Frailty describes a clinical state of diminished physiological reserves. A frail person can still function under everyday conditions — but the slightest stressor tips them into a crisis that a non-frail person would absorb without difficulty. In geriatrics, frailty is therefore the decisive link between chronological age and biological age. An overview of the entire field is provided in the article on geriatrics and medicine for the elderly.
Three distinctions are important:
- Frailty is not the same as multimorbidity: One can have many illnesses and at the same time not be frail — and vice versa.
- Frailty is not the same as disability: Disability describes what someone can no longer do. Frailty describes how well someone can cope with a stressor.
- Frailty is not the same as sarcopenia: Sarcopenia (muscle loss) is a central building block, but frailty encompasses more: cognitive, nutritional and social dimensions as well. Cognitive changes such as mild cognitive impairment (MCI) can intensify frailty and vice versa.
→ On the specific significance of muscle loss in old age: Sarcopenia — recognizing and stopping muscle loss.
Two validated models dominate clinical practice. Both have their justification, in different settings.
The Fried phenotype
In 2001, Linda Fried and colleagues defined five criteria. Anyone meeting three or more is considered frail; one to two as pre-frail; none as robust.
- Unintentional weight loss: More than 4.5 kilograms or 5 percent of body weight in the past year. This weight loss is frequently a sign of malnutrition in old age.
- Exhaustion: Subjectively reported exhaustion on three or more days per week.
- Weakness: Reduced grip strength, measured with a dynamometer.
- Slowness: Slowed walking speed over four meters.
- Low physical activity: Markedly reduced everyday activity, which in extreme cases can culminate in immobility in old age.
The Fried phenotype is particularly useful in research and in preoperative evaluation, because it can be measured objectively and reproducibly.
The Clinical Frailty Scale (CFS)
The CFS, developed by Kenneth Rockwood, is a 9-point scale that can be assessed clinically within a few minutes — without any special equipment. It ranges from CFS 1 (“very fit”) through CFS 5 (“mildly frail”) to CFS 9 (“terminally ill”).
The CFS has become established worldwide because it is immediately available in hectic clinical situations — emergency department, intensive care unit, preoperative clinic — and nevertheless provides highly significant prognostic information. In numerous studies, a CFS above 5 is associated with markedly increased mortality, longer length of stay and a higher rate of functional loss after hospitalization. The structured frailty screening describes which tests are used in concrete terms.
As a patient or relative, you can ask about the Clinical Frailty Scale before any major treatment decision: “Was the CFS assessed, and what value did it produce?” This is not a specialist question — it is a fundamental question of any modern medicine for the elderly.
- 65- to 74-year-olds: About 4 to 8 percent are frail, a further 30 percent pre-frail.
- 75- to 84-year-olds: Around 15 percent frail.
- Over-85-year-olds: 30 to 50 percent frail.
- In nursing homes: Over 60 percent of residents meet frailty criteria.
Frailty is thus one of the most common syndromes in medicine for the elderly — and one of the least frequently documented. Many discharge letters mention diabetes in old age, hypertension and atrial fibrillation in old age — but not a word about frailty. That is a systematic gap.
Frailty is not merely an epidemiological observation — it changes the entire level of clinical decision-making:
- Surgical planning: The frailty-adjusted risk assessment is superior to the conventional ASA score. A CFS of 5 or higher should factor into every risk-benefit consideration for elective procedures. Details on this are provided in the article on the surgical risk in old age.
- Drug therapy: In frail patients the benefit-risk ratios shift: some guideline-compliant therapy (strict blood sugar control, aggressive blood pressure reduction) becomes a net harm in frailty. The topic of polypharmacy in old age also plays a central role here.
- Rehabilitation: Frail patients benefit particularly — and specifically — from early geriatric rehabilitation. Standard protocols often do not take hold.
- Prognosis: In many cohort studies frailty is the strongest single predictor of 1-year mortality — stronger than many specific diagnoses, including existing heart failure in old age.
- Risk of delirium in hospital: After procedures or acute illnesses, frail patients develop delirium considerably more often. Targeted delirium prevention is therefore part of the standard in geriatric care.
- End-of-life decision-making: In pronounced frailty (CFS 7–8) treatment goals shift toward quality of life and symptom control. These conversations must be conducted early — and should ideally be safeguarded by an advance directive.
→ On preoperative assessment and risk modification: Surgical risk in old age.
