Verification Study and Reactivity Study for the Validity of QuQu Scale (QuQu)

Inclusion Criteria:

1. Alzheimer's Disease Dementia and patients with cognitive concern without Dementia
2. Written Informed consent by each subject and/or a legal representative, and study informant. If the doctor decides that the patient has no trouble in understanding this study, the written informed consent of a legal representative may be exempted. If not, this study needs a written informed consent by a legal representative and the patient except the case where the consent is hardly obtained due to the progression of the disease.

Exclusion Criteria:

1. patients with other types of dementia (e.g. vascular dementia, Levy body dementia, frontotemporal dementia)
2. patients with other diseases which cause secondary dementia prior to Alzheimer's Disease Dementia
3. patients with other severe neurological disease or psychiatric disorder without Alzheimer's Disease Dementia
4. patients with other medical conditions where the investigators determine that it is inappropriate for the subject of this study (e.g. inappropriate for the evaluation of dementia rating scale)