Physical and social environmental exposures shape the biological brain age in global populations

The latest findings from the Global Brain Health Institute (GBHI) at Trinity College Dublin identify important brain health implications for prevention, public health, and policy.

Trinity College Dublin

Physical and social environmental exposures shape the biological brain age in global populations

The latest findings from the Global Brain Health Institute (GBHI) at Trinity College Dublin identify important brain health implications for prevention, public health, and policy. 

An international study published across 34 countries shows that the biological age of the brain can be accelerated or delayed by environmental risk (air pollution, public housing conditions) and protective factors (socioeconomic equality, access to healthcare). The stronger effects arise from interactions among environmental, social, and political conditions. The paper is published today [Friday, 3rd April 2026] in the journal Nature Medicine.

How do the combined environments in which people live jointly shape the pace at which the human brain ages? Using data from 18,701 individuals across 34 countries, the study shows that the exposome (the cumulative set of environmental, social, and sociopolitical exposures that individuals experience throughout life) operates in a syndemic manner - when two or more health problems occur together and interact in a way that makes each other worse - with multiple co-occurring exposures having very large effects, shaping brain aging across both healthy individuals and those with neurodegenerative conditions.

The researchers quantified 73 different environmental factors measured at country level indicators spanning air pollution, climate variability, green space, water quality, socioeconomic inequality, and multiple indicators of political and democratic contexts. When modeled jointly, these factors explained up to 15 times more variance in brain aging than any single exposure alone. This finding highlights a key shift: environmental influences on brain health are cumulative and nonlinear, with interactions across domains amplifying their biological impact.

Agustín Ibáñez, lead investigator and corresponding author said: “we aimed to test whether the combined, syndemic effects of environmental exposures better explain variability in brain aging across populations than individual exposures or single clinical diagnoses”.

The study identifies distinct but complementary brain markers. Combined physical exposures (increased pollution, extreme temperatures and lack of green spaces) were primarily associated with structural brain aging, particularly affecting regions, central to memory, emotional regulation, and autonomic functions. These structural changes are consistent with mechanisms such as neuroinflammation, oxidative stress, and vascular dysfunction, all of which may contribute to tissue degeneration. 

In contrast, social exposomes like poverty, inequality, and lack of support can strongly affect how the brain ages. These pressures are linked to faster aging in brain areas responsible for thinking, emotions, and social behaviour.

This may happen because the brain is constantly adapting to long-term stress. In fact, these combined social challenges can have an even bigger impact on brain aging than diseases like dementia and cognitive impairment. Overall, this effect is consistent across different brain measures, clinical groups, and long-term assessments.

For Agustina Legaz, first author of the study, Atlantic Fellow at GBHI and researcher at San Andres University, the work: “provides a quantitative framework to understand how multiple environmental exposures jointly shape brain aging beyond individual determinants”. 

Sebastián Moguilner, co-first author, Atlantic Fellow, and researcher at Harvard University, added that: “combining multimodal brain imaging with nonlinear modeling allows us to identify complex factors linking large-scale environmental exposures to brain connectivity”. 

Hernán Hernández, co-lead author of the study and researcher at the Latin American Brain Health Institute (BrainLat), emphasized that: “the inclusion of multiple countries and clinical groups highlights the global diversity of syndemic effects on brain health.”

 

What are the implications and possibilities for change because of these findings?

The findings have important implications for prevention, public health, and policy. Current strategies to promote healthy brain aging often focus on individual behaviors (diet, exercise, or cognitive training) or on treating disease once symptoms emerge. While these approaches are critically important, they address only part of the risk landscape. Many drivers of brain aging operate at broader structural levels, including environmental conditions, social inequalities, and institutional stability. 

Policies that reduce air pollution, expand access to urban green spaces, improve water quality, and strengthen social protection systems may therefore have measurable benefits for brain health at the population level. 

Promoting brain health requires coordinated, multisectoral action that goes beyond healthcare systems alone. Effective strategies should integrate:

-environmental regulation (reducing black carbon emissions and improving urban design), 

-social policy (ensuring basic welfare and improving education and access to resources), and 

-institutional strengthening (supporting democracy by enhancing civic participation and expanding local representation). 

These results call for aligning efforts across public health, environmental, urban, and policy sectors to reduce cumulative exposome burden and support healthier brain aging trajectories at both individual and population levels.

Read the full article: The paper: ‘The exposome of brain ageing across 35 countries’ can be read in full at Nature Medicine at the following link:  https://doi.org/10.1038/s41591-026-04302-z which is available when the embargo lifts on Friday, 3rd April 2026 at 10am (BST). You can request a copy of the study on request before the embargo lifts.

Ends

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Journal

Nature Medicine

Method of Research

Experimental study

Subject of Research

People

Article Title

The exposome of brain ageing across 34 countries

Article Publication Date

3-Apr-2026