Elderly patients are often considered as a high-risk population for major abdominal surgery due to reduced functional reserve and increased comorbidities. Previous study reported that about 40 and 10% of elderly (60 yr and older) patients suffered from postoperative cognitive dysfunction (POCD) 7 days and 3 months, respectively, after noncardiac surgery. POCD is a central nervous system complication after anesthesia and an operation, whose risk factors include age, education level, the operation (time, type, and mode), anesthesia (methods, drugs, and time) and postoperative analgesia. In the study of Su X et al, elderly patients are also more prone to develop postoperative sleep disturbances after surgery with prolonged sleep latencies, fragmented sleep, decreased sleep efficiency and abnormally sleep stages. Increasing evidence showed that sleep and circadian rhythm disturbances after surgery could promote β-amyloid peptide (Aβ) accumulation by simultaneously upregulating Aβ synthesis and interfering with Aβ clearance. This insoluble Aβ aggregates to form brain extracellular senile plaques, which are one of the neuropathological hallmarks of numerous postoperative cognitive disorders such as Alzheimer's disease(AD), and can be measured by amyloid positron emission tomography (PET) imaging through injecting 18F-florbetapir, a novel imaging agent that binds with high affinity (Kd 3.1 nM+0.7) to β-amyloid peptide fibrils in brain amyloid plaques, to the patients.Transcutaneous electrical acupoint stimulation (TEAS) is a new acupuncture therapy developed by combining transcutaneous electrical nerve stimulation (TENS) in European and American countries and traditional Chinese acupuncture. TEAS treat disease through inputting a pulse current of different frequencies, intensities, and waveforms via electrode paste adhering to the skin. Previous studies proved that TEAS has been successfully applied in many different procedures through stimulating different acupoints such as reducing postoperative pain, postoperative nausea and vomiting (PONV), and improving postoperative sleep quality. However, whether TEAS could affect Aβ deposition by improving postoperative sleep quality and thus affect the development of long-term cognitive impairment is still unclear. The aim of our study is to conduct the TEAS intervention to elderly patients who received laparoscopic abdominal surgery, and then to examine its effect on postoperative sleep quality, postoperative cognition and complications. In this study, we utilized 18F-florbetapir imaging to assess the relationships between postoperative sleep disturbances and POCD and brain Aβ burden through measuring by PET imaging.

Inclusion Criteria:

• patient's age was 65 yr or older
• patient was scheduled to undergo elective major laparoscopic abdominal surgery (e.g., gastrointestinal and gynecologic surgery).
• the surgery was expected to last 2h or longer.

Exclusion Criteria:

• severe diseases in cardiovascular, respiratory, liver, kidney, or central nervous systems and having a life span of less than 3 months;
• a mini-mental status examination score (MMSE) of less than 23;
• a history of dementia or psychiatric illness;
• current use of sedatives, antidepressants or corticosteroids;
• alcoholism and drug dependence;
• difficulty with follow-up or poor compliance;
• patients with preoperative sleep disturbances;
• patients with sleep apnea or moderate and severe obstructive sleep apnea-hypopnea syndrome (OSAHS);
• patients with severe visual or hearing impairment or who were unable to communicate.