Summary: It isn’t just your genes or your diet that determines how fast your brain ages—it’s the air you breathe, the housing you live in, and the political stability of your country. A massive international study analyzed data from over 18,700 individuals across 34 countries to map the “exposome”—the cumulative environmental and social factors we face daily.
The researchers found that these factors act in a syndemic manner, meaning they don’t just add up; they multiply. When combined, environmental and social pressures explained 15 times more variance in brain aging than any single factor alone, proving that structural inequality is a direct driver of neurological decay.
Key Facts
- The Power of Interaction: Single factors like air pollution are risky, but when paired with poverty or lack of green space, the damage to the brain accelerates nonlinearly.
- Physical vs. Social Markers: * Physical Exposures (pollution, extreme heat): Primarily cause structural aging in areas responsible for memory and emotional regulation (linked to neuroinflammation and vascular dysfunction).
- Social Exposomes (inequality, lack of healthcare): Affect brain regions involved in complex thinking and social behavior, likely due to the biological toll of chronic, long-term stress.
- Bigger Than Disease: In some cases, the combined “social challenges” of a person’s environment had a larger impact on brain aging than a clinical diagnosis of dementia.
- Global Scope: The study is the first to provide a quantitative framework across 34 diverse countries, showing that brain health is a global policy issue, not just a medical one.
- Beyond Individual Choice: The findings suggest that “lifestyle” advice (exercise/diet) is insufficient if the person lives in a “syndemic” environment of pollution and instability.
Source: TCD
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 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.
Key Questions Answered:
A: It means 1 + 1 = 5. If you live in a polluted city, that’s a risk. If you live in a polluted city and have no access to healthcare or green space, those risks feed off each other to cause damage that is far worse than just the sum of the parts. They create a “perfect storm” for brain decay.
A: The study suggests that physical environments (like access to parks) are directly linked to better structural integrity in the brain’s memory centers. While you can’t “reverse” time, improving your physical and social environment can significantly slow the pace at which your brain ages.
A: Institutional stability and democracy provide “social protection.” When people have strong civic participation and reliable welfare systems, the chronic “survival stress” on the brain is lowered. Without that stability, the brain stays in a constant state of high-cortisol adaptation, which wears down the regions responsible for high-level thinking and emotional control.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this brain aging research news
Author: Ciara O’Shea
Source: TCD
Contact: Ciara O’Shea – TCD
Image: The image is credited to Neuroscience News
Original Research: Closed access.
“The exposome of brain ageing across 34 countries” by Agustina Legaz, Sebastian Moguilner, Pablo Barttfeld, Jhosmary Cuadros Castro, Dante Sebastián Galván Rial, Joaquin Migeot, Francesca R. Farina, Raul Gonzalez-Gomez, Salomón Salazar-Londoño, Tiago de Souza Azzi, Sarael Alcauter, Lucia Amoruso, Renato Anghinah, May Bakr, María Isabel Behrens, Martin A. Bruno, Juan Felipe Cardona, Christopher Chen, Olivier Colliot, Nilton Custodio, Quentin d’Acremont, Stéphanie Debette, Patrycja Dzianok, Bahar Güntekin, Jordi Huguet, Cecilia Jarne, Marc Joliot, Elissaios Karageorgiou, Eman M. Khedr, Sheri-Michelle Koopowitz, Ewa