Sarah Genon's research team at Forschungszentrum Jülich set out to answer a deceptively simple question: why do some people stay sharp into old age while others experience cognitive decline much earlier? The answer, it turns out, has little to do with any single factor—and everything to do with the intricate web of circumstances that shape a life.
Two landmark studies, one published in Nature Communications and another in Nature Medicine, reveal that brain health emerges from the constant interplay of lifestyle, environment, and social conditions across the entire lifespan. Rather than studying these influences in isolation, researchers led by Genon and including doctoral researcher Mostafa Mahdipour examined what scientists call the "exposome"—the totality of all environmental and lifestyle factors to which a person is exposed from birth onward. This concept encompasses everything from diet and exercise to diseases, air quality, and the social circumstances into which someone is born.
The first study analyzed data from the UK Biobank, a massive collection of health records from hundreds of thousands of people. Using two AI-based models, the team assessed how more than 260 different factors influence brain health and aging. One model determined the current state of the brain based on MRI imaging; the second linked that brain data to individual lifestyle and health records. The findings are striking in their specificity: it matters not only what risk factors exist in someone's life, but how long those factors persist and at what stage of life they take hold. Long-term exposures like high blood pressure or smoking are closely linked to unfavorable changes in brain structure. This suggests that identifying and reducing health risks early—before they accumulate over decades—could have profound protective effects on brain aging.
The second study dramatically expands this lens from individual to global. An international team of about 100 researchers examined data from roughly 18,700 people across 34 countries, linking personal health records to comprehensive information about environmental and societal conditions. What they discovered challenges a fundamental assumption: that brain aging is primarily a personal responsibility determined by individual choices. Instead, the research shows that the conditions in which people live measurably shape how their brains age. Air pollution, climate, socioeconomic inequality, and differences in access to healthcare and social security systems are all closely linked to the rate of brain aging—often independently of whether someone has existing diseases or individual risk factors.
The implications are profound. Brain health is not simply the sum of individual choices. A person living in a polluted city with limited healthcare access faces different odds than someone in a wealthy neighborhood with excellent medical services, even if their personal habits are identical. The two studies together demonstrate that mental sharpness in old age results from a complex, lifelong dance between what people do for themselves and the world around them.
This recognition opens new avenues for intervention. Preventive measures make sense at multiple levels—personal habits matter, but so do the air people breathe, the healthcare systems they can access, and the economic security they enjoy. Brain health, these studies suggest, is not an individual problem to be solved alone. It is a reflection of the entire ecosystem in which we live.