Effects of sarcopenia and visceral obesity on postoperative delirium in older adults: a prospective cohort study

Sarcopenia (operationally defined as low skeletal muscle mass) and visceral obesity are both metabolic disorders associated with cognitive decline. Understanding the outcomes of these combined conditions is crucial. This study aimed to investigate how sarcopenia, measured by skeletal muscle index (SMI), and visceral obesity influence the occurrence of postoperative delirium (POD) in older adults. This was a prospective cohort study. A total of 270 patients undergoing total hip arthroplasty (THA) were enrolled. Sarcopenia was operationally defined as low skeletal muscle mass quantified by CT-based SMI, rather than the full EWGSOP2 definition. Visceral obesity was assessed by waist circumference (WC). POD was identified through the confusion assessment method (CAM). Receiver operating characteristic (ROC) curve analysis and the Youden index were used to calculate SMI thresholds for predicting POD. Participants were classified as follows: Group A: sarcopenia alone; Group B: visceral obesity alone; Group C: both sarcopenia and visceral obesity; and Group D: normal. We employed multivariate logistic regression model to estimate the correlation between sarcopenia, visceral obesity, and POD. A total of 270 patients were included. ROC analysis and the Youden index identified sex-specific SMI thresholds: < 29.55 cm 2 /m 2 for males and < 23.62 cm 2 /m 2 for females, optimizing SMI’s predictive accuracy for POD. The prevalence of POD was 64.70% in Group A, 20.37% in Group B, 73.10% in Group C and 24.05% in Group D, with significant differences among groups ( P < 0.001). In the multivariate logistic regression analysis, sarcopenia alone (odds ratio [OR] 5.867, 95% confidence interval [CI] 2.779–12.386) and sarcopenia with visceral obesity (OR 9.585, 95% CI 3.923–23.418) were significantly associated with an increased risk of POD compared to normal patients. Among these, individuals with both sarcopenia and visceral obesity exhibited a markedly higher risk. In contrast, visceral obesity alone was not significantly associated with POD (OR 0.821, 95% CI 0.318–2.122). Sarcopenia, as operationally defined by CT-based SMI in this study, is a risk factor for POD in older adults, and this risk is markedly amplified when it coexists with visceral obesity. However, visceral obesity alone does not significantly affect the risk of POD. China Clinical Trial Registry at https://www.chictr.org.cn/ , registration number: ChiCTR2500100801, registration date: April 15, 2025.