Association between choroidal microvasculature in the eye and Alzheimer's disease risk in cognitively healthy midlife adults

Objective: To explore associations between measurements of the ocular microvasculature in the choroid (a highly vascularised layer posterior to the retina) and genetic Alzheimer's disease risk. Methods: We measured the choroidal vasculature appearing in optical coherence tomography scans of 69 healthy, mid-life individuals in the PREVENT cohort. The cohort was prospectively split into low, medium, and high-risk groups based on the presence of known risk factors (APOE4 genotype and family history of dementia). We used ordinal logistic regression to test for cross-sectional associations between choroidal measurements and pre-determined risk of future Alzheimer's disease. Results: We observed progressively increased choroidal vasculature between ordinal risk groups, and all choroidal measurements were significantly associated with risk group prediction. APOE4 carriers had significantly thicker choroids and larger vascular tissue compared to non-carriers. Similar trends were observed for those with a family history of dementia. In our sample, a 0.16 mm2 increase in choroidal vascular area was associated with a 2-fold increase in the likelihood of having one or more markers of Alzheimer's disease risk, compared with none. Conclusions: Our results suggest a potential link between the choroidal vasculature and risk of Alzheimer's disease. However, these findings are exploratory and should be replicated in a larger, more diverse sample.