No clear consensual definition regarding frailty seems to emerge from the literature after 30 years of research in the topic, and a large array of models and criteria has been proposed to define the syndrome. Controversy continues to exist on the choice of the components to be included in the frailty definition. Two main definitions based on clusters of components are found in literature: a physical phenotype of frailty, operationalized in 2001 by providing a list of 5 measurable items of functional impairments, which coexists with a multidomain phenotype, based on a frailty index constructed on the accumulation of identified deficits based on comprehensive geriatric assessment. The physical phenotype considers disability and comorbidities such as dementia as distinct entities and therefore outcomes of the frailty syndrome, whereas comorbidity and disability can be components of the multidomain phenotype. Expanded models of physical frailty (models that included clusters other than the original 5 items such as dementia) increased considerably the predicting capacity of poor clinical outcomes when compared with the predictive capacity of the physical phenotype. The unresolved controversy of the components shapes the clusters of original frailty syndrome, and the components depend very much on how frailty is defined. This update also highlights the growing evidence on gait speed to be considered as a single-item frailty screening tool. The evaluation of gait speed over a short distance emerges from the literature as a tool with the capacity to identify frail older adults, and slow gait speed has been proven to be a strong predictor for frailty-adverse outcomes.
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