Describe delirium and dementia. What are the main differences?

Delirium has a relatively rapid onset and is caused by a generalized disturbance in brain metabolism. Causal factors include head trauma, oxygen deprivation, drug withdrawal, and toxic and metabolic disturbances. Attention, perception, and memory are affected. Frequently the person becomes agitated and has disturbed sleep. Delirium rarely lasts more than one week. Dementia involves a progressive deterioration of brain function that begins with episodic, short-term memory loss and spreads to include impaired emotional control, motor control, learning, abstract thinking, and other functions. It typically affects older individuals and may be caused by strokes, infections, tumors, head injury, and degenerative diseases, particularly Alzheimer's disease.