Biomarkers

Area of Science:

• Ophthalmology
• Neurology
• Genetics

Background:

• Alzheimer's disease (AD) is a neurodegenerative disorder.
• The APOE ε4 allele is a significant genetic risk factor for late-onset AD.
• Retinal changes may serve as early biomarkers for neurodegenerative diseases like AD.

Purpose of the Study:

• To investigate differences in retinal structure and microvasculature.
• Compare individuals with Alzheimer's disease (AD), APOE ε4 carriers, and APOE ε4 noncarriers.
• Identify potential early AD biomarkers in the retina.

Main Methods:

• Optical coherence tomography (OCT) angiography was used to analyze retinal vessel density (VD) and perfusion density (PD).
• Measurements included peripapillary capillary perfusion density (CPD) and retinal thickness parameters (RNFL, GC-IPL, CST).
• Participants with diabetes, glaucoma, or vitreoretinal pathology were excluded; age and sex-adjusted generalized estimating equations were applied.

Main Results:

• APOE ε4 carriers showed significantly lower 6mm circle PD and 6mm inner ring VD compared to noncarriers.
• Individuals with AD had significantly lower CST, 6mm circle PD, 6mm circle VD, and 6mm inner ring VD compared to ε4 noncarriers.
• AD patients exhibited significantly higher peripapillary CPD compared to both ε4 carriers and noncarriers.

Conclusions:

• APOE ε4 carriers may exhibit early AD biomarker signs in retinal microvasculature, even without clinical symptoms.
• Differences in retinal microvasculature suggest potential utility as biomarkers across the AD spectrum.
• Longitudinal studies are recommended to further elucidate the role of these retinal biomarkers in AD progression.