Structural Medicine v1.8.1: Structural dynamics of neurodegenerative progression in ADNI

This study analyzes neurodegenerative progression using longitudinal cognitive data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) dataset. While conventional models describe progression as monotonic decline, we identify a two-stage structural process characterized by variance instability and directional collapse bias. We define structural persistence F(t) and derive a local decay rate λ(t) at the individual level. Across diagnostic groups (CN, SMC, EMCI, LMCI, AD), we observe: - A systematic increase in the variance of λ(t) prior to clinical conversion- A directional shift in asymmetry toward collapse-dominated dynamics- A statistically significant enrichment of variance peaks before conversion (66.8% vs random 64.0% ± 1.4%, Z = 2.07, p ≈ 0.019) These findings are consistent with early-warning signals observed in complex systems approaching critical transitions. We further propose a minimal structural interpretation using an asymmetric potential framework, providing a mechanistic link between instability and irreversible decline. This work provides a data-driven and structurally interpretable framework for understanding neurodegenerative dynamics, with potential applications in early prediction and longitudinal risk assessment.