Measuring and quantifying frailty

Gerontologists have defi ned frailty as a multi-dimensional syndrome characterized by the loss of physical and cognitive reserve that leads to increased vulnerability to adverse events [1]. Frailty overlaps and extends beyond disability (functional limitation) and comorbidity (coexistence of two diseases), and acknowledges that patients can be disabled and/or have comorbidities without being frail, and vice versa. Ageing is a complex interplay between genetics and environment that begins during embryonic and fetal develop ment. Th e mechanisms underlying the ageing pro cess are only beginning to be clarifi ed. In recognizing that ageing is a very heterogeneous process, many clinicians seek a method to quantify physiologic age rather than simply chronologic age. Since frailty has been shown to closely correlate with the ageing process [2], it has been suggested that the syndrome of frailty may be just such a measure. One hypothesis whereby ageing is associated with and may predispose to development of frailty relates to the concept of infl ammaging: the dynamic interplay between the protective proinfl ammatory response to invading microorganisms and the similarly protective com pensatory anti-infl ammatory system, which defends against uncontrolled infl ammation. Genetic polymorph isms in the proinfl ammatory and anti-infl ammatory responses have been proposed as one potential mechanism to explain some of the individual variability in the rate of ageing, and may partly explain the poor discriminatory power of age alone to predict outcome [3]. An excessively strong proinfl ammatory response that may be protective during the reproductive years may become maladaptive later in life [4]. By exhausting the compensatory antiinfl ammatory system, the proinfl ammatory response results in unintended damage to the host organism and predisposes to a vicious cycle of decreasing muscle mass, malnutrition and reduced energy expenditure. Th is cycle eventually culminates in the inability to maintain homeostasis and an ‘avalanche-like destruction of the organism’ [2,4]. One expres sion of this unbridled infl ammation may be the syndrome of frailty, a state in which physiologic defi cits accumulate that individually may be reversible but collectively often represent an insurmountable burden of disease and consequently vulnerability to adverse outcomes [5] (Figure 1).