What's the Difference Between Dementia and Delirium?

June 19, 2015
Male nurse assisting elderly patient

“They kept telling me in the hospital, ‘Everybody does this,’ and that his confusion would disappear.”

An article in the Washington Post describes the experience of a physician and his wife while the physician dealt with delirium during his recovery from a serious infection. He developed terrifying hallucinations, and many months after the hospitalization he was still battling the delirium.

In my experience as an occupational therapist working in long-term care and home health, I’d often seen persons with dementia return from the hospital and demonstrate a significant decline in function and changes in mood. A person might have been lethargic, or may have appeared anxious and overstimulated. Often the change was not diagnosed, but it was accepted that the change would dissipate over time. Sometimes more medication was provided in order to address the mood changes.

These experiences underline the growing need for care partners to be able to recognize and diagnose delirium.

What is delirium?

Delirium is an acute confusional state. A diagnosis of delirium is typically based on clinical observation of behaviors and cognition, because no diagnostic tests are available.

The essential features of delirium include:

  • Acute onset (hours/days) and a fluctuating course
  • Inattention or distraction
  • Disorganized thinking or an altered level of consciousness (which may include hallucinations or delusions)

Delirium can result from:

  • Infection
  • Drug interactions or sensitivity
  • Dehydration
  • Kidney failure
  • Liver failure
  • Brain tumors or other head trauma
  • Other physical problems

Because delirium is usually a sign that something potentially damaging is occurring, it’s important to seek medical help immediately if symptoms manifest. Unlike dementia, delirium is usually reversible if the underlying cause is treated [PDF].

Delirium can be easily overlooked in persons with dementia because some of the symptoms of delirium are shared with dementia. However, dementia and delirium are distinctly different illnesses.

The differences between dementia and delirium

Dementia develops over time, with a slow progression of cognitive decline. Delirium occurs abruptly, and symptoms can fluctuate during the day. The hallmark separating delirium from underlying dementia is inattention. The individual simply cannot focus on one idea or task.

Delirium often is unrecognized by healthcare professionals because changes in behavior in persons with dementia (such as agitation or sun downing) may be attributed to the dementia disease process, versus an acute problem.

Delirium may be the first and perhaps only clue of medical illness or adverse medication reaction in an individual with Alzheimer’s.

Often, persons with dementia develop delirium while hospitalized.

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