Abstract
IntroductionWe investigated the relationship of plasma amyloid beta (Aβ) with cerebral deposition of Aβ and tau on positron emission tomography (PET). MethodsForty-four participants (18 cognitively normal older adults [CN], 10 mild cognitive impairment, 16 Alzheimer's disease [AD]) underwent amyloid PET and a blood draw. Free and total plasma Aβ40 and Aβ42 were assessed using a validated assay. Thirty-seven participants (17 CN, 8 mild cognitive impairment, 12 AD) also underwent a [18F]flortaucipir scan. Scans were preprocessed by standard techniques, and mean global and regional amyloid and tau values were extracted. Free Aβ42/Aβ40 (Aβ F42:F40) and total Aβ42/Aβ40 (Aβ T42:T40) were evaluated for differences by diagnosis and relation to PET Aβ positivity. Relationships between these measures and cerebral Aβ and tau on both regional and voxel-wise basis were also evaluated. ResultsLower Aβ T42:T40 was associated with diagnosis and PET Aβ positivity. Lower plasma Aβ T42:T40 ratios predicted cerebral Aβ positivity, both across the full sample and in CN only. Finally, lower plasma Aβ T42:T40 ratios were associated with increased cortical Aβ and tau in AD-related regions on both regional and voxel-wise analyses. DiscussionPlasma Aβ measures may be useful biomarkers for predicting cerebral Aβ and tau. Additional studies in larger samples are warranted.
Highlights
Alzheimer’s disease (AD) is the most common neurodegenerative disease associated with aging
Expected differences in cognitive performance were observed, with patients with AD showing notable deficits compared with cognitively normal (CN) participants across cognitive domains
Patients with mild cognitive impairment (MCI) showed deficits compared with CN participants on episodic memory, semantic fluency, and executive function/attention tasks (Table 1)
Summary
Alzheimer’s disease (AD) is the most common neurodegenerative disease associated with aging. Detection is increasingly considered critical, in that interventions designed to slow or stop disease progression during early. Recent advances in blood-based assays have suggested that levels of amyloid beta (Ab) can be precisely measured and are associated with levels of Ab in the brain, making them good potential biomarkers for AD-risk screening and early detection.
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