Beyond the calendar: biologic age as a missing vital sign in chronic kidney disease

Chronic kidney disease (CKD) is commonly framed as a model of accelerated aging, yet clinical decisions still rely heavily on chronological age, which poorly captures heterogeneity in functional status, vascular health, cognition, and recovery potential. This narrative review argues that biologic age-a multidomain construct integrating frailty and physical performance, body composition, cardiovascular and vascular markers, inflammatory and metabolic profiles, and cognitive/psychosocial factors-should be treated as a "missing vital sign" in CKD. Such composite measures can refine risk stratification, guide choices between dialysis and conservative care, improve transplant candidate assessment, and inform cardiovascular prevention, ICU triage, and major surgery planning. The article also warns that biologic age metrics must be transparently developed and audited to prevent reinforcing existing inequities and to ensure they trigger supportive, not exclusionary, interventions.