Frailty (clinical syndrome and frailty index)

Frailty is a state of heightened vulnerability to stressors. It comes from deficits piling up across many body systems, which drains your reserve and resilience. Two main ways to measure it dominate the field. The first is the phenotype model of Fried and colleagues (2001, Cardiovascular Health Study). It flags frailty when you meet at least 3 of 5 criteria: unintentional weight loss, exhaustion, weak grip, slow walking, and low activity. The second is the Frailty Index of Mitnitski and Rockwood. It counts what fraction of 30 to 70 health deficits you have (symptoms, signs, diagnoses, lab values). Both predict bad outcomes (falls, hospitalization, disability, death) on top of your age alone. And frailty becomes much more common after 80. In geroscience, it is a key functional outcome for testing senolytics, senostatics, and other anti-aging interventions.

Last reviewed: June 22, 2026

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