What differentiates delirium from dementia?

Delirium Also called the acute confusional state, delirium is a medical condition that results in confusion and other disruptions in thinking and behavior, including changes in perception, attention, mood and activity level. In dementia, changes in memory and intellect are slowly evident over months or years. Delirium is a more abrupt confusion, emerging over days or weeks, and represents a suddenchange from the person's previous course of dementia. Thinking becomes more disorganized, and maintaining a coherent conversation may not be possible. The hallmark separating delirium from underlying dementia is inattention. The individual simply cannot focus on one idea or task REF : HARRSIONS 21ST ED