Chapter 1 Frailty: Definition, diagnosis, epidemiology

Oftentimes, frail individuals have a reasonable prospect of enhancing their health and improving their condition. However, traditional Japanese terms for frailty (such as kyojaku and rōsui) connote a biologically unavoidable eventuality; they fail to convey the nuance that frailty is reversible. Therefore, the Japan Geriatrics Society, in its May 2014 statement, proposed a new Japanese term for frailty, fureiru, in an effort to change public attitudes about prolonging a healthy lifespan in older people.1 In Western literature, frailty has been described as “a state of vulnerability to poor resolution of homoeostasis after a stressor event,”2 and it is believed to be “highly prevalent in old age and to confer high risk for falls, disability, hospitalization and mortality.”3 The literature also suggests that medical professionals must be wary of even seemingly minor issues when caring for frail older adults. Clegg et al., for instance, stated that “an apparently small insult (e.g. a new drug, “minor” infection or “minor” surgery) results in a dramatic and disproportionate change in health state: from independent to dependent; mobile to immobile; postural stability to falling; lucid to delirious.”2 At present, clinicians around the world still lack a generally accepted concept of frailty. A review by Abellan et al. showed that there is agreement on considering frailty a stage between robust and disability.4 In contrast, Rockwood et al. proposed the use of a scale that describes states of frailty, including from a high-risk state to severely disabled state.5 The Japan Geriatrics Society's statement adopted the first of these two stances, believing that this will encourage a focus on preventative care and thereby contribute to healthy longevity among older people.1 Frailty can involve multifaceted aspects. As noted in Gobbens et al., as well as the Japan Geriatrics Society statement, although the physical domain is the main component of frailty, the concept also includes other domains, such as the psychological domain and the social domain.1, 6 Recent concepts of frailty sometimes express the condition as “physical frailty,“7 “psychological frailty“6 and “social frailty” (see CQ9) based on the dominant aspect. However, in the absence of any generally accepted criteria, the definitions must be used advisedly. Additionally, there is a term, “sarcopenia,” that indicates an aspect similar to physical frailty, which has been defined as “a concept exclusively for describing loss of physical function associated with loss of muscle mass.”8 Whereas sarcopenia is a core component of physical frailty, frailty is thought to be a vulnerable state based on a broad body of factors associated with aging. Furthermore, it is worth noting that Kelaiditi et al. proposed that there is a subset of frailty that accompanies impaired cognitive function along with physical frailty as “cognitive frailty” within the psychological frailty9 (see CQ6). There are two main approaches to diagnosing frailty. The first is Fried et al.'s phenotype model, which measures frailty using the components of the CHS.3 The second is Mitnitski and Rockwood et al.'s accumulated deficit model, which presents the Frailty Index.10 Fried et al.'s phenotype describes age-related decline in physical capacities based on the following criteria: (i) unintentional weight loss; (ii) self-reported exhaustion; (iii) weakness (low grip strength); (iv) low physical activity; and (v) slow walking speed. According to this model, the presence of one or two of the aforementioned indicates pre-frail status, the presence of three or more indicates frailty status and the absence of any indicates robust status.7 According to Morley et al., this model represents a popular approach to defining physical frailty.7 However, a review by Theou et al. showed a lack of generally accepted criteria for measuring each component. It also noted that there are numerous other criteria based on the same phenotype.11 In regard to Japan, Satake et al. have advocated a Japanese version of the CHS criteria (J-CHS criteria; Table 1).12 The validity of the J-CHS criteria was shown by Makizako et al.13 Mitnitski and Rockwood et al.'s Frailty Index describes the proportion of accumulated deficits in the variables supporting health and independence. On the assumption that such accumulated deficits reflect frailty level, they recommended that the Frailty Index should be constructed from >30 variables (related to symptoms, signs, activities of daily living, disease, cognitive impairment etc.), so as to reflect properties “at the level of the whole organism rather than any given functional deficiency.”10 According to Searle et al., categorical, ordinal and interval variables can be coded so that 0 = absence of a deficit, and 1 = full expression of the deficit.14 Aside from the above, there are also a number of comprehensive geriatric assessments, the relatively popular of which are the Edmonton Frail Scale (Table 2),3, 15 Tilburg Frailty Indicator (Table 3)16 and Kihon Checklist (Table 4).17 There are also some screening tools, such as the FRAIL scale (Table 5)18 and five-item frailty screening index (Table 6).19 It should be noted that the 2017 Asia-Pacific Clinical Practice Guidelines for the Management of Frailty recommends using a “validated measurement tool to identify frailty.”20 In a systematic review of studies that examined the prevalence of frailty among community-dwelling older adults (aged ≥65 years), Collard et al. found that the prevalence varies widely depending on how frailty status is evaluated. When all the studies were analyzed together, the prevalence varied as much as 4.0–59.1%. For physical frailty, the prevalence was 9.9% (95% CI 9.6–10.2), and for the broad phenotype of frailty evaluated by Frailty Index and others, it was 13.6% (95% CI 13.2–14.0). The review also showed that prevalence increased with age and was higher in women than in men.21 In a Spanish study, Gar