Postoperative cognitive dysfunction (POCD) occurs mainly in aged patients. POCD may increase the mortality and morbidity. However, the mechanism of POCD is not clear yet and no effective therapy method was proved. According to our previous study, the central cholinergic system impaired by the anesthesia and surgery play a very important role in the POCD and donepezil an acetylcholinesterase inhibitor can prevent the POCD after isoflurane anesthesia in aged mice. Donepezil is a commercial medicine used for the Alzheimer Disease, which is tolerable and has minimal adverse events. In present study a multi-center randomized case control study was conducted and we hypothesized that donepezil attenuate the POCD.

Inclusion Criteria:

1. Elder than 60 years old
2. Speak Chinese Mandarin
3. Those who will undergo knee or hip replacement
4. Signed the inform consent
5. American Society of Anesthesiologists classification I to III

Exclusion Criteria:

1. Existing cerebral disease, or have a history of neurological and psychiatric diseases including Alzheimer Disease, stroke, epilepsy and psychosis;
2. existing cognitive impairment as evidenced by Mini-Mental State Examination scores below 24;
3. several audition or vision disorder;
4. unwillingness to comply with the protocol or procedures.
5. Can not communicated with Chinese Mandarin
6. Existing bradycardiac arrhythmia（Heart rate <60 bpm for any reasons）
7. Existing gastrointestinal ulcer
8. Existing urinary incontinence
9. Existing asthma or chronic obstructive pulmonary disease
10. Allegory to Donepezil