Fried Frailty Phenotype

The Fried frailty phenotype operationalizes frailty as a distinct biological syndrome of physical decline rather than as disease or disability. Introduced by Linda Fried and the Cardiovascular Health Study Collaborative Research Group in 2001, it defines frailty through five measurable criteria — unintentional weight loss, self-reported exhaustion, low physical activity, slow gait speed, and weak grip strength — and classifies older adults as robust, pre-frail, or frail by counting how many criteria are present. The phenotype gave gerontology a reproducible, predictive measure of vulnerability that forecasts falls, disability, hospitalization, and mortality, and it remains one of the two dominant operationalizations of frailty alongside the deficit-accumulation index.