The Effect of Exercise-Induced Irisin on Brain Function and Postoperative Delirium in Older Adults

Inclusion Criteria: * Aged ≥ 65 years; * Classified as ASA physical status I to III; * Scheduled for non-cardiovascular surgery under spinal anesthesia or combined spinal-epidural anesthesia; * Expected surgical duration of at least 2 hours; * Voluntarily provide written informed consent and agree to participate in this study. Exclusion Criteria: * Significant change in exercise status within the past 7 days due to injury or other reasons; * Contraindications to neuraxial anesthesia; * Unable to assess cognitive function or Montreal Cognitive Assessment (MoCA) score \< 23; * Preoperative diagnosis of delirium; * History of traumatic brain injury or neurosurgery; * Long-term opioid use or history of alcohol abuse; * Planned surgery cancelled or changed (including intraoperative events that significantly alter the procedure or duration); * Change in anesthesia method.