Atrophy in preclinical Alzheimer's disease maps to a network that predicts longitudinal decline

Brain atrophy may precede cognitive and functional impairment in Alzheimer's disease (AD), but at this "preclinical" stage, it remains unclear whether atrophy localizes to specific brain networks and whether such localization is associated with clinical outcomes. We investigated cortical thickness in 1778 cognitively unimpaired (CU) older adults with amyloid-β (Aβ) PET from the A4 (Anti-Amyloid Treatment in Asymptomatic Alzheimer's Disease) and LEARN (Longitudinal Evaluation of Amyloid Risk and Neurodegeneration) studies, with a subset (N = 445) with tau PET. We estimated the networks disrupted by each individual's cortical thinning using a large normative connectome database (N = 1000), and tested whether this preclinical AD atrophy network is associated with clinical manifestations and longitudinal cognitive (PACC) and functional (CDR) trajectories. Distinct networks connected to atrophy patterns were associated with Aβ and regional tau in CU older adults. These networks were similar to a previously published atrophy network for AD dementia (Aβ: r = 0.817, P = 0.006; tau: r = 0.712, P = 0.046). Atrophy connectivity to this preclinical AD network was associated with higher Aβ and tau, independent of total cortical atrophy, and cross-sectionally with lower cognition, greater subjective cognitive decline, and increased anxiety; longitudinally, it predicted faster cognitive and functional decline over ~5 years. After tau adjustment, the functional-decline effect was preserved while the cognitive-slope effect was largely attenuated. Atrophy in preclinical AD localizes to a network resembling AD dementia, and is independently associated with AD pathologies, clinical outcomes, and longitudinal decline. Network-level neurodegeneration is detectable and clinically informative in preclinical AD, supporting future network-based research and therapeutic development.