Aging clocks may be shaped by neurosyndemics, multiple interacting physical and social real-world environments jointly influencing brain health. Out in Nature Medicine (nature.com/articles/s41591-0…), we assessed 18,701 participants from 34 countries, showing that the combined aggregate-level exposome (73 physical, social, and political factors measured at country-level) predicts multimodal brain aging far better than isolated exposures (up to 15-fold more variance). Moving beyond single risks, we provide evidence that synergistic, nonlinear exposome burden accelerates brain clocks across health and disease, with physical exposures linking more strongly to structural brain aging and social exposures to functional brain aging. Exposome burden increased the risk of accelerated brain aging by 3.3–9.1-fold, in some cases exceeding the effects associated with dementia, and these findings held in out-of-sample, longitudinal, individual-level variation, and sensitivity analyses. Thus, the pace at which the brain ages may be shaped by syndemic environmental and societal conditions, calling for much more intersectoral policies. Congrats @AgustinaLegaz Sebastian Moguilner @HernHdezL & all coauthors. 1/5👇 @GBHI_Fellows