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, Garre-Olmo et al. examined the prevalence of the physical, psychological and social frailty phenotypes in a cohort of community-dwelling older people consisting of 875 people aged >74 years (mean age 81.7 years). They reported that the prevalence of any frailty phenotype was 38.8%, and that 17.3% showed the physical frailty phenotype, 20.2% showed the psychological frailty phenotype and 8.9% showed the social frailty phenotype.22 Choi et al. reviewed six articles that examined the prevalence of frailty as defined by the CHS criteria in community-dwelling older people. They found that the prevalence rate ranged from 4.9 to 27.3%.23 Similarly, Kojima et al. carried out a meta-analysis of studies that examined the prevalence of frailty by the CHS criteria among Japanese community-dwelling older people. Of the 11,940 individuals constituting the pooled prevalence of frailty, pre-frailty and robust status, 7.4% were frail. Like Collard et al., the analysis also suggested that frailty prevalence increases with age, and that it is slightly higher among women.24 Satake et al. examined the prevalence of frailty among 16,251 Japanese community-dwelling older people (mean age 75.1 years). Using a unified frailty criterion based on the J-CHS criteria, they found the prevalence to be 11.2% overall, 4.0% in the 65–74 years age range, 16.2% in the 75–84 years age range and 34.0% among those aged ≥85 years. Prevalence was 21.6% among the 777 individuals (mean age 76.5 years) receiving outpatient care for a chronic disease.12 As for the prevalence of frailty in nursing homes, a review of the literature by Kojima showed that as many as 46.9% of nursing home residents (mean age 81.8 years [our estimate]) were frail (95% CI 27.7–66.6).25 Frailty can be related to a lot of factors affecting aging. In a systematic review, Lorenzo-López identified several nutritional determinants of frailty.26 These include amount of protein intake,27-31 distribution of protein intake,31 intake of specific micronutrients,27, 32-34 quality of diet (intake diversity)35, 36 and anti-oxidant capacity of the diet.37 Other studies suggest that poor diet increases the likelihood of future frailty status. Specifically, León-Munoz et al. reported that adherence to a Mediterranean diet (which is recognized to be a high-quality diet) was associated with a decreased risk of frailty.38 Similarly, Shikany et al. reported that diet quality (as measured by the Diet Quality Index) was inversely correlated with future frailty status.39 Other reported predictors of frailty include low serum micronutrient concentrations34 and low serum vitamin D concentration.40, 41 In regard to the latter, Shardell et al. reported that adults in a pre-frail state (which they defined as an "at risk" state) are more likely to recover than to decline if they have a high serum vitamin D concentration.42 The literature also suggests that individuals are more likely to become frail if they are physically inactive. Peterson et al. analyzed a sample of 2,964 older adults aged in their 70s, some of whom regularly engaged in exercise >1000 kcal/week and some of whom were sedentary. The latter were more likely to develop frailty over a 5-year period than the former (adjusted OR 1.45, 95% CI 1.04–2.01). Additionally, of those who became frail during follow up, those in the "sedentary group" or the "lifestyle active" group (>2700 kcal/week in physical activities) were much more likely than those in the "exercise active" group (>1000 kcal/week in exercise activities) to deteriorate to severe frailty status.43 García-Esquinas et al. analyzed two independent European cohorts of community-dwelling older adults and reported that longer television viewing time was associated with frailty incidence. However, the study found no association between other types of sedentary behavior (time seated at the computer, commuting, lying in the sun, listening to music/reading, internet use).44 These results suggest that frailty incidence is not associated with being sedentary per se, but rather with specific sedentary activities. As for the psychological risk factors, a review by Vaughan et al.45 highlighted the significance of depression, and a review by Ayers et al. found apathy to be another risk factor.46 Monin et al. reported a partner effect whereby an individual's frailty predicted the spouse's frailty.47 Other physical factors reported to be significantly associated with incident frailty include hearing impairment,48 chronic widespread pain49 and polypharmacy50, 51 (see CQ37). Diseases reported to be predictors of frailty include lifestyle diseases, such as diabetes,52 chronic kidney disease53 and obesity.54 Other diseases include cardiovascular disease55 and HIV56 (see the CQs for these diseases). Frailty has been associated with a number of health issues of older people, such as those shown in Figure 1. Accordingly, geriatricians have underscored the importance of assessing frailty as part of geriatric care. Some of the health issues can be both an outcome and cause of frailty. In such cases, the influence is two-way, and the issue might accelerate the downward spiral. Vermeiren et al. carried out a systematic review of cohort studies of community-dwelling older people in which they meta-analyzed 24 studies that examined the relationship between frailty and mortality risk. They found that frailty significantly increased the likelihood of mortality – the absolute odds ratio being 2.34 (95% CI 1.77–3.09) and the relative risk being 1.83 (95% CI 1.68–1.98). Furthermore, the relationship between frailty and mortality was present irrespective of the frailty instruments, which they had categorized into physical frailty instruments (e.g. CHS criteria, Short Physical Performance Battery), multidimensional instruments (e.g. Tilburg Frailty Indicator) and deficit instruments (e.g. accumulated deficit model). The meta-analysis also covered the relationship between frailty and hazards, and showed that frailty significantly increases the likelihood of the following hazards: hospitalization (1.2–1.8-fold), institutionalization (1.7-fold), development of disabilities in basic activities of daily living (1.6–2.0-fold), physical restriction (1.5–2.6-fold), and falls/fractures (1.2–2.8-fold).57 Frailty is also reported to increase the likelihood of dementia. Kojima et al. carried out a systematic review of literature on community-dwelling older people and meta-analyzed seven studies. The meta-analysis showed frailty to be a significant predictor of Alzheimer's disease (hazard ratio 1.28, 95% CI 1.00–1.63), vascular dementia (hazard ratio 2.70, 95% CI 1.40–5.23) and all dementia (hazard ratio 1.33, 95% CI 1.07–1.67).58 On the relationship between frailty and postoperative outcomes, Lin et al. reviewed 23 studies that included patients undergoing cardiac, cancer, general, vascular and hip fracture surgeries. The review revealed frailty to be significantly associated with increased mortality at 30 days, 90 days and 1 year, as well as with postoperative complications and length of hospital stay.59 Veronese et al. carried out a study involving 1,754 community-dwelling older people without type 2 diabetes mellitus at baseline. The participants were categorized as frail, pre-frail or non-frail according to the CHS criteria. The frail participants were 1.87-fold more likely to develop type 2 diabetes mellitus (OR 1.87, 95% CI 1.31–2.13), and the pre-frail participants were 1.60-fold more likely to develop the condition (OR 1.87, 95% CI 1.27–2.00).60 In addition to the above, Sergi et al. reported that pre-frailty was independently associated with a higher risk of developing cardiovascular disease,61 and Khan et al. reported that frailty was independently associated with risk of heart failure.62 No conflicts of interest to disclose.