Multiple factors are responsible for the development of sleep disturbances after surgery. These include (1) environmental factors, such as noises, lights, medical and nursing activities, etc.; (2) comorbid diseases, such as cardiovascular disease, inflammatory reaction, infections, etc.; (3) stress response and pain stimulation provoked by surgery, especially major surgery; (4) mechanical ventilation. Studies found significantly disordered circadian rhythms, fragmented sleep and absent REM sleep in mechanically ventilated patients; and (5) multiple medications, such as benzodiazepines, opioids, non-steroidal anti-inflammatory drugs, and glucocorticoids,.