Biological versus functional frailty in hospitalised older adults with cardiovascular disease: discordant phenotypes and long-term mortality

Background Simplified nursing-based frailty scores have gained attention as pragmatic tools. We sought to evaluate the relevance of biologically measured frailty compared with clinically assessed functional status in older patients with cardiovascular disease. Methods We analysed hospitalised patients aged ≥65 years with cardiovascular disease, assessing biological frailty using a laboratory-based frailty index (FI-Lab) and functional frailty using a nursing-based score. The primary endpoint was 5-year all-cause mortality. Cox proportional hazards models were adjusted for age, sex, and Charlson index (CCI). Independent effects of biological and functional frailty in combined models and across discordant frailty phenotypes were evaluated. Results Among 1693 patients (mean age 76.2 ± 7.0 years; 38% women), 368 (21.7%) deaths occurred during follow-up. In age, sex, and CCI adjusted models, both FI-Lab (HR 1.12 per 0.1 increase; 95% CI 1.03–1.22; p=0.008) and severe functional frailty (HR 1.53; 95% CI 1.17–1.98; p=0.002) were associated with mortality. However, after mutual adjustment, FI-Lab attenuated (HR 1.08; 95% CI 0.99–1.19; p=0.07), while severe functional frailty remained independently predictive (HR 1.41; 95% CI 1.07–1.86; p=0.01). In discordance analyses, mortality was lowest with low biological and functional frailty (15.4%). Isolated severe functional frailty exhibited increased mortality (28.1%) comparable with combined high biological and severe functional frailty (27.3%). Conclusion Biological and functional frailty capture overlapping but non-identical dimensions of vulnerability. Severe functional frailty was associated with a high-risk phenotype in which additional biological deficit burden was not associated with a further increase in mortality.Heatmap