Table 3.

Differential expression of BBBMs between hereditary and sporadic Alzheimer’s disease.

Biomarker	Hereditary AD (Early Onset)	Sporadic AD (Late Onset)
Aβ42/Aβ40 Ratio	Decreased earlier, often in the preclinical phase	Decreased later, closer to symptom onset
P-tau181	Increases 6–10 years before symptoms; correlates with Aβ pathology	Rises later but remains a strong marker of tau pathology
T-tau	Poor discriminatory power; less significant changes	Variable changes; lacks a strong association with AD progression
NfL	Increases closer to symptom onset; higher variability	Rises later; more consistent correlation with neurodegeneration
GFAP	Rises ten years before symptoms, indicating early astrocytic activation	Early rise, but slightly later than in hereditary forms

Aβ: amyloid-beta; P-tau181: phosphorylated tau at threonine 181; T-tau: total tau; NfL: neurofilament light chain; GFAP: glial fibrillary acidic protein; AD: Alzheimer’s disease.