The cause of POD is associated with multiple risk factors, such as preexisting dementia, functional impairment, preoperative anemia, drug or alcohol abuse, intraoperative blood loss, surgical duration > 3 h, general anesthesia, electrolyte imbalance, low albumin, postoperative sleep disorders, and frequent hypotension [5,18,19,20]. Here, ALB is linked to anemia (phenotype).