Study reveals how social inequalities affect brain aging and dementia

Researchers from Trinity College Dublin worked with international partners to investigate whether social inequality affects our brains. Their research paper is published in Aging Nature today, [Friday, December 27th] by an international team of researchers from the Multipartner Consortium for the Expansion of Dementia Research in Latin America (ReDLat), the Brain Health Institute of Latin America (BrainLat), the GIobal Brain Health Institute (GBHI) at Trinity College Dublin and others centers around the world. The study reveals a direct link between structural inequality – such as socioeconomic inequalities measured by the country-level index (GINI) – and changes in brain structure and connectivity associated with aging and dementia.

The study also sheds light on how social inequalities are biologically embedded, particularly in underrepresented populations in Latin America and the United States.

Key findings

1. The researchers found that higher levels of inequality were associated with reduced brain volume and impaired connectivity, especially in temporal-posterior and cerebellar regions essential for memory and cognition. These effects were most pronounced in Latin America, highlighting the unique vulnerability of Latin American populations to macroeconomic-level socioeconomic stressors.

2. The findings also revealed that Latinos with Alzheimer’s disease experience the most severe effects, suggesting that environmental demands linked to structural inequality may exacerbate neurodegeneration in aging populations. In contrast, the milder effects observed in frontotemporal lobar degeneration support the hypothesis of a more important genetic influence in this condition. Reduced brain volume and connectivity are frequently observed in patients with dementia and are associated with disease progression and severity.

3. Notably, the associations remained even after individual factors such as education, age, gender, and cognitive ability were taken into account, highlighting the independent role of macro-level factors in shaping brain health. Living in a context of global inequality affects brain health regardless of socioeconomic status, demonstrating the far-reaching consequences of social inequalities on the brain.

First author Agustina Legaz, PhD from the ReDLat consortium, said,

“Our findings highlight the urgent need to incorporate not only individual social determinants of health into global brain health research, but also macro-level exponential factors such as social and physical variables. These findings pave the way for future studies that explore the biological mechanisms linking global disparity in aging and neurodegeneration.”

Dr. Agustín Ibáñez, PhD, professor of global brain health at Trinity College, and director of BrainLat and corresponding author, added:

“This research highlights the critical role of structural inequality in shaping brain health. Considering dementia rates are rising particularly in low- and middle-income countries, our findings highlight the need for targeted interventions to address the root causes of inequalities in brain health, which appear to be region-specific.”

The study calls for a multi-level approach to brain health equity, examining the biological integration of other macro-level exponential factors beyond socioeconomic inequality. These may include variables such as democratic governance, air pollution, migration, climate change and access to green space. Identifying and addressing these region-specific regulators could lead to targeted interventions that mitigate accelerated brain aging and reduce the burden of dementia in disadvantaged communities.