Abstract
Dementia is a significant public health challenge, with research indicating greater risk in Hispanic adults. Macrostructural MRI studies suggest the vascular contribution to dementia may be more pronounced within the Hispanic population than the neurodegenerative. However, advanced diffusion MRI is sensitive and specific to brain microstructural integrity associated with cognitive decline and may better detect and characterize ethnic variation in MRI biomarkers of dementia. While advanced diffusion MRI has recently become implemented in clinical studies of brain health and dementia, there is insufficient representation of Hispanic individuals. This dissertation addresses this gap in literatures by using advanced diffusion MRI to better characterize brain microstructural integrity in an ethnically diverse cohort. We report ethnic variation in the relationship between brain microstructure and cognition and found the importance of these relationships varied by ethnicity within each sex group. A stronger association was found for advanced diffusion MRI metrics in the hippocampus in non-Hispanic adults, while the vascular contribution was suggested to be stronger in Hispanic participants. Furthermore, sex-specific analysis revealed microstructural integrity in the hippocampal, amygdala, and cerebral cortex were strongest in non-Hispanic women and Hispanic men, while the vascular contribution was more pronounced in Hispanic women. We also found advanced diffusion MRI models were sensitive and specific to detecting and characterizing this variation. This study adds to the literature by presenting a precision medicine approach to characterizing potential interventional biomarkers of dementia. Further research is encouraged to study these advanced diffusion MRI models in larger and more ethnically diverse cohorts for better outcomes for people of all backgrounds.