Shaping the next steps of research on frailty: challenges and opportunities

Excerpt

The term “frail elderly” was first introduced by the US Federal Council on Aging under the leadership of Monsignor Charles F. Fahey in the early 1970s [1]. However, until the early 1990s, a frail older adult was stereotyped as someone of old age, having disability/dependency, or multimorbidity; its determination was arbitrary and subjective [2]. In 2001, a seminal paper published by Fried and colleagues defined frailty as a distinct clinical syndrome based on a biological model, and proposed diagnostic criteria characterizing a phenotype of physical frailty (PF) [3]. This phenotypic model of frailty focusing on physical function has since been validated both as a syndromic construct and a robust predictor of relevant adverse health outcomes, independent of age and comorbidity [4]. Around the same time, Rockwood and Mitnitski advanced the deficit accumulation theory to explain and define frailty [5]. Named as the Frailty Index (FI), this instrument can be seen as a biological marker of aging with good mathematical properties [6]. The FI represents a popular tool for risk stratification in various settings; its predictive validity has been established in humans and other species including dogs and mice [7‐10]. It is important to note that frailty through the lens of the FI is a multidimensional comorbidity index that is agnostic regarding the correlation, temporal order, and underlying etiology of its composite criteria. As such, the PF and the FI, although sharing the same nomenclature, often yield alarmingly low agreement on frailty classification [11, 12]. While the PF and the FI are the most cited frailty instruments in the research literature, there has been a proliferation of frailty instruments that extend beyond variants of PF and FI to also include subtypes focusing on specific functional domains such as cognitive, psychological, or social frailty [13]. The lack of guidance for proper selection of frailty assessment tool to match goals of care, limited understanding of its biology, and insufficient evidence on interventions have hampered adoption to patients’ health management. …