**1.2 Definition of frailty**

Frailty, a condition in which older people lose the ability to perform activities, is defined as "a state of multiple declines in physical functions with reserve capacity approaching or exceeding a clinically disabling threshold, assuming there is a threshold for clinical impairment" and falls between normal health and the need for nursing care [7, 8]. Frailty progresses because of not only the age-related deterioration of physical functions such as muscle strength, balance, and walking ability, but also psychological problems such as cognitive impairment and depression, and social problems such as living alone and economic deprivation, which can lead to outcomes such as functional disability, the need for nursing care, and even death [7, 9–11]. Both the prevention and remediation of frailty are important because decreased activity levels in older people increase the risk of developing frailty and, with respect to older people with underlying medical conditions, the risk of requiring long-term care [12, 13]. Frailty is characterized by vulnerability to functional decline even under mild stress and is notably reversible, allowing a return to a robust state, if appropriate measures are taken. Frailty encompasses not only physical, but also mental, cognitive, social, and other aspects (**Figure 1**). The physical aspect of frailty is based on the concept of the phenotype model proposed by Fried et al. [7]. Rockwood et al. have also proposed the deficit accumulation model [14]. The deficit accumulation model is useful for comprehensive assessment of functional impairment in the selection of clinical interventions and prediction of life expectancy and risk of institutionalization, including for those with disabilities or at end-of-life stages. Of the two models, the accumulation model is more complex to use in clinical practice, so the phenotypic

#### **Figure 1.**

*Conceptual diagram of frailty for older people, there is concern about the progression of frailty, in which a small amount of stress can lead to major deteriorations in health. Prepared by the author with reference to Kuzuya M (2009) [13].*

*Overarching Goal and Intervention for Healthy Aging in Older People… DOI: http://dx.doi.org/10.5772/intechopen.106787*

model definition is often used in studies of community-dwelling elderly, and the phenotypic model focusing on physical aspects will be used in this paper.

#### **1.3 Assessment of frailty**

The Cardiovascular Health Study (CHS) criteria proposed by Fried [7] are often used to consider disability prevention for older individuals living in the community. These criteria assess five items—fatigue, weight loss, decreased physical activity, decreased walking speed, and decreased muscle strength—with those meeting the criteria for three or more items being considered to be frail, and one or two items pre-frail. The revised Japanese version of the CHS criteria (J-CHS) [15] and the Frailty Screening Index [16] are commonly used in Japan. The former includes measures of walking speed and grip strength and focuses on the physical aspects of frailty, whereas the latter is a more general assessment, as all questions are binary choice and some focus on memory. The Kihon Checklist, which has been used to identify people eligible for secondary prevention projects and lifestyle support services, is also used. A total score of eight points or more is considered to indicate frailty, and a score of 4–7 points pre-frailty, suggesting an increased risk of requiring nursing care and even death [17].

#### **1.4 Evidence of interventions for frailty**

Intervention studies on older individuals with reduced mobility have reported the effectiveness of muscle strengthening exercises, stretching, aerobic exercises, and balance exercises on lower limb muscle strength, and many of these studies have reported that exercises combining two or more of these exercises are more effective [18]. However, evidence for interventions in older adults with frailty remains weak because the definition of "frailty" differs from country to country and study to study, and the target population is not sufficiently uniform. It is therefore desirable to establish the same definition of frailty, clarify the inclusion criteria, and accumulate larger samples.
