Comparing the predictive value of three definitions of frailty: Results from the Three-City study

Background: Despite several attempts to reach a single definition of frailty, no consensus has been reached. The definitions previously published have tried to prove its utility in predicting negative health outcomes. The objective of the present study is to compare the predictive value of 3 different frailty instruments, for selected outcomes.

Methods: The study sample includes 1278 participants of the Three-City study, a French prospective population-based study, assessed for frailty using Fried's phenotype criteria, Rockwood's Frailty Index and Tilburg Frailty Indicator. To assess the risk of mortality, incident disability, falls, institutionalization and hospitalization for a follow up period of 12 years, Cox proportional hazard models with delayed entry have been used. The area under the time-dependent ROC curve has been used to estimate and compare the ability of the three instruments of frailty to predict the previous adverse outcomes at 12 years.

Results: Five hundred ninety four participants were identified as non-robust with Fried's criteria; 169 with Rockwood's FI and 303 with TFI. The three scales consistently identified 91 participants as non-robust and 574 as robust. Rockwood's FI was a statistically significant predictor of mortality, incident disability and falls, and a strong predictor of hospitalization.

Conclusion: In the absence of a "gold standard" definition of frailty, a debate on what measures and how to include them is open. A clue may be that one should select the appropriate definition according to the to-be predicted outcome, the setting and the underlying etiology of frailty.