Cognitive-frailty phenotyping and postoperative delirium risk in older surgical patients: a retrospective cohort study.

BACKGROUND: Postoperative delirium remains a common complication in older surgical patients. Frailty and cognitive impairment are established risk factors but are often assessed independently. We examined whether a pragmatic 2×2 cognitive-frailty phenotype framework stratifies postoperative delirium risk. METHODS: This retrospective cohort study included patients aged ≥70 yr undergoing elective noncardiac, noncranial surgery at a tertiary centre from February 2022 to July 2024. Cognition and frailty were assessed using the Mini-Cog and Clinical Frailty Scale. Patients were classified into four phenotypes: intact, frail-only, cognitive-only, and cognitive-frailty. POD was assessed using the 4A's Test (4AT) in the PACU on the day of surgery and in surgical wards on postoperative days 1 and 2. The primary outcome was overall postoperative delirium, defined as at least one positive 4AT assessment. The secondary outcome was postoperative length of stay (LOS). RESULTS: Among 3353 patients, 61% were intact, 20% frail-only, 11% cognitive-only, and 8% cognitive-frailty. Overall postoperative delirium incidence was 7.5%, increasing from 4.2% in the intact to 24.0% in the cognitive-frailty phenotype (P<0.001). Compared with intact, postoperative delirium risk was highest in the cognitive-frailty phenotype (adjusted odds ratio [aOR] 4.79, 95% confidence interval [CI] 3.22-7.11), followed by the cognitive-only phenotype (aOR 2.41, 95% CI 1.60-3.63) and the frail-only phenotype (aOR 1.72, 95% CI 1.20-2.47). Median postoperative LOS increased from 2.6 to 4.5 days across phenotypes (P<0.001). CONCLUSIONS: In this cohort of older surgical patients, a pragmatic two-dimensional cognitive-frailty framework based on bedside screening tools demonstrated a clear gradient in postoperative delirium risk. This might support perioperative risk stratification, preventive strategies, and future research.