Frailty Thy Name Is ... Phrailty?

THE precise characterization of frailty as a state of physiologic vulnerability has been extremely useful for research (1,2). In particular, the frailty index first validated in the Cardiovascular Health Study (CHS) is a reliable predictor of adverse outcomes and a valuable and versatile tool (3–7). In contrast, conceptualizing frailty as physiologic vulnerability can be problematic, partly because clinicians typically apply the word “frail” to functionally limited or even overtly disabled elders who are suffering the cumulative effects of disease-related, psychosocial, and environmental challenges (8–13). Thus, the research definition creates cognitive dissonance because it does not fully equate to what many physicians have in mind when they envision a frail elder (Figure 1). If a state of pure physiologic vulnerability exists, perhaps we should call it “phrailty” (physiologic frailty), with “F–frailty” (full-blown functional frailty) reserved for multifactorial vulnerability that is accompanied by functional limitations and almost always reflects comorbidities as well as environmental and psychosocial interactions. To be clear, we introduce this terminology to make a point and are not proposing that the field should actually adopt new vocabulary. After all, if phrailty in the most extreme sense refers to physiologic vulnerability before any apparent clinical manifestations, it would be impossible to identify phrail patients for observation and study, and the definition would have little practical utility. For the sake of discussion, however, let us imagine phrailty and F-frailty as overlapping states within a spectrum that encompasses both the research definition, which relies heavily on physiologic compromise, and a more traditional notion of frailty, which takes into account functional limitations and external factors such as environment and social support (Figure 2).