Research progress on intrinsic capacity in older adults: Concepts, epidemiology, assessments, influencing factors, adverse outcomes, and interventions.

Intrinsic capacity (IC), introduced by the World Health Organization, is a core concept in the framework of healthy ageing. This study reviews the relevant concepts, epidemiology, assessments, influencing factors, adverse outcomes, and interventions concerning IC. IC refers to the composite of physical and mental capacities that an individual can draw on to live independently and thrive. Although IC is closely related to frailty and physiological reserve (PR), there are conceptual differences: IC represents the inherent functional reserve, frailty reflects the cumulative state of functional deficits, and physiological reserve emphasizes the ability to resist functional physical decline. IC assessments include comprehensive screening instruments of Integrated Care for Older People (ICOPE) and combinations of domain-specific scales; however, these approaches face challenges such as the inability to provide quantifiable results and the lack of standardized criteria, highlighting the urgent need to develop a standardized IC assessment system. Biomarkers may serve as supportive assessment tools, but their application is limited by cost and insufficient evidence, underscoring the need for future development of predictive models that integrate them. The main factors influencing IC include sociodemographic characteristics, physical health, psychosocial factors, and lifestyle. IC is strongly associated with health outcomes, serving as an effective predictor of several adverse outcomes. Interventions targeting IC primarily include ICOPE-guided multidomain interventions, along with other interventions such as multicomponent exercise, cognitive stimulation therapy, and dietary intervention; however, high-quality controlled trials remain limited, and the optimal timing and mechanisms of intervention require further investigation. This review offers important insights for clinical practice and research aimed at promoting healthy ageing among older populations.