Where you live could shape how your brain ages, with neighborhood inequality and environmental stressors leaving measurable biological traces linked to Alzheimer’s disease.
Study: Associations of place-based social determinants of health with biomarkers of Alzheimer's disease and related dementias. Image credit: Bored Photography/Shutterstock.com
A new study published in the journal Alzheimer's & Dementia: Behavior & Socioeconomics of Aging reveals that individuals living in neighborhoods with higher levels of social vulnerability, environmental injustice, and socioeconomic disadvantage are associated with biological patterns linked to Alzheimer’s disease and related dementias.
Background
Place-based social determinants of health are nonmedical factors within a person’s physical environment and community. These elements play a vital role in shaping an individual’s health, functioning, and quality of life.
The basic social determinants of health include socioeconomic status, healthcare access, education access, healthy food availability, housing quality, violence, racism, discrimination, social support networks, and many more. Addressing these factors can improve health, reduce inequalities, and promote quality of life.
Existing evidence has linked these factors to cardiometabolic health and cognition. An association between the Area Deprivation Index (ADI) and cortical thickening in Alzheimer’s disease-specific brain regions has also been observed in individuals with unpaired cognitive functioning. ADI, a composite measure of social determinants of health, is used to measure socioeconomic disadvantages at the neighborhood level to identify communities with higher risk of adverse health outcomes.
Despite potential involvement of place-based social determinants of health in determining cognitive health, it remains largely unknown whether these factors influence vital biomarkers of Alzheimer’s disease and related dementias.
In the current study, researchers from the Wake Forest University School of Medicine aimed to investigate the associations of three composite measures of place-based social determinants of health, including ADI, the Social Vulnerability Index (SVI), and the Environmental Justice Index (EJI), with neuroimaging and plasma biomarkers of Alzheimer’s disease and related dementias in more than 600 Black and White participants aged 54 years or above.
SVI is used to measure the preparedness of a community to respond to a disaster, and the EJI is used to measure the cumulative impacts of environmental burden.
Key findings
The study reported that the scores of all three social determinants of health indices were higher among Black participants compared to those among White participants. This finding indicates that Black participants live in regions with higher levels of neighborhood disadvantage, social vulnerability, and environmental injustice.
The analysis of the association between these indices and Alzheimer’s disease and dementia biomarkers revealed that among Black participants, higher SVI and EJI scores are associated with higher variability in cerebral blood flow in the brain gray matter; higher ADI scores are associated with lower cerebral blood flow in the gray matter, and higher ADI and SVI scores are associated with lower cortical thickness.
Among White participants, the analysis revealed a modest negative association between SVI scores and glial fibrillary acidic protein, a plasma biomarker of Alzheimer’s disease and dementia.
Study significance
The study findings suggest that place-based social determinants of health are moderately associated with less favorable Alzheimer’s disease and dementia biomarkers among Blacks or African Americans, but not among Whites.
The study analysis comparing participants with and without cognitive impairments reveals that higher neighborhood-level socioeconomic disadvantage is associated with lower cortical thickness among participants with dementia. Similar negative associations have been observed between social vulnerability and environmental injustice and cortical thickness among participants with mild cognitive impairments. However, these associations were absent among participants without cognitive impairment.
The observed associations between place-based social determinants of health and neuroimaging biomarkers only among Black participants indicate that place-based distribution of resources and opportunities may differentially impact biomarkers of Alzheimer’s disease and dementia based on racialized identities and experiences.
The study used three indices that capture a broad range of place-based social determinants of health, including social characteristics related to income, education, and housing, household characteristics, transportation, racial and ethnic minority status, and environmental characteristics (pollution, toxic waste disposal sites, and chronic disease burden). These determinants may partially capture the effects of structural racism, indicating that the observed associations may partially be influenced by structural racism.
The study findings suggest that social vulnerability may be associated with brain health and that this measure could help identify neighborhoods where monitoring social determinants of health may have a significant impact. However, only some of the observed associations remained statistically significant after correction for multiple comparisons, and further replication is needed before drawing firm conclusions.
Overall, the study findings highlight the need for further research to examine the impact of structural racism on biomarkers of Alzheimer’s disease and dementia in more racially, ethnically, socioeconomically, and geographically diverse cohorts.
Interventions targeting elements of structural racism and the inequitable distribution of place-based social determinants of health are needed to improve outcomes of Alzheimer’s disease and dementia. Grassroots initiatives and policy efforts must address these determinants in neighborhoods with higher disadvantage, social vulnerability, and environmental injustice to reduce risk and progression and improve outcomes of Alzheimer’s disease and dementia.
The study could not investigate the impact of long-term exposure to social determinants of health on the tested biomarkers. Similarly, it remains uncertain whether early-life and mid-life exposure to these determinants affects later-life levels of Alzheimer’s disease and dementia biomarkers. Future studies with longitudinal life-course residential data are needed to address these limitations.
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