As people get older, they have more things wrong with them. And the more things they have wrong with them, the more likely they are to die. But everyone accumulates deficits at a different rate, and not all people of the same age have the same short-term risk of dying. This variable susceptibility to death and other adverse outcomes in older people of the same age is called frailty.1
Frailty poses special challenges to how we organize and deliver health care. These challenges are sometimes seen most starkly when people are most frail, especially as they approach the end of life.
In this paper, we will review how frailty is conceptualized and defined, consider how frailty affects the care of people at the end of their lives, and suggest practices that can make end-of-life care better for frail older adults.
As with all complex systems, when frail people become acutely unwell their highest-order functions fail first. Thus, cognitive impairment, functional decline, impaired mobility, and social withdrawal are hallmark presentations of the further accumulation of deficits in vulnerable seniors.
Delirium and falls are important clues that a person’s resilience is becoming compromised and that the person is at risk of further insults in a downward spiral or acceleration of things going wrong.1,2 Frailty is associated with poor health outcomes, from disability to institutionalization and death.3
This idea of frailty as vulnerability arising from dysregulation of multiple physiologic systems is reasonably non-controversial. Even so, there are competing views on how to systematically quantify those who are at an increased risk of adverse sequelae.
Quantifying frailty is particularly important if it can tell us if a patient is at high risk of further decline and death. As frailty advances, it is appropriate to shift the focus of care to palliation, with the goal of optimizing quality of life and easing symptoms.4 Identifying someone as frail can aid decision-making in the setting of critical illness, where the system commonly defaults to an “always do everything” mode without considering the ramifications of such an approach. Furthermore, without a routine means of measuring frailty, it is often left to critical care units or rapid-response medical teams to initiate a discussion about whether an aggressive course of care is appropriate or desired.5,6
Frailty as a syndrome
Fried et al7 defined frailty as a syndrome arising from the “physiologic triad” of sarcopenia and immune and neuroendocrine dysregulation. Patients are considered frail if they have three or more of the following five criteria:
- Reduced activity
- Slowing of mobility
- Weight loss
- Diminished handgrip strength
Someone who has only one or two of these items is said to be “pre-frail”; someone with none is said to be “robust.”
The frailty index
An alternative viewpoint is that frailty is a state arising from the accumulation of deficits, which can be counted in a frailty index.
The frailty index is based on the concept that frailty is a consequence of interacting physical, psychological, and social factors. As deficits accumulate, people become increasingly vulnerable to adverse outcomes.
The frailty index is calculated as the number of deficits the patient has, divided by the number of deficits considered. For example, in a frailty index based on a comprehensive geriatric assessment, an individual with impairments in 4 of 10 domains and with 10 of 24 possible comorbidities would have 14 of 34 possible deficits, for a frailty index of 0.41.8
A criticism of the frailty index is that it includes functional dependence as a deficit. The criticism stems from the view that frailty should be seen as occurring prior to disability. According to this view, including dependence in instrumental and basic activities of daily living as a deficit confuses disability with frailty.
Proponents of the frailty index counter that frailty is not “all or none” and needs to be graded. The frailty index can distinguish between people with and without disability by means of the number of deficits that they have, which is most important. For example, a person disabled by a paraplegic injury would have a lower frailty index score and therefore would be considered less frail than a person with advanced cancer affecting multiple body systems. (This is assuming the person who has suffered the injury resulting in paraplegia doesn’t have a concomitant condition such as renal failure or heart disease. In the absence of other health insults, such patients are less at risk of further morbidity or death than the patient with advanced cancer until they get another health insult or insults added to their frailty.)
In any case, functional capacity is fundamental in medical decision-making and when estimating prognoses. An example is the use of the Eastern Cooperative Oncology Group’s functional status measure.9,10
Sum of physical and psychological stressors
Consensus is growing for the concept that frail people are made more vulnerable by the combination of both physical and psychological stressors. This is particularly important to bear in mind for patients who may appear physically robust but whose total health burden makes them vulnerable to further insults.
For example, think of a relatively young overweight patient with hypertension, diabetes, dyslipidemia, and ischemic white matter changes (which can manifest as low mood and even mild vascular cognitive impairment). In such a patient, an acute illness could result in cognitive and functional decline that can be permanent.
Balance of assets and deficits
About 20 years ago, we used the metaphor of a balance beam to describe how frailty comes about in older adults. In this view, there is an interplay of physiological and functional health determinants. Assets such as health, resources, and caregivers are balanced against deficits such as illnesses, dependency on others, and support burden.8
For the most part, later concepts of frailty have focused on the individual, with social factors construed separately as social vulnerability.11