Lower thickness of inner retinal layers is associated with an increased risk of incident dementia and Alzheimer’s disease – an individual participant data analysis of four prospective cohort studies (69,955 participants)

Abstract

Purpose : Retinal imaging tools may be biomarkers for the early identification of individuals at risk for dementia. Currently, it remains unclear whether retinal neurodegeneration precedes the onset of clinical dementia as few prospective data have been published. The objective
To investigate whether retinal neurodegeneration, estimated from lower thickness of inner retinal layers, was associated with incident all-cause dementia and Alzheimer’s disease.

Methods : We performed an individual participant data meta-analysis using data from four prospective cohort studies with a total of 69,955 participants (n=1,087 cases of incident all-cause dementia; n=520 cases incident Alzheimer’s disease; follow-up time median [interquartile range; IQR] 11.3 [8.8 - 11.5] years). We investigated the associations of baseline macular retinal nerve fiber layer (mRNFL) thickness and ganglion cell-inner plexiform layer (mGCIPL) thickness (expressed per standard deviation lower thickness) with incident dementia. We used Cox proportional hazards models adjusted for age, sex, educational level, and other key dementia risk factors. Missing data for covariables were imputed. We tested for interaction with age, sex, and apolipoprotein E (APOE) genotype status

Results : After adjustment for age, sex, educational level, and key dementia risk factors, lower baseline mRNFL thickness was significantly associated with higher incidence of all-cause dementia and Alzheimer’s disease (per SD lower mRNFL thickness, hazard risk [95% confidence interval], 1.10 [1.02; 1.17] and 1.11 [1.001; 1.23], respectively); and lower mGCIPL thickness was not significantly associated with these outcomes (per SD lower mGCIPL thickness, 1.04 [0.99; 1.10] and 1.01 [0.94; 1.09], respectively). Age, sex, apolipoprotein E (APOE) genotype status did not modify these associations.

Conclusions : This individual participant data meta-analysis found that lower baseline thickness of inner retinal layers was associated with up to an approximately 10% higher risk of incident all-cause dementia and Alzheimer’s disease. These findings suggest that retinal neurodegeneration precedes the onset of clinical dementia and that retinal imaging tools may be biomarkers for the early identification of individuals at risk for dementia.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.