What is frailty?
Frailty in older persons refers to a state of being more vulnerable to adverse health outcomes. Individuals identified as frail are more likely to experience medical complications, disability, institutionalization or even death, compared to their non-frail counterparts, especially when exposed to stressors such as surgery, chemotherapy or falls. The identification of frailty status is therefore of interest to clinicians, since it provides the possibility to moderate stressors and provide more tailored care to this vulnerable sub-population.
Although clinicians and researchers largely concur that frailty is a useful concept in understanding the health status of older persons, we are still far from a unified definition or diagnostic criteria.
Research perspectives on frailty
Despite a rapid expansion in research on frailty in the past three decades, there continue to be important disparities in how frailty is described and identified. Most experts agree that frailty is the manifestation of impairments in multiple organ systems that results in increased susceptibility to poor health outcomes1. The specific characteristics of frailty, however, remain an important point of contention.
Some have proposed that frailty fits the model of a medical syndrome, whereby all of its symptoms are linked through a single underlying biological mechanism. The most widely used definition of frailty fitting that approach includes five criteria: shrinking (i.e., weight loss), weakness (i.e., loss of muscle strength), exhaustion, slowness (i.e., decreased walking speed), and low levels of physical activity. An individual with any three or more of these five criteria is classified as frail2.
Another widely applied approach is to define frailty as an indicator of global health status, whereby an individual’s level of frailty is ascertained through a wide range of factors that may contribute to their well-being. A definition fitting this approach may pull together up to 100 different characteristics ranging from visual impairment to poor social conditions, chronic diseases and disability, into a single index of frailty3,4. For each characteristic, an individual is rated as either having a deficit or not. The frailty index is calculated as a proportion representing the number of deficits over the total number of characteristics assessed. By this approach, the more individuals have wrong with them, the more likely they are to be frail5.
While these different approaches do overlap in their identification of frail individuals, they represent very different notions of what it is to be frail6. The choice of approach has important implications for clinical applicability, as well as the potential interventions and prevention of frailty.
Thus far, research has provided substantial evidence that frailty, however it may be defined, is a risk factor for various poor health outcomes7–12. Based on this, many experts are advocating screening for frailty in all older patients13. It has been shown, however, that risk factors that demonstrate high statistical significance may not be good predictors at the patient-level. In fact, very little is known about the contribution of frailty in improving patient-level prediction14. This needs to be investigated further in order to justify the adoption of frailty as a prognostic tool.
What frailty means to older persons
Older persons themselves may have their own perspectives of what it is to be frail. Aspects such as mood, for example, have been cited as important to patients and their families, but are often overlooked by clinicians and researchers1,15,16. Psychological health plays an important role in older persons’ beliefs about aging successfully. In a study of older persons where only 15% experienced no physical illness, 92% reported feeling like they were aging successfully17.
Research has demonstrated that stereotypes of aging, both positive and negative, are internalized by older persons and can have both short- and long-term effects18. Exposure to negative aging stereotypes has been shown to have a negative impact on performing memory tasks, handwriting and walking speed, as well as on physiological measures such as blood pressure, pulse rate and skin conductance. In fact, in one study the observed increase in walking speed for those exposed to positive aging stereotypes was comparable to that seen with several weeks of rigorous exercise. Negative stereotypes act as cardiovascular stressors while positive stereotypes reduce evidence of cardiovascular stress. Positive perceptions about aging have impressive long-term effects as well. Individuals with positive self-perceptions of aging have been found to have better functional abilities over a period of 18 years.
These findings should serve as a caution about a potential self-fulfilling prophecy when labelling older persons as “frail”. It is yet to be demonstrated whether the benefits of targeted interventions and care for individuals identified as “frail” outweigh the harm that may result from the labelling. This, of course, may depend largely on which definition of frailty one chooses to apply.
Bottom line on frailty
Thus far, research on frailty has been heavily based on establishing associations between various definitions of frailty and poor health outcomes. A limited number of studies on the perspectives of older persons offer a very different characterization of frailty and the potential impact of labelling.
While several expert meetings over the past decade have called for a unified operational definition of frailty14, varied definitions continue to abound, suggesting that researchers are still not ready to close the debate on what defines frailty. The integration of findings from the diverse perspectives, including those of the older persons themselves, is essential when considering the potential for a meaningful clinical tool.
Furthermore, studies examining the contribution of frailty in improving prediction of adverse health outcomes are needed in order to assess the potential utility of frailty as a prognostic tool. Despite the enthusiasm of clinicians and researchers to utilize frailty as a prognostic instrument 11,13,19,20, frailty will only be relevant if it can be empirically demonstrated either that frailty is reversible, or that its adverse outcomes are amenable to intervention14.
