Effect of Reading Rehabilitation for Age-Related Macular Degeneration on Cognitive Functioning: Protocol for a Nonrandomized Pre-Post Intervention Study

Genetic and Epigenetic Biomarkers Linking Alzheimer's Disease and Age-Related Macular Degeneration

Alzheimer's disease (AD) represents a prominent neurodegenerative disorder (NDD), accounting for the majority of dementia cases worldwide. In addition to memory deficits, individuals with AD also experience alterations in the visual system. As the retina is an extension of the central nervous system (CNS), the loss in retinal ganglion cells manifests clinically as decreased visual acuity, narrowed visual field, and reduced contrast sensitivity. Among the extensively studied retinal disorders, age-related macular degeneration (AMD) shares numerous aging processes and risk factors with NDDs such as cognitive impairment that occurs in AD. Histopathological investigations have revealed similarities in pathological deposits found in the retina and brain of patients with AD and AMD. Cellular aging processes demonstrate similar associations with organelles and signaling pathways in retinal and brain tissues. Despite these similarities, there are distinct genetic backgrounds underlying these diseases. This review comprehensively explores the genetic similarities and differences between AMD and AD. The purpose of this review is to discuss the parallels and differences between AMD and AD in terms of pathophysiology, genetics, and epigenetics.

Accelerated Brain Atrophy, Microstructural Decline and Connectopathy in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) has recently been linked to cognitive impairment. We hypothesized that AMD modifies the brain aging trajectory, and we conducted a longitudinal diffusion MRI study on 40 participants (20 with AMD and 20 controls) to reveal the location, extent, and dynamics of AMD-related brain changes. Voxel-based analyses at the first visit identified reduced volume in AMD participants in the cuneate gyrus, associated with vision, and the temporal and bilateral cingulate gyrus, linked to higher cognition and memory. The second visit occurred 2 years after the first and revealed that AMD participants had reduced cingulate and superior frontal gyrus volumes, as well as lower fractional anisotropy (FA) for the bilateral occipital lobe, including the visual and the superior frontal cortex. We detected faster rates of volume and FA reduction in AMD participants in the left temporal cortex. We identified inter-lingual and lingual-cerebellar connections as important differentiators in AMD participants. Bundle analyses revealed that the lingual gyrus had a lower streamline length in the AMD participants at the first visit, indicating a connection between retinal and brain health. FA differences in select inter-lingual and lingual cerebellar bundles at the second visit showed downstream effects of vision loss. Our analyses revealed widespread changes in AMD participants, beyond brain networks directly involved in vision processing.

Visual and cognitive functioning among older adults with low vision before vision rehabilitation: A pilot study

Introduction

The occurrence of age-related vision changes is inevitable. However, some of these changes can become pathological. Research indicates that vision and hearing loss is correlated with age-related cognitive decline, and with a higher risk of developing dementia due to Alzheimer's disease. Low vision rehabilitation could possibly be a protective factor against cognitive decline, as it provides the clients with compensatory strategies to overcome their visual deficits.

Objectives and hypothesis

The aim of this pilot study was to assess correlations between visual and cognitive functions in older adults referred for low vision rehabilitation. We hypothesized that more severe impairment of visual acuity and contrast sensitivity would be correlated with more advanced levels of cognitive impairment. The second objective was to examine which of these correlations would remain significant once established variables that influence cognition are statistically removed (e.g., age, education).

Methods

Thirty-eight older adults (age range: 66-97 years old) with a visual impairment (acuity <20/70) were recruited before the onset of their low vision rehabilitation. They underwent vision (reading acuity, reading speed, contrast sensitivity), hearing (audiogram, speech-in-noise perception) and cognitive (global cognition, memory, executive functions) testing, and demographic information was obtained.

Results and discussion

Correlations among global cognition and visual aid use, memory and reading speed, memory and contrast sensitivity, memory, and visual aid use, and between executive functions and contrast sensitivity were significant. Correlations between contrast sensitivity and memory, as well as between global cognition and visual aid use remained significant after controlling for age and education. The present study is relevant to clinicians who are assessing the cognitive status of older adults, such as neuropsychologists, because it highlights the importance of considering low vision when administering neuropsychological tests, especially to persons who have not yet received rehabilitation for their visual impairment.

Cognitive decline, sensory impairment, and the use of audio-visual aids by long-term care facility residents

BACKGROUND

Hearing and vision impairments and the use of audio-visual aids are associated with cognitive decline in community-dwelling older people, but effects in long-term care facilities (LFCF) are unclear. We hypothesize that visual and hearing impairment are associated with cognitive decline and these relationships are mediated by using visual and hearing aids.

METHODS

Secondary data analysis of a longitudinal study was conducted in the 7 government-subsidized LTCF operated by one of the largest non-governmental organizations in Hong Kong using data between 2005 and 2016. Eligible residents were ≥ 60 years of age without severe cognitive impairment at baseline who had stayed in the facilities for more than 3 years. All variables were measured by using the Minimum Data Set-Resident Assessment Instrument Version 2.0, Hong Kong version. The outcome was cognitive decline. Predictors were visual and hearing impairments. Mediators were the use of visual and hearing aids. General linear models were employed to test the hypotheses.

RESULTS

Results for 2,233 residents were analyzed, with a mean age of 82.1 ± 8.2 years and a mean follow-up period of 4.4 ± 0.8 years. Results showed that those who had visual impairment (p = 0.004) and hearing impairments (p = 0.022) had a higher risk of cognitive decline. Using hearing aids (coefficient = 0.0186, p < 0.05) positively mediates the effect of hearing impairment on cognitive decline. Using visual aids (coefficient = -0.0881, p < 0.05) negatively mediates the effects of visual impairment on cognitive decline.

CONCLUSION

In LTCF, hearing and visual impairments are associated with a higher risk of cognitive decline. Hearing aids often-users were associated with a higher risk of cognitive decline. LTCF residents with visual impairment did not use visual aids. Use of visual aids demonstrated potential effects in slowing cognitive decline. A future study with a larger and more diverse sample with attention to quality of devices is proposed to confirm its effects.