Introduction: Frailty is increasingly recognized as a predictor of adverse outcomes in critical illness, yet the combined effect of frailty and chronological aging on patients who stay for a long duration (≥ 7 days) in the intensive care unit (ICU) has not been fully elucidated.
Methods: We conducted a single‑center, retrospective cohort study of adults (≥ 18 y) admitted to a mixed medical–surgical ICU between October 2021 and December 2024 who remained in the ICU for ≥ 7 days. Upon admission, frailty was assessed using the Clinical Frailty Scale (CFS). Patients were stratified into four mutually exclusive groups: Non‑frail/non‑elderly (reference) – CFS ≤ 4 & age < 75, Frail/non‑elderly – CFS ≥ 5 & age < 75 y, Non‑frail/elderly – CFS ≤ 4 & age ≥ 75 y, Frail/elderly – CFS ≥ 5 & age ≥ 75 y. The primary outcome was all-cause in-hospital mortality censored at 90 days. A multivariable Cox proportional-hazards model adjusted for the APACHE II score and Charlson Comorbidity Index was used to quantify the associations.
Results: Among the 2,034 consecutive ICU admissions, 310 (15.2 %) met the long-stay criterion. Group distributions were: Non‑frail/non‑elderly 133 (42.9 %); Frail/non‑elderly 39 (12.6 %); Non‑frail/elderly 86 (27.7 %); Frail‑elderly 52 (16.8 %). The crude in-hospital mortality differed significantly (27.1 %, 41.0 %, 34.9 %, and 59.6 %, respectively; p = 0.001). After adjustment, only the Frail‑elderly group showed a significantly higher hazard of in‑hospital death within 90 days compared with the reference (adjusted HR = 1.76, 95 % CI 1.07–2.92; p = 0.027). Frailty and age alone did not reach statistical significance.
Conclusions: Among adult ICU patients with stays of ≥ 7 days, the coexistence of frailty and advanced age confers the greatest risk of in‑hospital mortality (59.6 %). These findings highlight the need for early frailty screening and tailored management strategies in elderly patients with frailty, rather than focusing on frailty or age in isolation.
