Intrinsic capacity is associated with cardiovascular rehabilitation outcome in older adults: a multidimensional comparison with frailty.

OBJECTIVES: To test whether Intrinsic Capacity (IC), a construct centred on individuals' positive physical and mental attributes, is associated with functional outcome in older adults undergoing Cardiac Rehabilitation (CR), and to compare its predictive value with Frailty Index (FI), a deficit-accumulation model. DESIGN: Observational, single-centre cohort study. SETTING: Cardiovascular Rehabilitation Unit, Istituti Clinici Scientifici Maugeri IRCCS, Telese Terme Institute, Italy. PARTICIPANTS: 551 consecutively enrolled patients aged ≥65 years, hospitalized for exercise-based rehabilitation following heart failure exacerbation, coronary syndromes, valvular heart disease or cardiac surgery. MEASUREMENTS: Before starting CR, all participants underwent Comprehensive Geriatric Assessment (CGA), including a CGA-based FI and two alternative four-domain IC z-scores (cognition, psychological status, locomotion, vitality), the latter operationalized either through handgrip strength (IC) or the Mini Nutritional Assessment (InCa). Functional outcome was assessed with the six-minute walking test (6MWT), expressed as distance and as ratio to predicted values, before and at the end of the CR programme. Associations were tested with multivariable regression and linear mixed-effects models adjusted for age, sex and diagnosis at admission. RESULTS: Median age was 72 (69-78) years; 68.97% were men. All geriatric constructs were significantly associated with 6MWT ratio at the end of CR: IC showed the strongest association (β = 0.571) and explanatory power (R²adj = 0.362), followed by InCa (β = 0.498; R²adj = 0.347), while FI showed a smaller, negative association (β = -0.281; R²adj = 0.235). Adjusted mixed-effects models confirmed these findings for 6MWT distance (IC β = 61.3, InCa β = 53.0, FI β = -29.6; all p < 0.001). CONCLUSION: Among older adults undergoing in-hospital CR, IC was more strongly and consistently associated with functional outcome than FI, particularly when vitality was operationalized through handgrip strength. These findings support incorporating IC assessment into the multidimensional evaluation of older CR candidates, promoting a function-centred approach to geriatric care.