Clinical Efficacy of Ginkgo Biloba Extract in the Treatment of Alzheimer's Disease

Inclusion Criteria: 1. All patients were diagnosed with dementia caused by AD in 2011, the latest diagnostic criteria for Alzheimer's disease (NIA-AA), according to the patient's clinical and cranial imaging findings 2. Improved Hachinski ischemic scale score \<4 3. All patients underwent head CT and / or MRI examinations and laboratory tests to rule out other causes of dementia 4. MMSE(High school≤24,Primary school≤20;illiteracy≤17) 5. CDR 1-2 6. The subjects and nurses signed informed consent, and the nursing staff were able to take responsibility for the supervision of the participants 7. The subjects were stable 8. Cooperate, willing to complete all parts of the research, and have the ability to complete the study alone or with the help of the nursing staff 9. To cooperate with the study, do not live alone, such as living alone should keep in touch with the nurse every day. Exclusion Criteria: 1. Heart lung kidney disease, may interfere to evaluate the efficacy and safety of patients at risk or special disease,for example:Congestive heart failure et al. 2. According to NINDS-AIREN standard (Roman GC et al 1993) is currently diagnosed as possible vascular dementia 3. Improved Hachinski ischemic scale score（MHIS）≥4 4. Diagnosis of severe depression, schizophrenia, and other major neurodegenerative disorders, according to the DSM-IV axis 5. Neurological or other medical disorders that affect the function of the central nervous system,like Moderate anemia,Vitamin B12 or folic acid deficiency, et al. Not with the cognitive function examination (including blindness, deafness, severe language disorders).