Kublik, Jinkook Lee, Leon Aksman, Susanna Lopez, Paula Margaretic, Diana Matallana, Sophie Matis, Andreas Miltiadous, Gabriela Novotni, Patricio Orio, Mario A. Parra, Simone Reppermund, Elisa de Paula França Resende, Giovanni Abrahão Salum, Andrea Slachevsky, Ana Luisa Sosa Ortiz, Leonel Tadao Takada, An Qi Toh, Alexandros Tzallas, Wei Wen, Robert Whelan, Görsev Yener, Jonathan Adrián Zegarra Valdivia, Athanasia Alexoudi, Faheem Arshad, Haisam Atta, Jose Alberto Avila-Funes, Jasmin Bonilla Santos, Ricardo Bruña, Sandra Milena Castelblanco-Toro, Brenda Nadia Chino Vilca, Carlos Coronel-Oliveros, Fabrice Crivello, Josephine Cruzat, Damián Dellavale, Catherina Dhooge, Gaetano Di Caterina, Javier Escudero, Juan Manuel Esquivias Farias, Laz Ude Eze, Tavia E. Evans, Temitope Farombi, Alberto Fernández, Sol Fittipaldi, Florencia Portillo, Gonzalo Forno Martinic, Adolfo M. García, Indira Garcia-Cordero, Rahul Gaurav, Maria Eugenia Godoy, Cecilia Gonzalez Campo, Alfredis González Hernández, Lütfü Hanoğlu, Jessica L. Hazelton, Rubén Herzog, Burcin Ikiz, Alfred Kongnyu Njamnshi, Ramon Landin-Romero, María Eugenia López, Marcelo Adrián Maito, Vicente Medel, Juan Pablo Morales Sepúlveda, John Fredy Ochoa Gómez, Chukwuanugo Ogbuagu, Maira Okada de Oliveira, Mehmet Ozansoy, Javier Palma-Espinosa, Saima Hilal, Juan Helen Zhou, Stefanie Danielle Piña Escudero, Julie Kay Pitman, Pavel Prado, Diego Ramírez González, Pablo Reyes, Hernando Santamaría García, Johannes Schröder, Jacobo Diego Sitt, Radwa Kamel Soliman, Marcio Soto-Añari, Nithin Thanissery, Lucas Toshio Ito, Ami Tsuchida, Christophe Tzourio, Harun Yırıkoğulları, Jennifer S. Yokoyama, David Aguillon, Bruce Miller, Suvarna Alladi, Yang Jiang, Arcadi Navarro, Claudio Babiloni, David Huepe Artigas, Olivier Piguet, Pedro Antonio Valdes Sosa, Cyprian M. Mostert, Masoud Tahmasian, Peng Li, Kun Hu, Sarah Genon, Dan J. Stein, Fernando Maestú, Michela Pievani, Mohamed Salama, Henry Brodaty, Perminder S. Sachdev, Brian Lawlor, Harris A. Eyre, J. Jaime Miranda, Sandra Baez, Enzo Tagliazucchi, Claudia Duran-Aniotz, Hernan Hernandez & Agustin Ibanez. Nature Medicine
DOI:10.1038/s41591-026-04302-z
Abstract
The exposome of brain ageing across 34 countries
The physical and social exposome affects human aging, and brain clocks may track its effects. However, most studies neglect multidomain exposures (physical, social and political) across diverse settings globally and their associations with brain aging.
In this study, we characterized the associations between 73 country-level physical and social exposomal factors and multimodal brain age in 18,701 participants from 34 countries (healthy individuals and those with Alzheimer’s disease, frontotemporal lobar degeneration or mild cognitive impairment).
Exposome effects were assessed using generalized additive models and meta-analytic frameworks. Aggregated exposome models explained up to 15.5-fold more variance than individual exposures (delta Akaike information criterion (ΔAIC): 2,034–3,127).
Physical exposome was primarily associated with accelerated structural brain aging (limbic, subcortical and cerebellar regions), whereas social exposome was more strongly associated with functional brain aging (frontotemporal and limbic networks).
Exposome burden accounted for 3.3−9.1-fold higher risk of accelerated aging, exceeding effects of clinical diagnoses. Findings were out-of-sample validated in cross-sectional and longitudinal designs, remained consistent across clinical subgroups and persisted after adjustment for demographics, age correction bias, cognition, scanner type and data quality.
The exposome accelerates brain aging in health and disease, underscoring the need to address physical, social and political inequities.
