The relationship between retinal layers and brain areas in asymptomatic first-degree relatives of sporadic forms of Alzheimer's disease: an exploratory analysis

Background Two main genetic risks for sporadic Alzheimer's disease (AD) are a family history and e4 allele of apolipoprotein E. The brain and retina are part of the central nervous system and share pathophysiological mechanisms in AD. Methods We performed a cross-sectional study with 30 participants without a family history of sporadic AD (FH-) and noncarriers of ApoE e4 (ApoE e4-) as a control group and 34 participants with a family history of sporadic AD (FH+) and carriers of at least one e4 allele (ApoE e4+). We analyzed the correlations between macular volumes of retinal layers and thickness of the peripapillary retinal nerve fiber layer (pRNFL) measured by optical coherence tomography (OCT) with the brain area parameters measured by magnetic resonance imaging (MRI) in participants at high genetic risk of developing AD (FH+ ApoE e4+). Results We observed a significant volume reduction in the FH+ ApoE e4+ group compared with the control group in some macular areas of (i) macular RNFL (mRNFL), (ii) inner plexiform layer (IPL), (iii) inner nuclear layer (INL), and (iv) outer plexiform layer (OPL). Furthermore, in the FH+ ApoE e4+ group, the retinal sectors that showed statistically significant volume decrease correlated with brain areas that are affected in the early stages of AD. In the same group, the peripapillary retinal nerve fiber layer (pRNFL) did not show statistically significant changes in thickness compared with the control group. However, correlations of these sectors with the brain areas involved in this disease were also found. Conclusions In cognitively healthy participants at high genetic risk of developing sporadic forms of AD, there are significant correlations between retinal changes and brain areas closely related to AD such as the entorhinal cortex, the lingual gyrus, and the hippocampus.

Automated summary

In individuals at high genetic risk of developing sporadic AD, significant correlations were found between retinal changes and brain areas closely related to the disease.