Effect of Electroacupuncture Combined With Donepezil for Treating Alzheimer's Disease

* Patient registry: Participants experiencing cognitive impairment will be recruited will be recruited at Guang'anmen Hospital, Beijing, China, via web or posters. A neurologist will make the diagnosis. Randomization will be performed by the pharmacological assessment center at Guang'anmen Hospital. * Sample size: The calculation of sample size is based on the primary outcome that the change from baseline in ADAS-cog. According to previous studies \[26\], 39% of patients showed an improvement of at least 4 points on the ADAS-cog after treating by donepezil. We estimated the rate 39% in the donepezil group and 55% in the EA combined with donepezil group. 304 participants were needed to provide 80% power at a significant level of 5% using analysis of variance. The total sample size required for the study is 334 (167 each group) assuming a 10% loss to follow-up. * Quality control 1. Investigators participating in this trial will take a strict course about the process of randomization, manipulation of electroacupuncture, selection of patients, the whole process of this trial and request for filling out case report form in order to improve the internal consistency of observation between different researchers. 2. The process of randomization will be under a rigorous control. 3. This trial has a specific inclusion and exclusion criteria. 4. Both outcome assessors and statisticians will be blinding. 5. Patients will sign the informed consent voluntarily and a good relationship between researchers and patients will be established in order to improve patients' compliance. Participants will have a detailed record of the contact information easy for follow-up. 6. The standard of the drugs, acupuncture apparatus, inspection equipment are consistent for the patients in the two groups. * Outcome assessment, completion of case report forms and data management will be under a rigorous supervision.