## Delirium vs Dementia: Key Distinguishing Features **Key Point:** Delirium is characterized by acute onset (hours to days) and a fluctuating course throughout the day, whereas dementia has an insidious onset and progressive decline over months to years. ### Temporal Course Comparison | Feature | Delirium | Dementia | | --- | --- | --- | | **Onset** | Acute (hours to days) | Insidious (months to years) | | **Course** | Fluctuating, waxing-waning | Steadily progressive | | **Duration** | Hours to weeks (usually) | Years | | **Reversibility** | Often reversible if cause treated | Usually irreversible | ### Cognitive Profile Differences **Delirium:** - Attention and consciousness are PRIMARILY affected - Disorientation (especially to time and place) - Fluctuating level of alertness (hyperactive, hypoactive, or mixed) - Memory impairment secondary to inattention **Dementia:** - Memory loss is the PRIMARY and earliest feature - Attention relatively preserved early - Gradual, progressive decline in all cognitive domains - Consciousness and alertness remain normal until late stages **High-Yield:** The fluctuating course of delirium is pathognomonic — it worsens in the evening (sundowning) and improves in the morning. Dementia shows no such diurnal variation. **Clinical Pearl:** A patient with dementia who suddenly develops acute confusion with fluctuating consciousness likely has delirium superimposed on dementia — a common and often missed diagnosis in hospitalized elderly patients.
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.