Social inequality is directly linked with changes in brain, known to be related to ageing and dementia, a study has revealed.

As dementia cases are projected to rise in the years to come, especially in low and middle-income countries, the findings stressed that interventions targeted at addressing the local socioeconomic landscape are needed for treating the root causes of brain health disparities, said researchers, including those from Trinity College Dublin, Ireland.

They looked at the relationship between structural inequality -- as measured by national indices -- and brain volume and connectivity. Over 2,100 individuals with neurodegenerative conditions, including Alzheimer's disease, and healthy ones from Latin America and the US were recruited.

Socioeconomic disparities measured by country-level indices were directly linked to changes in brain structure and connectivity, especially in regions essential for memory and cognitive function, which are known to be affected with aging and dementia.

"Greater structural inequality was linked to reduced brain volume and connectivity, with stronger effects in Latin America, especially in the temporo-cerebellar, fronto-thalamic and hippocampal regions," the authors wrote in the study published in the journal Nature Aging.

Latinos with Alzheimer's disease were found to experience the most severe impacts, suggesting that growing old in an environment of societal inequality may worsen neurodegeneration in ageing populations.

The researchers said that the links persisted despite adjusting for individual factors such as education, age, sex and cognitive ability.

The result highlighted the independent role of macro-level social factors in shaping brain health, they said.

"Our findings emphasise 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," said first author Agustina Legaz, Latin American Brain Health Institute (BrainLat), Chile.

"These findings pave the way for future studies exploring the biological mechanisms linking aggregate inequality to aging and neurodegeneration," Legaz said.

Demonstrating the far-reaching consequences of societal disparities on one's brain, the study sheds light on how societal inequities can become biologically embedded, particularly in underrepresented populations across Latin America and the US, the authors said.

"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 emphasise the need for targeted interventions to address the root causes of brain health disparities, which appear to be specific to each region," said corresponding author Agustín Ibáñez, a professor of global brain health at Trinity College.

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