Association between malnutrition and frailty and postoperative mortality in older surgical patients

BACKGROUND AND AIMS: Malnutrition and frailty independently predict prolonged hospitalization and mortality; however, their combined impact on older patients undergoing elective surgery remains unclear. The study examined the combined association of malnutrition and frailty with postoperative all-cause mortality and adverse outcomes. METHODS: This prospective multicenter cohort study enrolled across 5 centers in China between December 17, 2023, and October 17, 2024, with follow-up completed on October 18, 2025. The study population included patients 65 years or older who underwent elective surgery. Malnutrition assessed by the Global Leadership Initiative on Malnutrition (GLIM) and frailty assessed by the Fried phenotype before the surgery. The primary outcome was all-cause mortality within one year, analysed using Cox proportional-hazards models adjusted for hospital ID, age, sex, ethnicity, educational level, smoking status, alcohol consumption, age-adjusted Charlson Comorbidity Index (aCCI), American Society of Anesthesiologists (ASA) physical status, and surgical approach. Secondary outcomes included 90-day mortality, major postoperative complications (POCs), and prolonged length of stay (LOS). RESULTS: Among 1361 older adults undergoing elective surgery (median age 71 years), 818 had neither malnutrition nor frailty, 229 had malnutrition only, 130 had frailty only, and 184 had both conditions. After multivariable adjustment, malnutrition alone and frailty alone were each associated with modestly increased risks of adverse outcomes, whereas the highest risks were observed among participants with concurrent malnutrition and frailty. Compared with those with neither condition, concurrent malnutrition and frailty were associated with higher risks of 1-year mortality (hazard ratio [HR], 5.36; 95% confidence interval [CI], 3.00-9.56), 90-day mortality (HR, 13.22; 95% CI, 5.10-34.32), major POCs (odds ratio [OR], 4.83; 95% CI, 2.53-9.19), and prolonged LOS (OR, 2.61; 95% CI, 1.94-3.51). The combined presence of malnutrition and frailty was associated with a 4.44-fold excess risk of 1-year mortality beyond additivity, with 63% of the risk attributable to their interaction. CONCLUSION: Concurrent preoperative malnutrition and frailty identified a high-risk phenotype independently associated with increased risks of 1-year and 90-day all-cause mortality, major POCs, and prolonged LOS, supporting its use in preoperative risk stratification among older adults undergoing surgery.