Browsing by Author "Younes, Kyan"

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    Amyloid PET predicts longitudinal functional and cognitive trajectories in a heterogeneous cohort
    (Wiley, 2025) Younes, Kyan; Johns, Emily; Young, Christina B.; Kennedy, Gabriel; Mukherjee, Shubhabrata; Vossler, Hillary A.; Winer, Joseph; Cody, Karly; Henderson, Victor W.; Poston, Kathleen L.; Betthauser, Tobey J.; Bevis, Bill; Brooks, William M.; Burns, Jeffrey M.; Coombes, Stephen A.; DeCarli, Charles; DiFilippo, Frank P.; Duara, Ranjan; Fan, Audrey P.; Gibbons, Laura E.; Golde, Todd; Johnson, Sterling C.; Lepping, Rebecca J.; Leverenz, James; McDougall, Sean; Rogalski, Emily; Sanders, Elizabeth; Pasaye, Joshua; Sridhar, Jaiashre; Saykin, Andrew J.; Sridharan, Anjali; Swerdlow, Russell; Trittschuh, Emily H.; Vaillancourt, David; Vidoni, Eric; Wang, Wei-En; Mez, Jesse; Hohman, Timothy J.; Tosun, Duygu; Biber, Sarah; Kukull, Walter A.; Crane, Paul K.; Mormino, Elizabeth C.; Radiology and Imaging Sciences, School of Medicine
    Introduction: Amyloid positron emission tomography (PET) is increasingly available for diagnosis of Alzheimer`s disease (AD); however, its practical implications in heterogenous cohorts are debated. Methods: Amyloid PET from 890 National Alzheimer`s Coordinating Center participants with up to 10 years post-PET follow up was analyzed. Cox proportional hazards and linear mixed models were used to investigate amyloid burden prediction of etiology and prospective functional status and cognitive decline. Results: Amyloid positivity was associated with progression from unimpaired to mild cognitive impairment and dementia. Amyloid burden in the unimpaired group was associated with lower initial memory levels and faster decline in memory, language, and global cognition. In the Impaired group, amyloid was associated with lower initial levels and faster decline for memory, language, executive function, and global cognition. Discussion: Amyloid burden is an important prognostic marker in a clinically heterogeneous cohort. Future work is needed to establish the proportion of decline driven by AD versus non-AD processes in the context of mixed pathology. Highlights: Our findings highlight the importance of amyloid positron emission tomography (PET) in heterogenous cohorts, including diverse demographics, clinical syndromes, and underlying etiologies. The results also provide evidence that higher amyloid levels were linked to functional progression from unimpaired cognition to mild cognitive impairment (MCI) and from MCI to dementia. In cognitively unimpaired individuals, higher amyloid burden was associated with poorer memory at baseline and subsequent declines in memory, language, and global cognition. Among individuals with cognitive impairment, amyloid burden was associated with worse initial memory, language, executive function, and global cognition, and faster declines over time.
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    Divergent Cortical Tau Positron Emission Tomography Patterns Among Patients With Preclinical Alzheimer Disease
    (American Medical Association, 2022) Young, Christina B.; Winer, Joseph R.; Younes, Kyan; Cody, Karly A.; Betthauser, Tobey J.; Johnson, Sterling C.; Schultz, Aaron; Sperling, Reisa A.; Greicius, Michael D.; Cobos, Inma; Poston, Kathleen L.; Mormino, Elizabeth C.; Alzheimer’s Disease Neuroimaging Initiative; Harvard Aging Brain Study; Radiology and Imaging Sciences, School of Medicine
    Importance: Characterization of early tau deposition in individuals with preclinical Alzheimer disease (AD) is critical for prevention trials that aim to select individuals at risk for AD and halt the progression of disease. Objective: To evaluate the prevalence of cortical tau positron emission tomography (PET) heterogeneity in a large cohort of clinically unimpaired older adults with elevated β-amyloid (A+). Design, setting, and participants: This cross-sectional study examined prerandomized tau PET, amyloid PET, structural magnetic resonance imaging, demographic, and cognitive data from the Anti-Amyloid Treatment in Asymptomatic AD (A4) Study from April 2014 to December 2017. Follow-up analyses used observational tau PET data from the Alzheimer's Disease Neuroimaging Initiative (ADNI), the Harvard Aging Brain Study (HABS), and the Wisconsin Registry for Alzheimer's Prevention and the Wisconsin Alzheimer's Disease Research Center (together hereinafter referred to as Wisconsin) to evaluate consistency. Participants were clinically unimpaired at the study visit closest to the tau PET scan and had available amyloid and tau PET data (A4 Study, n = 447; ADNI, n = 433; HABS, n = 190; and Wisconsin, n = 328). No participants who met eligibility criteria were excluded. Data were analyzed from May 11, 2021, to January 25, 2022. Main outcomes and measures: Individuals with preclinical AD with heterogeneous cortical tau PET patterns (A+T cortical+) were identified by examining asymmetrical cortical tau signal and disproportionate cortical tau signal relative to medial temporal lobe (MTL) tau. Voxelwise tau patterns, amyloid, neurodegeneration, cognition, and demographic characteristics were examined. Results: The 447 A4 participants (A+ group, 392; and normal β-amyloid group, 55), with a mean (SD) age of 71.8 (4.8) years, included 239 women (54%). A total of 36 individuals in the A+ group (9% of the A+ group) exhibited heterogeneous cortical tau patterns and were further categorized into 3 subtypes: asymmetrical left, precuneus dominant, and asymmetrical right. A total of 116 individuals in the A+ group (30% of the A+ group) showed elevated MTL tau (A+T MTL+). Individuals in the A+T cortical+ group were younger than those in the A+T MTL+ group (t61.867 = -2.597; P = .03). Across the A+T cortical+ and A+T MTL+ groups, increased regional tau was associated with reduced hippocampal volume and MTL thickness but not with cortical thickness. Memory scores were comparable between the A+T cortical+ and A+T MTL+ groups, whereas executive functioning scores were lower for the A+T cortical+ group than for the A+T MTL+ group. The prevalence of the A+T cortical+ group and tau patterns within the A+T cortical+ group were consistent in ADNI, HABS, and Wisconsin. Conclusions and relevance: This study suggests that early tau deposition may follow multiple trajectories during preclinical AD and may involve several cortical regions. Staging procedures, especially those based on neuropathology, that assume a uniform trajectory across individuals are insufficient for disease monitoring with tau imaging.