Objective <p>Healthy aging is considered an effective way to deal with the challenges of aging. Intrinsic capacity (IC, A composite indicator of physical and mental ability) and functional ability (FA, including the inherent capabilities of the individual, the environment in which the individual lives, and the interaction of people with their environment.) are two key elements of this concept. However, the structure, intensity, and mediation analysis of longitudinal changes in IC and FA have not been specifically studied.</p> Methods <p>A theoretical model was constructed by analyzing the concept of “health aging”. A national database (China Health and Retirement Longitudinal Study, CHARLS) was used as the data source for the study. A range of physical and mental measures were employed to construct intrinsic abilities using factor analysis, and a measure of disability was used as a proxy for FA. Descriptive and regression analyses were also conducted to preliminarily assess the distribution of the variables on the IC). This study used cross-lagged models to examine structural and effect differences between IC and FA in the longitudinal study, along with mediation analysis to analyze the mechanism of the two.</p> Results <p>IC shows a normal distribution and is positively correlated with education and income. In the structural analysis, IC and FA indicate significant cross-lagged effects in the longitudinal direction. The effect of IC on FA is also greater than that of FA on IC; such an effect also tends to intensify over time. Furthermore, multimorbidity mediates the effect of IC on FA, but the mediating effect is not very large. Finally, social participation did not significantly mediate the effect of FA on IC.</p> Conclusion <p>By analyzing the structure, strength, and interaction path between IC and FA, research has found that diseases are just a process of FA development. However, the source variable - patient’s IC - has received less attention. This suggests that policymakers should not only focus on identifying a disease, but also on assessing, maintaining, and providing intervention before the disease. The authorities should also promote the implementation of people-centered rather than disease-centered measures in the health delivery system to achieve value transformation.</p>