was not associated with changes in episodic memory (ps > 0.23). These relationships may reflect neurobiological influences that affect both TL and brain structure, as well as the effect of TL on brain aging via mechanisms such as cellular senescence and inflammation.