A new era of cumulative threats
Winds of change are blowing everywhere. One can think of technological transformations, geopolitical shifts, infodemics, or the dawn of new conflicts. A core aspect is a compound instability that penetrates nearly every aspect of life. Climate change is already reshaping ecosystems, displacing populations, and triggering health crises worldwide. Socioeconomic inequalities have reached unprecedented levels, exacerbated by inflation, war, and unequal access to healthcare and education. Mass migration, often driven by violence, poverty, or climate disasters, challenges the capacity of nations and the fabric of communities. Meanwhile, democratic institutions around the globe are eroding, and trust in political systems continues to decline, fueled by polarization, misinformation, and governance failures.
These interconnected threats form a new syndemic, characterized by co-occurring crises that intensify the sense of despair. We are exposed to simultaneous stressors at a scale and complexity that are novel in human history. These stressors are embedding themselves in our societies, economies, and biology. Mainstream political and economic frameworks have explained these shifts through the lenses of globalization, neoliberalism, and post-industrial transitions. Cultural theorists highlight a planetary shift toward precarity, uncertainty, and fragmentation. Health disparities are often addressed through social determinants frameworks, emphasizing income, education, and access to care. Yet these perspectives usually fail to capture the biological consequences of living in a world under constant stress. Environmental degradation, inequality, and institutional decay are not only sociopolitical phenomena but physiological burdens.
The biology of the compound exposome
Global environmental demands are external pressures that act as biological agents, slowly reshaping our bodies and minds. That is the core hypothesis of a growing body of research: the idea that the exposome—the totality of physical, social, and policy environments in which we live—can be biologically embedded through chronic inflammation, immune dysregulation, endocrine dysfunction, and neurovascular damage.
The cumulative burden of continuous adaptations is captured in the concept of allostatic interoceptive overload, which refers to the physiological wear and tear on the body resulting from repeated or chronic stress. When our bodies face constant challenges such as heat waves, air pollution, social exclusion, or economic precarity, they must continually adapt, leading to resilience. Over time, these adaptations themselves become damaging, accelerating aging processes across multiple systems, including the brain.
Recent research has extended this concept to the study of accelerated aging, utilizing machine learning models to predict an individual's biological age based on their physiology or neuroimaging data. The difference between this predicted age and a person’s chronological age—known as the age gap—is emerging as a robust biomarker of brain health. A higher gap suggests accelerated aging and has been associated with cognitive decline, dementia risk, and mortality. However, the role of global exposome factors in shaping these age gaps has mainly remained unexplored until now.
Mapping the global exposome of accelerated aging
Our work, recently published in Nature Medicine, tackled this critical gap using a large and diverse dataset across 40 countries. The study analyzed 161,981 participants from 40 countries to assess how biobehavioral age gaps (BBAGs; the discrepancy between estimated age based on protective/risk factors and chronological age) reflect patterns of accelerated or healthy aging. BBAGs accurately predicted chronological age and revealed substantial regional differences, with Europe exhibiting the healthiest aging profiles (Figure 1). At the same time, African countries showed the most accelerated aging, with Asia and Latin America presenting intermediate profiles. Accelerated aging was more pronounced in Eastern and Southern Europe and strongly associated with lower income levels globally. The exposome effects on BBAGs were broad and robust, encompassing physical (e.g., poor air quality), social (e.g., socioeconomic and gender inequality, migration), and sociopolitical domains (e.g., limited representation, reduced party freedom, suffrage restrictions, and weaker democracies), all with significant effects. Crucially, BBAGs were strong predictors of future outcomes, including functional and cognitive decline, as well as accelerated aging (2-4 years). In brief, physical, social, and sociopolitical exposures are deeply embedded in aging trajectories and vary substantially across global regions.
Figure 1. Main results. a, Feature importance, assessed via MDI, enabled the prediction of chronological age using biobehavioral factors. The sample size for the analyses reported in this figure included 161,981 individuals. Goodness-of-fit and feature importance metrics are provided. b, MDI facilitated the characterization of groups with more delayed (left panel) and more accelerated (right panel) aging. Goodness-of-fit and feature importance metrics are provided. c, Average BBAG distribution by continent. The color bar indicates younger and older BBAGs. d, BBAG comparisons by continent and by European regions. e, BBAG comparisons between low- and high-income countries, based on GNI and GDP indicators. f, Linear regression models were used to assess the interaction between BBAGs and all exposomal factors, as well as the combined effects of social, physical and sociopolitical exposomes. g, Linear regression models were applied to examine the associations between BBAGs and individual social (gender equality, migration and structural equality) and physical (air quality) exposomal factors. h, Linear regression models were used to assess the relationship between BBAGs and individual sociopolitical exposomal factors (democracy indicators). Extended Data Figs. 2 and 3 present additional results.
A new science for a new world
Our findings underscore a sobering message: the challenges of our era, including climate change, socioeconomic disparity, gender inequality, displacement, migration, violence, and institutional decay, are also accelerating the rate at which we biologically age. In a world shaped by syndemic crises, aging must be defined not only by our genes or lifestyles, but by the exposome that surrounds us. Through the BBAGs, we demonstrate how the physical, social, and sociopolitical exposome exerts measurable influence on the aging process across diverse global populations. Aging becomes not solely a genetic or medical phenomenon, but a deeply ecological and sociopolitical one. Addressing accelerated aging in the 21st century requires a new scientific lens that integrates synergistic brain health models with global health, environmental justice, policy reform, and the fight against systemic inequality. Our world has changed; our models of aging must evolve accordingly.
The poster figure was created by ChatGPT with oversight from the authors.