Delirium is a state of acute dysfunction of the higher neurological centers with a predominant increase in excitability. The main clinical manifestations are blurred consciousness, disorientation, confusion, agitation, and garbled speech. It is also called acute brain syndrome because of its acute onset, short duration and rapid progression. Delirium is characterized by impaired consciousness, confusion, inability to concentrate and reduced clarity of surroundings and things. If an elderly person is usually in good mental condition, but suddenly appears to have a reduced level of cognition, such as being in a trance, listless and sleepy during the day; confused about time and place, or even not recognizing family members; or having a lack of concentration, doing things upside down, speaking incoherently, or even having transient hallucinations or delusions, such as being able to see something strange or hear a special sound. When you encounter this situation with an elderly person at home, don’t think it’s a sudden confusion, it’s probably delirium.