Social inequality has been linked to aging and dementia.

The differences among individuals, stemming from psychological and physiological traits, are referred to as natural. However, disparities in income, education, and power are attributed to social differences, which arise from factors such as the division of labor, lifestyle, and societal roles. Researchers have long linked the unfair distribution of resources to declining health, yet the exact biological mechanism behind this phenomenon (especially concerning diseases like dementia) has remained a mystery. 

An article, published in the journal Nature Aging at the end of December 2024, clarified the situation by demonstrating the impact of living in a society with high levels of social inequality on the brain. By analyzing data from over two thousand participants, including both healthy individuals and volunteers suffering from Alzheimer’s disease or frontotemporal dementia, researchers compared brain volume metrics and the functional connectivity between its regions with the level of social inequality across various regions of Latin America and the United States. 

The level of inequality was measured using the Gini coefficient—a statistical indicator of the degree of stratification in a specific country or region based on a studied characteristic. The research team, led by Agustina Legaz from Adolfo Ibáñez University (Chile) and Agustín Ibáñez from Trinity College in Dublin (Ireland), found that higher levels of inequality corresponded to reduced brain volume and weakened neural network connectivity. 

The most pronounced changes, particularly in the posterior regions of the temporal lobes and the cerebellum (areas responsible for memory and cognitive functions), were observed among participants from Latin America. Notably, the impact of social inequality on brain structures was more pronounced in subjects diagnosed with Alzheimer’s disease. According to the authors of the study, this indicates a significant influence of living standards on brain health. 

“Structural inequality plays a crucial role in shaping brain health. In developing countries, dementia is becoming increasingly prevalent, highlighting the urgent need for targeted strategies aimed at addressing social issues,” explained the lead author of the article to Medical Express. 

The researchers also noted the influence of genetic factors on the development of frontotemporal dementia, and the connection between “inequality and declining brain health” persisted even when accounting for the education level, age, gender, and cognitive abilities of the participants.

The results indicated that high levels of social inequality adversely affect the brain, regardless of an individual's socio-economic status, accelerating the aging process and the progression of dementia. This finding once again underscores that efforts to reduce inequality can not only enhance people's quality of life but also impact their health at a fundamental level.

The study was limited to Latin America and the United States, which makes its conclusions clearly not universal. For instance, on the map of Alzheimer’s disease prevalence, countries like Sweden, Norway, and Finland face much more severe conditions than the U.S. and Latin America. At the same time, social inequality there is much lower than in the U.S. or Latin America.