Healthy longevity in a mobile world: expatriates as quasi-experimental populations for understanding life-course transitions.

Healthy longevity frameworks increasingly emphasise life-course perspectives, prevention, and the maintenance of functional ability across ageing. However, most existing models implicitly assume populations are embedded within stable national contexts and insufficiently account for the growing role of international mobility. Expatriates experience repeated transitions across healthcare systems, sociocultural environments, and physical contexts that may influence healthy longevity trajectories over time. We propose a conceptual framework for understanding healthy longevity in a mobile world, drawing on purposively selected literature from life-course epidemiology, migration and health, healthy longevity, and health systems research to develop a hypothesis-generating conceptual framework. The framework integrates established concepts from life-course epidemiology with contemporary perspectives on migration as a dynamic and multistage process characterised by changing exposures across origin, destination, and return settings. We propose that repeated geographic transitions represent important life-course inflection points that may reshape healthcare system exposures, sociocultural and behavioural contexts, and psychosocial and environmental conditions. These cumulative exposures may influence awareness, knowledge, motivation, preventive engagement, and continuity of care across systems, thereby affecting pathways associated with mental health, cardiometabolic risk, immune regulation, functional ability, and healthy longevity. The framework further identifies potential modifiers, including age, timing of migration, sex and gender, socioeconomic position, insurance coverage, legal status, digital health infrastructure, and social support. Finally, we generated several empirically testable propositions to guide future longitudinal, comparative, and mixed-method research. We propose that expatriates may serve as quasi-experimental populations for understanding how mobility and life-course transitions shape healthy longevity. Integrating mobility into conceptual and empirical models of healthy ageing may improve the contextual relevance, implementation, and global applicability of interventions aimed at extending healthspan in increasingly interconnected societies.