A study spanning 34 countries suggests that differences in brain aging may reflect more than genes and lifestyle alone.
Key Takeaways
A large international study suggests that social and physical environmental conditions—from pollution and access to green space to poverty and inequality—may help shape differences in brain aging across populations.
The Study
Researchers analyzed brain imaging data from more than 18,000 people across 34 countries. Using machine-learning models known as brain clocks, they estimated whether a person’s brain appeared older or younger than expected for their age. A brain that appears older than expected may reflect accelerated brain aging, while a younger-looking brain may reflect delayed aging or resilience.
After estimating each participant’s brain age, the researchers asked whether differences in physical and social environmental conditions were associated with differences in brain aging. To do this, they examined a broad set of exposures, including pollution, climate conditions, green space, poverty, inequality, and political stability. Together, these factors make up what researchers call the exposome: the cumulative social and physical environmental conditions people experience over the course of their lives.
Study at a Glance
Published: Nature Medicine (April 2026)
Researchers: Led by Agustín Ibáñez and colleagues at the Latin American Brain Health Institute (BrainLat), the Global Brain Health Institute, and an international consortium of researchers from North America, Latin America, Europe, Africa, Asia, and Oceania.
Key concept: “Exposome,” the cumulative physical and social environmental conditions people experience over their lifetimes.
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Why It Matters for Cognitive Aging
Researchers have spent decades trying to understand why some people remain cognitively healthy into later life while others experience greater decline. Much of that work has focused on factors such as genetics, exercise, education, and cardiovascular health.
This study broadens that picture by examining how the environments people inhabit may shape brain aging over time. The findings suggest that differences in brain aging may also reflect the social and environmental conditions people experience throughout life.
“The most important message is that cognitive aging is not only something that happens inside the brain. Our brains age within the environments where we live,” said senior author Agustín Ibáñez, a neuroscientist and Scientific Director of the Latin American Brain Health Institute (BrainLat).
Different Exposures, Different Brain Signatures
The researchers also found that different types of environmental exposures appeared to leave different signatures on the brain.
Physical exposures, including factors such as air pollution, temperature, and access to green space, were more strongly associated with structural brain aging, meaning changes in the brain’s physical architecture. Social exposures, including inequality, democratic stability, and socioeconomic conditions, were more strongly associated with functional brain aging, which reflects how different brain regions communicate and work together.
For Ibáñez, another surprise was that the combined effect of multiple exposures appeared to matter more than any single factor alone.
“The interaction among multiple environmental factors can generate much stronger effects on accelerated or delayed brain aging than isolated factors considered separately,” he said.
The findings suggest that social and physical environmental conditions may influence brain aging through multiple biological pathways rather than a single mechanism.
Understanding the Evidence
This was an observational study, meaning researchers looked for patterns across populations rather than testing an intervention in a controlled experiment.
While environmental and social conditions were linked to differences in brain aging, the study cannot determine whether those conditions directly caused those differences.
Why MBRF Is Paying Attention
One of the central questions in cognitive aging research is why people age differently. Decades of research have shown that genes matter. Lifestyle also matters. But this study suggests that social and physical environmental conditions may also help shape the brain’s vulnerability and resilience across the lifespan.
Understanding why people age differently—and how biology, environment, and lived experience interact over time—may ultimately help researchers identify new ways to support brain health and resilience across the lifespan.