The purpose of the study is to estimate the Chinese economic burden in patients with Alzheimer's Disease (AD).

This observational study covered all the 30 provincials/municipals/autonomous in mainland China except Hong Kong and Macau. Tier 3 hospitals, psychiatric hospitals, elderly hospitals, nursing home and communities were randomly selected as research centers, and more than 2500 patients with AD and their caregivers were enrolled at last. The main outcome of this study was assessed not only by the electronic medical system of communities and hospitals, but also by questionnaires. Using a societal prevalence-based gross COI approach to estimated the total yearly costs of AD in China.

Inclusion Criteria:

1. New patients who are diagnosed with AD in this investigation or old patients who were diagnosed prior to this investigation were eligible；
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.
3. 60-year-old and above, men or women.
4. Normal vision or corrected visual, normal audition or corrected auditory, and cooperate with inspections and treatments.
5. Consent to participate with a signed informed consent by himself/herself or guardians.

Exclusion Criteria:

1. Patient with vascular dementia or dementia caused by other reasons, such as major depression or other major psychiatric illnesses, thyroid dysfunction, encephalitis, multiple sclerosis, and other dementia which includes frontotemporal dementia (FTD), dementia with Lewy bodies (DLB), and Parkinson's dementia (PDD).
2. MRI and laboratory tests (blood cell counts, liver and renal function, electrolyte, vitamin B12/folic, HIV, syphilis, and so on) do not support or rule out AD diagnoses.
3. Has a history of alcoholism and drug abuse.

Patients with Alzhemer's disease and their caregivers.

All-cause mortality, serious, and other (not including serious) adverse events were not monitored/assessed.

All-cause mortality, serious, and other (not including serious) adverse events were not monitored/assessed.