Age and ageing
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two popular operational definitions of frailty, the frailty phenotype and Frailty index (FI), are based on different theories. Although FI was shown to be superior in predicting mortality to the frailty phenotype, no meta-analysis on mortality risk according to FI has been found in the literature. ⋯ this systematic review and meta-analysis was the first to quantitatively demonstrate that frailty measured by the FI is a significant predictor of mortality.