Abstract
Postoperative delirium is a common and serious complication of surgery, particularly in older adults. Despite its impact on outcomes and healthcare costs, effective preoperative tools to identify high-risk patients remain limited. This review evaluates the potential role of olfactory dysfunction as a noninvasive biomarker for predicting postoperative delirium, based on its strong association with brain vulnerability and neurodegenerative risk. Olfactory dysfunction is prevalent in patients with neurodegenerative and psychiatric disorders, as well as in aging populations—groups already at high risk for postoperative cognitive complications. It reflects key pathophysiological mechanisms shared with delirium, including neuroinflammation, cholinergic disruption, and corticolimbic network breakdown. Recent studies in surgical populations, including cardiac procedures, suggest that preoperative olfactory testing correlates with increased incidence and severity of postoperative delirium. Olfactory testing is inexpensive, rapid, and scalable, making it a feasible addition to preoperative evaluations. Its integration may enable personalized risk stratification and proactive cognitive management in perioperative care. Olfactory dysfunction offers a promising, biologically grounded strategy to identify patients at risk for postoperative delirium. Future studies should standardize testing protocols, validate its predictive value, and explore its role within multimodal perioperative risk models.