Intrinsic capacity and the physical frailty phenotype as complementary predictors of mortality in older Indian adults

Intrinsic capacity (IC) and frailty both predict mortality and are increasingly advocated for organising older people's care, yet whether they are distinct or redundant is unclear. We examined whether intrinsic capacity adds to the physical frailty phenotype in predicting mortality, which component carries that information, and whether the physical phenotype alone leaves a high-risk group unidentified.

We studied 3,260 adults aged ≥60 in the Longitudinal Aging Study in India - Diagnostic Assessment of Dementia (LASI-DAD), followed up to seven years (642 deaths). Intrinsic capacity (six domains) and the Fried phenotype were entered into Cox proportional-hazards models; IC was decomposed by domain, discordant participants examined, and findings tested in split-sample analysis.

The two measures were only moderately correlated (r = -0.35) and each predicted mortality independently (adjusted HR 0.85 and 1.26 per SD), indicating complementarity rather than redundancy. The only domain adding information beyond the physical phenotype was cognition (HR 0.73 per SD; likelihood-ratio χ² = 53, p < 0.001) - the one domain a physical assessment cannot capture. Physically robust but low-IC participants died at roughly twice the rate of robust, high-IC participants (HR 2.0), comparable to those meeting frailty criteria, with the excess attributable to cognition. Findings replicated in both sample halves.

In older Indians, intrinsic capacity and the physical phenotype capture different vulnerabilities; the information the physical phenotype lacks is specifically cognitive. A physically robust older adult with low IC may carry mortality risk comparable to a frail individual while undetected by physical frailty screening.