There is no single best definition of frailty; it does not fit easily with the typical organ specific model of disease (Xue, 2011). Frailty remains an evolving concept lacking both a unique definition and diagnostic criteria to be used in clinical practice and epidemiological researches (Bergman et al., 2007).
Prior to the mid-1990s, the term frail was used to describe older persons who were disabled, failed to thrive, were institutionalized, or were near the end of life. In the mid-to-late 1990s, Rockwood and Colleagues proposed that frailty be defined as a state in which there was a dependence on others for performing functions of daily living. Later, this group developed a Frailty Index, a longer Clinical Frailty