Developing intrinsic capacity measures for research and practice in an Australian context

Introduction: Intrinsic capacity is a key construct for healthy ageing; however, its measurement remains heterogeneous, with insufficient attention to context, data availability, and intended purpose. We operationalised intrinsic capacity to facilitate its assessment in both research and clinical settings. Method: Using data from Concord Health and Ageing in Men Project (CHAMP; 2005-2007; 1,705 Australian men aged [&ge;]70 years), we developed three intrinsic capacity models using confirmatory factor analysis (CFA): literature-based (21 commonly used indicators), minimum-set (10 indicators), and clinically informed (10 indicators selected for clinical feasibility). Convergent validity was assessed using activities of daily living (ADL) and instrumental activities of daily living (IADL) as indicators of functional ability. Predictive validity was examined using 2-year incident ADL and IADL dependency and 10-year mortality follow-up data. Results: All models demonstrated acceptable model fit (robust root mean square error of approximation <0.06). The second-order level of CFA showed significant associations with the cognition, locomotor function, psychological well-being, and vitality domains, but not the sensory domain. Higher intrinsic capacity scores were associated with lower ADL (e.g., ICclinically informed 0.91 [0.90-0.92]) and IADL dependence (e.g., ICclinically informed 0.92 [0.92-0.93]) at baseline, lower incident dependency at follow-up, and lower all-cause mortality (e.g., ICminimum-set 0.96 [0.96-0.97]), demonstrating convergent and predictive validity. Conclusion: This study developed and evaluated three intrinsic capacity models to address measurement challenges and intended use, supporting a validated yet flexible approach to measuring intrinsic capacity in research and practice. Their adoption across diverse research and clinical contexts would facilitate comparability and strengthen the evidence base.