Is Age-related Macular Degeneration related to Alzheimer’s Disease? Evidence from neuroimaging and behavioural data.

Although age-related macular degeneration (AMD) is an eye disease and Alzheimer’s disease (AD) is a dementia caused by neurodegeneration in the brain, both are common diseases affecting older people, and studies have suggested a link between them. Cognitive impairments in language and memory, and biological changes in the eye have been found in both AD and AMD. The first aims of this thesis were to compare atrophy patterns in brain structure in AMD, AD, and age-matched controls both cross-sectionally and longitudinally. Cross-sectional data revealed significantly thinner entorhinal cortex and angular gyrus in late AMD compared to controls, while longitudinal results found accelerated thinning in entorhinal cortex and decelerated thinning in the inferior frontal gyrus in early AMD (non-significant patterns). Both cross-sectional and longitudinal results suggest that there are shared patterns of neurodegeneration for AMD and mild AD. However, comparing participants with early and late-stage AMD found that entorhinal cortex is affected in early AMD, while the occipital pole is affected in late AMD, suggesting AMD has its own neurodegenerative pattern. Finally, the relationship between brain structure, physical activity levels (lifestyle and exercise), and cognitive function was assessed in AMD and control participants. A positive correlation was found between lifestyle and exercise physical activity and entorhinal cortex (non-significant medium-to-large effect), but only lifestyle was positively correlated with the hippocampus (non-significant medium effect). However, cortical measures were not positively associated with Montreal Cognitive Assessment scores measuring global cognitive function. Overall, this thesis reveals that AMD and AD have similar but diverging patterns of change in brain structures, and that changes in physical activity levels may modulate brain changes. Altogether, the findings suggest that AMD patients are at risk of experiencing atrophying brain structures involved in cognitive function beyond occipital visual regions that may increase the risk of developing AD.