Structural Inequalities Contribute to Changes in Brain Structure and Connectivity

Research shows that there is a direct link between structural inequality, such as the socioeconomic disparities as measured by a country-level index (GINI), and changes in the brain structure and connectivity associated with aging and dementia. Additionally, the investigators also observe how these social inequities are biologically embedded, notably in underrepresented populations.¹

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Structural inequality, or the uneven distribution of resources and opportunities, are known to influence health outcomes. Despite this evidence, the investigators the biological embedding of these inequities within aging and dementia was previously unknown. For this study, the investigators examined potential associations between structural inequality—at both the state- and country-level—brain volume and connectivity. A total of 2135 healthy controls and individuals with Alzheimer disease and frontotemporal lobe degeneration from Latin America and the US were enrolled and observed.¹

According to the findings, higher levels of structural inequality was associated with a reduced brain volume and connectivity, with stronger effects present in Latin America compared with the US. These effects were especially noticeable in the temporo-cerebellar, fronto-thalamic, and hippocampal regions of the brain. Conversely, milder effects were observed in the insular-cingular and temporal areas within US participants.¹

“Our findings emphasize the urgency of integrating not only individual social determinants of health into global brain health research but also macro-level exposome factors, such as social and physical variables. These findings pave the way for future studies exploring the biological mechanisms linking aggregate inequality to aging and neurodegeneration,” Agustina Legaz, PhD, from the ReDLat consortium, said in a news release. ²

Additionally, the research also showed that Latinx patients had the most severe impacts, with indications that environmental demands linked to structural inequality may exacerbate neurodegeneration in aging populations. Reduced brain volume and connectivity are frequently observed in patients with dementia and are correlated with disease progression and severity. The milder effects observed in the frontotemporal lobar degeneration, according to the authors, support the idea that there may be significant genetic influence in Alzheimer disease.^1,2

Further, the results were more pronounced in Alzheimer disease and effects persisted even after considering age, sex, education, cognition, and other confounding factors. This is significant because it reaffirms the role of structural inequality in aging and dementia. According to the authors, this emphasizes the biological embedding of macrosocial factors and the need for targeted interventions in underserved populations.^1,2

“This research highlights the critical role of structural inequality in shaping brain health. Considering dementia rates rise particularly in low- and middle-income countries, our findings emphasize the need for targeted interventions to address the root causes of brain health disparities, which appear to be specific to each region,” Agustín Ibáñez, PhD, professor in global brain health at Trinity College, Dublin and director of the Latin American Brain Health Institute (BrainLat), said in the news release.²

The authors call for a multi-level approach to brain health equity by further assessing other macro-level exposome factors beyond socioeconomic disparities. Such variables may include democratic governance, air pollution, migration, climate change, and easy access to green spaces and nature. Identifying and addressing region-specific modulators such as these may contribute to targeted intervention methods that mitigate accelerated brain aging, potentially reducing the burden of dementia and Alzheimer disease in underrepresented communities.^1,2

REFERENCES

1. Legaz A, Altschuler F, Gonzalez-Gomez R. et al. Structural inequality linked to brain volume and network dynamics in aging and dementia across the Americas. Nat Aging (2024). doi:10.1038/s43587-024-00781-2

2. Societal inequality linked to reduced brain health in aging and dementia. News release. Trinity College Dublin. December 27, 2024. Accessed January 6, 2025. https://www.eurekalert.org/news-releases/1069058