Inclusion Criteria:

1. Age is greater than or equal to 60 years old
2. It is planned to undergo elective non-cardiac surgery under general anesthesia, with the expected operation duration being greater than or equal to 2 hours
3. ASA I-III

Exclusion Criteria:

1. There was a clear diagnosis of mental illness before the surgery (such as schizophrenia, severe depression, etc.) or the patient had been using antidepressants or anti-psychotic drugs for a long time.
2. Preoperative presence of sleep-wake disorder-related diseases (such as narcolepsy, untreated moderate to severe obstructive sleep apnea syndrome, etc.) or long-term use of orexin receptor antagonists or agonists
3. Preoperatively, there was severe liver dysfunction (Child-Pugh grade B or C), severe renal dysfunction (estimated glomerular filtration rate eGFR < 30 ml/min/1.73㎡), and severe anemia (Hb < 80 g/L)
4. Perform deep sedation for extubation, plan to transfer to the ICU, or experience severe complications during the recovery period (such as anaphylactic shock, laryngospasm, etc.)
5. There are cases where individuals have severe visual or hearing impairments, or are aphasic, and thus are unable to cooperate in completing the cognitive assessment.
6. Having a history of alcohol abuse or drug addiction
7. Emergency surgery, neurosurgery surgery
8. The researchers considered it inappropriate to include in this study