Altered mental status (AMS) is common in older patients. However there is a lack of standardization in the definition and documentation of this compliant. Different perception of AMS can cause negative impact on interpretation and obtaining scientific data. Although definition of AMS is so complicated, clinical documentation can be detected in these patients with AMS.

Basically, consciousness is the state of full awareness of the self and one's relationship to the environment. There are 2 related areas of neurologic function that are connected to consciousness: content (orientation and memory) and level (arousal and response to stimuli).

The mental changes are best looked for in terms of arousal, attention, alertness, orientation, cognition, memory, affect, and perception. Arousal (level of consciousness) can be detected by the Richmond Agitation and Sedation Scale. Others are related to content of consciousness and can be evaluated by cognitive tests. After one month pilot study, the investigators chose 5 features of content of consciousness due to easy applicable and detectable;

1. Attention (counting numbers backwards from 20) (>1 error positive)
2. Cognition (disorganized thinking; meaningless speech, irrelevant explanations)
3. Perception (visual or auditory hallucinations)
4. Memory (3 items recall) (>1 error positive)
5. Orientation (day of week, month and year) (>1 error positive)

These features are also combination of six item screener test and delirium symptoms.

All elderly patients (65 aged and older) presented to the emergency department, will be assessed according to these two methods; content and level of consciousness. And also, every patient's baseline status of consciousness will be obtained from surrogates who knows the patient best. All changes from patient's baseline status will be recorded. The investigators will investigate how changes are reflected in the clinic.

Inclusion Criteria:

• All older ED patients

Exclusion Criteria:

• Unknown baseline status, any trauma, and unable to assess mental status due to acute clinical condition (STE MI, severe dyspnea, etc)

All older emergency department patients aged 65 and older.