Neither the phenotype model nor the FI are particularly feasible however in routine clinical practice, so simpler tools are more commonly used such as the Clinical Frailty Scale [4] or the Edmonton Frail Scale [13]. The Clinical Frailty Scale uses descriptors covering the domains of mobility, energy, physical activity, and function to enable a standard clinical assessment to characterise seven levels from very fit, healthy to very severely frail (Fig. 4.2). This provides a feasible description based on routine clinical assessment but does not conceptually distinguish frailty from multimorbidity or disability. Its mortality prediction is comparable to that of the more detailed FI.

In community or primary care settings, the issue may be to identify a target group for health-promoting interventions such as optimising nutrition and increasing physical activity levels. Here a more simple screening approach may be needed. A recent systematic review assessing available tools suggested that PRISMA-7 may be the most accurate [14], a score of 3 or more suggesting increased likelihood of incident disability [15] (Fig. 4.3).

Sarcopenia is characterised by motor neurone loss, reduced muscle mass per motor unit, relatively more loss of fast twitch fibres and reduced strength per unit of cross sectional area.

Muscle fibres are lost by drop-out of motor neurones. Reinnervation of fibres by sprouting from surviving neurones cause a less even distribution of fibre types cross-sectionally and a relatively greater loss of type II fibres which are associated with generation of power (the product of force generation and speed of muscle contraction) [19]. Loss of efficiency also results from an accumulation of fat within and between fibres and an increase in non-contractile connective tissue material. Leg power accounts for 40 % of the decline in functional status with ageing [20]. Men who maintain physical activity into their 80s show compensatory hypertrophy of muscle fibres to compensate for the decrease in fibre number.

Muscle fibre development occurs before birth but fibres enlarge during childhood reaching a peak in early adulthood. Mass and function then gradually decline into older age [21]. Peak mass is affected by maternal, genetic and early life influences. Decline is affected by physical activity, nutrition and sex. Decline is more pronounced in women from menopause onwards. Adding to the inevitable moderate decline of some 15–25 % by old age is the impact of acute illness or chronic conditions, which have generally negative effects through the mechanisms of catabolic stress, reduced food intake and physical activity.

The loss of muscle mass is thought to be multifactorial with potential factors illustrated in Fig. 4.4.

The factors implicated in sarcopenia overlap with those for frailty. A central feature of sarcopenia is a decrease in the rate of muscle protein synthesis. This leads to reduced protein levels including mitochondrial oxidative enzymes responsible for enabling work intensity. The age-related shift of the hormonal balance towards low testosterone, growth hormone and IGF-I contributes to the lower muscle protein synthesis rates, which also limits the structural recovery from muscle damage or apoptosis and possibly reduces the synthetic stimulus of exercise [22].

The role of cytokines such as interleukins IL-1β and IL-6, and TNF-α is less certain. They play a role in the catabolic processes of acute illness and chronic inflammatory conditions, but whether the small differences in circulating levels associated with frailty reported from some population studies is relevant to the age related sarcopenia is not established.

There are several different diagnostic definitions resulting in variable prevalence rates being reported in community dwelling populations of older people. A consensus definition and approach to screening and classification has been proposed by the European Union Geriatric Medicine Society [23]. This is shown in Fig. 4.5.

Measuring gait speed is feasible in almost any setting and is a useful global indicator of health, slower gait being associated with greater likelihood of incident disability, falls, institutionalisation and death [24]. Grip strength was chosen as it is a portable, simple, reliable and valid proxy measure of body strength, and has good correlation with lower limb physical performance. Low grip strength of community dwelling older people is associated with falls, increased incident disability and earlier mortality. It also predicts slower and less complete functional recovery from illness in men [25]. Measurement of muscle mass can be done with CT scan or, less accurately, with impedance techniques.

Falls rates vary internationally but in most populations studied they occur in about one third of community dwelling individuals aged over 65 each year, about half of these being multiple falls, and rates then increase with age to over 50 % of those 80 plus [27, 28]. Falls rates seem higher among Caucasian populations compared with the Chinese. Rates are particularly high in older people with dementia unless mobility is lost [27, 29]. Living in long-term care facilities is also associated with higher falls rates. This relates both to the clinical characteristics of the residents and the complexity of the environment. WHO reported in 2007 from international data that falls result in 5.5–8.9 Emergency Department attendance visits per 10,000 people aged 60 plus, with about a third being admitted [30]. Falls account for over half of all injury-related hospital admissions for older people aged 65 plus, head injuries and fractures being the most common and serious. Older women fall relatively more than men but sustain relatively fewer injuries. People with lower socioeconomic status and those living alone have more falls.

Prospective observational studies have produced a long list of risk factors that may help identification of higher risk groups [28]. Falls happen to individuals with intrinsic impairments, performing specific activities in specific environments. It is the combination that matters. Most falls are associated with impairments of mobility function and/or cognitive decline, particularly of higher-order functions that affect gait pattern, balance, and executive function. Low muscle strength itself has been reported to increase risk but it is functional mobility that seems more important. Environmental hazards alone are seldom responsible. Likewise, most fallers were doing something fairly routine, even mundane. For an individual with dynamic balance that is only just sufficient for their usual activities, the fall may occur from chance variation in performance, or may have been compromised by cognitive distraction, pain or anxiety. For someone with limited functional mobility reserve, intercurrent illness will often determine the exact time and place of the fall. For example, a urinary tract infection may require more frequent visits to the toilet, perhaps at night in the dark and may prompt the individual to move faster than usual.