Delirium is a state of confusion that comes on very suddenly and lasts hours to days. If your loved one becomes delirious, it means she/he cannot think very clearly, can’t pay attention and is not really aware of their environment. Sometimes people will call it other things such as a change in mental status, "sundowning" or "ICU psychosis", but it is all delirium.
Many things can cause delirium including medications, infections and lack of sleep. Often, a combination of problems causes delirium. Many things can make delirium worse including physical restraints, bed rest, bladder catheters and certain medications. The important point is that doctors and other health care providers should look for the causes and treat them; and they should be careful not to do things that might make delirium worse.
Delirium and dementia can exist at same time but they are not the same. Dementia comes on gradually and is a permanent condition. Delirium can develop suddenly and usually goes away in days to weeks if treated properly. It is important to note though, that people who have dementia are at an increased risk of developing delirium.