Researchers from Trinity College Dublin, in collaboration with international partners, have made groundbreaking strides in understanding the impact of societal inequality on the brain. Their research, published in Nature Aging on December 27th, explored the relationship between structural inequality—such as socioeconomic disparities—and changes in brain structure and connectivity, particularly in the context of aging and dementia. The study, titled “Structural inequality linked to brain volume and network dynamics in aging and dementia across the Americas,” was carried out by a global team from the Multipartner Consortium to Expand Dementia Research in Latin America (ReDLat), the Latin American Brain Health Institute (BrainLat), the Global Brain Health Institute (GBHI) at Trinity College Dublin, and other institutions worldwide.
This innovative research reveals a significant connection between the structural inequality experienced in various regions—measured using a country-level index called the Gini coefficient—and alterations in brain structure, as well as disruptions in brain network connectivity associated with aging and dementia. One of the key findings of the study is the way societal inequities become biologically embedded, particularly in underrepresented populations across Latin America and the United States. By focusing on these populations, the researchers were able to explore how systemic factors, such as poverty and social inequality, can manifest as physiological changes in the brain, contributing to cognitive decline and neurodegeneration.
The team found a notable correlation between higher levels of structural inequality and reduced brain volume, along with disruptions in brain connectivity—especially in the temporo-posterior and cerebellar regions of the brain. These areas are crucial for cognitive function and memory. The impact of these socioeconomic disparities on brain health was found to be especially pronounced in Latin American populations, suggesting that these populations may be uniquely vulnerable to the stressors that stem from macro-level socioeconomic inequalities. The findings are particularly striking given that these effects were consistent even after accounting for individual variables such as education, age, sex, and cognitive ability, reinforcing the notion that structural inequality, at a societal level, has independent and far-reaching consequences on brain health.
One of the most significant discoveries in the study was that Latinos with Alzheimer’s disease exhibited the most severe impacts of structural inequality on their brain health. This suggests that environmental stressors linked to inequality could exacerbate neurodegeneration in aging populations, leading to more severe cognitive decline and faster progression of Alzheimer’s disease. This finding is particularly alarming given the rising rates of dementia in low- and middle-income countries, where the effects of inequality are often more pronounced. On the other hand, the study also found that individuals with frontotemporal lobar degeneration (FTLD) experienced milder effects, which supports the hypothesis that genetic factors may play a more significant role in this condition than in Alzheimer’s.
The study’s results also highlight the complex interplay between genetics and environmental factors. While genetics certainly influences the onset and progression of neurodegenerative diseases, the environmental factors—especially those shaped by structural inequality—appear to have a considerable impact on brain health. This finding underscores the need for a holistic approach to understanding brain aging and dementia, one that considers not just individual risk factors like genetic predisposition but also the broader societal forces that shape health outcomes across populations.
First author Agustina Legaz, Ph.D., from the ReDLat consortium, emphasized the importance of broadening the scope of global brain health research to include not only individual social determinants of health but also macro-level exposome factors. Exposome refers to the cumulative environmental exposures that individuals experience throughout their lives, including both physical and social variables. Dr. Legaz’s comments highlight the need for future research that explores the biological mechanisms linking aggregate inequality to aging and neurodegeneration. This could include further investigation into how inequality-related stressors, such as social unrest or unequal access to healthcare, contribute to the biological embedding of disparities in brain health.
Dr. Agustín Ibáñez, Ph.D., a professor of global brain health at Trinity College Dublin and the director of BrainLat, added that the findings of this study underscore the critical role that structural inequality plays in shaping brain health. He pointed out that dementia rates are particularly high in low- and middle-income countries, which tend to experience more severe levels of inequality. Given the disproportionate impact of dementia on these regions, the research calls for targeted interventions that address the root causes of brain health disparities. Dr. Ibáñez also emphasized the need for region-specific strategies to mitigate the effects of these disparities, as the social and economic factors influencing brain health may differ across countries.
The study advocates for a multi-level approach to brain health equity, one that goes beyond addressing individual factors like socioeconomic status, education, and access to healthcare. The researchers call for a closer examination of other macro-level exposome factors that can influence brain health, such as the quality of governance, air pollution, migration, climate change, and access to green spaces. These factors are often shaped by systemic policies and societal structures, making it imperative to consider them when developing interventions to address brain aging and dementia. Identifying and addressing these region-specific factors could help mitigate the accelerated aging of the brain in disadvantaged communities, ultimately reducing the burden of dementia and improving quality of life for aging populations.
The findings of this research have profound implications for public health policy and the future of dementia care. By identifying the links between societal inequality and brain health, the study opens the door for a new approach to dementia prevention and treatment. Instead of focusing solely on individual risk factors, policymakers and healthcare providers may need to consider structural inequalities when designing interventions. This could include advocating for policy changes that reduce income inequality, improve access to education and healthcare, and address environmental factors that disproportionately affect disadvantaged communities.
The study also highlights the need for global collaboration in tackling the growing dementia crisis. As the global population ages, the prevalence of dementia is expected to rise, particularly in regions where structural inequality is most pronounced. By working together across borders and disciplines, researchers, healthcare providers, and policymakers can develop more effective strategies for preventing and managing dementia, ultimately improving the lives of millions of people worldwide.
Reference: Agustina Legaz et al, Structural inequality linked to brain volume and network dynamics in aging and dementia across the Americas, Nature Aging (2024). DOI: 10.1038/s43587-024-00781-2