Frailty
Frailty is a clinical syndrome of reduced physiological reserve across several organ systems, producing disproportionate decline in function and health after minor stressors such as an infection, a new drug or a change of environment. It is distinct from ageing itself, from disability, and from multimorbidity, although the three often coexist.
Clinical relevance. Frailty predicts falls, delirium, hospital admission, longer stay, institutionalisation, complications of surgery and death, and it changes treatment goals and the balance of benefit and harm for many interventions.
Mechanisms. Sarcopenia, chronic low grade inflammation (raised interleukin 6 and C reactive protein), neuroendocrine dysregulation, immune ageing, mitochondrial dysfunction, malnutrition and accumulated chronic disease combine to lower homeostatic capacity.
Classification.
- Phenotype model: three or more of unintentional weight loss (4.5 kg or 5% of body weight over a year), self reported exhaustion, weak grip strength, slow walking speed and low physical activity indicates frailty. One or two features indicates pre-frailty.
- Deficit accumulation model: a frailty index counts the proportion of health deficits present. The Clinical Frailty Scale grades function from 1 (very fit) to 9 (terminally ill); a score of 5 or more is frail. Scores 5 to 7 correspond to mild, moderate and severe frailty, 8 to very severe.
Temporal patterns. Frailty usually progresses over months to years with sudden step downs after acute illness. A decline over days or weeks should prompt a search for acute illness, delirium, depression or malignancy rather than being attributed to frailty.
Key distinctions. Frailty is a state of vulnerability, not a disease. It is distinct from dependence, since a person with stable disability may be fit in other respects. Tools are not interchangeable and validation is weakest in people under 65 and in those with lifelong disability.
