Millions of Americans survive critical illness each year, only to be faced with new life-altering impairments in physical, cognitive, and mental health function that alter their ability to live independently. The mechanisms underlying these sequelae of critical illness are incompletely understood but are believed to develop as a function of the severity of the critical illness and the patient’s underlying vulnerability. Clinically, a patient’s underlying vulnerability can be understood as the syndrome of frailty.

Frailty affects 30% of those with critical illness and over 40% of survivors of critical illness. The presence of frailty at ICU admission confers a greater risk of death and, among survivors, disability in activities of daily living. Validated tools including the Clinical Frailty Scale, the frailty index, and the frailty phenotype can be used to identify frailty in those affected by critical illness. While effective interventions such as physical activity, nutritional support, and palliative care can reduce age-related frailty among community-dwelling older adults, the efficacy of these interventions in those along the continuum of critical illness is an area of ongoing study.