“You have two strikes against you”: relationship among racism, allostatic load, and changes in medial temporal lobe volumes in older adults
OA Version
Citation
Abstract
Age-related cognitive impairment is a growing public health problem. Black Americans have a greater prevalence of Alzheimer's disease (AD) than Americans of European ancestry (AD). Furthermore, they are twice as likely as their white counterparts to be afflicted by Alzheimer’s disease. However, the reasoning as to why or how this racial disparity persists is unclear. In addition, little is known about the role chronic experiences of racism might play in contributing to deleterious changes in the medial temporal lobes–notably the hippocampus and amygdala–regions that exhibit profound neurodegeneration in AD. Consequently, we must move towards distinguishing social and structural factors perpetuating disparities in brain aging.
Racial discrimination is a chronic stressor affecting minority populations. In this way, racialized chronic stress may contribute to disparities in AD. In the United States, Black Americans, the largest minority group, often suffer from racism and social discrimination. Both AD and chronic stress negatively impact the medial temporal lobes–a region relied upon in forming memories.
Within the medial temporal lobes— the hippocampus contributes to learning and memory while supporting emotion processing with the amygdala. As a result, this research aims to examine how racism burden influences medial temporal lobe structural measures in older Black adults (65 years and older) as well as hypotheses related to etiological biological mechanisms, such as allostatic (over)load as a proxy for the stress engendered by experiencing racism.
Allostatic load is the cumulative result of an allostatic state, which can be considered a beneficial and adaptive condition. However, unpredictable events, disease, human interference, and social interactions can augment allostatic load and cause it to become allostatic overload.
The brain controls physiological and behavioral responses to stress. Stress hormones act on brain receptors, causing allostasis and allostatic load. The amygdala and hippocampus play critical roles in interpreting what is stressful and deciding what to do.
Furthermore, chronic stress has been linked to hippocampal integrity from a neurobiological perspective. It has been demonstrated that chronic stress decreases hippocampal plasticity mechanisms due to the large number of binding sites for cortisol in both the hippocampus and amygdala.
Thus, using existing structural MRI scans and biomarker assays from participants of the Framingham Heart Study to examine allostatic load, we can investigate how chronic stress resulting from racism and social discrimination may adversely affect brain structure and, ultimately, cognitive function in Black older adults.
Description
2024
License
Attribution-NonCommercial-NoDerivatives 4.0 International