Peripapillary retinal nerve fiber layer and macular outer retinal layers are reduced in cognitively unimpaired older adults at high risk of AD. Preliminary results from a five ‐year longitudinal study

Abstract

AbstractBackgroundThe retina, an extension of the central nervous system, shows promise for development of non‐invasive, low cost AD risk screening biomarkers. Most studies do not answer the question of whether retinal biomarkers are useful in the pre‐symptomatic phase of AD for assessment of early disease risk. In this study1, we investigated structural changes in the retinal neural layers between low and high risk cognitively unimpaired (CU) older adults using Spectral Domain Optical Coherence tomography (SD‐OCT).MethodThese data were provided from an ongoing trial that will conclude enrolment in the summer of 2022.1 Macular (30×25‐degree) and optic disc centered (radii of 3.5, 4.1, and 4.7 mm) SD‐OCT images of 13 CU low risk (age mean: 67 years; range: 56‐75 years) and 60 CU older adults at high risk for AD (age mean: 66 years; range: 55‐81 years; no significant difference in age between the two groups, p = 0.43) were acquired using the Spectralis imaging device. Participants had MoCA score ≥ 26, and RBANS‐U DMI score ≥ 85. Vendor software was used to segment and compute average retinal thickness in the 9 ETDRS maps for the macular and 7 glaucoma fields for the optic disk. Independent sample t test was used to compare retinal layer thickness between the two groups. A p‐value < 0.05 assessed statistical significance. Cohen’s d served as effect size measure.ResultIn the macular region, there were reduced retinal volume/thickness measurements for high risk vs. low risk CU older adults (outer plexiform layer volume in the inner inferior region; 0.054 vs. 0.062 mm3, p = 0.047, d = 0.62; central outer nuclear layer, ONL thickness; 97 vs. 102 µm, p = 0.041, d = 0.64; central ONL volume; 0.076 vs. 0.16 mm3, p = 0.023, d = 0.71). In the peripapillary region, there was reduced retinal nerve fiber layer (RNFL) thickness in the temporal region for high risk vs. low risk CU older adults (3.5 mm radius; 66.7 vs. 75.6 µm, p = 0.011, d = 0.80; 4.1 mm radius; 59.7 vs. 68.3 µm, p = 0.006, d = 0.87; 4.7 mm radius; 54.2 vs. 62.2 µm, p = 0.006, d = 0.87).ConclusionOur initial analysis shows reduced peripapillary RNFL and macular outer retinal layers in CU high risk vs. low risk group.