→ How early geriatric rehabilitation works specifically in frail patients: Early geriatric rehabilitation.
Frailty is multifactorial. The most important mechanisms — and thus the most important points of intervention for prevention and therapy — are:
- Sarcopenia: The age-related loss of muscle mass and muscle strength. Without targeted training, about 1 to 2 percent per year from the age of 50. More on this in the article on sarcopenia.
- Malnutrition: Protein deficit in particular: the recommended daily protein intake for older people (1.0 to 1.2 g per kg of body weight) is not reached by most. Detailed background is provided in the article on malnutrition in old age.
- Chronic inflammatory burden: Elevated levels of interleukin-6, CRP, TNF-alpha — a phenomenon often referred to as inflammaging.
- Hormonal changes: Decline of testosterone, growth hormone, vitamin D. A confirmed vitamin D deficiency is closely linked with osteoporosis in old age.
- Lack of physical activity: The most important modifiable cause. Every day with less activity makes one frail — a vicious circle that in extreme cases leads to immobility in old age.
- Social isolation: Loneliness is an independent risk factor — biologically measurable, not only psychologically relevant. There are also close interactions with depression in old age.
- Multimorbidity and polypharmacy: Not identical with frailty, but one of the strongest driving forces. On reducing medication in old age: deprescribing.
The most important misconception: that frailty is a final state. The evidence speaks against this. Studies show that about one third of pre-frail patients return to the robust state within a year — and even in pronounced frailty, stabilization or partial reversion is possible when the right interventions work together.
What the evidence supports
- Progressive strength training: By far the strongest single lever. Studies show strength gains of 30 to 100 percent within a few months — even in 85- and 90-year-olds.
- Protein-rich nutrition: With a focus on distribution across the day. Protein-rich breakfasts are more important than a single large evening meal.
- Vitamin D supplementation in confirmed deficiency: Not across the board for everyone. A deficiency is frequently associated with osteoporosis in old age and an increased risk of falls.
- Medication review: Deprescribing not only reduces side effects but frequently improves energy and muscle strength directly.
- Treatment of hidden illnesses: Anemia, thyroid disorders, depression in old age, obstructive sleep apnoea syndrome — each is a potential amplifier of frailty. An unrecognised dementia in old age or mild cognitive impairment (MCI) can also obscure the frailty picture.
- Fall prevention: Since frail patients carry a markedly increased risk of falls — with consequences such as a femoral neck fracture in old age — targeted fall prevention is among the most important accompanying measures.
- Social activity: Participation, volunteering, structured group programs — measurably effective.
- Geriatric assessment as a structure: The geriatric assessment is not a single intervention but the tool with which the right interventions are identified. It records mobility, cognition, nutritional status, fall risk and medication systematically.
→ What a targeted nutritional intervention in older people looks like: Malnutrition in old age.
→ Why lack of movement and immobility are more dangerous than many think: Immobility in old age.
For relatives who want to assess the condition of an elderly family member realistically, the following everyday observations help:
- Can he or she walk 400 meters without a break?
- Climb a flight of stairs without a handrail?
- Rise from a deep armchair without bracing on the arms?
- Carry a shopping bag with a few groceries?
- Has there been unintentional weight loss in the last six months?
- Has activity noticeably reduced compared with the previous year?
- Does the person report persistent exhaustion?
- Are there indications of urinary incontinence in old age? This frequently concealed symptom too can be a sign of declining physical reserves.
If several of these questions are answered with No, or Yes on the final points, a geriatric work-up is worthwhile. Initial pointers are provided by the structured frailty screening.
Frailty is not always obvious. The following situations are good occasions to obtain a geriatric second opinion:
- Before any elective major operation in patients over 75 — the surgical risk in old age depends decisively on the frailty status.
- After a hospital stay with visible functional loss
- In the case of repeated falls or newly occurring gait unsteadiness — further information can be found in the article on falls in old age
- In the case of unintentional weight loss of over 5 percent in six months
- In the case of polypharmacy with five or more long-term medications
- When a serious diagnosis such as cancer or heart failure in old age calls for treatment decisions
On these questions the geriatrician brings a perspective that is often missing in organ-based specialties: the question of how resilient the patient is as a whole system — and which interventions pay off before the next stressor comes.
→ Which tests are used exactly in frailty screening is described in our article Frailty screening — practical implementation.
