Developing intrinsic capacity measures for research and practice in an Australian context
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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 ≥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., IC clinically informed 0.91 [0.90-0.92]) and IADL dependence (e.g., IC clinically informed 0.92 [0.92-0.93]) at baseline, lower incident dependency at follow-up, and lower all-cause mortality (e.g., IC minimum-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.
Key Points
Intrinsic capacity, the composite of an individual’s physical and cognitive capacities, is a key construct for healthy ageing. Purpose-built operationalisations of intrinsic capacity tailored to research and clinical contexts are needed.
Three intrinsic capacity models were developed addressing current challenges related to data availability, measurement feasibility, and intended use, all demonstrating good model fit and convergent and predictive validity.
A clinically informed model developed with geriatrician input demonstrated that a parsimonious set of indicators can perform comparably to a comprehensive literature-based model, without compromising validity.
Adoption of these models across diverse populations and settings would strengthen the evidence base and facilitate comparability, ultimately informing policy and practice.
