Intrinsic Capacity in a Nationally Representative US Population.

BACKGROUND

Intrinsic capacity (IC) is defined by the World Health Organization as the sum of an individual's physical and mental abilities that support health and well-being. While well validated internationally, it has not been operationalized and validated in a nationally representative US cohort.

METHODS

Using data from 5,834 community-dwelling older adults from Round 12 (2022) of the National Health and Aging Trends Study (NHATS) survey, we identified measures related to IC domains (cognition, locomotion, vitality, psychological, sensory). We performed exploratory factor analysis (EFA), omega hierarchical reliability testing, and confirmatory factor analysis (CFA) using bi-factor and second-order structures. We also constructed the Integrated Care for Older People (ICOPE) screening tool. Descriptive statistics and regression models were used to examine the associations of IC and ICOPE scores with demographic and health characteristics. Age- and sex-specific reference centile curves were developed using empirical percentiles.

RESULTS

EFA consistently supported a six-factor structure (vision and hearing were separate). Omega hierarchical analysis supported a strong general factor (ω = 0.92; ωₕ=0.72), and the bi-factor model demonstrated excellent fit. IC and ICOPE scores showed strong correlation (r = 0.71). Higher IC scores were associated with younger age, higher level of education, and income. Prevalence of comorbidities, frailty, ADL and IADL disability increased from the highest to the lowest IC and ICOPE quartiles. Reference centile curves demonstrated progressive age-related decline, with females showing lower IC scores than males.

CONCLUSION

We demonstrate IC operationalization in a nationally representative U.S. cohort and provide the first US-specific reference centile curves. The findings provide a foundation for future IC research in the US.