Preoperative prognostic nutritional index value as a predictive factor for postoperative delirium in older adult patients with hip fractures: a secondary analysis

Background Malnutrition is a common geriatric syndrome and can be targeted preoperatively to decrease the risk of postoperative delirium (POD) in older adult patients. To analyze the value of the prognostic nutritional index (PNI) to predict the incidence of POD in older adult patients with hip fractures. Methods This was a prospective, observational, cohort study of older adult patients with hip fractures. Preoperative PNI was calculated as 10 × serum albumin (g/dL) + 0.005 × total lymphocyte count (/μL) using preoperative laboratory results. Patients were divided into POD and non-POD groups using the Confusion Assessment Method (CAM). The risk factors associated with POD as well as the relationship between PNI values and the incidence of POD were analyzed using univariate and multivariate logistic regression analyses. The predictive value of PNI for POD was assessed using receiver operating characteristic curve analysis. Results In this cohort of 369 patients who underwent hip fracture surgery, 67 patients (18.2%) were diagnosed with POD by the CAM results. Low PNI increased the risk of POD (odds ratio (OR) = 0.928, 95% confidence interval (CI): 0.864–0.997). General anesthesia (OR = 2.307, 95% CI: 1.279–4.162) and Mini-Mental State Examination (MMSE) score (OR = 0.956, 95% CI: 0.920–0.994) were also identified as risk factors for POD. Receiver operating characteristic curve analysis suggested that PNI combined with the anesthetic method and MMSE score may be used as a potential predictive indicator of POD after hip fracture surgery. Conclusion Preoperative PNI value is related to POD in older adult patients with hip fractures. Trial registration This secondary analysis study was approved by the Peking University Third Hospital Medical Science Research Ethics Committee (approval No. M2022578) and registered in the Chinese Clinical Trial Registry (ChiCTR2300070569).