Intergenerational educational mobility and intrinsic capacity in later life: a harmonised analysis of individuals from five countries

Background: The World Health Organization's intrinsic capacity (IC) framework shifts focus from disease to functional ageing. Despite education's role in health, the impact of intergenerational educational mobility (IEM) on IC trajectories remains understudied. We aimed to examine the cross-national association between IEM and IC, its effect on biological ageing rates, and underlying mechanisms. Methods: We analysed harmonised longitudinal data from five nationally representative cohorts: China Health and Retirement Longitudinal Study, Health and Retirement Study (USA), Survey of Health, Ageing and Retirement in Europe, Korean Longitudinal Study of Ageing, and Mexican Health and Aging Study, including 495,028 observations from 100,362 individuals aged ≥50. We standardised IC as a composite of cognition, locomotion, vitality, sensory, and psychological domains. We used a two-stage individual participant data meta-analysis, growth curve modelling, and the Karlson-Holm-Breen mediation method to assess associations, trajectories, and pathways via wealth, behaviours, and chronic conditions. Results: Upward IEM was robustly linked to higher IC (pooled β = 0.25; 95% confidence interval = 0.24, 0.26; P < 0.001). Linear mixed-effects models showed distinct intra-individual ageing patterns: upward mobility significantly decelerated the rate of IC decline ('delayed ageing') in China, Europe, South Korea, and Mexico. Conversely, a 'parallel ageing' pattern emerged in the USA, where mobility massively elevated baseline capacity but did not alter the slope of age-related decline. Conclusions: The IEM confers consistent health advantages across countries, but the magnitude and trajectory of these benefits are context-dependent. The unique 'US exception' of parallel ageing suggests that while mobility elevates early-life health capital, systemic environmental or healthcare factors may equalise subsequent late-life decline. Enhancing mobility remains a critical global strategy for healthy longevity.