The Effect of Transcutaneous Auricular Vagus Nerve Stimulation on Postoperative Sleep Quality in Elderly Patients Undergoing Lumbar Spine Surgery and Its Association with Melatonin Circadian Rhythm

INTERVENTION: intervention group:Using standard treatment parameters, the frequency of the Transcutaneous Auricular Vagus Nerve Stimulation device was set to 25 Hz, the pulse width was 250 µs, and the current intensity was the maximum value that the subject could tolerate without experiencing pain.;control group:Using low‐frequency treatment parameters, the frequency of the Transcutaneous Auricular Vagus Nerve Stimulation device was set to 1 Hz, the pulse width was 250 µs, and the current intensity was the maximum value that the subject could tolerate without experiencing pain.; CONDITION: Postoperative sleep disorder PRIMARY OUTCOME: The incidence rate (percentage) of sleep disorders on the 4th day after surgery; SECONDARY OUTCOME: Melatonin rhythm;Cortisol rhythm;Sleep bracelet sleep monitoring parameters;Resting/Moving State VAS Score;Cognitive and Delirium Assessment;Postoperative nausea and vomiting score;TNF‐a;IL‐6; INCLUSION CRITERIA: 1. Age between 65 and 75 years old, with ASA classification of I‐III; 2. Planned to undergo elective single‐segment or double‐segment posterior lumbar interbody fusion surgery (TLIF); expected operation time >= 2 hours; postoperative hospital stay >= 4 days; 3. Patients without sleep disorders before the surgery: PSQI <= 7; AIS score for sleep disorder on the first day after surgery >= 6; 4. Signed the informed consent form.