2. AD diagnosis must meet criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) and the National Institute of Neurologic and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA). The diagnosis should also meet the following: Modified Hachinski Ischemic Scale (MHIS) score≤4, Activity of Daily Living Scale (ADL) score≥23, Geriatric Depression Scale (GDS) score＜11. Neuroimaging MRI support AD diagnosis (exist atrophy in medial temporal lobe, white matter lesions score≤2 minutes according to the Fazekas criteria. AD disease classification according to mini-mental state examination (MMSE) scale (for illiterate dementia: mild: 21~24 points; moderate: 11~20 points; severe: 10 points or less; for lettered dementia: mild: 16~19 points; moderate: 8~15 points; severe: 7 points or less). The diagnosis of AD was confirmed by brain CT or MRI scans and by laboratory tests to rule out any other significant comorbidity.