Early Biomarkers for Neurodegenerative Diseases: A Longitudinal Study on Alzheimer’s Detection

Abstract

Background: The clinical challenge in treating neurodegenerative diseases, particularly Alzheimer’s Disease (AD), lies in the "silent phase"—a period of decades where neuropathology accumulates before cognitive symptoms emerge. By the time clinical dementia is diagnosed, significant neuronal loss has often occurred, rendering many therapeutic interventions ineffective. Identifying reliable biomarkers during this preclinical stage is the "Holy Grail" of modern neurology.

Objective: This chapter presents a longitudinal analysis of emerging biological markers that can predict the onset of Alzheimer's Disease years, or even decades, before the first signs of memory loss.

Discussion: The study evaluates three primary categories of biomarkers: Fluid-based (Cerebrospinal fluid and plasma levels of Amyloid-beta 42/40 ratios and Phosphorylated Tau), Imaging-based (Amyloid and Tau PET imaging, and structural MRI for hippocampal atrophy), and Digital/Retinal markers (using optical coherence tomography to detect thinning of the retinal nerve fiber layer). We analyze data from long-term patient cohorts to determine the "cascade" of biomarker changes—how protein misfolding leads to synaptic dysfunction and, eventually, visible brain shrinkage.

Significance: Moving from a symptomatic diagnosis to a biomarker-driven "biological" diagnosis allows for the recruitment of patients into clinical trials much earlier. This longitudinal perspective shifts the focus from palliative care to preventative neurology, providing a window where lifestyle and pharmacological interventions have the highest probability of preserving brain volume and cognitive function.