Frailty and Sarcopenia

Introduction

Frailty is a distinct clinical state, not simply a synonym for old age or a description of multiple diagnoses. It describes a loss of physiological reserve across multiple organ systems such that homeostatic mechanisms are compromised, and a relatively minor stressor - a urinary tract infection, a new medication, a change of environment - can trigger a disproportionately large and sometimes precipitous decline in health and function.¹

Recognising frailty matters because it independently predicts adverse outcomes - falls, hospitalisation, disability, care home admission and mortality - better than age or disease count alone, and because it changes how care should be delivered: the same intervention (a new antihypertensive, an elective operation, an admission itself) carries different risks and should be approached differently in a frail person than in a fit person of the same age.

Prevalence rises steeply with age - roughly 10% of people over 65 and between a quarter and a half of those over 85 are frail - but frailty is not synonymous with old age, and a substantial proportion of people in their nineties remain fit by these measures. Frailty can also occur at younger ages in the context of severe chronic disease, which is why it is defined by physiological reserve rather than by a birthday.

Distinguishing frailty from ageing and multimorbidity

A person can have several diagnosed long-term conditions and be robust, while another with few coded diagnoses can be profoundly frail - this is why frailty is assessed as its own construct rather than inferred from a disease count.

Two influential models of frailty

The frailty phenotype (Fried)

Defines frailty as the presence of 3 or more of five physical criteria, with 1-2 criteria representing 'pre-frailty':³

• Unintentional weight loss
• Self-reported exhaustion
• Weakness (reduced grip strength)
• Slow gait speed
• Low physical activity

The cumulative deficit model (Rockwood)

Defines frailty as an accumulation of deficits - symptoms, signs, diseases, disabilities and abnormal test results - expressed as a ratio of deficits present to deficits assessed. This model underlies the tools used most in routine UK practice, because it can be operationalised from data already recorded in a clinical record rather than requiring a dedicated physical assessment.⁴

Identifying frailty in practice

Electronic Frailty Index (eFI)

The eFI is calculated automatically from routinely recorded primary care data (36 deficits including diagnoses, symptoms and functional problems) and stratifies every patient in a practice population aged 65 and over as fit, mildly frail, moderately frail, or severely frail, without needing an in-person assessment. It is used for population-level identification and to trigger proactive review, forming the basis of the NHS contractual requirement to identify and manage frailty in primary care.⁵

Rockwood Clinical Frailty Scale (CFS)

A 9-point scale from 1 (very fit) to 9 (terminally ill), assigned by clinical judgement based on function in the preceding 2 weeks (or baseline, if acutely unwell). It is quick, widely used at the point of care - particularly in acute admissions and pre-operative assessment - and correlates with outcomes including mortality and length of stay.

Simple bedside tests

• Gait speed: under 0.8 m/s over a short walk is associated with frailty and adverse outcomes
• Timed Up and Go (TUG): time taken to stand from a chair, walk 3 metres, turn, return and sit - over 12 seconds suggests increased falls risk and possible frailty
• Grip strength measured by dynamometer, a simple proxy for sarcopenia

Sarcopenia

Sarcopenia is the progressive, generalised loss of skeletal muscle mass, strength and physical performance with age, and is a key physical driver of the frailty phenotype - muscle weakness underlies slow gait speed, poor grip strength and exhaustion. It results from a combination of reduced physical activity, inadequate protein intake, chronic low-grade inflammation, hormonal change, and disuse during illness or hospitalisation.⁶

The loss is not uniform across fibre types: type II (fast-twitch) fibres are lost preferentially, which is why older people lose muscle power (force generated quickly) faster than they lose absolute strength. This matters functionally, because recovering from a stumble depends on generating a rapid corrective step, and it explains why resistance training that includes a speed component is more protective against falls than slow strength work alone.

Management

Sarcopenia-specific measures

• Resistance/strength exercise is the single most effective intervention, with evidence for improved muscle mass, strength and function even in very old and frail populations - it should be offered actively, not withheld on the assumption that a frail patient cannot tolerate it
• Adequate protein intake (generally higher than standard adult recommendations in older people, roughly 1.0-1.2 g/kg/day, more in acute illness) supports muscle protein synthesis alongside exercise
• Vitamin D correction where deficient supports musculoskeletal health, though evidence for reversing sarcopenia with vitamin D alone (without exercise) is weaker
• Avoiding unnecessary bed rest during acute illness or hospitalisation, since even a few days of immobility can cause significant, sometimes irreversible, muscle loss in an older person

Frailty-specific measures

Comprehensive Geriatric Assessment (CGA) is the evidence-based, structured response to identified frailty - a multidimensional assessment across medical, functional, psychological and social domains, leading to a coordinated management plan. It is covered in detail as its own topic; see ⁷.

• Medication review and deprescribing, since frail patients are more susceptible to adverse drug effects and polypharmacy compounds frailty-related risk
• Falls risk assessment and intervention, given the strong overlap between frailty and falls
• Nutritional assessment and support where malnutrition risk is identified
• Advance/anticipatory care planning, discussing ceiling of care and preferences before a crisis forces the decision

Frailty and clinical decision-making

Identifying frailty is only useful if it changes something. Its main practical value is that it alters the risk-benefit calculation of almost any intervention, and it does so more reliably than chronological age - which is why frailty scoring, not date of birth, should inform these decisions.

Frailty syndromes: atypical presentation of illness

A defining clinical feature of frailty is that acute illness often presents atypically - not with the textbook symptom of the underlying problem, but with a non-specific decline in one of the five classic frailty syndromes:

• Falls
• Delirium (acute confusion)
• Incontinence (new urinary or faecal)
• Immobility (sudden 'off legs' presentation)
• Susceptibility to medication side effects, even at previously well-tolerated doses

Red flags

Prognosis

Frailty is a dynamic, not fixed, state - it can worsen (particularly after an acute illness or hospitalisation) but can also improve with targeted intervention, especially exercise, nutrition and medication optimisation, particularly in mild-to-moderate frailty. Severe frailty is associated with markedly reduced life expectancy and higher risk from any given intervention, which should inform - though not automatically preclude - decisions about investigation, treatment intensity and surgery.

The practical value of identifying frailty early is that it enables proactive, individualised planning - CGA, exercise and nutrition intervention, anticipatory care planning - rather than only reacting once a crisis (a fall, an admission, a rapid functional decline) has already occurred.

A particularly important point is that hospitalisation itself accelerates frailty. Bed rest during an acute admission causes rapid loss of muscle mass and strength - measurable within days in an older person - and a patient can be discharged medically improved but functionally worse than on admission. This is the rationale for early mobilisation, avoiding unnecessary catheters and restraints, encouraging patients to dress in their own clothes and eat sitting out of bed, and minimising length of stay where safe. Preventing hospital-acquired deconditioning is a genuine clinical intervention, not merely good ward etiquette.