Delirium and dementia 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.
Comparing Delirium and Dementia
Feature | Delirium | Dementia |
|---|---|---|
Development | Sudden, sometimes with a definite beginning point | Slow, with an uncertain beginning point |
Cause | Almost always another condition, such as an infection, dehydration, or use or stopping of certain medications | Usually a brain disorder, such as Alzheimer disease, vascular dementia, or dementia with Lewy bodies |
Main early symptom | Inability to pay attention | Loss of memory, especially for recent events |
Effect at night | Almost always worse | Often worse |
Level of alertness (consciousness) | Impaired to varying degrees, can vary from being hyperalert to sluggish | Normal until late stages |
Orientation to surroundings | Varies | Impaired |
Effect on language | Slowed speech, often with incoherent and inappropriate language | Sometimes difficulty finding the right word |
Memory | Varies | Lost, especially for recent events |
Progression | Causes variations in mental function—people are alert one moment and sluggish and drowsy the next | Slowly progresses, gradually but eventually greatly impairing all mental functions |
Duration | Days to weeks, sometimes longer | Almost always permanent |
Need for treatment | Immediate | Needed but less urgently |
Effect of treatment | Usually resolution of the symptoms | May slow progression but cannot reverse or cure the disorder |
