Delirium Delirium Delirium is a sudden, fluctuating, and usually reversible disturbance of mental function. It is characterized by an inability to pay attention, disorientation, an inability to think clearly... read more and dementia Dementia Dementia is a slow, progressive decline in mental function including memory, thinking, judgment, and the ability to learn. Typically, symptoms include memory loss, problems using language and... read more are the most common causes of mental (cognitive) dysfunction—the inability to acquire, retain, and use knowledge normally.
Although delirium and dementia may occur together, they are quite different:
Delirium begins suddenly, causes fluctuations in mental function, and is usually reversible.
Dementia begins gradually, progresses slowly, and is usually irreversible.
Also, the two disorders affect mental function differently:
Delirium affects mainly attention.
Dementia affects mainly memory.
Both delirium and dementia may occur at any age but are much more common among older people because of age-related changes in the brain Effects of Aging on the Nervous System (See also the aging brain and nervous system.) Brain function varies normally as people pass from childhood through adulthood to old age. During childhood, the ability to think and reason steadily... read more .