Urbanization exacerbates age-associated declines in cardiometabolic health in Turkana and Orang Asli.

Declines in cardiometabolic health among older individuals are so ubiquitous in Western, high-income countries that non-communicable diseases (NCDs) like type 2 diabetes, hypertension, and cardiovascular disease have been termed "diseases of aging". In contrast, research from non-industrial contexts has found low rates of cardiometabolic NCDs in old age, suggesting protective effects of lifestyle. To test if industrialization and urbanization generates or magnifies age-associated cardiometabolic health patterns, within-population analyses are needed. We worked with Turkana pastoralists of Kenya and Orang Asli mixed subsistence groups of Peninsular Malaysia-two groups that are transitioning from non-industrial to urban, market-integrated lifestyles. We find that rural, non-industrial environments produce minimal to modest age-dependent increases in body size, lipid, and blood pressure traits, and that urban environments significantly amplify age effects in repeatable ways across two distinct populations. However, we did not find that urban environments consistently accelerate biomarkers of more generalized functional capacity and biological aging, namely grip strength, walking speed, and epigenetic age. Together, these findings challenge the view that cardiometabolic "diseases of aging" are an intrinsic feature of aging, instead implicating urban lifestyle features as drivers of age-associated variation; however, these same lifestyle exposures may have heterogeneous effects on biological aging. These results underscore the urgency of understanding how rapid lifestyle changes shape aging trajectories, especially in populations undergoing industrial transitions.