When an older adult suddenly becomes confused, agitated, or disoriented, it’s often assumed to be dementia. But in many cases, it may be something else: delirium.

Delirium is a sudden and severe change in mental status. It often occurs in hospitalized or medically compromised patients, particularly those over 65. And while delirium is temporary, it can sometimes signal an underlying vulnerability — including the early stages of dementia.

Delirium vs. Dementia: What’s the Difference?

The key distinction is onset and progression:

• Delirium: Appears suddenly (over hours or days), often triggered by infection, medication, dehydration, or surgery.
• Dementia: Develops slowly over months or years and involves gradual memory, reasoning, and behavioral changes.

That said, people with early dementia are more prone to delirium, and those who experience delirium may be at increased risk of future cognitive decline.

Why Does Delirium Matter in Dementia Diagnosis?

Delirium can:

• Unmask preclinical dementia that has not yet been diagnosed
• Accelerate cognitive decline in vulnerable individuals
• Lead to long-term changes in brain function if not treated promptly

In fact, a 2021 study in The Lancet Psychiatry found that older adults who experienced delirium were three times more likely to develop dementia within a few years.

When to Seek Help

If a loved one experiences:

• Sudden confusion or trouble speaking
• Hallucinations or paranoia
• Fluctuations in alertness
• Restlessness or unusual drowsiness

…it’s important to seek immediate medical attention. Delirium is often reversible if the underlying cause is treated — but it also serves as a red flag for further cognitive evaluation.

Final Thoughts

Delirium isn’t the same as dementia, but it can be an important early warning sign. Recognizing and treating it quickly not only improves outcomes in the short term but may also offer a valuable opportunity for early detection and proactive dementia care.